QByteArray 类

QByteArray class provides an array of bytes. 更多...

Header: #include <QByteArray>
qmake: QT += core

注意: 此类的所有函数 可重入 .

公共类型

enum Base64Option { Base64Encoding, Base64UrlEncoding, KeepTrailingEquals, OmitTrailingEquals }
flags Base64Options
typedef const_iterator
typedef const_reverse_iterator
typedef iterator
typedef reverse_iterator

公共函数

QByteArray ()
QByteArray (const char * data , int size = -1)
QByteArray (int size , char ch )
QByteArray (const QByteArray & other )
QByteArray (QByteArray && other )
~QByteArray ()
QByteArray & append (const QByteArray & ba )
QByteArray & append (int count , char ch )
QByteArray & append (const char * str )
QByteArray & append (const char * str , int len )
QByteArray & append (char ch )
QByteArray & append (const QString & str )
char at (int i ) const
char back () const
QByteRef back ()
QByteArray::iterator begin ()
QByteArray::const_iterator begin () const
int capacity () const
QByteArray::const_iterator cbegin () const
QByteArray::const_iterator cend () const
void chop (int n )
QByteArray chopped (int len ) const
void clear ()
int compare (const char * c , Qt::CaseSensitivity cs = ...) const
int compare (const QByteArray & a , Qt::CaseSensitivity cs = ...) const
QByteArray::const_iterator constBegin () const
const char * constData () const
QByteArray::const_iterator constEnd () const
bool contains (const QByteArray & ba ) const
bool contains (const char * str ) const
bool contains (char ch ) const
int count (const QByteArray & ba ) const
int count (const char * str ) const
int count (char ch ) const
int 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 (const QByteArray & ba ) const
bool endsWith (char ch ) const
bool endsWith (const char * str ) const
QByteArray & fill (char ch , int size = -1)
char front () const
QByteRef front ()
int indexOf (const QByteArray & ba , int from = 0) const
int indexOf (const char * str , int from = 0) const
int indexOf (char ch , int from = 0) const
int indexOf (const QString & str , int from = 0) const
QByteArray & insert (int i , const QByteArray & ba )
QByteArray & insert (int i , int count , char ch )
QByteArray & insert (int i , const char * str )
QByteArray & insert (int i , const char * str , int len )
QByteArray & insert (int i , char ch )
QByteArray & insert (int i , const QString & str )
bool isEmpty () const
bool isLower () const
bool isNull () const
bool isUpper () const
int lastIndexOf (const QByteArray & ba , int from = -1) const
int lastIndexOf (const char * str , int from = -1) const
int lastIndexOf (char ch , int from = -1) const
int lastIndexOf (const QString & str , int from = -1) const
QByteArray left (int len ) const
QByteArray leftJustified (int width , char fill = ' ', bool truncate = false) const
int length () const
QByteArray mid (int pos , int len = -1) const
QByteArray & prepend (const QByteArray & ba )
QByteArray & prepend (int count , char ch )
QByteArray & prepend (const char * str )
QByteArray & prepend (const char * str , int len )
QByteArray & prepend (char ch )
void push_back (const QByteArray & other )
void push_back (const char * str )
void push_back (char ch )
void push_front (const QByteArray & other )
void push_front (const char * str )
void push_front (char ch )
QByteArray::reverse_iterator rbegin ()
QByteArray::const_reverse_iterator rbegin () const
QByteArray & remove (int pos , int len )
QByteArray::reverse_iterator rend ()
QByteArray::const_reverse_iterator rend () const
QByteArray repeated (int times ) const
QByteArray & replace (int pos , int len , const QByteArray & after )
QByteArray & replace (int pos , int len , const char * after , int alen )
QByteArray & replace (int pos , int len , const char * after )
QByteArray & replace (char before , const char * after )
QByteArray & replace (char before , const QByteArray & after )
QByteArray & replace (const char * before , const char * after )
QByteArray & replace (const char * before , int bsize , const char * after , int asize )
QByteArray & replace (const QByteArray & before , const QByteArray & after )
QByteArray & replace (const QByteArray & before , const char * after )
QByteArray & replace (const char * before , const QByteArray & after )
QByteArray & replace (char before , char after )
QByteArray & replace (const QString & before , const char * after )
QByteArray & replace (char before , const QString & after )
QByteArray & replace (const QString & before , const QByteArray & after )
void reserve (int size )
void resize (int size )
QByteArray right (int len ) const
QByteArray rightJustified (int width , char fill = ' ', bool truncate = false) const
QByteArray & setNum (int n , int base = 10)
QByteArray & setNum (ushort n , int base = 10)
QByteArray & setNum (short n , int base = 10)
QByteArray & setNum (uint 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 , uint size )
void shrink_to_fit ()
QByteArray simplified () const
int size () const
QList<QByteArray> split (char sep ) const
void squeeze ()
bool startsWith (const QByteArray & ba ) const
bool startsWith (char ch ) const
bool startsWith (const char * str ) const
void swap (QByteArray & other )
QByteArray toBase64 () const
QByteArray toBase64 (QByteArray::Base64Options options ) const
CFDataRef toCFData () const
double toDouble (bool * ok = nullptr) const
float toFloat (bool * ok = nullptr) const
QByteArray toHex () const
QByteArray toHex (char separator ) 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 (int 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+= (const char * str )
QByteArray & operator+= (char ch )
QByteArray & operator+= (const QString & str )
bool operator< (const QString & str ) const
bool operator<= (const QString & str ) const
QByteArray & operator= (const QByteArray & other )
QByteArray & operator= (const char * str )
QByteArray & operator= (QByteArray && other )
bool operator== (const QString & str ) const
bool operator> (const QString & str ) const
bool operator>= (const QString & str ) const
QByteRef operator[] (int i )
char operator[] (uint i ) const
char operator[] (int i ) const
QByteRef operator[] (uint i )

