QByteArray 类提供字节数组。 更多...
| 头： | #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 .
| class | FromBase64Result |
| enum | Base64Option { Base64Encoding, Base64UrlEncoding, KeepTrailingEquals, OmitTrailingEquals, IgnoreBase64DecodingErrors, AbortOnBase64DecodingErrors } |
| flags | Base64Options |
| const_iterator | |
| const_reverse_iterator | |
| iterator | |
| reverse_iterator |
| 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 ) const |
| qsizetype | lastIndexOf (char ch , qsizetype from = -1) const |
| qsizetype | lastIndexOf (QByteArrayView bv ) 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 format = 'g', int precision = 6) |
| QByteArray & | setNum (double n , char format = 'g', int precision = 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 |
| 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 format = 'g', int precision = 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 ) |
| QByteArray | operator""_qba (const char * str , size_t size ) |
| 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 ) |
| QByteArrayLiteral ( ba ) | |
| QT_NO_CAST_FROM_BYTEARRAY |
QByteArray 可以被用于存储原生字节 (包括 \0) 和传统 8 位以 \0 结尾的字符串。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 *
到其构造函数。例如，以下代码创建包含数据 Hello 大小为 5 的字节数组：
QByteArray ba("Hello");
尽管 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 深拷贝 的出现。
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 ( 线性时间 ) 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 ().
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.
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 .
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).
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.
Functions that perform conversions between numeric data types and string representations are performed in the C locale, regardless of the user's locale settings. Use QLocale to perform locale-aware conversions between numbers and strings.
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 .
[since 5.2]
enum QByteArray::
Base64Option
This enum contains the options available for encoding and decoding Base64. Base64 is defined by RFC 4648 , with the following options:
| 常量 | 值 | 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.
此 typedef 提供 STL 样式 const 迭代器为 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 .
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 .
[static, since 5.15]
QByteArray::FromBase64Result
QByteArray::
fromBase64Encoding
(
QByteArray
&&
base64
,
QByteArray::Base64Options
options
= Base64Encoding)
[static, since 5.15]
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
包含
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
包含
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 ().
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.
指针仍然有效只要不发生分离和
QByteArray
is not modified. This operator is mostly useful to pass a byte array to a function that accepts a
const char *
.
可以禁用此运算符通过定义
QT_NO_CAST_FROM_BYTEARRAY
when you compile your applications.
注意：
QByteArray
可以存储任何字节值 (包括 \0)，但大多数函数需要
char *
自变量，假定数据在遇到首个 \0 时结束。
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。
构造副本为 other .
此操作花费 常量时间 , 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 线性时间 .
另请参阅 operator= ().
构造字节数组大小为 size with every byte set to ch .
另请参阅 fill ().
构造字节数组包含前 size 字节的数组 data .
若 data 为 0，构造 null 字节数组。
若 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 ().
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。
赋值 other 到此字节数组，并返回此字节数组的引用。
销毁字节数组。
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 是 隐式共享 类。因此，若追加到空字节数组，那么字节数组将仅仅共享的数据保持在 ba 。在这种情况下，不进行数据拷贝，花费 常量时间 。若共享实例被修改，它将被拷贝 (写时拷贝)，花费 线性时间 .
若要追加到的字节数组非空，履行数据深拷贝，花费 线性时间 .
append() 函数通常非常快 ( 常量时间 )，因为 QByteArray 预分配额外空间在数据末尾，所以它可以增长无需每次重新分配整个数组。
另请参阅 operator+= (), prepend ()，和 insert ().
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。
若 count is negative or zero nothing is appended to the byte array.
该函数在 Qt 5.7 引入。
这是重载函数。
追加 \0 结尾字符串 str 到此字节数组。
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.
若 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 ().
若 len is zero or str is null, nothing is appended to the byte array. Ensure that len is not longer than str .
这是重载函数。
追加 data 到此字节数组。
Returns the byte at index position i 在字节数组中。
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[] ().
返回 STL 样式迭代器 指向字节数组第一字节。
警告： 返回迭代器在分离时是无效的或当 QByteArray 被修改。
另请参阅 constBegin () 和 end ().
此函数重载 begin()。
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.
[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： 返回迭代器在分离时是无效的或当 QByteArray 被修改。
该函数在 Qt 5.0 引入。
[since 5.0]
QByteArray::const_iterator
QByteArray::
cend
() const
返回常量 STL 样式迭代器 指向字节数组中仅仅最后字节之后。
警告： 返回迭代器在分离时是无效的或当 QByteArray 被修改。
该函数在 Qt 5.0 引入。
移除 n bytes from the end of the byte array.
