Qt关于QByteArray类

Qt GUI API中使用Unicode类型的字符串类QString。使用Unicode的好处是可以支持更多的地区语言，ASCII是Uncode的子集。

QByteArray和QString的方法和属性相似，可以参考QString。另外有一些与QByteArray相关的非成员函数：

//Related Non-Members  

  

//计算CRC16校验和  

quint16 qChecksum ( const char * data, uint len )  

//压缩data，并返回新的值，参数compressionLevel的值是0~9  

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

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

//解压缩  

QByteArray  qUncompress ( const QByteArray & data )  

QByteArray  qUncompress ( const uchar * data, int nbytes )  

//格式化字符串  

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

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

//比较字符串  

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

//复制字符串  

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

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

//分配空间复制字符串返回  

char *  qstrdup ( const char * src )  

//忽略大小写的字符串比较  

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

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

//返回字符串的长度  

uint    qstrlen ( const char * str )  

uint    qstrnlen ( const char * str, uint maxlen )  

//固定长度内的字符串比较  

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

//相关QByteArray和const char *的运算符  

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 )  

QByteArray与QString之间的转换：

示例：

QByteArray cstr("abcd"); QString s = cstr;

QByteArray cstr("abcd"); QString s; s.prepend(cstr);

QString s("hello"); QByteArray cstr = s.toAscii();

QString s("hello"); QByteArray cstr = s.toLatin1();

QByteArray类同样不以'\0'为结尾：如

QByteArray s;  

s.resize(5);  

s = '1';  

s = '2';  

s = '3';  

s = '\0';  

s = 'a';  

  

cout << s << endl;  

屏幕打印的是：“123 a”