静态公共成员

QByteArray fromBase64 (const QByteArray & base64 )
QByteArray fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options )
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 , int 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 (qlonglong n , int base = 10)
QByteArray number (qulonglong n , int base = 10)
QByteArray number (double n , char f = 'g', int prec = 6)
quint16 qChecksum (const char * data , uint len )
quint16 qChecksum (const char * data , uint len , Qt::ChecksumType standard )
QByteArray qCompress (const uchar * data , int nbytes , int compressionLevel = -1)
QByteArray qCompress (const QByteArray & data , int compressionLevel = -1)
QByteArray qUncompress (const uchar * data , int nbytes )
QByteArray qUncompress (const QByteArray & data )
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 )
uint qstrlen (const char * str )
int qstrncmp (const char * str1 , const char * str2 , uint len )
char * qstrncpy (char * dst , const char * src , uint len )
int qstrnicmp (const char * str1 , const char * str2 , uint len )
uint qstrnlen (const char * str , uint 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 class provides an array of bytes.

QByteArray can be used to store both raw bytes (including '\0's) and traditional 8-bit '\0'-terminated strings. Using QByteArray is much more convenient than using const char * . Behind the scenes, it always ensures that the data is followed by a '\0' terminator, and uses 隐式共享 (copy-on-write) to reduce memory usage and avoid needless copying of data.

In addition to QByteArray , Qt also provides the QString class to store string data. For most purposes, QString is the class you want to use. It stores 16-bit Unicode characters, making it easy to store non-ASCII/non-Latin-1 characters in your application. 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' character 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 performance reasons you don't want to take a deep copy of the character data, use QByteArray::fromRawData () instead.)

Another approach is to set the size of the array using resize () and to initialize the data byte per 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 (int i = 0; i < ba.size(); ++i) {
    if (ba.at(i) >= 'a' && ba.at(i) <= 'f')
        cout << "Found character in range [a-f]" << endl;
}
							

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

To extract many bytes at a time, use left (), right (),或 mid ().

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' character, 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 character data, 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 a 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"
							

replace () 和 remove () functions' first two arguments are the position from which to start erasing and the number of bytes that should be erased.

When you append () data to a non-empty array, the array will be reallocated and the new data copied to it. You can avoid this behavior by calling reserve (), which preallocates a certain amount of memory. You can also call capacity () to find out how much memory QByteArray actually allocated. Data appended to an empty array is not copied.

A frequent requirement is to remove whitespace characters from a byte array ('\n', '\t', ' ', etc.). If you want to remove whitespace from both ends of a QByteArray ,使用 trimmed (). If you want to remove whitespace from both ends and replace multiple consecutive whitespaces with a single space character within the byte array, use simplified ().

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

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

If you simply want to check whether a QByteArray contains a particular character or substring, use contains (). If you want to find out how many times a particular character or substring 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 characters 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 pointer to a '\0' character for a null byte array ( not a null pointer), and QByteArray () compares equal to QByteArray (""). We recommend that you always use isEmpty () and avoid isNull ().

区域设置注意事项

数字字符串转换

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

8 位字符比较

In QByteArray , the notion of uppercase and lowercase and of which character is greater than or less than another character is locale dependent. This affects functions that support a case insensitive option or that compare or lowercase or uppercase their arguments. Case insensitive operations and comparisons will be accurate if both strings contain only ASCII characters. (If $LC_CTYPE is set, most Unix systems do "the right thing".) Functions that this affects include contains (), indexOf (), lastIndexOf (), operator<(), operator<=(), operator>(), operator>=(), isLower (), isUpper (), toLower () 和 toUpper ().