若 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 ().
Clears the contents of the byte array and makes it null.
[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 .
返回常量 STL 样式迭代器 指向字节数组第一字节。
警告： 返回迭代器在分离时是无效的或当 QByteArray 被修改。
返回以字节数组形式存储的 const 数据指针。指针可以用于访问组成数组的字节。数据以 \0 结尾，除非 QByteArray 对象是从原生数据创建的。
指针仍然有效只要不发生分离和 QByteArray 不被修改。
此函数主要用于将字节数组传递给的函数接受
const char *
.
注意：
QByteArray
可以存储任何字节值 (包括 \0)，但大多数函数需要
char *
自变量，假定数据在遇到首个 \0 时结束。
另请参阅 data (), operator[] ()，和 fromRawData ().
返回常量 STL 样式迭代器 指向字节数组中仅仅最后字节之后。
警告： 返回迭代器在分离时是无效的或当 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。
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 ().
这是重载函数。
Returns the number of occurrences of byte ch 在字节数组中。
另请参阅 contains () 和 indexOf ().
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： 返回迭代器在分离时是无效的或当 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： 返回迭代器在分离时是无效的或当 QByteArray 被修改。
该函数在 Qt 5.6 引入。
另请参阅 end (), rend ()，和 rbegin ().
返回以字节数组形式存储的数据指针。指针可以用于访问和修改组成数组的字节。数据以 \0 结尾，即指针返回后可以访问的字节数是只要没有发生分离并且 xx 指针保持有效 size () + 1，包括 \0 终止符。
范例：
QByteArray ba("Hello world"); char *data = ba.data(); while (*data) { cout << "[" << *data << "]" << Qt::endl; ++data; }
指针仍然有效只要不发生分离和 QByteArray 不被修改。
对于只读访问， constData () 更快，因为它从不导致 深拷贝 的出现。
此函数主要用于将字节数组传递给的函数接受
const char *
.
以下范例制作由 data() 返回的 char* 副本，但会破坏堆并导致崩溃，因为它没有为末尾 \0 分配字节：
QString tmp = "test"; QByteArray text = tmp.toLocal8Bit(); char *data = new char[text.size()]; strcpy(data, text.data()); delete [] data;
这个分配了正确的空间数量：
QString tmp = "test"; QByteArray text = tmp.toLocal8Bit(); char *data = new char[text.size() + 1]; strcpy(data, text.data()); delete [] data;
注意：
QByteArray
可以存储任何字节值 (包括 \0)，但大多数函数需要
char *
自变量，假定数据在遇到首个 \0 时结束。
另请参阅 constData () 和 operator[] ().
这是重载函数。
返回 STL 样式迭代器 指向字节数组中仅仅最后字节之后。
警告： 返回迭代器在分离时是无效的或当 QByteArray 被修改。
此函数重载 end()。
[since 6.0]
bool
QByteArray::
endsWith
(
QByteArrayView
bv
) const
返回
true
若此字节数组的结尾为字节视图序列
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 ().
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。
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
包含
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
包含
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 是 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 ().
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 ( 线性时间 ), 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 ().
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 ().
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 在字节数组中。
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。
这是重载函数。
Inserts byte ch at index position i 在字节数组中。
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 .
这是重载函数。
插入 len bytes, starting at data , at position i 在字节数组中。
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 .
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。
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。
[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
) 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 search starts at the last character; if from is -2, at the next to last character and so on. 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
注意：
When searching for a 0-length
bv
, the match at the end of the data is excluded from the search by a negative
from
, even though
-1
is normally thought of as searching from the end of the byte array: the match at the end is
after
the last character, so it is excluded. To include such a final empty match, either give a positive value for
from
or omit the
from
parameter entirely.
该函数在 Qt 6.0 引入。
另请参阅 indexOf (), contains ()，和 count ().
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 ().
[since 6.2]
qsizetype
QByteArray::
lastIndexOf
(
QByteArrayView
bv
) const
这是重载函数。
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 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 6.2 引入。
另请参阅 indexOf (), contains ()，和 count ().
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 ().
Returns a byte array of size width that contains this byte array padded with the fill byte.
若 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.
若 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 ().
如同 size ().
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.
若 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 representing the whole number n as text.
Returns a byte array containing a string representing n ，使用指定 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.
[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
format
= 'g',
int
precision
= 6)
这是重载函数。
Returns a byte-array representing the floating-point number n as text.
Returns a byte array containing a string representing n , with a given format and precision , with the same meanings as for QString::number (double, char, int). For example:
QByteArray ba = QByteArray::number(12.3456, 'E', 3); // ba == 1.235E+01
另请参阅 toDouble () 和 QLocale::FloatingPointPrecisionOption .
