QByteArray 类

QByteArray 类提供字节数组。 更多...

Header: #include <QByteArray>
CMake: find_package(Qt6 COMPONENTS Core REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: QT += core

注意: 此类的所有函数 可重入 .

公共类型

class FromBase64Result
enum Base64Option { Base64Encoding, Base64UrlEncoding, KeepTrailingEquals, OmitTrailingEquals, IgnoreBase64DecodingErrors, AbortOnBase64DecodingErrors }
flags Base64Options
const_iterator
const_reverse_iterator
iterator
reverse_iterator

公共函数

QByteArray (QByteArray && other )
QByteArray (const QByteArray & other )
QByteArray (qsizetype size , char ch )
QByteArray (const char * data , qsizetype size = -1)
QByteArray ()
QByteArray & operator= (QByteArray && other )
QByteArray & operator= (const QByteArray & other )
~QByteArray ()
QByteArray & append (const QByteArray & ba )
QByteArray & append (char ch )
QByteArray & append (qsizetype count , char ch )
QByteArray & append (const char * str )
QByteArray & append (const char * str , qsizetype len )
QByteArray & append (QByteArrayView data )
char at (qsizetype i ) const
char back () const
char & back ()
QByteArray::iterator begin ()
QByteArray::const_iterator begin () const
qsizetype capacity () const
QByteArray::const_iterator cbegin () const
QByteArray::const_iterator cend () const
void chop (qsizetype n )
QByteArray chopped (qsizetype len ) const
void clear ()
int compare (QByteArrayView bv , Qt::CaseSensitivity cs = Qt::CaseSensitive) const
QByteArray::const_iterator constBegin () const
const char * constData () const
QByteArray::const_iterator constEnd () const
bool contains (QByteArrayView bv ) const
bool contains (char ch ) const
qsizetype count (QByteArrayView bv ) const
qsizetype count (char ch ) const
qsizetype count () const
QByteArray::const_reverse_iterator crbegin () const
QByteArray::const_reverse_iterator crend () const
char * data ()
const char * data () const
QByteArray::iterator end ()
QByteArray::const_iterator end () const
bool endsWith (QByteArrayView bv ) const
bool endsWith (char ch ) const
QByteArray::iterator erase (QByteArray::const_iterator first , QByteArray::const_iterator last )
QByteArray & fill (char ch , qsizetype size = -1)
QByteArray first (qsizetype n ) const
char front () const
char & front ()
qsizetype indexOf (QByteArrayView bv , qsizetype from = 0) const
qsizetype indexOf (char ch , qsizetype from = 0) const
QByteArray & insert (qsizetype i , QByteArrayView data )
QByteArray & insert (qsizetype i , const char * s )
QByteArray & insert (qsizetype i , const QByteArray & data )
QByteArray & insert (qsizetype i , qsizetype count , char ch )
QByteArray & insert (qsizetype i , char ch )
QByteArray & insert (qsizetype i , const char * data , qsizetype len )
bool isEmpty () const
bool isLower () const
bool isNull () const
bool isUpper () const
QByteArray last (qsizetype n ) const
qsizetype lastIndexOf (QByteArrayView bv , qsizetype from = -1) const
qsizetype lastIndexOf (char ch , qsizetype from = -1) const
QByteArray left (qsizetype len ) const
QByteArray leftJustified (qsizetype width , char fill = ' ', bool truncate = false) const
qsizetype length () const
QByteArray mid (qsizetype pos , qsizetype len = -1) const
QByteArray & prepend (QByteArrayView ba )
QByteArray & prepend (char ch )
QByteArray & prepend (qsizetype count , char ch )
QByteArray & prepend (const char * str )
QByteArray & prepend (const char * str , qsizetype len )
QByteArray & prepend (const QByteArray & ba )
void push_back (const QByteArray & other )
void push_back (char ch )
void push_back (const char * str )
void push_back (QByteArrayView str )
void push_front (const QByteArray & other )
void push_front (char ch )
void push_front (const char * str )
void push_front (QByteArrayView str )
QByteArray::reverse_iterator rbegin ()
QByteArray::const_reverse_iterator rbegin () const
QByteArray & remove (qsizetype pos , qsizetype len )
QByteArray & removeIf (Predicate pred )
QByteArray::reverse_iterator rend ()
QByteArray::const_reverse_iterator rend () const
QByteArray repeated (qsizetype times ) const
QByteArray & replace (qsizetype pos , qsizetype len , QByteArrayView after )
QByteArray & replace (qsizetype pos , qsizetype len , const char * after , qsizetype alen )
QByteArray & replace (char before , QByteArrayView after )
QByteArray & replace (const char * before , qsizetype bsize , const char * after , qsizetype asize )
QByteArray & replace (QByteArrayView before , QByteArrayView after )
QByteArray & replace (char before , char after )
void reserve (qsizetype size )
void resize (qsizetype size )
QByteArray right (qsizetype len ) const
QByteArray rightJustified (qsizetype width , char fill = ' ', bool truncate = false) const
QByteArray & setNum (int n , int base = 10)
QByteArray & setNum (short n , int base = 10)
QByteArray & setNum (ushort n , int base = 10)
QByteArray & setNum (uint n , int base = 10)
QByteArray & setNum (long n , int base = 10)
QByteArray & setNum (ulong n , int base = 10)
QByteArray & setNum (qlonglong n , int base = 10)
QByteArray & setNum (qulonglong n , int base = 10)
QByteArray & setNum (float n , char f = 'g', int prec = 6)
QByteArray & setNum (double n , char f = 'g', int prec = 6)
QByteArray & setRawData (const char * data , qsizetype size )
void shrink_to_fit ()
QByteArray simplified () const
qsizetype size () const
QByteArray sliced (qsizetype pos , qsizetype n ) const
QByteArray sliced (qsizetype pos ) const
QList<QByteArray> split (char sep ) const
void squeeze ()
bool startsWith (QByteArrayView bv ) const
bool startsWith (char ch ) const
void swap (QByteArray & other )
QByteArray toBase64 (QByteArray::Base64Options options = Base64Encoding) const
CFDataRef toCFData () const
double toDouble (bool * ok = nullptr) const
float toFloat (bool * ok = nullptr) const
QByteArray toHex (char separator = '\0') const
int toInt (bool * ok = nullptr, int base = 10) const
long toLong (bool * ok = nullptr, int base = 10) const
qlonglong toLongLong (bool * ok = nullptr, int base = 10) const
QByteArray toLower () const
NSData * toNSData () const
QByteArray toPercentEncoding (const QByteArray & exclude = QByteArray(), const QByteArray & include = QByteArray(), char percent = '%') const
CFDataRef toRawCFData () const
NSData * toRawNSData () const
short toShort (bool * ok = nullptr, int base = 10) const
std::string toStdString () const
uint toUInt (bool * ok = nullptr, int base = 10) const
ulong toULong (bool * ok = nullptr, int base = 10) const
qulonglong toULongLong (bool * ok = nullptr, int base = 10) const
ushort toUShort (bool * ok = nullptr, int base = 10) const
QByteArray toUpper () const
QByteArray trimmed () const
void truncate (qsizetype pos )
const char * operator const char * () const
const void * operator const void * () const
bool operator!= (const QString & str ) const
QByteArray & operator+= (const QByteArray & ba )
QByteArray & operator+= (char ch )
QByteArray & operator+= (const char * str )
bool operator< (const QString & str ) const
bool operator<= (const QString & str ) const
QByteArray & operator= (const char * str )
bool operator== (const QString & str ) const
bool operator> (const QString & str ) const
bool operator>= (const QString & str ) const
char & operator[] (qsizetype i )
char operator[] (qsizetype i ) const

静态公共成员

QByteArray fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)
QByteArray::FromBase64Result fromBase64Encoding (QByteArray && base64 , QByteArray::Base64Options options = Base64Encoding)
QByteArray::FromBase64Result fromBase64Encoding (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)
QByteArray fromCFData (CFDataRef data )
QByteArray fromHex (const QByteArray & hexEncoded )
QByteArray fromNSData (const NSData * data )
QByteArray fromPercentEncoding (const QByteArray & input , char percent = '%')
QByteArray fromRawCFData (CFDataRef data )
QByteArray fromRawData (const char * data , qsizetype size )
QByteArray fromRawNSData (const NSData * data )
QByteArray fromStdString (const std::string & str )
QByteArray number (int n , int base = 10)
QByteArray number (uint n , int base = 10)
QByteArray number (long n , int base = 10)
QByteArray number (ulong n , int base = 10)
QByteArray number (qlonglong n , int base = 10)
QByteArray number (qulonglong n , int base = 10)
QByteArray number (double n , char f = 'g', int prec = 6)
qsizetype erase (QByteArray & ba , const T & t )
qsizetype erase_if (QByteArray & ba , Predicate pred )
quint16 qChecksum (QByteArrayView data , Qt::ChecksumType standard = Qt::ChecksumIso3309)
QByteArray qCompress (const QByteArray & data , int compressionLevel = -1)
QByteArray qCompress (const uchar * data , qsizetype nbytes , int compressionLevel = -1)
QByteArray qUncompress (const QByteArray & data )
QByteArray qUncompress (const uchar * data , qsizetype nbytes )
int qsnprintf (char * str , size_t n , const char * fmt , ...)
int qstrcmp (const char * str1 , const char * str2 )
char * qstrcpy (char * dst , const char * src )
char * qstrdup (const char * src )
int qstricmp (const char * str1 , const char * str2 )
size_t qstrlen (const char * str )
int qstrncmp (const char * str1 , const char * str2 , size_t len )
char * qstrncpy (char * dst , const char * src , size_t len )
int qstrnicmp (const char * str1 , const char * str2 , size_t len )
size_t qstrnlen (const char * str , size_t maxlen )
int qvsnprintf (char * str , size_t n , const char * fmt , va_list ap )
bool operator!= (const QByteArray & a1 , const QByteArray & a2 )
bool operator!= (const QByteArray & a1 , const char * a2 )
bool operator!= (const char * a1 , const QByteArray & a2 )
const QByteArray operator+ (const QByteArray & a1 , const QByteArray & a2 )
const QByteArray operator+ (const QByteArray & a1 , const char * a2 )
const QByteArray operator+ (const QByteArray & a1 , char a2 )
const QByteArray operator+ (const char * a1 , const QByteArray & a2 )
const QByteArray operator+ (char a1 , const QByteArray & a2 )
bool operator< (const QByteArray & a1 , const QByteArray & a2 )
bool operator< (const QByteArray & a1 , const char * a2 )
bool operator< (const char * a1 , const QByteArray & a2 )
QDataStream & operator<< (QDataStream & out , const QByteArray & ba )
bool operator<= (const QByteArray & a1 , const QByteArray & a2 )
bool operator<= (const QByteArray & a1 , const char * a2 )
bool operator<= (const char * a1 , const QByteArray & a2 )
bool operator== (const QByteArray & a1 , const QByteArray & a2 )
bool operator== (const QByteArray & a1 , const char * a2 )
bool operator== (const char * a1 , const QByteArray & a2 )
bool operator> (const QByteArray & a1 , const QByteArray & a2 )
bool operator> (const QByteArray & a1 , const char * a2 )
bool operator> (const char * a1 , const QByteArray & a2 )
bool operator>= (const QByteArray & a1 , const QByteArray & a2 )
bool operator>= (const QByteArray & a1 , const char * a2 )
bool operator>= (const char * a1 , const QByteArray & a2 )
QDataStream & operator>> (QDataStream & in , QByteArray & ba )

详细描述

QByteArray 可以被用于存储原生字节 (包括 \0) 和传统 8 位 \0 终止字符串。使用 QByteArray 更方便比使用 const char * 。在幕后,它始终确保数据之后紧跟 \0 终止符,并使用 隐式共享 (写入时拷贝) 以缩减内存使用量和避免不必要的数据拷贝。

除 QByteArray 外,Qt 还提供 QString 类以存储字符串数据。对于大多数目的, QString is the class you want to use. It understands its content as Unicode text (encoded using UTF-16) where QByteArray aims to avoid assumptions about the encoding or semantics of the bytes it stores (aside from a few legacy cases where it uses ASCII). Furthermore, QString is used throughout in the Qt API. The two main cases where QByteArray is appropriate are when you need to store raw binary data, and when memory conservation is critical (e.g., with Qt for Embedded Linux).