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

另请参阅 QString and QBitArray .

成员类型文档编制

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::fromBase64 () ignores the KeepTrailingEquals and OmitTrailingEquals options and will not flag errors in case they are missing or if there are too many of them.

This enum was introduced or modified in Qt 5.2.

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

typedef QByteArray:: const_iterator

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

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

typedef QByteArray:: const_reverse_iterator

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

This typedef was introduced in Qt 5.6.

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

typedef QByteArray:: iterator

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

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

typedef QByteArray:: reverse_iterator

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

This typedef was introduced in Qt 5.6.

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

成员函数文档编制

QByteArray:: QByteArray ()

Constructs an empty byte array.

另请参阅 isEmpty ().

QByteArray:: QByteArray (const char * data , int 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 nul-terminated string and its length is determined dynamically. The terminating nul-character is not considered part of the byte array.

QByteArray makes a deep copy of the string data.

另请参阅 fromRawData ().

QByteArray:: QByteArray ( int size , char ch )

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

另请参阅 fill ().

QByteArray:: QByteArray (const QByteArray & other )

构造副本为 other .

This operation takes constant time , because QByteArray is implicitly shared . 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 ( QByteArray && other )

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

This function was introduced in Qt 5.2.

QByteArray:: ~QByteArray ()

Destroys the byte array.

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

Appends the byte array ba onto the end of this byte array.

范例:

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

This is the same as insert( size (), ba ).

注意: QByteArray is an implicitly shared 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 operator+= (), prepend (),和 insert ().

QByteArray &QByteArray:: append ( int count , char ch )

这是重载函数。

追加 count copies of character 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.

This function was introduced in Qt 5.7.

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

这是重载函数。

Appends the string str 到此字节数组。

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

This function overloads append ().

Appends the first len characters of the string str 到此字节数组,并返回此字节数组的引用。

len is negative, the length of the string 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 .

QByteArray &QByteArray:: append ( char ch )

这是重载函数。

Appends the character ch 到此字节数组。

QByteArray &QByteArray:: append (const QString & str )

这是重载函数。

Appends the string str to this byte array. The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

char QByteArray:: at ( int i ) const

Returns the character 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[] ().

char QByteArray:: back () const

Returns the last character 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.

This function was introduced in Qt 5.10.

另请参阅 front (), at (),和 operator[] ().

QByteRef QByteArray:: back ()

Returns a reference to the last character 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.

This function was introduced in Qt 5.10.

另请参阅 front (), at (),和 operator[] ().

QByteArray::iterator QByteArray:: begin ()

Returns an STL 样式迭代器 pointing to the first character in the byte-array.

另请参阅 constBegin () 和 end ().

QByteArray::const_iterator QByteArray:: begin () const

This function overloads begin ().

int 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 ().

另请参阅 reserve () 和 squeeze ().

QByteArray::const_iterator QByteArray:: cbegin () const

返回常量 STL 样式迭代器 pointing to the first character in the byte-array.

This function was introduced in Qt 5.0.

另请参阅 begin () 和 cend ().

QByteArray::const_iterator QByteArray:: cend () const

返回常量 STL 样式迭代器 pointing to the imaginary character after the last character in the list.

This function was introduced in Qt 5.0.

另请参阅 cbegin () 和 end ().

void QByteArray:: chop ( int n )

移除 n bytes from the end of the byte array.

n is greater than 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 left ().

QByteArray QByteArray:: chopped ( int len ) const

Returns a byte array that contains the leftmost size () - len bytes of this byte array.

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

This function was introduced in Qt 5.10.

另请参阅 endsWith (), left (), right (), mid (), chop (),和 truncate ().

void QByteArray:: clear ()

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

另请参阅 resize () 和 isNull ().

int QByteArray:: compare (const char * c , Qt::CaseSensitivity cs = ...) const

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

This function was introduced in Qt 5.12.

另请参阅 operator== .

int QByteArray:: compare (const QByteArray & a , Qt::CaseSensitivity cs = ...) const

这是重载函数。

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

This function was introduced in Qt 5.12.

另请参阅 operator== .

QByteArray::const_iterator QByteArray:: constBegin () const

返回常量 STL 样式迭代器 pointing to the first character in the byte-array.

另请参阅 begin () 和 constEnd ().

const char *QByteArray:: constData () const

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 unless the QByteArray object was created from raw data. The pointer remains valid as long as the byte array isn't reallocated or destroyed.