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 ( 常量时间 )，因为 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 ).
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。
这是重载函数。
Prepends the '\0'-terminated string str 到此字节数组。
这是重载函数。
前置 len bytes starting at str to this byte array. The bytes prepended may include '\0' bytes.
这是重载函数。
前置 ba 到此字节数组。
This function is provided for STL compatibility. It is equivalent to append( other ).
这是重载函数。
如同 append( ch ).
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。
This function is provided for STL compatibility. It is equivalent to prepend( other ).
这是重载函数。
如同 prepend( ch ).
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： 返回迭代器在分离时是无效的或当 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。
移除 len bytes from the array, starting at index position pos , and returns a reference to the array.
若 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： 返回迭代器在分离时是无效的或当 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。
Returns a copy of this byte array repeated the specified number of times .
若 times is less than 1, an empty byte array is returned.
范例：
QByteArray ba("ab"); ba.repeated(4); // returns "abababab"
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!"
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.
这是重载函数。
Replaces every occurrence of the byte before with the byte array after .
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。
这是重载函数。
Replaces every occurrence of the byte before with the byte after .
试图分配内存为至少 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 ().
把字节数组的尺寸设为 size 字节。
若 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.
若 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 ().
Returns a byte array of size width 包含 fill byte followed by this byte array.
若 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.
若 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 ().
Represent the whole number n as text.
Sets this byte array to a string representing n in base base (ten by default) and returns a reference to this byte array. Bases 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.
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.
这是重载函数。
另请参阅 toShort ().
这是重载函数。
另请参阅 toUShort ().
这是重载函数。
另请参阅 toUInt ().
这是重载函数。
另请参阅 toLong ().
这是重载函数。
另请参阅 toULong ().
这是重载函数。
另请参阅 toLongLong ().
这是重载函数。
另请参阅 toULongLong ().
这是重载函数。
Represent the floating-point number n as text.
Sets this byte array to a string representing n , with a given format and precision (with the same meanings as for QString::number (double, char, int)), and returns a reference to this byte array.
另请参阅 toFloat ().
这是重载函数。
Represent the floating-point number n as text.
Sets this byte array to a string representing n , with a given format and precision (with the same meanings as for QString::number (double, char, int)), and returns a reference to this byte array.
另请参阅 toDouble () 和 QLocale::FloatingPointPrecisionOption .
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
()
提供此函数是为兼容 STL。它相当于 squeeze ().
该函数在 Qt 5.10 引入。
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 .
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 automatically unless a 深拷贝 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'
[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 ().
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.
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。
这是重载函数。
返回
true
if this byte array starts with byte
ch
；否则返回
false
.
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 ().
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).
若
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 ().
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).
若
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.
若 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 ().
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.
若 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。
若
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 ().
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.
若 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。
若
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 ().
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.
若 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。
若
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 ().
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 ().
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 ().
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.
若 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。
若
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 ().
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.
若 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。
若
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 ().
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.
若 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。
若
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 ().
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.
若 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。
若
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 ().
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.
若 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。
若
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 ().
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 .
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 .
Truncates the byte array at index position pos .
若 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 ().
返回
true
若此字节数组不等于 UTF-8 编码的
str
；否则返回
false
.
比较是区分大小写的。
可以禁用此运算符通过定义
QT_NO_CAST_FROM_ASCII
当编译应用程序时。那么需要调用
QString::fromUtf8
(),
QString::fromLatin1
()，或
QString::fromLocal8Bit
() explicitly if you want to convert the byte array to a
QString
before doing the comparison.
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 是 隐式共享 类。因此，若追加到空字节数组，那么字节数组将仅仅共享的数据保持在 ba 。在这种情况下，不进行数据拷贝，花费 常量时间 。若共享实例被修改，它将被拷贝 (写时拷贝)，花费 线性时间 .
若要追加到的字节数组非空，履行数据深拷贝，花费 线性时间 .
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.
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.
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.
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。
可以禁用此运算符通过定义
QT_NO_CAST_FROM_ASCII
当编译应用程序时。那么需要调用
QString::fromUtf8
(),
QString::fromLatin1
()，或
QString::fromLocal8Bit
() explicitly if you want to convert the byte array to a
QString
before doing the comparison.
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。
可以禁用此运算符通过定义
QT_NO_CAST_FROM_ASCII
当编译应用程序时。那么需要调用
QString::fromUtf8
(),
QString::fromLatin1
()，或
QString::fromLocal8Bit
() explicitly if you want to convert the byte array to a
QString
before doing the comparison.