One way to initialize a QByteArray is simply to pass a const char * to its constructor. For example, the following code creates a byte array of size 5 containing the data "Hello":

QByteArray ba("Hello");
							

Although the size () is 5, the byte array also maintains an extra '\0' byte at the end so that if a function is used that asks for a pointer to the underlying data (e.g. a call to data ()), the data pointed to is guaranteed to be '\0'-terminated.

QByteArray makes a deep copy of the const char * data, so you can modify it later without experiencing side effects. (If, for example for performance reasons, you don't want to take a deep copy of the data, use QByteArray::fromRawData () instead.)

Another approach is to set the size of the array using resize () and to initialize the data byte by byte. QByteArray uses 0-based indexes, just like C++ arrays. To access the byte at a particular index position, you can use operator[](). On non-const byte arrays, operator[]() returns a reference to a byte that can be used on the left side of an assignment. For example:

QByteArray ba;
ba.resize(5);
ba[0] = 0x3c;
ba[1] = 0xb8;
ba[2] = 0x64;
ba[3] = 0x18;
ba[4] = 0xca;
							

For read-only access, an alternative syntax is to use at ():

for (qsizetype i = 0; i < ba.size(); ++i) {
    if (ba.at(i) >= 'a' && ba.at(i) <= 'f')
        cout << "Found character in range [a-f]" << Qt::endl;
}
							

at () can be faster than operator[](), because it never causes a deep copy to occur.

要每次提取多个字节,使用 first (), last (),或 sliced ().

A QByteArray can embed '\0' bytes. The size () function always returns the size of the whole array, including embedded '\0' bytes, but excluding the terminating '\0' added by QByteArray. For example:

QByteArray ba1("ca\0r\0t");
ba1.size();                     // Returns 2.
ba1.constData();                // Returns "ca" with terminating \0.
QByteArray ba2("ca\0r\0t", 3);
ba2.size();                     // Returns 3.
ba2.constData();                // Returns "ca\0" with terminating \0.
QByteArray ba3("ca\0r\0t", 4);
ba3.size();                     // Returns 4.
ba3.constData();                // Returns "ca\0r" with terminating \0.
const char cart[] = {'c', 'a', '\0', 'r', '\0', 't'};
QByteArray ba4(QByteArray::fromRawData(cart, 6));
ba4.size();                     // Returns 6.
ba4.constData();                // Returns "ca\0r\0t" without terminating \0.
							

If you want to obtain the length of the data up to and excluding the first '\0' byte, call qstrlen () on the byte array.

After a call to resize (), newly allocated bytes have undefined values. To set all the bytes to a particular value, call fill ().

To obtain a pointer to the actual bytes, call data () 或 constData (). These functions return a pointer to the beginning of the data. The pointer is guaranteed to remain valid until a non-const function is called on the QByteArray. It is also guaranteed that the data ends with a '\0' byte unless the QByteArray was created from raw data . This '\0' byte is automatically provided by QByteArray and is not counted in size ().

QByteArray provides the following basic functions for modifying the byte data: append (), prepend (), insert (), replace (),和 remove ()。例如:

QByteArray x("and");
x.prepend("rock ");         // x == "rock and"
x.append(" roll");          // x == "rock and roll"
x.replace(5, 3, "&");       // x == "rock & roll"
							

In the above example the replace () function's first two arguments are the position from which to start replacing and the number of bytes that should be replaced.

When data-modifying functions increase the size of the array, they may lead to reallocation of memory for the QByteArray object. When this happens, QByteArray expands by more than it immediately needs so as to have space for further expansion without reallocation until the size of the array has greatly increased.

insert (), remove () and, when replacing a sub-array with one of different size, replace () functions can be slow ( linear time ) for large arrays, because they require moving many bytes in the array by at least one position in memory.

If you are building a QByteArray gradually and know in advance approximately how many bytes the QByteArray will contain, you can call reserve (), asking QByteArray to preallocate a certain amount of memory. You can also call capacity () to find out how much memory the QByteArray actually has allocated.

Note that using non-const operators and functions can cause QByteArray to do a deep copy of the data, due to 隐式共享 .

QByteArray provides STL 样式迭代器 ( QByteArray::const_iterator and QByteArray::iterator ). In practice, iterators are handy when working with generic algorithms provided by the C++ standard library.

注意: Iterators and references to individual QByteArray elements are subject to stability issues. They are often invalidated when a QByteArray-modifying operation (e.g. insert () 或 remove ()) is called. When stability and iterator-like functionality is required, you should use indexes instead of iterators as they are not tied to QByteArray's internal state and thus do not get invalidated.

注意: Iterators over a QByteArray, and references to individual bytes within one, cannot be relied on to remain valid when any non-const method of the QByteArray is called. Accessing such an iterator or reference after the call to a non-const method leads to undefined behavior. When stability for iterator-like functionality is required, you should use indexes instead of iterators as they are not tied to QByteArray's internal state and thus do not get invalidated.

If you want to find all occurrences of a particular byte or sequence of bytes in a QByteArray, use indexOf () 或 lastIndexOf (). The former searches forward starting from a given index position, the latter searches backward. Both return the index position of the byte sequence if they find it; otherwise, they return -1. For example, here's a typical loop that finds all occurrences of a particular string:

QByteArray ba("We must be <b>bold</b>, very <b>bold</b>");
qsizetype j = 0;
while ((j = ba.indexOf("<b>", j)) != -1) {
    cout << "Found <b> tag at index position " << j << Qt::endl;
    ++j;
}
							

If you simply want to check whether a QByteArray contains a particular byte sequence, use contains (). If you want to find out how many times a particular byte sequence occurs in the byte array, use count (). If you want to replace all occurrences of a particular value with another, use one of the two-parameter replace () overloads.

QByteArray s can be compared using overloaded operators such as operator<(), operator<=(), operator==(), operator>=(), and so on. The comparison is based exclusively on the numeric values of the bytes and is very fast, but is not what a human would expect. QString::localeAwareCompare () is a better choice for sorting user-interface strings.

For historical reasons, QByteArray distinguishes between a null byte array and an empty byte array. A null byte array is a byte array that is initialized using QByteArray's default constructor or by passing (const char *)0 to the constructor. An empty byte array is any byte array with size 0. A null byte array is always empty, but an empty byte array isn't necessarily null:

QByteArray().isNull();          // returns true
QByteArray().isEmpty();         // returns true
QByteArray("").isNull();        // returns false
QByteArray("").isEmpty();       // returns true
QByteArray("abc").isNull();     // returns false
QByteArray("abc").isEmpty();    // returns false
							

All functions except isNull () treat null byte arrays the same as empty byte arrays. For example, data () returns a valid pointer ( not nullptr) to a '\0' byte for a null byte array and QByteArray() compares equal to QByteArray(""). We recommend that you always use isEmpty () and avoid isNull ().

最大尺寸和内存不足情况

The maximum size of QByteArray depends on the architecture. Most 64-bit systems can allocate more than 2 GB of memory, with a typical limit of 2^63 bytes. The actual value also depends on the overhead required for managing the data block. As a result, you can expect the maximum size of 2 GB minus overhead on 32-bit platforms, and 2^63 bytes minus overhead on 64-bit platforms. The number of elements that can be stored in a QByteArray is this maximum size.

When memory allocation fails, QByteArray throws a std::bad_alloc exception if the application is being compiled with exception support. Out of memory conditions in Qt containers are the only case where Qt will throw exceptions. If exceptions are disabled, then running out of memory is undefined behavior.

Note that the operating system may impose further limits on applications holding a lot of allocated memory, especially large, contiguous blocks. Such considerations, the configuration of such behavior or any mitigation are outside the scope of the QByteArray API.

C 区域设置和 ASCII 函数

QByteArray generally handles data as bytes, without presuming any semantics; where it does presume semantics, it uses the C locale and ASCII encoding. Standard Unicode encodings are supported by QString , other encodings may be supported using QStringEncoder and QStringDecoder to convert to Unicode. For locale-specific interpretation of text, use QLocale or QString .

C Strings

Traditional C strings, also known as '\0'-terminated strings, are sequences of bytes, specified by a start-point and implicitly including each byte up to, but not including, the first '\0' byte thereafter. Methods that accept such a pointer, without a length, will interpret it as this sequence of bytes. Such a sequence, by construction, cannot contain a '\0' byte.

Other overloads accept a start-pointer and a byte-count; these use the given number of bytes, following the start address, regardless of whether any of them happen to be '\0' bytes. In some cases, where there is no overload taking only a pointer, passing a length of -1 will cause the method to use the offset of the first '\0' byte after the pointer as the length; a length of -1 should only be passed if the method explicitly says it does this (in which case it is typically a default argument).

Spacing Characters

A frequent requirement is to remove spacing characters from a byte array ('\n', '\t', ' ', etc.). If you want to remove spacing from both ends of a QByteArray, use trimmed (). If you want to also replace each run of spacing characters with a single space character within the byte array, use simplified (). Only ASCII spacing characters are recognized for these purposes.

数字字符串转换

Functions that perform conversions between numeric data types and strings are performed in the C locale, regardless of the user's locale settings. Use QLocale to perform locale-aware conversions between numbers and strings.

Character Case

In QByteArray, the notion of uppercase and lowercase and of case-independent comparison is limited to ASCII. Non-ASCII characters are treated as caseless, since their case depends on encoding. This affects functions that support a case insensitive option or that change the case of their arguments. Functions that this affects include contains (), indexOf (), lastIndexOf (), isLower (), isUpper (), toLower () 和 toUpper ().

This issue does not apply to QString s since they represent characters using Unicode.

另请参阅 QByteArrayView , QString ,和 QBitArray .

