Qt入门-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[0] = '1';
	s[1] = '2';
	s[2] = '3';
	s[3] = '\0';
	s[4] = 'a';

	cout << s << endl;

屏幕打印的是：“123 a”