JNI字符集的转换

写Java JNI的时候最头痛的莫过于字符集的转换问题，众所周知，Java里字符串是以Unicode编码存储的，而C/C++里大部分是单字节处理，这就涉及到一个转换的问题，下面是两个函数用来在JString到Char*之间的转换：

//author Naven 2003 for both Win32 and Unix os

//为了便于使用，无需另连接库，Win32里需自己写双字节memset函数

#ifdefined(_WIN32) || defined(__WIN32__)

wchar_t *mywmemset(wchar_t *_S, wchar_t _C, size_t _N)

{

wchar_t *_Su = _S;

for (; 0 < _N; ++_Su, --_N)

*_Su = _C;

return (_S);

}

#endif

//将Java里jstring类型转换成单字节字符串

size_t JStringToChars(JNIEnv *env,

const jstring jstr, char *mbstr, const size_t mbslen)

{

const jchar *jwstr;

wchar_t *wbuf=0;

size_t nsize=0;

jsize jlen=0;

register int i=0;

memset(mbstr, 0, mbslen);

if( jstr == NULL ) return 0;

jwstr = (*env)->GetStringChars(env, jstr, 0);

jlen = (*env)->GetStringLength(env, jstr);

if( jlen <= 0 ) return 0;

#ifdefined(_WIN32) || defined(__WIN32__)

wbuf = (wchar_t *) jwstr;

nsize = wcstombs(mbstr, wbuf, mbslen-1);

#else

wbuf = (wchar_t *) malloc((jlen+1)*sizeof(wchar_t));

mywmemset(wbuf, (wchar_t)0, (size_t)(jlen+1));

for( i = 0; i < jlen; i ++ )

wbuf[i] = (wchar_t)jwstr[i];

nsize = wcstombs(mbstr, wbuf, mbslen-1);

free(wbuf);

#endif

if( nsize >= 0 && nsize < mbslen )

mbstr[nsize] = 0;

return nsize;

}

//将单字节字符串转换成Java里可使用的jstring类型

size_t CharsToJString(JNIEnv *env,

const char *mbstr, jstring *jstr)

{

jchar *jwstr=0;

wchar_t *wcstr=0;

size_t slen=0, nsize=0;

register int i=0;

if( mbstr != NULL )

slen = strlen(mbstr);

if( mbstr == NULL || slen <= 0 ) {

*jstr = (*env)->NewStringUTF(env, "");

return 0;

}

wcstr = (wchar_t *) malloc((slen+1)*sizeof(wchar_t));

mywmemset(wcstr, 0, slen+1);

nsize = mbstowcs(wcstr, mbstr, slen*2);

jwstr = (jchar *) wcstr;

#ifdefined(_WIN32) || defined(__WIN32__)

#else

for(i =0; i < (int)nsize; i ++) {

jwstr[i] = jwstr[i*2];

}

jwstr[nsize] = 0;

#endif

if( nsize <= 0 )

*jstr = (*env)->NewStringUTF(env, "");

else

*jstr = (*env)->NewString(env, jwstr, nsize);

free(wcstr);

return nsize;

}