成员类型文档编制

[since 5.2] enum QByteArray:: Base64Option
flags QByteArray:: Base64Options

This enum contains the options available for encoding and decoding Base64. Base64 is defined by RFC 4648 , with the following options:

常量 描述
QByteArray::Base64Encoding 0 (default) The regular Base64 alphabet, called simply "base64"
QByteArray::Base64UrlEncoding 1 An alternate alphabet, called "base64url", which replaces two characters in the alphabet to be more friendly to URLs.
QByteArray::KeepTrailingEquals 0 (default) Keeps the trailing padding equal signs at the end of the encoded data, so the data is always a size multiple of four.
QByteArray::OmitTrailingEquals 2 Omits adding the padding equal signs at the end of the encoded data.
QByteArray::IgnoreBase64DecodingErrors 0 When decoding Base64-encoded data, ignores errors in the input; invalid characters are simply skipped. This enum value has been added in Qt 5.15.
QByteArray::AbortOnBase64DecodingErrors 4 When decoding Base64-encoded data, stops at the first decoding error. This enum value has been added in Qt 5.15.

QByteArray::fromBase64Encoding () 和 QByteArray::fromBase64 () ignore the KeepTrailingEquals and OmitTrailingEquals options. If the IgnoreBase64DecodingErrors option is specified, they will not flag errors in case trailing equal signs are missing or if there are too many of them. If instead the AbortOnBase64DecodingErrors is specified, then the input must either have no padding or have the correct amount of equal signs.

该枚举在 Qt 5.2 引入或被修改。

The Base64Options type is a typedef for QFlags <Base64Option>. It stores an OR combination of Base64Option values.

QByteArray:: const_iterator

This typedef provides an STL-style const iterator for QByteArray .

另请参阅 QByteArray::const_reverse_iterator and QByteArray::iterator .

[since 5.6] QByteArray:: const_reverse_iterator

This typedef provides an STL-style const reverse iterator for QByteArray .

该 typedef 在 Qt 5.6 引入。

另请参阅 QByteArray::reverse_iterator and QByteArray::const_iterator .

QByteArray:: iterator

This typedef provides an STL-style non-const iterator for QByteArray .

另请参阅 QByteArray::reverse_iterator and QByteArray::const_iterator .

[since 5.6] QByteArray:: reverse_iterator

This typedef provides an STL-style non-const reverse iterator for QByteArray .

该 typedef 在 Qt 5.6 引入。

另请参阅 QByteArray::const_reverse_iterator and QByteArray::iterator .

成员函数文档编制

[static] QByteArray::FromBase64Result QByteArray:: fromBase64Encoding ( QByteArray && base64 , QByteArray::Base64Options options = Base64Encoding)

[static] QByteArray::FromBase64Result QByteArray:: fromBase64Encoding (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

这是重载函数。

Decodes the Base64 array base64 , using the options defined by options 。若 options contains IgnoreBase64DecodingErrors (the default), the input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters. If options contains AbortOnBase64DecodingErrors , then decoding will stop at the first invalid character.

例如:

void process(const QByteArray &);
if (auto result = QByteArray::fromBase64Encoding(encodedData))
    process(*result);
							

The algorithm used to decode Base64-encoded data is defined in RFC 4648 .

Returns a QByteArrayFromBase64Result object, containing the decoded data and a flag telling whether decoding was successful. If the AbortOnBase64DecodingErrors option was passed and the input data was invalid, it is unspecified what the decoded data contains.

该函数在 Qt 5.15 引入。

另请参阅 toBase64 ().

const char *QByteArray:: operator const char * () const

const void *QByteArray:: operator const void * () const

注意: 使用 constData () instead in new code.

Returns a pointer to the data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated.

The pointer remains valid as long as no detach happens and the QByteArray is not modified. This operator is mostly useful to pass a byte array to a function that accepts a const char * .

You can disable this operator by defining QT_NO_CAST_FROM_BYTEARRAY when you compile your applications.

注意: QByteArray can store any byte values including '\0's, but most functions that take char * arguments assume that the data ends at the first '\0' they encounter.

另请参阅 constData ().

[since 5.2] QByteArray:: QByteArray ( QByteArray && other )

Move-constructs a QByteArray instance, making it point at the same object that other 所指向的。

该函数在 Qt 5.2 引入。

QByteArray:: QByteArray (const QByteArray & other )

构造副本为 other .

This operation takes constant time , because QByteArray is 隐式共享 . This makes returning a QByteArray from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), taking linear time .

另请参阅 operator= ().

QByteArray:: QByteArray ( qsizetype size , char ch )

Constructs a byte array of size size with every byte set to ch .

另请参阅 fill ().

QByteArray:: QByteArray (const char * data , qsizetype size = -1)

Constructs a byte array containing the first size bytes of array data .

data is 0, a null byte array is constructed.

size is negative, data is assumed to point to a '\0'-terminated string and its length is determined dynamically.

QByteArray makes a deep copy of the string data.

另请参阅 fromRawData ().

QByteArray:: QByteArray ()

构造空字节数组。

另请参阅 isEmpty ().

[since 5.2] QByteArray &QByteArray:: operator= ( QByteArray && other )

移动赋值 other 到此 QByteArray 实例。

该函数在 Qt 5.2 引入。

QByteArray &QByteArray:: operator= (const QByteArray & other )

赋值 other 到此字节数组,并返回此字节数组的引用。

QByteArray:: ~QByteArray ()

销毁字节数组。

QByteArray &QByteArray:: append (const QByteArray & ba )

追加字节数组 ba 到此字节数组的末尾。

范例:

QByteArray x("free");
QByteArray y("dom");
x.append(y);
// x == "freedom"
							

这如同 insert( size (), ba ).

注意: QByteArray 隐式共享 class. Consequently, if you append to an empty byte array, then the byte array will just share the data held in ba . In this case, no copying of data is done, taking constant time . If a shared instance is modified, it will be copied (copy-on-write), taking linear time .

If the byte array being appended to is not empty, a deep copy of the data is performed, taking linear time .

The append() function is typically very fast ( constant time ), because QByteArray preallocates extra space at the end of the data, so it can grow without reallocating the entire array each time.

另请参阅 operator+= (), prepend (),和 insert ().

QByteArray &QByteArray:: append ( char ch )

这是重载函数。

追加字节 ch 到此字节数组。

[since 5.7] QByteArray &QByteArray:: append ( qsizetype count , char ch )

这是重载函数。

追加 count copies of byte ch 到此字节数组,并返回此字节数组的引用。

count is negative or zero nothing is appended to the byte array.

该函数在 Qt 5.7 引入。

QByteArray &QByteArray:: append (const char * str )

这是重载函数。

追加 \0 结尾字符串 str 到此字节数组。

QByteArray &QByteArray:: append (const char * str , qsizetype len )

这是重载函数。

Appends the first len bytes starting at str to this byte array and returns a reference to this byte array. The bytes appended may include '\0' bytes.

len is negative, str will be assumed to be a '\0'-terminated string and the length to be copied will be determined automatically using qstrlen ().

len is zero or str is null, nothing is appended to the byte array. Ensure that len is not longer than str .

QByteArray &QByteArray:: append ( QByteArrayView data )

这是重载函数。

追加 data 到此字节数组。

char QByteArray:: at ( qsizetype i ) const

Returns the byte at index position i in the byte array.

i must be a valid index position in the byte array (i.e., 0 <= i < size ()).

另请参阅 operator[] ().

[since 5.10] char QByteArray:: back () const

Returns the last byte in the byte array. Same as at(size() - 1) .

This function is provided for STL compatibility.

警告: Calling this function on an empty byte array constitutes undefined behavior.

该函数在 Qt 5.10 引入。

另请参阅 front (), at (),和 operator[] ().

[since 5.10] char &QByteArray:: back ()

Returns a reference to the last byte in the byte array. Same as operator[](size() - 1) .

This function is provided for STL compatibility.

警告: Calling this function on an empty byte array constitutes undefined behavior.

该函数在 Qt 5.10 引入。

另请参阅 front (), at (),和 operator[] ().

QByteArray::iterator QByteArray:: begin ()

返回 STL 样式迭代器 指向字节数组第一字节。

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另请参阅 constBegin () 和 end ().

QByteArray::const_iterator QByteArray:: begin () const

此函数重载 begin()。

qsizetype QByteArray:: capacity () const

Returns the maximum number of bytes that can be stored in the byte array without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QByteArray 's memory usage. In general, you will rarely ever need to call this function. If you want to know how many bytes are in the byte array, call size ().

注意: a statically allocated byte array will report a capacity of 0, even if it's not empty.

注意: The free space position in the allocated memory block is undefined. In other words, one should not assume that the free memory is always located after the initialized elements.

另请参阅 reserve () 和 squeeze ().

[since 5.0] QByteArray::const_iterator QByteArray:: cbegin () const

返回常量 STL 样式迭代器 指向字节数组第一字节。

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

该函数在 Qt 5.0 引入。

另请参阅 begin () 和 cend ().

[since 5.0] QByteArray::const_iterator QByteArray:: cend () const

返回常量 STL 样式迭代器 pointing just after the last byte in the byte-array.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

该函数在 Qt 5.0 引入。

另请参阅 cbegin () 和 end ().

void QByteArray:: chop ( qsizetype n )

移除 n bytes from the end of the byte array.

n 大于 size (), the result is an empty byte array.

范例:

QByteArray ba("STARTTLS\r\n");
ba.chop(2);                 // ba == "STARTTLS"
							

另请参阅 truncate (), resize (),和 first ().

[since 5.10] QByteArray QByteArray:: chopped ( qsizetype len ) const

返回的字节数组包含最左 size () - len 字节在此字节数组。

注意: The behavior is undefined if len is negative or greater than size ().

该函数在 Qt 5.10 引入。

另请参阅 endsWith (), first (), last (), sliced (), chop (),和 truncate ().

void QByteArray:: clear ()

Clears the contents of the byte array and makes it null.

另请参阅 resize () 和 isNull ().

[since 6.0] int QByteArray:: compare ( QByteArrayView bv , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns an integer less than, equal to, or greater than zero depending on whether this QByteArray sorts before, at the same position as, or after the QByteArrayView bv . The comparison is performed according to case sensitivity cs .

该函数在 Qt 6.0 引入。

另请参阅 operator== and Character Case .

QByteArray::const_iterator QByteArray:: constBegin () const

返回常量 STL 样式迭代器 指向字节数组第一字节。

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另请参阅 begin () 和 constEnd ().

const char *QByteArray:: constData () const

Returns a pointer to the const data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated unless the QByteArray object was created from raw data.

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

This function is mostly useful to pass a byte array to a function that accepts a const char * .

注意: QByteArray can store any byte values including '\0's, but most functions that take char * arguments assume that the data ends at the first '\0' they encounter.

另请参阅 data (), operator[] (),和 fromRawData ().

QByteArray::const_iterator QByteArray:: constEnd () const

返回常量 STL 样式迭代器 pointing just after the last byte in the byte-array.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另请参阅 constBegin () 和 end ().

[since 6.0] bool QByteArray:: contains ( QByteArrayView bv ) const

返回 true if this byte array contains an occurrence of the sequence of bytes viewed by bv ;否则返回 false .

该函数在 Qt 6.0 引入。

另请参阅 indexOf () 和 count ().

bool QByteArray:: contains ( char ch ) const

这是重载函数。

返回 true 若字节数组包含字节 ch ;否则返回 false .