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

Note: A 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 to the imaginary character after the last character in the list.

另请参阅 constBegin () 和 end ().

bool QByteArray:: contains (const QByteArray & ba ) const

返回 true if the byte array contains an occurrence of the byte array ba ;否则返回 false .

另请参阅 indexOf () 和 count ().

bool QByteArray:: contains (const char * str ) const

这是重载函数。

返回 true if the byte array contains the string str ;否则返回 false .

bool QByteArray:: contains ( char ch ) const

这是重载函数。

返回 true if the byte array contains the character ch ;否则返回 false .

int QByteArray:: count (const QByteArray & ba ) const

Returns the number of (potentially overlapping) occurrences of byte array ba in this byte array.

另请参阅 contains () 和 indexOf ().

int QByteArray:: count (const char * str ) const

这是重载函数。

Returns the number of (potentially overlapping) occurrences of string str in the byte array.

int QByteArray:: count ( char ch ) const

这是重载函数。

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

另请参阅 contains () 和 indexOf ().

int QByteArray:: count () const

这是重载函数。

如同 size ().

QByteArray::const_reverse_iterator QByteArray:: crbegin () const

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

This function was introduced in Qt 5.6.

另请参阅 begin (), rbegin (),和 rend ().

QByteArray::const_reverse_iterator QByteArray:: crend () const

返回常量 STL-style reverse iterator pointing to one past the last character in the byte-array, in reverse order.

This function was introduced in Qt 5.6.

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 in the returned character string is size () + 1 for the '\0' terminator.

范例:

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

The pointer remains valid as long as the byte array isn't reallocated or destroyed. For read-only access, 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;
							

Note: A 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 ()

Returns an STL 样式迭代器 pointing to the imaginary character after the last character in the byte-array.

另请参阅 begin () 和 constEnd ().

QByteArray::const_iterator QByteArray:: end () const

This function overloads end ().

bool QByteArray:: endsWith (const QByteArray & ba ) const

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

范例:

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

另请参阅 startsWith () 和 right ().

bool QByteArray:: endsWith ( char ch ) const

这是重载函数。

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

bool QByteArray:: endsWith (const char * str ) const

这是重载函数。

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

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

Sets every byte in the byte array to character 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 ().

[static] QByteArray QByteArray:: fromBase64 (const QByteArray & base64 )

Returns a decoded copy of the Base64 array base64 . 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::fromBase64("UXQgaXMgZ3JlYXQh");
text.data();            // returns "Qt is great!"
							

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

另请参阅 toBase64 ().

[static] QByteArray QByteArray:: fromBase64 (const QByteArray & base64 , QByteArray::Base64Options options )

这是重载函数。

Returns a decoded copy of the Base64 array base64 , using the alphabet defined by options . 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::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 .

This function was introduced in Qt 5.2.

另请参阅 toBase64 ().

[static] QByteArray QByteArray:: fromCFData ( CFDataRef data )

构造新 QByteArray containing a copy of the CFData data .

This function was introduced in Qt 5.3.

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] QByteArray QByteArray:: fromNSData (const NSData * data )

构造新 QByteArray containing a copy of the NSData data .

This function was introduced in Qt 5.3.

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: Given invalid input (such as a string containing the sequence "%G5", which is not a valid hexadecimal number) the output will be invalid as well. As an example: the sequence "%G5" could be decoded to 'W'.

This function was introduced in Qt 4.4.

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

[static] QByteArray QByteArray:: fromRawCFData ( CFDataRef data )

构造 QByteArray that uses the bytes of the CFData data .

data 的字节不被拷贝。

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

This function was introduced in Qt 5.3.

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

[static] QByteArray QByteArray:: fromRawData (const char * data , int 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 is an implicitly shared 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 does not take ownership of 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 null-terminated, unless the raw data contains a 0 character 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] QByteArray QByteArray:: fromRawNSData (const NSData * data )

构造 QByteArray that uses the bytes of the NSData data .

data 的字节不被拷贝。

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

This function was introduced in Qt 5.3.

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

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

返回副本为 str string as a QByteArray .

This function was introduced in Qt 5.4.

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

char QByteArray:: front () const

Returns the first character 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.

This function was introduced in Qt 5.10.

另请参阅 back (), at (),和 operator[] ().

QByteRef QByteArray:: front ()

Returns a reference to the first character 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.

This function was introduced in Qt 5.10.

另请参阅 back (), at (),和 operator[] ().

int QByteArray:: indexOf (const QByteArray & ba , int from = 0) const

Returns the index position of the first occurrence of the byte array ba in this byte array, searching forward from index position from . Returns -1 if ba could not be found.