这是重载函数。
赋值 str 到此字节数组。
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。
可以禁用此运算符通过定义
QT_NO_CAST_FROM_ASCII
当编译应用程序时。那么需要调用
QString::fromUtf8
(),
QString::fromLatin1
()，或
QString::fromLocal8Bit
() explicitly if you want to convert the byte array to a
QString
before doing the comparison.
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。
可以禁用此运算符通过定义
QT_NO_CAST_FROM_ASCII
当编译应用程序时。那么需要调用
QString::fromUtf8
(),
QString::fromLatin1
()，或
QString::fromLocal8Bit
() explicitly if you want to convert the byte array to a
QString
before doing the comparison.
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。
可以禁用此运算符通过定义
QT_NO_CAST_FROM_ASCII
当编译应用程序时。那么需要调用
QString::fromUtf8
(),
QString::fromLatin1
()，或
QString::fromLocal8Bit
() explicitly if you want to convert the byte array to a
QString
before doing the comparison.
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 ().
这是重载函数。
如同 at( i ).
[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。
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).
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.
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 ().
这是重载函数。
Uncompresses the first nbytes of data and returns a new byte array with the uncompressed data.
可移植 snprintf() 函数，调用 qvsnprintf。
fmt
是
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 ().
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 ().
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： 若 dst and src overlap, the behavior is undefined.
另请参阅 qstrncpy ().
返回复制字符串。
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[]
.
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 ().
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 ().
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 ().
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
，返回
nullptr
立即。
This function assumes that dst is at least len characters long.
注意： 若 dst and src overlap, the behavior is undefined.
另请参阅 qstrcpy ().
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 ().
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 ().
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
是
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 ().
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 ().
这是重载函数。
返回
true
若字节数组
a1
不等于以 \0 结尾的字符串
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
这是重载函数。
返回
true
若以 \0 结尾的字符串
a1
不等于字节数组
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
[since 6.2]
QByteArray
operator""_qba
(const
char
*
str
,
size_t
size
)
文字运算符创建的 QByteArray out of the first size characters in the char string literal str .
QByteArray is created at compile time, and the generated string data is stored in the read-only segment of the compiled object file. Duplicate literals may share the same read-only memory. This functionality is interchangeable with QByteArrayLiteral , but saves typing when many string literals are present in the code.
以下代码创建 QByteArray :
auto str = "hello"_qba;
该函数在 Qt 6.2 引入。
另请参阅 QByteArrayLiteral and QtLiterals::operator""_qs (const char16_t *str, size_t size).
返回的字节数组结果是串联字节数组 a1 和字节数组 a2 .
另请参阅 QByteArray::operator+= ().
这是重载函数。
返回的字节数组结果是串联字节数组 a1 and '\0'-terminated string a2 .
这是重载函数。
返回的字节数组结果是串联字节数组 a1 and byte a2 .
这是重载函数。
Returns a byte array that is the result of concatenating '\0'-terminated string a1 和字节数组 a2 .
这是重载函数。
Returns a byte array that is the result of concatenating byte a1 和字节数组 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 ().
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 ().
这是重载函数。
返回
true
若以 \0 结尾的字符串
a1
词汇上小于字节数组
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
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 .
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 ().
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 ().
这是重载函数。
返回
true
若以 \0 结尾的字符串
a1
词法上小于等于字节数组
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
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 ().
这是重载函数。
返回
true
若字节数组
a1
等于以 \0 结尾的字符串
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
这是重载函数。
返回
true
若以 \0 结尾的字符串
a1
等于字节数组
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
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 ().
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 ().
这是重载函数。
返回
true
若以 \0 结尾的字符串
a1
词法上大于字节数组
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
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 ().
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 ().
这是重载函数。
返回
true
若以 \0 结尾的字符串
a1
词法上大于等于字节数组
a2
；否则返回
false
.
另请参阅 QByteArray::compare ().
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 .
宏生成数据为 QByteArray 从字符串文字 ba 在编译时。创建 QByteArray 是自由的在此情况下，且生成的字节数组数据是存储在编译对象文件的只读段中。
例如：
QByteArray ba = QByteArrayLiteral("byte array contents");
使用 QByteArrayLiteral 而不是带双引号的纯 C++ 字符串文字可以显著加速创建 QByteArray 实例从编译时的已知数据。
另请参阅 QStringLiteral .
禁用自动转换从 QByteArray 到 const char * 或 const void *。
另请参阅 QT_NO_CAST_TO_ASCII and QT_NO_CAST_FROM_ASCII .