[since 6.0] qsizetype QByteArray:: count ( QByteArrayView bv ) const

Returns the number of (potentially overlapping) occurrences of the sequence of bytes viewed by bv in this byte array.

该函数在 Qt 6.0 引入。

另请参阅 contains () 和 indexOf ().

qsizetype QByteArray:: count ( char ch ) const

这是重载函数。

Returns the number of occurrences of byte ch in the byte array.

另请参阅 contains () 和 indexOf ().

qsizetype QByteArray:: count () const

这是重载函数。

如同 size ().

[since 5.6] QByteArray::const_reverse_iterator QByteArray:: crbegin () const

返回常量 STL-style reverse iterator pointing to the first byte in the byte-array, in reverse order.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

该函数在 Qt 5.6 引入。

另请参阅 begin (), rbegin (),和 rend ().

[since 5.6] QByteArray::const_reverse_iterator QByteArray:: crend () const

返回常量 STL-style reverse iterator pointing just after the last byte in the byte-array, in reverse order.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

该函数在 Qt 5.6 引入。

另请参阅 end (), rend (),和 rbegin ().

char *QByteArray:: data ()

Returns a pointer to the data stored in the byte array. The pointer can be used to access and modify the bytes that compose the array. The data is '\0'-terminated, i.e. the number of bytes you can access following the returned pointer is size () + 1, including the '\0' terminator.

范例:

QByteArray ba("Hello world");
char *data = ba.data();
while (*data) {
    cout << "[" << *data << "]" << Qt::endl;
    ++data;
}
							

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

对于只读访问, constData () is faster because it never causes a deep copy to occur.

This function is mostly useful to pass a byte array to a function that accepts a const char * .

The following example makes a copy of the char* returned by data(), but it will corrupt the heap and cause a crash because it does not allocate a byte for the '\0' at the end:

QString tmp = "test";
QByteArray text = tmp.toLocal8Bit();
char *data = new char[text.size()];
strcpy(data, text.data());
delete [] data;
							

This one allocates the correct amount of space:

QString tmp = "test";
QByteArray text = tmp.toLocal8Bit();
char *data = new char[text.size() + 1];
strcpy(data, text.data());
delete [] data;
							

注意: QByteArray can store any byte values including '\0's, but most functions that take char * arguments assume that the data ends at the first '\0' they encounter.

另请参阅 constData () 和 operator[] ().

const char *QByteArray:: data () const

这是重载函数。

QByteArray::iterator QByteArray:: end ()

返回 STL 样式迭代器 pointing just after the last byte in the byte-array.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

另请参阅 begin () 和 constEnd ().

QByteArray::const_iterator QByteArray:: end () const

此函数重载 end()。

[since 6.0] bool QByteArray:: endsWith ( QByteArrayView bv ) const

返回 true if this byte array ends with the sequence of bytes viewed by bv ;否则返回 false .

范例:

QByteArray url("http://qt-project.org/doc/qt-5.0/qtdoc/index.html");
if (url.endsWith(".html"))
    ...
							

该函数在 Qt 6.0 引入。

另请参阅 startsWith () 和 last ().

bool QByteArray:: endsWith ( char ch ) const

这是重载函数。

返回 true if this byte array ends with byte ch ;否则返回 false .

[since 6.1] QByteArray::iterator QByteArray:: erase ( QByteArray::const_iterator first , QByteArray::const_iterator last )

Removes from the byte array the characters in the half-open range [ first , last ). Returns an iterator to the character referred to by last before the erase.

该函数在 Qt 6.1 引入。

QByteArray &QByteArray:: fill ( char ch , qsizetype size = -1)

Sets every byte in the byte array to ch 。若 size is different from -1 (the default), the byte array is resized to size size beforehand.

范例:

QByteArray ba("Istambul");
ba.fill('o');
// ba == "oooooooo"
ba.fill('X', 2);
// ba == "XX"
							

另请参阅 resize ().

[since 6.0] QByteArray QByteArray:: first ( qsizetype n ) const

返回第一 n bytes of the byte array.

注意: The behavior is undefined when n < 0 or n > size ().

范例:

QByteArray x("Pineapple");
QByteArray y = x.first(4);
// y == "Pine"
							

该函数在 Qt 6.0 引入。

另请参阅 last (), sliced (), startsWith (), chopped (), chop (),和 truncate ().

[static, since 5.2] QByteArray QByteArray:: fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options = Base64Encoding)

Returns a decoded copy of the Base64 array base64 , using the options defined by options 。若 options contains IgnoreBase64DecodingErrors (the default), the input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters. If options contains AbortOnBase64DecodingErrors , then decoding will stop at the first invalid character.

例如:

QByteArray text = QByteArray::fromBase64("UXQgaXMgZ3JlYXQh");
text.data();            // returns "Qt is great!"
QByteArray::fromBase64("PHA+SGVsbG8/PC9wPg==", QByteArray::Base64Encoding); // returns "<p>Hello?</p>"
QByteArray::fromBase64("PHA-SGVsbG8_PC9wPg==", QByteArray::Base64UrlEncoding); // returns "<p>Hello?</p>"
							

The algorithm used to decode Base64-encoded data is defined in RFC 4648 .

Returns the decoded data, or, if the AbortOnBase64DecodingErrors option was passed and the input data was invalid, an empty byte array.

注意: fromBase64Encoding () function is recommended in new code.

该函数在 Qt 5.2 引入。

另请参阅 toBase64 () 和 fromBase64Encoding ().

[static, since 5.3] QByteArray QByteArray:: fromCFData ( CFDataRef data )

构造新的 QByteArray containing a copy of the CFData data .

该函数在 Qt 5.3 引入。

另请参阅 fromRawCFData (), fromRawData (), toRawCFData (),和 toCFData ().

[static] QByteArray QByteArray:: fromHex (const QByteArray & hexEncoded )

Returns a decoded copy of the hex encoded array hexEncoded . Input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters.

例如:

QByteArray text = QByteArray::fromHex("517420697320677265617421");
text.data();            // returns "Qt is great!"
							

另请参阅 toHex ().

[static, since 5.3] QByteArray QByteArray:: fromNSData (const NSData * data )

构造新的 QByteArray containing a copy of the NSData data .

该函数在 Qt 5.3 引入。

另请参阅 fromRawNSData (), fromRawData (), toNSData (),和 toRawNSData ().

[static] QByteArray QByteArray:: fromPercentEncoding (const QByteArray & input , char percent = '%')

Returns a decoded copy of the URI/URL-style percent-encoded input percent parameter allows you to replace the '%' character for another (for instance, '_' or '=').

例如:

QByteArray text = QByteArray::fromPercentEncoding("Qt%20is%20great%33");
text.data();            // returns "Qt is great!"
							

注意: 给定无效输入 (譬如:包含 %G5 序列的字符串,不是有效十六进制数字),输出也将无效。例如:%G5 序列可以解码为 W。

另请参阅 toPercentEncoding () 和 QUrl::fromPercentEncoding ().

[static, since 5.3] QByteArray QByteArray:: fromRawCFData ( CFDataRef data )

构造 QByteArray that uses the bytes of the CFData data .

data 的字节不拷贝。

The caller guarantees that the CFData will not be deleted or modified as long as this QByteArray object exists.

该函数在 Qt 5.3 引入。

另请参阅 fromCFData (), fromRawData (), toRawCFData (),和 toCFData ().

[static] QByteArray QByteArray:: fromRawData (const char * data , qsizetype size )

构造 QByteArray that uses the first size bytes of the data array. The bytes are not copied. The QByteArray will contain the data pointer. The caller guarantees that data will not be deleted or modified as long as this QByteArray and any copies of it exist that have not been modified. In other words, because QByteArray 隐式共享 class and the instance returned by this function contains the data pointer, the caller must not delete data or modify it directly as long as the returned QByteArray and any copies exist. However, QByteArray 未拥有所有权对于 data , so the QByteArray destructor will never delete the raw data , even when the last QByteArray referring to data 被销毁。

A subsequent attempt to modify the contents of the returned QByteArray or any copy made from it will cause it to create a deep copy of the data array before doing the modification. This ensures that the raw data array itself will never be modified by QByteArray .

Here is an example of how to read data using a QDataStream on raw data in memory without copying the raw data into a QByteArray :

 static const char mydata[] = {
    '\x00', '\x00', '\x03', '\x84', '\x78', '\x9c', '\x3b', '\x76',
    '\xec', '\x18', '\xc3', '\x31', '\x0a', '\xf1', '\xcc', '\x99',
    ...
    '\x6d', '\x5b'
};
QByteArray data = QByteArray::fromRawData(mydata, sizeof(mydata));
QDataStream in(&data, QIODevice::ReadOnly);
...
							

警告: A byte array created with fromRawData() is not '\0'-terminated, unless the raw data contains a '\0' byte at position size . While that does not matter for QDataStream or functions like indexOf (), passing the byte array to a function accepting a const char * expected to be '\0'-terminated will fail.

另请参阅 setRawData (), data (),和 constData ().

[static, since 5.3] QByteArray QByteArray:: fromRawNSData (const NSData * data )

构造 QByteArray that uses the bytes of the NSData data .

data 的字节不拷贝。

The caller guarantees that the NSData will not be deleted or modified as long as this QByteArray object exists.

该函数在 Qt 5.3 引入。

另请参阅 fromNSData (), fromRawData (), toRawNSData (),和 toNSData ().

[static, since 5.4] QByteArray QByteArray:: fromStdString (const std::string & str )

返回副本为 str string as a QByteArray .

该函数在 Qt 5.4 引入。

另请参阅 toStdString () 和 QString::fromStdString ().

[since 5.10] char QByteArray:: front () const

Returns the first byte in the byte array. Same as at(0) .

This function is provided for STL compatibility.

警告: Calling this function on an empty byte array constitutes undefined behavior.

该函数在 Qt 5.10 引入。

另请参阅 back (), at (),和 operator[] ().

[since 5.10] char &QByteArray:: front ()

Returns a reference to the first byte in the byte array. Same as operator[](0) .

This function is provided for STL compatibility.

警告: Calling this function on an empty byte array constitutes undefined behavior.

该函数在 Qt 5.10 引入。

另请参阅 back (), at (),和 operator[] ().

[since 6.0] qsizetype QByteArray:: indexOf ( QByteArrayView bv , qsizetype from = 0) const

Returns the index position of the start of the first occurrence of the sequence of bytes viewed by bv in this byte array, searching forward from index position from . Returns -1 if no match is found.

范例:

QByteArray x("sticky question");
QByteArrayView y("sti");
x.indexOf(y);               // returns 0
x.indexOf(y, 1);            // returns 10
x.indexOf(y, 10);           // returns 10
x.indexOf(y, 11);           // returns -1
							

该函数在 Qt 6.0 引入。

另请参阅 lastIndexOf (), contains (),和 count ().

qsizetype QByteArray:: indexOf ( char ch , qsizetype from = 0) const

这是重载函数。

Returns the index position of the start of the first occurrence of the byte ch in this byte array, searching forward from index position from . Returns -1 if no match is found.

范例:

QByteArray ba("ABCBA");
ba.indexOf("B");            // returns 1
ba.indexOf("B", 1);         // returns 1
ba.indexOf("B", 2);         // returns 3
ba.indexOf("X");            // returns -1
							

另请参阅 lastIndexOf () 和 contains ().