范例:

QByteArray x("sticky question");
QByteArray 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
							

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

int QByteArray:: indexOf (const char * str , int from = 0) const

这是重载函数。

Returns the index position of the first occurrence of the string str in the byte array, searching forward from index position from . Returns -1 if str could not be found.

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

这是重载函数。

Returns the index position of the first occurrence of the character ch in the byte array, searching forward from index position from . Returns -1 if ch could not be 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 ().

int QByteArray:: indexOf (const QString & str , int from = 0) const

这是重载函数。

Returns the index position of the first occurrence of the string str in the byte array, searching forward from index position from . Returns -1 if str could not be found.

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

QByteArray &QByteArray:: insert ( int i , const QByteArray & ba )

Inserts the byte array ba at index position i and returns a reference to this byte array.

范例:

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

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

QByteArray &QByteArray:: insert ( int i , int count , char ch )

这是重载函数。

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

i is greater than size (), the array is first extended using resize ().

This function was introduced in Qt 5.7.

QByteArray &QByteArray:: insert ( int i , const char * str )

这是重载函数。

Inserts the string str 在位置 i in the byte array.

i is greater than size (), the array is first extended using resize ().

QByteArray &QByteArray:: insert ( int i , const char * str , int len )

这是重载函数。

插入 len bytes of the string str 在位置 i in the byte array.

i is greater than size (), the array is first extended using resize ().

This function was introduced in Qt 4.6.

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

这是重载函数。

Inserts character ch at index position i in the byte array. If i is greater than size (), the array is first extended using resize ().

QByteArray &QByteArray:: insert ( int i , const QString & str )

这是重载函数。

Inserts the string str at index position i in the byte array. The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

i is greater than size (), the array is first extended using resize ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

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 ().

bool QByteArray:: isLower () const

返回 true if this byte array contains only lowercase letters, otherwise returns false . The byte array is interpreted as a Latin-1 encoded string.

This function was introduced in Qt 5.12.

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 ().

bool QByteArray:: isUpper () const

返回 true if this byte array contains only uppercase letters, otherwise returns false . The byte array is interpreted as a Latin-1 encoded string.

This function was introduced in Qt 5.12.

另请参阅 isLower () 和 toUpper ().

int QByteArray:: lastIndexOf (const QByteArray & ba , int from = -1) const

Returns the index position of the last occurrence of the byte array ba in this byte array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last byte. Returns -1 if ba could not be found.

范例:

QByteArray x("crazy azimuths");
QByteArray 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
							

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

int QByteArray:: lastIndexOf (const char * str , int from = -1) const

这是重载函数。

Returns the index position of the last occurrence of the string str in the byte array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last ( size () - 1) byte. Returns -1 if str could not be found.

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

这是重载函数。

Returns the index position of the last occurrence of character ch in the byte array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last ( size () - 1) byte. Returns -1 if ch could not be 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 ().

int QByteArray:: lastIndexOf (const QString & str , int from = -1) const

这是重载函数。

Returns the index position of the last occurrence of the string str in the byte array, searching backward from index position from 。若 from is -1 (the default), the search starts at the last ( size () - 1) byte. Returns -1 if str could not be found.

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

QByteArray QByteArray:: left ( int len ) const

Returns a byte array that contains the leftmost len bytes of this byte array.

The entire byte array is returned if len is greater than size ().

范例:

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

另请参阅 startsWith (), right (), mid (), chopped (), chop (),和 truncate ().

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

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

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 ().

int QByteArray:: length () const

如同 size ().

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

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

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.

范例:

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

另请参阅 left (), right (), chopped (), chop (),和 truncate ().

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

Returns a byte array containing the string equivalent of the number n to base base (10 by default). The base can be any value between 2 and 36.

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 irrespective of the user's locale.

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 ( 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:

Format 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 irrespective of the user's locale.

另请参阅 toDouble ().

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

前置字节数组 ba 到此字节数组,并返回此字节数组的引用。

范例:

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

这如同 insert(0, ba ).

注意: QByteArray is an implicitly shared class. Consequently, if you prepend 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 prepended to is not empty, a deep copy of the data is performed, taking linear time .

另请参阅 append () 和 insert ().

QByteArray &QByteArray:: prepend ( int count , char ch )

这是重载函数。

前置 count copies of character ch 到此字节数组。

This function was introduced in Qt 5.7.

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

这是重载函数。

前置字符串 str 到此字节数组。

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

这是重载函数。

前置 len bytes of the string str 到此字节数组。

This function was introduced in Qt 4.6.