[since 6.0] QByteArray &QByteArray:: insert ( qsizetype i , QByteArrayView data )

插入 data at index position i and returns a reference to this byte array.

范例:

QByteArray ba("Meal");
ba.insert(1, QByteArrayView("ontr"));
// ba == "Montreal"
							

For large byte arrays, this operation can be slow ( linear time ), because it requires moving all the bytes at indexes i and above by at least one position further in memory.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

该函数在 Qt 6.0 引入。

另请参阅 append (), prepend (), replace (),和 remove ().

QByteArray &QByteArray:: insert ( qsizetype i , const char * s )

插入 s at index position i and returns a reference to this byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

The function is equivalent to insert(i, QByteArrayView(s))

另请参阅 append (), prepend (), replace (),和 remove ().

QByteArray &QByteArray:: insert ( qsizetype i , const QByteArray & data )

插入 data at index position i and returns a reference to this byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

另请参阅 append (), prepend (), replace (),和 remove ().

[since 5.7] QByteArray &QByteArray:: insert ( qsizetype i , qsizetype count , char ch )

这是重载函数。

插入 count copies of byte ch at index position i in the byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

该函数在 Qt 5.7 引入。

QByteArray &QByteArray:: insert ( qsizetype i , char ch )

这是重载函数。

Inserts byte ch at index position i in the byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

QByteArray &QByteArray:: insert ( qsizetype i , const char * data , qsizetype len )

这是重载函数。

插入 len bytes, starting at data , at position i in the byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i .

bool QByteArray:: isEmpty () const

返回 true if the byte array has size 0; otherwise returns false .

范例:

QByteArray().isEmpty();         // returns true
QByteArray("").isEmpty();       // returns true
QByteArray("abc").isEmpty();    // returns false
							

另请参阅 size ().

[since 5.12] bool QByteArray:: isLower () const

返回 true if this byte array contains only lowercase ASCII letters, otherwise returns false .

该函数在 Qt 5.12 引入。

另请参阅 isUpper () 和 toLower ().

bool QByteArray:: isNull () const

返回 true if this byte array is null; otherwise returns false .

范例:

QByteArray().isNull();          // returns true
QByteArray("").isNull();        // returns false
QByteArray("abc").isNull();     // returns false
							

Qt makes a distinction between null byte arrays and empty byte arrays for historical reasons. For most applications, what matters is whether or not a byte array contains any data, and this can be determined using isEmpty ().

另请参阅 isEmpty ().

[since 5.12] bool QByteArray:: isUpper () const

返回 true if this byte array contains only ASCII uppercase letters, otherwise returns false .

该函数在 Qt 5.12 引入。

另请参阅 isLower () 和 toUpper ().

[since 6.0] QByteArray QByteArray:: last ( qsizetype n ) const

Returns the last n bytes of the byte array.

注意: The behavior is undefined when n < 0 or n > size ().

范例:

QByteArray x("Pineapple");
QByteArray y = x.last(5);
// y == "apple"
							

该函数在 Qt 6.0 引入。

另请参阅 first (), sliced (), endsWith (), chopped (), chop (),和 truncate ().

[since 6.0] qsizetype QByteArray:: lastIndexOf ( QByteArrayView bv , qsizetype from = -1) const

Returns the index position of the start of the last occurrence of the sequence of bytes viewed by bv in this byte array, searching backward from index position from 。若 from is -1 (the default), the search starts from the end of the byte array. Returns -1 if no match is found.

范例:

QByteArray x("crazy azimuths");
QByteArrayView y("az");
x.lastIndexOf(y);           // returns 6
x.lastIndexOf(y, 6);        // returns 6
x.lastIndexOf(y, 5);        // returns 2
x.lastIndexOf(y, 1);        // returns -1
							

该函数在 Qt 6.0 引入。

另请参阅 indexOf (), contains (),和 count ().

qsizetype QByteArray:: lastIndexOf ( char ch , qsizetype from = -1) const

这是重载函数。

Returns the index position of the start of the last occurrence of byte ch in this byte array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last byte (at index size () - 1). Returns -1 if no match is found.

范例:

QByteArray ba("ABCBA");
ba.lastIndexOf("B");        // returns 3
ba.lastIndexOf("B", 3);     // returns 3
ba.lastIndexOf("B", 2);     // returns 1
ba.lastIndexOf("X");        // returns -1
							

另请参阅 indexOf () 和 contains ().

QByteArray QByteArray:: left ( qsizetype len ) const

Returns a byte array that contains the first len 字节在此字节数组。

If you know that len cannot be out of bounds, use first () instead in new code, because it is faster.

返回整个字节数组若 len 大于 size ().

返回空 QByteArray if len is smaller than 0.

另请参阅 first (), last (), startsWith (), chopped (), chop (),和 truncate ().

QByteArray QByteArray:: leftJustified ( qsizetype width , char fill = ' ', bool truncate = false) const

Returns a byte array of size width that contains this byte array padded with the fill byte.

truncate is false and the size () of the byte array is more than width , then the returned byte array is a copy of this byte array.

truncate is true and the size () of the byte array is more than width , then any bytes in a copy of the byte array after position width are removed, and the copy is returned.

范例:

QByteArray x("apple");
QByteArray y = x.leftJustified(8, '.');   // y == "apple..."
							

另请参阅 rightJustified ().

qsizetype QByteArray:: length () const

如同 size ().

QByteArray QByteArray:: mid ( qsizetype pos , qsizetype len = -1) const

Returns a byte array containing len bytes from this byte array, starting at position pos .

If you know that pos and len cannot be out of bounds, use sliced () instead in new code, because it is faster.

len is -1 (the default), or pos + len >= size (), returns a byte array containing all bytes starting at position pos until the end of the byte array.

另请参阅 first (), last (), sliced (), chopped (), chop (),和 truncate ().

[static] QByteArray QByteArray:: number ( int n , int base = 10)

Returns a byte array containing the printed value of the number n to base base (ten by default). Bases 2 through 36 are supported, using letters for digits beyond 9: A is ten, B is eleven and so on.

范例:

int n = 63;
QByteArray::number(n);              // returns "63"
QByteArray::number(n, 16);          // returns "3f"
QByteArray::number(n, 16).toUpper();  // returns "3F"
							

注意: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 setNum () 和 toInt ().

[static] QByteArray QByteArray:: number ( uint n , int base = 10)

这是重载函数。

另请参阅 toUInt ().

[static] QByteArray QByteArray:: number ( long n , int base = 10)

这是重载函数。

另请参阅 toLong ().

[static] QByteArray QByteArray:: number ( ulong n , int base = 10)

这是重载函数。

另请参阅 toULong ().

[static] QByteArray QByteArray:: number ( qlonglong n , int base = 10)

这是重载函数。

另请参阅 toLongLong ().

[static] QByteArray QByteArray:: number ( qulonglong n , int base = 10)

这是重载函数。

另请参阅 toULongLong ().

[static] QByteArray QByteArray:: number ( double n , char f = 'g', int prec = 6)

这是重载函数。

Returns a byte array that contains the printed value of n , formatted in format f with precision prec .

Argument n is formatted according to the f format specified, which is g by default, and can be any of the following:

格式 含义
e format as [-]9.9e[+|-]999
E format as [-]9.9E[+|-]999
f format as [-]9.9
g use e or f format, whichever is the most concise
G use E or f format, whichever is the most concise

With 'e', 'E', and 'f', prec is the number of digits after the decimal point. With 'g' and 'G', prec is the maximum number of significant digits (trailing zeroes are omitted).

QByteArray ba = QByteArray::number(12.3456, 'E', 3);
// ba == 1.235E+01
							

注意: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 toDouble ().

QByteArray &QByteArray:: prepend ( QByteArrayView ba )

Prepends the byte array view ba 到此字节数组,并返回此字节数组的引用。

This operation is typically very fast ( constant time ), because QByteArray preallocates extra space at the beginning of the data, so it can grow without reallocating the entire array each time.

范例:

QByteArray x("ship");
QByteArray y("air");
x.prepend(y);
// x == "airship"
							

这如同 insert(0, ba ).

另请参阅 append () 和 insert ().

QByteArray &QByteArray:: prepend ( char ch )

这是重载函数。

Prepends the byte ch 到此字节数组。

[since 5.7] QByteArray &QByteArray:: prepend ( qsizetype count , char ch )

这是重载函数。

前置 count copies of byte ch 到此字节数组。

该函数在 Qt 5.7 引入。

QByteArray &QByteArray:: prepend (const char * str )

这是重载函数。

Prepends the '\0'-terminated string str 到此字节数组。

QByteArray &QByteArray:: prepend (const char * str , qsizetype len )

这是重载函数。

前置 len bytes starting at str to this byte array. The bytes prepended may include '\0' bytes.

QByteArray &QByteArray:: prepend (const QByteArray & ba )

这是重载函数。

前置 ba 到此字节数组。

void QByteArray:: push_back (const QByteArray & other )

This function is provided for STL compatibility. It is equivalent to append( other ).

void QByteArray:: push_back ( char ch )

这是重载函数。

如同 append( ch ).

void QByteArray:: push_back (const char * str )

这是重载函数。

如同 append( str ).

[since 6.0] void QByteArray:: push_back ( QByteArrayView str )

这是重载函数。

如同 append( str ).

该函数在 Qt 6.0 引入。

void QByteArray:: push_front (const QByteArray & other )

This function is provided for STL compatibility. It is equivalent to prepend( other ).

void QByteArray:: push_front ( char ch )

这是重载函数。

如同 prepend( ch ).

void QByteArray:: push_front (const char * str )

这是重载函数。

如同 prepend( str ).

[since 6.0] void QByteArray:: push_front ( QByteArrayView str )

这是重载函数。

如同 prepend( str ).

该函数在 Qt 6.0 引入。

[since 5.6] QByteArray::reverse_iterator QByteArray:: rbegin ()

返回 STL-style reverse iterator pointing to the first byte in the byte-array, in reverse order.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

该函数在 Qt 5.6 引入。

另请参阅 begin (), crbegin (),和 rend ().

[since 5.6] QByteArray::const_reverse_iterator QByteArray:: rbegin () const

这是重载函数。

该函数在 Qt 5.6 引入。

QByteArray &QByteArray:: remove ( qsizetype pos , qsizetype len )

移除 len bytes from the array, starting at index position pos , and returns a reference to the array.

pos is out of range, nothing happens. If pos is valid, but pos + len is larger than the size of the array, the array is truncated at position pos .

范例:

QByteArray ba("Montreal");
ba.remove(1, 4);
// ba == "Meal"
							

Element removal will preserve the array's capacity and not reduce the amount of allocated memory. To shed extra capacity and free as much memory as possible, call squeeze () after the last change to the array's size.

另请参阅 insert (), replace (),和 squeeze ().

[since 6.1] template <typename Predicate> QByteArray &QByteArray:: removeIf ( Predicate pred )

Removes all bytes for which the predicate pred returns true from the byte array. Returns a reference to the byte array.

该函数在 Qt 6.1 引入。

另请参阅 remove ().

[since 5.6] QByteArray::reverse_iterator QByteArray:: rend ()

返回 STL-style reverse iterator pointing just after the last byte in the byte-array, in reverse order.

警告: The returned iterator is invalidated on detachment or when the QByteArray 被修改。

该函数在 Qt 5.6 引入。

另请参阅 end (), crend (),和 rbegin ().

[since 5.6] QByteArray::const_reverse_iterator QByteArray:: rend () const

这是重载函数。

该函数在 Qt 5.6 引入。

QByteArray QByteArray:: repeated ( qsizetype times ) const

Returns a copy of this byte array repeated the specified number of times .

times is less than 1, an empty byte array is returned.

范例:

QByteArray ba("ab");
ba.repeated(4);             // returns "abababab"
							

QByteArray &QByteArray:: replace ( qsizetype pos , qsizetype len , QByteArrayView after )

替换 len bytes from index position pos with the byte array after , and returns a reference to this byte array.

范例:

QByteArray x("Say yes!");
QByteArray y("no");
x.replace(4, 3, y);
// x == "Say no!"
							

另请参阅 insert () 和 remove ().

QByteArray &QByteArray:: replace ( qsizetype pos , qsizetype len , const char * after , qsizetype alen )

这是重载函数。

替换 len bytes from index position pos with alen bytes starting at position after . The bytes inserted may include '\0' bytes.

QByteArray &QByteArray:: replace ( char before , QByteArrayView after )

这是重载函数。

Replaces every occurrence of the byte before with the byte array after .

QByteArray &QByteArray:: replace (const char * before , qsizetype bsize , const char * after , qsizetype asize )

这是重载函数。

Replaces every occurrence of the bsize bytes starting at before 采用 asize bytes starting at after . Since the sizes of the strings are given by bsize and asize , they may contain '\0' bytes and do not need to be '\0'-terminated.

[since 6.0] QByteArray &QByteArray:: replace ( QByteArrayView before , QByteArrayView after )

这是重载函数。

Replaces every occurrence of the byte array before with the byte array after .

范例:

QByteArray ba("colour behaviour flavour neighbour");
ba.replace(QByteArray("ou"), QByteArray("o"));
// ba == "color behavior flavor neighbor"
							

该函数在 Qt 6.0 引入。

QByteArray &QByteArray:: replace ( char before , char after )

这是重载函数。

Replaces every occurrence of the byte before with the byte after .

void QByteArray:: reserve ( qsizetype size )

Attempts to allocate memory for at least size 字节。

If you know in advance how large the byte array will be, you can call this function, and if you call resize () often you are likely to get better performance.

If in doubt about how much space shall be needed, it is usually better to use an upper bound as size , or a high estimate of the most likely size, if a strict upper bound would be much bigger than this. If size is an underestimate, the array will grow as needed once the reserved size is exceeded, which may lead to a larger allocation than your best overestimate would have and will slow the operation that triggers it.

警告: reserve() reserves memory but does not change the size of the byte array. Accessing data beyond the end of the byte array is undefined behavior. If you need to access memory beyond the current end of the array, use resize ().

The sole purpose of this function is to provide a means of fine tuning QByteArray 's memory usage. In general, you will rarely ever need to call this function.

另请参阅 squeeze () 和 capacity ().

void QByteArray:: resize ( qsizetype size )

把字节数组的尺寸设为 size 字节。

size is greater than the current size, the byte array is extended to make it size bytes with the extra bytes added to the end. The new bytes are uninitialized.

size is less than the current size, bytes beyond position size are excluded from the byte array.

注意: While resize() will grow the capacity if needed, it never shrinks capacity. To shed excess capacity, use squeeze ().

另请参阅 size (), truncate (),和 squeeze ().

Returns a byte array that contains the last len 字节在此字节数组。

If you know that len cannot be out of bounds, use last () instead in new code, because it is faster.

返回整个字节数组若 len 大于 size ().

返回空 QByteArray if len is smaller than 0.

另请参阅 endsWith (), last (), first (), sliced (), chopped (), chop (),和 truncate ().

QByteArray QByteArray:: rightJustified ( qsizetype width , char fill = ' ', bool truncate = false) const

Returns a byte array of size width that contains the fill byte followed by this byte array.

truncate is false and the size of the byte array is more than width , then the returned byte array is a copy of this byte array.

truncate is true and the size of the byte array is more than width , then the resulting byte array is truncated at position width .

范例:

QByteArray x("apple");
QByteArray y = x.rightJustified(8, '.');    // y == "...apple"
							

另请参阅 leftJustified ().

QByteArray &QByteArray:: setNum ( int n , int base = 10)

Sets the byte array to the printed value of n in base base (ten by default) and returns a reference to the byte array. Bases 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on. For bases other than ten, n is treated as an unsigned integer.

范例:

QByteArray ba;
int n = 63;
ba.setNum(n);           // ba == "63"
ba.setNum(n, 16);       // ba == "3f"
							

注意: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number () 和 toInt ().

QByteArray &QByteArray:: setNum ( short n , int base = 10)

这是重载函数。

另请参阅 toShort ().

QByteArray &QByteArray:: setNum ( ushort n , int base = 10)

这是重载函数。

另请参阅 toUShort ().

QByteArray &QByteArray:: setNum ( uint n , int base = 10)

这是重载函数。

另请参阅 toUInt ().

QByteArray &QByteArray:: setNum ( long n , int base = 10)

这是重载函数。

另请参阅 toLong ().

QByteArray &QByteArray:: setNum ( ulong n , int base = 10)

这是重载函数。

另请参阅 toULong ().

QByteArray &QByteArray:: setNum ( qlonglong n , int base = 10)

这是重载函数。

另请参阅 toLongLong ().

QByteArray &QByteArray:: setNum ( qulonglong n , int base = 10)

这是重载函数。

另请参阅 toULongLong ().

QByteArray &QByteArray:: setNum ( float n , char f = 'g', int prec = 6)

这是重载函数。

Sets the byte array to the printed value of n , formatted in format f with precision prec , and returns a reference to the byte array.

注意: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 toFloat ().

QByteArray &QByteArray:: setNum ( double n , char f = 'g', int prec = 6)

这是重载函数。

Sets the byte array to the printed value of n , formatted in format f with precision prec , and returns a reference to the byte array.

格式 f 可以是下列任一:

格式 含义
e format as [-]9.9e[+|-]999
E format as [-]9.9E[+|-]999
f format as [-]9.9
g use e or f format, whichever is the most concise
G use E or f format, whichever is the most concise

With 'e', 'E', and 'f', prec is the number of digits after the decimal point. With 'g' and 'G', prec is the maximum number of significant digits (trailing zeroes are omitted).

注意: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 toDouble ().

QByteArray &QByteArray:: setRawData (const char * data , qsizetype size )

Resets the QByteArray to use the first size bytes of the data array. The bytes are not copied. The QByteArray will contain the data pointer. The caller guarantees that data will not be deleted or modified as long as this QByteArray and any copies of it exist that have not been modified.

This function can be used instead of fromRawData () to re-use existing QByteArray objects to save memory re-allocations.

另请参阅 fromRawData (), data (),和 constData ().

[since 5.10] void QByteArray:: shrink_to_fit ()

此函数是为兼容 STL 而提供的。它相当于 squeeze ().

该函数在 Qt 5.10 引入。

QByteArray QByteArray:: simplified () const

Returns a copy of this byte array that has spacing characters removed from the start and end, and in which each sequence of internal spacing characters is replaced with a single space.

The spacing characters are those for which the standard C++ isspace() 函数返回 true in the C locale; these are the ASCII characters tabulation '\t', line feed '\n', carriage return '\r', vertical tabulation '\v', form feed '\f', and space ' '.

范例:

QByteArray ba("  lots\t of\nwhitespace\r\n ");
ba = ba.simplified();
// ba == "lots of whitespace";
							

另请参阅 trimmed (), QChar::SpecialCharacter ,和 Spacing Characters .

qsizetype QByteArray:: size () const

返回此字节数组的字节数。

The last byte in the byte array is at position size() - 1. In addition, QByteArray ensures that the byte at position size() is always '\0', so that you can use the return value of data () 和 constData () as arguments to functions that expect '\0'-terminated strings. If the QByteArray object was created from a raw data that didn't include the trailing '\0'-termination byte, then QByteArray doesn't add it automaticall unless a deep copy is created.

范例:

QByteArray ba("Hello");
qsizetype n = ba.size();    // n == 5
ba.data()[0];               // returns 'H'
ba.data()[4];               // returns 'o'
ba.data()[5];               // returns '\0'
							

另请参阅 isEmpty () 和 resize ().

[since 6.0] QByteArray QByteArray:: sliced ( qsizetype pos , qsizetype n ) const

Returns a byte array containing the n bytes of this object starting at position pos .

注意: The behavior is undefined when pos < 0, n < 0, or pos + n > size ().

范例:

QByteArray x("Five pineapples");
QByteArray y = x.sliced(5, 4);     // y == "pine"
QByteArray z = x.sliced(5);        // z == "pineapples"
							

该函数在 Qt 6.0 引入。

另请参阅 first (), last (), chopped (), chop (),和 truncate ().

[since 6.0] QByteArray QByteArray:: sliced ( qsizetype pos ) const

这是重载函数。

Returns a byte array containing the bytes starting at position pos in this object, and extending to the end of this object.

注意: The behavior is undefined when pos < 0 or pos > size ().

该函数在 Qt 6.0 引入。

另请参阅 first (), last (), sliced (), chopped (), chop (),和 truncate ().

QList < QByteArray > QByteArray:: split ( char sep ) const

Splits the byte array into subarrays wherever sep occurs, and returns the list of those arrays. If sep does not match anywhere in the byte array, split() returns a single-element list containing this byte array.

void QByteArray:: squeeze ()

Releases any memory not required to store the array's data.

The sole purpose of this function is to provide a means of fine tuning QByteArray 's memory usage. In general, you will rarely ever need to call this function.

另请参阅 reserve () 和 capacity ().

[since 6.0] bool QByteArray:: startsWith ( QByteArrayView bv ) const

返回 true if this byte array starts with the sequence of bytes viewed by bv ;否则返回 false .

范例:

QByteArray url("ftp://ftp.qt-project.org/");
if (url.startsWith("ftp:"))
    ...
							

该函数在 Qt 6.0 引入。

另请参阅 endsWith () 和 first ().

bool QByteArray:: startsWith ( char ch ) const

这是重载函数。

返回 true if this byte array starts with byte ch ;否则返回 false .

void QByteArray:: swap ( QByteArray & other )

Swaps byte array other with this byte array. This operation is very fast and never fails.

[since 5.2] QByteArray QByteArray:: toBase64 ( QByteArray::Base64Options options = Base64Encoding) const

Returns a copy of the byte array, encoded using the options options .