QByteArray &QByteArray:: prepend ( char ch )

这是重载函数。

前置字符 ch 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 (const char * str )

这是重载函数。

如同 append( str ).

void QByteArray:: push_back ( char ch )

这是重载函数。

如同 append( ch ).

void QByteArray:: push_front (const QByteArray & other )

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

void QByteArray:: push_front (const char * str )

这是重载函数。

如同 prepend( str ).

void QByteArray:: push_front ( char ch )

这是重载函数。

如同 prepend( ch ).

QByteArray::reverse_iterator QByteArray:: rbegin ()

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

This function was introduced in Qt 5.6.

另请参阅 begin (), crbegin (),和 rend ().

QByteArray::const_reverse_iterator QByteArray:: rbegin () const

这是重载函数。

This function was introduced in Qt 5.6.

QByteArray &QByteArray:: remove ( int pos , int 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"
							

另请参阅 insert () 和 replace ().

QByteArray::reverse_iterator QByteArray:: rend ()

返回 STL-style reverse iterator pointing to one past the last character in the byte-array, in reverse order.

This function was introduced in Qt 5.6.

另请参阅 end (), crend (),和 rbegin ().

QByteArray::const_reverse_iterator QByteArray:: rend () const

这是重载函数。

This function was introduced in Qt 5.6.

QByteArray QByteArray:: repeated ( int 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"
							

This function was introduced in Qt 4.5.

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

这是重载函数。

替换 len bytes from index position pos with alen bytes from the string after . after is allowed to have '\0' characters.

This function was introduced in Qt 4.7.

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

这是重载函数。

替换 len bytes from index position pos with the zero terminated string after .

Notice: this can change the length of the byte array.

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

这是重载函数。

Replaces every occurrence of the character before with the string after .

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

这是重载函数。

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

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

这是重载函数。

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

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

这是重载函数。

Replaces every occurrence of the string before with the string after . Since the sizes of the strings are given by bsize and asize , they may contain zero characters and do not need to be zero-terminated.

QByteArray &QByteArray:: replace (const QByteArray & before , const QByteArray & 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"
							

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

这是重载函数。

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

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

这是重载函数。

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

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

这是重载函数。

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

QByteArray &QByteArray:: replace (const QString & before , const char * after )

这是重载函数。

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

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

这是重载函数。

Replaces every occurrence of the character before with the string after . The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

QByteArray &QByteArray:: replace (const QString & before , const QByteArray & after )

这是重载函数。

Replaces every occurrence of the string before with the byte array after . The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

void QByteArray:: reserve ( int size )

Attempts to allocate memory for at least size bytes. 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 size is an underestimate, the worst that will happen is that the QByteArray will be a bit slower.

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 change the size of the byte array, call resize ().

另请参阅 squeeze () 和 capacity ().

void QByteArray:: resize ( int size )

Sets the size of the byte array to 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 are removed from the end.

另请参阅 size () 和 truncate ().

Returns a byte array that contains the rightmost len bytes of this byte array.

The entire byte array is returned if len is greater than size ().

范例:

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

另请参阅 endsWith (), left (), mid (), chopped (), chop (),和 truncate ().

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

Returns a byte array of size width that contains the fill character 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 (10 by default) and returns a reference to the byte array. The base can be any value between 2 and 36. For bases other than 10, 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 irrespective of the user's locale.

另请参阅 number () 和 toInt ().

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

这是重载函数。

另请参阅 toUShort ().

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

这是重载函数。

另请参阅 toShort ().

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

这是重载函数。

另请参阅 toUInt ().

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 irrespective of the user's locale.

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:

Format 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 irrespective of the user's locale.

另请参阅 toDouble ().

QByteArray &QByteArray:: setRawData (const char * data , uint 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.

This function was introduced in Qt 4.7.

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

void QByteArray:: shrink_to_fit ()

此函数是为兼容 STL 而提供的。它相当于 squeeze ().

This function was introduced in Qt 5.10.

QByteArray QByteArray:: simplified () const

Returns a byte array that has whitespace removed from the start and the end, and which has each sequence of internal whitespace replaced with a single space.

Whitespace means any character for which the standard C++ isspace() function returns true in the C locale. This includes the ASCII isspace() function returns true in the C locale. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.

范例:

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

另请参阅 trimmed ().

int 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 null-termination character then QByteArray doesn't add it automaticall unless the deep copy is created.

范例:

QByteArray ba("Hello");
int 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 ().

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 ().

bool QByteArray:: startsWith (const QByteArray & ba ) const

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

范例:

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

另请参阅 endsWith () 和 left ().

bool QByteArray:: startsWith ( char ch ) const

这是重载函数。

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

bool QByteArray:: startsWith (const char * str ) const

这是重载函数。

返回 true if this byte array starts with string str ;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.