QByteArray text("Qt is great!");
text.toBase64();        // returns "UXQgaXMgZ3JlYXQh"
QByteArray text("<p>Hello?</p>");
text.toBase64(QByteArray::Base64Encoding | QByteArray::OmitTrailingEquals);      // returns "PHA+SGVsbG8/PC9wPg"
text.toBase64(QByteArray::Base64Encoding);                                       // returns "PHA+SGVsbG8/PC9wPg=="
text.toBase64(QByteArray::Base64UrlEncoding);                                    // returns "PHA-SGVsbG8_PC9wPg=="
text.toBase64(QByteArray::Base64UrlEncoding | QByteArray::OmitTrailingEquals);   // returns "PHA-SGVsbG8_PC9wPg"
							

The algorithm used to encode Base64-encoded data is defined in RFC 4648 .

该函数在 Qt 5.2 引入。

另请参阅 fromBase64 ().

[since 5.3] CFDataRef QByteArray:: toCFData () const

创建 CFData 从 QByteArray .

调用者拥有 CFData 对象并负责释放它。

该函数在 Qt 5.3 引入。

另请参阅 toRawCFData (), fromCFData (), fromRawCFData (),和 fromRawData ().

double QByteArray:: toDouble ( bool * ok = nullptr) const

Returns the byte array converted to a double 值。

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray string("1234.56");
bool ok;
double a = string.toDouble(&ok);   // a == 1234.56, ok == true
string = "1234.56 Volt";
a = str.toDouble(&ok);             // a == 0, ok == false
							

警告: QByteArray content may only contain valid numerical characters which includes the plus/minus sign, the character e used in scientific notation, and the decimal point. Including the unit or additional characters leads to a conversion error.

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

此函数忽略前导和结尾空格。

另请参阅 number ().

float QByteArray:: toFloat ( bool * ok = nullptr) const

Returns the byte array converted to a float 值。

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray string("1234.56");
bool ok;
float a = string.toFloat(&ok);    // a == 1234.56, ok == true
string = "1234.56 Volt";
a = str.toFloat(&ok);              // a == 0, ok == false
							

警告: QByteArray content may only contain valid numerical characters which includes the plus/minus sign, the character e used in scientific notation, and the decimal point. Including the unit or additional characters leads to a conversion error.

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

此函数忽略前导和结尾空格。

另请参阅 number ().

[since 5.9] QByteArray QByteArray:: toHex ( char separator = '\0') const

Returns a hex encoded copy of the byte array.

The hex encoding uses the numbers 0-9 and the letters a-f.

separator is not '\0', the separator character is inserted between the hex bytes.

范例:

QByteArray macAddress = QByteArray::fromHex("123456abcdef");
macAddress.toHex(':'); // returns "12:34:56:ab:cd:ef"
macAddress.toHex(0);   // returns "123456abcdef"
							

该函数在 Qt 5.9 引入。

另请参阅 fromHex ().

int QByteArray:: toInt ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to an int using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray str("FF");
bool ok;
int hex = str.toInt(&ok, 16);     // hex == 255, ok == true
int dec = str.toInt(&ok, 10);     // dec == 0, ok == false
							

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

long QByteArray:: toLong ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to a long int using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

QByteArray str("FF");
bool ok;
long hex = str.toLong(&ok, 16);   // hex == 255, ok == true
long dec = str.toLong(&ok, 10);   // dec == 0, ok == false
							

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

qlonglong QByteArray:: toLongLong ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to a long long using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

QByteArray QByteArray:: toLower () const

Returns a copy of the byte array in which each ASCII uppercase letter converted to lowercase.

范例:

QByteArray x("Qt by THE QT COMPANY");
QByteArray y = x.toLower();
// y == "qt by the qt company"
							

另请参阅 isLower (), toUpper (),和 Character Case .

[since 5.3] NSData *QByteArray:: toNSData () const

创建 NSData 从 QByteArray .

The NSData object is autoreleased.

该函数在 Qt 5.3 引入。

另请参阅 fromNSData (), fromRawNSData (), fromRawData (),和 toRawNSData ().

QByteArray QByteArray:: toPercentEncoding (const QByteArray & exclude = QByteArray(), const QByteArray & include = QByteArray(), char percent = '%') const

Returns a URI/URL-style percent-encoded copy of this byte array. The percent parameter allows you to override the default '%' character for another.

By default, this function will encode all bytes that are not one of the following:

ALPHA ("a" to "z" and "A" to "Z") / DIGIT (0 to 9) / "-" / "." / "_" / "~"

To prevent bytes from being encoded pass them to exclude . To force bytes to be encoded pass them to include percent character is always encoded.

范例:

QByteArray text = "{a fishy string?}";
QByteArray ba = text.toPercentEncoding("{}", "s");
qDebug(ba.constData());
// prints "{a fi%73hy %73tring%3F}"
							

The hex encoding uses the numbers 0-9 and the uppercase letters A-F.

另请参阅 fromPercentEncoding () 和 QUrl::toPercentEncoding ().

[since 5.3] CFDataRef QByteArray:: toRawCFData () const

Constructs a CFData that uses the bytes of the QByteArray .

QByteArray 的字节不拷贝。

The caller guarantees that the QByteArray will not be deleted or modified as long as this CFData object exists.

该函数在 Qt 5.3 引入。

另请参阅 toCFData (), fromRawCFData (), fromCFData (),和 fromRawData ().

[since 5.3] NSData *QByteArray:: toRawNSData () const

Constructs a NSData that uses the bytes of the QByteArray .

QByteArray 的字节不拷贝。

The caller guarantees that the QByteArray will not be deleted or modified as long as this NSData object exists.

该函数在 Qt 5.3 引入。

另请参阅 fromRawNSData (), fromNSData (), fromRawData (),和 toNSData ().

short QByteArray:: toShort ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to a short using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal; otherwise, if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

[since 5.4] std::string QByteArray:: toStdString () const

Returns a std::string object with the data contained in this QByteArray .

This operator is mostly useful to pass a QByteArray to a function that accepts a std::string object.

该函数在 Qt 5.4 引入。

另请参阅 fromStdString () 和 QString::toStdString ().

uint QByteArray:: toUInt ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to an 无符号 int using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

ulong QByteArray:: toULong ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to an unsigned long int using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

qulonglong QByteArray:: toULongLong ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to an unsigned long long using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

ushort QByteArray:: toUShort ( bool * ok = nullptr, int base = 10) const

Returns the byte array converted to an unsigned short using base base , which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal; otherwise, if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

返回 0,若转换失败。

ok 不是 nullptr , failure is reported by setting * ok to false , and success by setting * ok to true .

注意: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

另请参阅 number ().

QByteArray QByteArray:: toUpper () const

Returns a copy of the byte array in which each ASCII lowercase letter converted to uppercase.

范例:

QByteArray x("Qt by THE QT COMPANY");
QByteArray y = x.toUpper();
// y == "QT BY THE QT COMPANY"
							

另请参阅 isUpper (), toLower (),和 Character Case .

QByteArray QByteArray:: trimmed () const

Returns a copy of this byte array with spacing characters removed from the start and end.

The spacing characters are those for which the standard C++ isspace() 函数返回 true in the C locale; these are the ASCII characters tabulation '\t', line feed '\n', carriage return '\r', vertical tabulation '\v', form feed '\f', and space ' '.

范例:

QByteArray ba("  lots\t of\nwhitespace\r\n ");
ba = ba.trimmed();
// ba == "lots\t of\nwhitespace";
							

不像 simplified (), trimmed() leaves internal spacing unchanged.

另请参阅 simplified (), QChar::SpecialCharacter ,和 Spacing Characters .

void QByteArray:: truncate ( qsizetype pos )

Truncates the byte array at index position pos .

pos is beyond the end of the array, nothing happens.

范例:

QByteArray ba("Stockholm");
ba.truncate(5);             // ba == "Stock"
							

另请参阅 chop (), resize (),和 first ().

bool QByteArray:: operator!= (const QString & str ) const

返回 true if this byte array is not equal to the UTF-8 encoding of str ;否则返回 false .

比较是区分大小写的。

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8 (), QString::fromLatin1 (),或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

QByteArray &QByteArray:: operator+= (const QByteArray & ba )

追加字节数组 ba onto the end of this byte array and returns a reference to this byte array.

范例:

QByteArray x("free");
QByteArray y("dom");
x += y;
// x == "freedom"
							

注意: QByteArray 隐式共享 class. Consequently, if you append to an empty byte array, then the byte array will just share the data held in ba . In this case, no copying of data is done, taking constant time . If a shared instance is modified, it will be copied (copy-on-write), taking linear time .

If the byte array being appended to is not empty, a deep copy of the data is performed, taking linear time .

This operation typically does not suffer from allocation overhead, because QByteArray preallocates extra space at the end of the data so that it may grow without reallocating for each append operation.

另请参阅 append () 和 prepend ().

QByteArray &QByteArray:: operator+= ( char ch )

这是重载函数。

追加字节 ch onto the end of this byte array and returns a reference to this byte array.

QByteArray &QByteArray:: operator+= (const char * str )

这是重载函数。

追加 \0 结尾字符串 str onto the end of this byte array and returns a reference to this byte array.

bool QByteArray:: operator< (const QString & str ) const

返回 true if this byte array is lexically less than the UTF-8 encoding of str ;否则返回 false .

比较是区分大小写的。

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8 (), QString::fromLatin1 (),或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

bool QByteArray:: operator<= (const QString & str ) const

返回 true if this byte array is lexically less than or equal to the UTF-8 encoding of str ;否则返回 false .

比较是区分大小写的。

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8 (), QString::fromLatin1 (),或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

QByteArray &QByteArray:: operator= (const char * str )

这是重载函数。

赋值 str 到此字节数组。

bool QByteArray:: operator== (const QString & str ) const

返回 true if this byte array is equal to the UTF-8 encoding of str ;否则返回 false .

比较是区分大小写的。

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8 (), QString::fromLatin1 (),或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

bool QByteArray:: operator> (const QString & str ) const

返回 true if this byte array is lexically greater than the UTF-8 encoding of str ;否则返回 false .

比较是区分大小写的。

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8 (), QString::fromLatin1 (),或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

bool QByteArray:: operator>= (const QString & str ) const

返回 true if this byte array is greater than or equal to the UTF-8 encoding of str ;否则返回 false .

比较是区分大小写的。

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8 (), QString::fromLatin1 (),或 QString::fromLocal8Bit () explicitly if you want to convert the byte array to a QString before doing the comparison.

char &QByteArray:: operator[] ( qsizetype i )

Returns the byte at index position i as a modifiable reference.

i must be a valid index position in the byte array (i.e., 0 <= i < size ()).

范例:

QByteArray ba("Hello, world");
cout << ba[0]; // prints H
ba[7] = 'W';
// ba == "Hello, World"
							

另请参阅 at ().

char QByteArray:: operator[] ( qsizetype i ) const

这是重载函数。

如同 at( i ).

相关非成员

[since 6.1] template <typename T> qsizetype erase ( QByteArray & ba , const T & t )

Removes all elements that compare equal to t from the byte array ba . Returns the number of elements removed, if any.

该函数在 Qt 6.1 引入。

另请参阅 erase_if .

[since 6.1] template <typename Predicate> qsizetype erase_if ( QByteArray & ba , Predicate pred )

Removes all elements for which the predicate pred returns true from the byte array ba . Returns the number of elements removed, if any.

该函数在 Qt 6.1 引入。

另请参阅 erase .

[since 5.9] quint16 qChecksum ( QByteArrayView data , Qt::ChecksumType standard = Qt::ChecksumIso3309)

Returns the CRC-16 checksum of data .

The checksum is independent of the byte order (endianness) and will be calculated accorded to the algorithm published in standard . By default the algorithm published in ISO 3309 ( Qt::ChecksumIso3309 ) is used.

注意: This function is a 16-bit cache conserving (16 entry table) implementation of the CRC-16-CCITT algorithm.

该函数在 Qt 5.9 引入。

QByteArray qCompress (const QByteArray & data , int compressionLevel = -1)

Compresses the data byte array and returns the compressed data in a new byte array.

compressionLevel parameter specifies how much compression should be used. Valid values are between 0 and 9, with 9 corresponding to the greatest compression (i.e. smaller compressed data) at the cost of using a slower algorithm. Smaller values (8, 7, ..., 1) provide successively less compression at slightly faster speeds. The value 0 corresponds to no compression at all. The default value is -1, which specifies zlib's default compression.

另请参阅 qUncompress (const QByteArray &data).

QByteArray qCompress (const uchar * data , qsizetype nbytes , int compressionLevel = -1)

这是重载函数。

Compresses the first nbytes of data at compression level compressionLevel and returns the compressed data in a new byte array.

QByteArray qUncompress (const QByteArray & data )

Uncompresses the data byte array and returns a new byte array with the uncompressed data.

返回空 QByteArray 若输入数据被破坏。

This function will uncompress data compressed with qCompress () from this and any earlier Qt version, back to Qt 3.1 when this feature was added.

注意: If you want to use this function to uncompress external data that was compressed using zlib, you first need to prepend a four byte header to the byte array containing the data. The header must contain the expected length (in bytes) of the uncompressed data, expressed as an unsigned, big-endian, 32-bit integer.

另请参阅 qCompress ().

QByteArray qUncompress (const uchar * data , qsizetype nbytes )

这是重载函数。

Uncompresses the first nbytes of data and returns a new byte array with the uncompressed data.

int qsnprintf ( char * str , size_t n , const char * fmt , ...)

可移植 snprintf() 函数,调用 qvsnprintf。

fmt printf() format string. The result is put into str , which is a buffer of at least n 字节。

警告: Call this function only when you know what you are doing since it shows different behavior on certain platforms. Use QString::asprintf () to format a string instead.

另请参阅 qvsnprintf () 和 QString::asprintf ().

int qstrcmp (const char * str1 , const char * str2 )

安全 strcmp() 函数。

比较 str1 and str2 . Returns a negative value if str1 is less than str2 , 0 if str1 等于 str2 or a positive value if str1 大于 str2 .

若两字符串为 nullptr , they are deemed equal; otherwise, if either is nullptr , it is treated as less than the other (even if the other is an empty string).

另请参阅 qstrncmp (), qstricmp (), qstrnicmp (), Character Case ,和 QByteArray::compare ().

char * qstrcpy ( char * dst , const char * src )

Copies all the characters up to and including the '\0' from src into dst and returns a pointer to dst 。若 src is nullptr , it immediately returns nullptr .

This function assumes that dst is large enough to hold the contents of src .

注意: dst and src overlap, the behavior is undefined.

另请参阅 qstrncpy ().

char * qstrdup (const char * src )

Returns a duplicate string.

Allocates space for a copy of src , copies it, and returns a pointer to the copy. If src is nullptr , it immediately returns nullptr .

Ownership is passed to the caller, so the returned string must be deleted using delete[] .

int qstricmp (const char * str1 , const char * str2 )

安全 stricmp() 函数。

比较 str1 and str2 , ignoring differences in the case of any ASCII characters.

Returns a negative value if str1 is less than str2 , 0 if str1 等于 str2 or a positive value if str1 大于 str2 .

若两字符串为 nullptr , they are deemed equal; otherwise, if either is nullptr , it is treated as less than the other (even if the other is an empty string).

另请参阅 qstrcmp (), qstrncmp (), qstrnicmp (), Character Case ,和 QByteArray::compare ().

size_t qstrlen (const char * str )

安全 strlen() 函数。

Returns the number of characters that precede the terminating '\0', or 0 if str is nullptr .

另请参阅 qstrnlen ().

int qstrncmp (const char * str1 , const char * str2 , size_t len )

安全 strncmp() 函数。

比较最多 len bytes of str1 and str2 .

Returns a negative value if str1 is less than str2 , 0 if str1 等于 str2 or a positive value if str1 大于 str2 .

若两字符串为 nullptr , they are deemed equal; otherwise, if either is nullptr , it is treated as less than the other (even if the other is an empty string or len is 0).

另请参阅 qstrcmp (), qstricmp (), qstrnicmp (), Character Case ,和 QByteArray::compare ().

char * qstrncpy ( char * dst , const char * src , size_t len )

安全 strncpy() 函数。

拷贝最多 len 字节来自 src (stopping at len or the terminating '\0' whichever comes first) into dst and returns a pointer to dst . Guarantees that dst is '\0'-terminated. If src or dst is nullptr , returns nullptr immediately.

This function assumes that dst is at least len characters long.

注意: dst and src overlap, the behavior is undefined.

另请参阅 qstrcpy ().

int qstrnicmp (const char * str1 , const char * str2 , size_t len )

安全 strnicmp() 函数。

比较最多 len bytes of str1 and str2 , ignoring differences in the case of any ASCII characters.

Returns a negative value if str1 is less than str2 , 0 if str1 等于 str2 or a positive value if str1 大于 str2 .

若两字符串为 nullptr , they are deemed equal; otherwise, if either is nullptr , it is treated as less than the other (even if the other is an empty string or len is 0).

另请参阅 qstrcmp (), qstrncmp (), qstricmp (), Character Case ,和 QByteArray::compare ().

size_t qstrnlen (const char * str , size_t maxlen )

安全 strnlen() 函数。

Returns the number of characters that precede the terminating '\0', but at most maxlen 。若 str is nullptr , returns 0.

另请参阅 qstrlen ().

int qvsnprintf ( char * str , size_t n , const char * fmt , va_list ap )

可移植 vsnprintf() 函数。会调用 ::vsnprintf() , ::_vsnprintf() ,或 ::vsnprintf_s depending on the system, or fall back to an internal version.

fmt printf() format string. The result is put into str , which is a buffer of at least n 字节。

The caller is responsible to call va_end() on ap .

警告: Since vsnprintf() shows different behavior on certain platforms, you should not rely on the return value or on the fact that you will always get a 0 terminated string back.

Ideally, you should never call this function but use QString::asprintf () 代替。

另请参阅 qsnprintf () 和 QString::asprintf ().

bool operator!= (const QByteArray & a1 , const QByteArray & a2 )

这是重载函数。

返回 true 若字节数组 a1 不等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator!= (const QByteArray & a1 , const char * a2 )

这是重载函数。

返回 true 若字节数组 a1 is not equal to the '\0'-terminated string a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator!= (const char * a1 , const QByteArray & a2 )

这是重载函数。

返回 true if '\0'-terminated string a1 不等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

const QByteArray operator+ (const QByteArray & a1 , const QByteArray & a2 )

Returns a byte array that is the result of concatenating byte array a1 and byte array a2 .

另请参阅 QByteArray::operator+= ().

const QByteArray operator+ (const QByteArray & a1 , const char * a2 )

这是重载函数。

Returns a byte array that is the result of concatenating byte array a1 and '\0'-terminated string a2 .

const QByteArray operator+ (const QByteArray & a1 , char a2 )

这是重载函数。

Returns a byte array that is the result of concatenating byte array a1 and byte a2 .

const QByteArray operator+ (const char * a1 , const QByteArray & a2 )

这是重载函数。

Returns a byte array that is the result of concatenating '\0'-terminated string a1 and byte array a2 .

const QByteArray operator+ ( char a1 , const QByteArray & a2 )

这是重载函数。

Returns a byte array that is the result of concatenating byte a1 and byte array a2 .

bool operator< (const QByteArray & a1 , const QByteArray & a2 )

这是重载函数。

返回 true 若字节数组 a1 词汇上小于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator< (const QByteArray & a1 , const char * a2 )

这是重载函数。

返回 true 若字节数组 a1 is lexically less than the '\0'-terminated string a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator< (const char * a1 , const QByteArray & a2 )

这是重载函数。

返回 true if '\0'-terminated string a1 词汇上小于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

QDataStream & operator<< ( QDataStream & out , const QByteArray & ba )

写入字节数组 ba 到流 out 并返回流引用。

另请参阅 序列化 Qt 数据类型 .

bool operator<= (const QByteArray & a1 , const QByteArray & a2 )

这是重载函数。

返回 true 若字节数组 a1 词法上小于等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator<= (const QByteArray & a1 , const char * a2 )

这是重载函数。

返回 true 若字节数组 a1 is lexically less than or equal to the '\0'-terminated string a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator<= (const char * a1 , const QByteArray & a2 )

这是重载函数。

返回 true if '\0'-terminated string a1 词法上小于等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator== (const QByteArray & a1 , const QByteArray & a2 )

这是重载函数。

返回 true 若字节数组 a1 等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator== (const QByteArray & a1 , const char * a2 )

这是重载函数。

返回 true 若字节数组 a1 is equal to the '\0'-terminated string a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator== (const char * a1 , const QByteArray & a2 )

这是重载函数。

返回 true if '\0'-terminated string a1 等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator> (const QByteArray & a1 , const QByteArray & a2 )

这是重载函数。

返回 true 若字节数组 a1 词法上大于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator> (const QByteArray & a1 , const char * a2 )

这是重载函数。

返回 true 若字节数组 a1 is lexically greater than the '\0'-terminated string a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator> (const char * a1 , const QByteArray & a2 )

这是重载函数。

返回 true if '\0'-terminated string a1 词法上大于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator>= (const QByteArray & a1 , const QByteArray & a2 )

这是重载函数。

返回 true 若字节数组 a1 词法上大于等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator>= (const QByteArray & a1 , const char * a2 )

这是重载函数。

返回 true 若字节数组 a1 is lexically greater than or equal to the '\0'-terminated string a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

bool operator>= (const char * a1 , const QByteArray & a2 )

这是重载函数。

返回 true if '\0'-terminated string a1 词法上大于等于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

QDataStream & operator>> ( QDataStream & in , QByteArray & ba )

读取字节数组到 ba 从流 in 并返回流引用。

另请参阅 序列化 Qt 数据类型 .

宏文档编制

QByteArrayLiteral ( ba )

The macro generates the data for a QByteArray out of the string literal ba at compile time. Creating a QByteArray from it is free in this case, and the generated byte array data is stored in the read-only segment of the compiled object file.

例如:

QByteArray ba = QByteArrayLiteral("byte array contents");
							

Using QByteArrayLiteral instead of a double quoted plain C++ string literal can significantly speed up creation of QByteArray instances from data known at compile time.

另请参阅 QStringLiteral .

QT_NO_CAST_FROM_BYTEARRAY

禁用自动转换从 QByteArray to const char * or const void *.

另请参阅 QT_NO_CAST_TO_ASCII and QT_NO_CAST_FROM_ASCII .