This function was introduced in Qt 4.8.

QByteArray QByteArray:: toBase64 () const

Returns a copy of the byte array, encoded as Base64.

QByteArray text("Qt is great!");
text.toBase64();        // returns "UXQgaXMgZ3JlYXQh"
							

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

另请参阅 fromBase64 ().

QByteArray QByteArray:: toBase64 ( QByteArray::Base64Options options ) const

这是重载函数。

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

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 .

This function was introduced in Qt 5.2.

另请参阅 fromBase64 ().

CFDataRef QByteArray:: toCFData () const

创建 CFData 从 QByteArray . The caller owns the CFData object and is responsible for releasing it.

This function was introduced in Qt 5.3.

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

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

Returns the byte array converted to a double value.

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, irrespective of the user's locale.

This function ignores leading and trailing whitespace.

另请参阅 number ().

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

Returns the byte array converted to a float value.

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, irrespective of the user's locale.

This function ignores leading and trailing whitespace.

另请参阅 number ().

QByteArray QByteArray:: toHex () const

Returns a hex encoded copy of the byte array. The hex encoding uses the numbers 0-9 and the letters a-f.

另请参阅 fromHex ().

QByteArray QByteArray:: toHex ( char separator ) const

这是重载函数。

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"
							

This function was introduced in Qt 5.9.

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 10 by default and must be between 2 and 36, or 0.

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; 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 .

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, irrespective of the user's locale.

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 10 by default and must be between 2 and 36, or 0.

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; 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 .

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, irrespective of the user's locale.

This function was introduced in Qt 4.1.

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 10 by default and must be between 2 and 36, or 0.

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; 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, irrespective of the user's locale.

另请参阅 number ().

QByteArray QByteArray:: toLower () const

Returns a lowercase copy of the byte array. The bytearray is interpreted as a Latin-1 encoded string.

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 8 位字符比较 .

NSData *QByteArray:: toNSData () const

创建 NSData 从 QByteArray . The NSData object is autoreleased.

This function was introduced in Qt 5.3.

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 characters that are not one of the following:

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

To prevent characters from being encoded pass them to exclude . To force characters 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.

This function was introduced in Qt 4.4.

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

CFDataRef QByteArray:: toRawCFData () const

Constructs a CFData that uses the bytes of the QByteArray .

QByteArray 的字节不被拷贝。

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

This function was introduced in Qt 5.3.

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

NSData *QByteArray:: toRawNSData () const

Constructs a NSData that uses the bytes of the QByteArray .

QByteArray 的字节不被拷贝。

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

This function was introduced in Qt 5.3.

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 10 by default and must be between 2 and 36, or 0.

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; 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, irrespective of the user's locale.

另请参阅 number ().

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.

This function was introduced in Qt 5.4.

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 10 by default and must be between 2 and 36, or 0.

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; 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, irrespective of the user's locale.

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 10 by default and must be between 2 and 36, or 0.

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; 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, irrespective of the user's locale.

This function was introduced in Qt 4.1.

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 10 by default and must be between 2 and 36, or 0.

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; 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, irrespective of the user's locale.

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 10 by default and must be between 2 and 36, or 0.

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; 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, irrespective of the user's locale.

另请参阅 number ().

QByteArray QByteArray:: toUpper () const

Returns an uppercase copy of the byte array. The bytearray is interpreted as a Latin-1 encoded string.

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 8 位字符比较 .

QByteArray QByteArray:: trimmed () const

Returns a byte array that has whitespace removed from the start and the end.

Whitespace means any character for which the standard C++ isspace() function returns true in the C locale. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.

范例:

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

不像 simplified (), trimmed() leaves internal whitespace alone.

另请参阅 simplified ().

void QByteArray:: truncate ( int 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 left ().

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

返回 true if this byte array is not equal to string str ;否则返回 false .

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

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 )

Appends the byte array 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 is an implicitly shared 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+= (const char * str )

这是重载函数。

Appends the string str onto the end of this byte array and returns a reference to this byte array.

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

这是重载函数。

Appends the character ch onto the end of this byte array and returns a reference to this byte array.

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

这是重载函数。

Appends the string str onto the end of this byte array and returns a reference to this byte array. The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

You can disable this function by defining QT_NO_CAST_TO_ASCII when you compile your applications. You then need to call QString::toUtf8 () (or QString::toLatin1 () 或 QString::toLocal8Bit ()) explicitly if you want to convert the data to const char * .

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

返回 true if this byte array is lexically less than string str ;否则返回 false .

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

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 string str ;否则返回 false .

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

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 & other )

赋值 other 到此字节数组,并返回此字节数组的引用。

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

这是重载函数。

赋值 str 到此字节数组。

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

移动赋值 other 到此 QByteArray 实例。

This function was introduced in Qt 5.2.

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

返回 true if this byte array is equal to string str ;否则返回 false .

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

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 string str ;否则返回 false .

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

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 string str ;否则返回 false .

The Unicode data is converted into 8-bit characters using QString::toUtf8 ().

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.

QByteRef QByteArray:: operator[] ( int i )

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

If an assignment is made beyond the end of the byte array, the array is extended with resize () before the assignment takes place.

范例:

QByteArray ba;
for (int i = 0; i < 10; ++i)
    ba[i] = 'A' + i;
// ba == "ABCDEFGHIJ"
							

The return value is of type QByteRef, a helper class for QByteArray . When you get an object of type QByteRef, you can use it as if it were a char &. If you assign to it, the assignment will apply to the character in the QByteArray from which you got the reference.

另请参阅 at ().

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

这是重载函数。

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

这是重载函数。

如同 at( i ).

QByteRef QByteArray:: operator[] ( uint i )

这是重载函数。

相关非成员

quint16 qChecksum (const char * data , uint len )

Returns the CRC-16 checksum of the first len bytes of data .

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

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

quint16 qChecksum (const char * data , uint len , Qt::ChecksumType standard )

Returns the CRC-16 checksum of the first len bytes of data .

The checksum is independent of the byte order (endianness) and will be calculated accorded to the algorithm published in standard .

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

This function was introduced in Qt 5.9.

QByteArray qCompress (const uchar * data , int 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 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 ().

QByteArray qUncompress (const uchar * data , int nbytes )

这是重载函数。

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

QByteArray qUncompress (const QByteArray & data )

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

返回空 QByteArray 若输入数据损坏。

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 ().

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

A portable snprintf() function, calls qvsnprintf.

fmt is the 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。

Compares str1 and str2 . Returns a negative value if str1 is less than str2 , 0 if str1 is equal to str2 or a positive value if str1 is greater than str2 .

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns an arbitrary non-zero value if str1 is nullptr or str2 is nullptr (but not both).

另请参阅 qstrncmp (), qstricmp (), qstrnicmp (), 8 位字符比较 ,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。

Compares str1 and str2 ignoring the case of the characters. The encoding of the strings is assumed to be Latin-1.

Returns a negative value if str1 is less than str2 , 0 if str1 is equal to str2 or a positive value if str1 is greater than str2 .

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns a random non-zero value if str1 is nullptr or str2 is nullptr (but not both).

另请参阅 qstrcmp (), qstrncmp (), qstrnicmp (), 8 位字符比较 ,和 QByteArray::compare ().

uint 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 , uint len )

安全 strncmp() 函数。

Compares at most len bytes of str1 and str2 .

Returns a negative value if str1 is less than str2 , 0 if str1 is equal to str2 or a positive value if str1 is greater than str2 .

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns a random non-zero value if str1 is nullptr or str2 is nullptr (but not both).

另请参阅 qstrcmp (), qstricmp (), qstrnicmp (), 8 位字符比较 ,和 QByteArray::compare ().

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

安全 strncpy() 函数。

Copies at most 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.

注意: When compiling with Visual C++ compiler version 14.00 (Visual C++ 2005) or later, internally the function strncpy_s will be used.

另请参阅 qstrcpy ().

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

安全 strnicmp() 函数。

Compares at most len bytes of str1 and str2 ignoring the case of the characters. The encoding of the strings is assumed to be Latin-1.

Returns a negative value if str1 is less than str2 , 0 if str1 is equal to str2 or a positive value if str1 is greater than str2 .

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns a random non-zero value if str1 is nullptr or str2 is nullptr (but not both).

另请参阅 qstrcmp (), qstrncmp (), qstricmp (), 8 位字符比较 ,和 QByteArray::compare ().

uint qstrnlen (const char * str , uint 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.

This function was introduced in Qt 4.2.

另请参阅 qstrlen ().

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

A portable vsnprintf() function. Will call ::vsnprintf() , ::_vsnprintf() ,或 ::vsnprintf_s depending on the system, or fall back to an internal version.

fmt is the 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 不等于字符串 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 若字符串 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 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 character 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 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 character 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 词汇上小于字符串 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 若字符串 a1 词汇上小于字节数组 a2 ;否则返回 false .

另请参阅 QByteArray::compare ().

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

另请参阅 QByteArray::compare ().

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

另请参阅 QByteArray::compare ().

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

另请参阅 QByteArray::compare ().

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 .