Android之NDK编码转(UTF8->GBK)

基于NDK下的编码转换，当然是直接调用C/C++下的实现效率更高，下面介绍2种方案（不建议通过JNI调用J***A的实现，尽管这样也能实现编码的转换）。
1. 采用Android系统自带的libicuuc.so库,此库的源代码在/home/george/source/rk3168_v4.2/external/icu4c/common下
2. 采用第三方编码转换库libiconv，源码链接：http://ftp.gnu.org/pub/gnu/libiconv/

libiconv的使用有3个函数:

a) iconv_t iconv_open (const char* tocode, const char* fromcode);

b) size_t iconv (iconv_t cd, const char* * inbuf , size_t * inbytesleft, char* * outbuf , size_t * outbytesleft);

inbytesleft：inbuf的字符串长度；

outbytesleft：输入为outbuf所指向的缓冲区长度，输出为剩余没用到的缓冲区长度；因此转换后的字符串长度为(outbuflen - outbytesleft)；

inbuf, outbuf：返回时指针都后移了，需要注意。

c) int iconv_close (iconv_t cd);

这里采用Android系统自带的库进行编码转换，当然也可采用第三方支持。以下贴出代码段

（gbk和Unicode的互转因为没有用到，所以未贴出，但我想你应该要会了吧）：

#include "libcnv.h"

/* use dl API include file */

#include <dlfcn.h>

/* typedef a function pointer to pointer ucnv_convert method */

/*

see the source code define

int32_t ucnv_convert(const char *toConverterName, const char *fromConverterName,

char *target, int32_t targetSize,

const char *source, int32_t sourceSize,

int32_t * err)

*/

typedef int32_t (*TUCNVCONVERT)(const char *lpcOutEcd, const char *lpcInEcd,

char* lpOutBuf, int32_t nOutBufLen,

const char* lpcInStr, int32_t nInStrLen,

int32_t *pnErrCode);

/* pointer libicuuc.so dl lib */

static void* g_lpdlIcuuc = 0;

/* ucnv_convert method pointer */

static TUCNVCONVERT g_lpfnUcnvConvert = 0;

//在libicuuc.so中找到函数ucnv_convert

int dl_icuuc_init()

{

g_lpfnUcnvConvert = 0;

g_lpdlIcuuc = dlopen("/system/lib/libicuuc.so", RTLD_LAZY);

if (g_lpdlIcuuc != 0)

{

int i, j;

char szDLFnName[32]={0};

i = 3;

j = 8;

//android2.1, ucnv_convert_3_8

//android2.2, ucnv_convert_4_2

//android2.3, ucnv_convert_44

//android4.0, ucnv_convert_46

//android4.0, ucnv_convert_46

//android4.1, ucnv_convert_47

//android4.2, ucnv_convert_48

//android4.3, ucnv_convert_50

//android4.4, ucnv_convert_51

//其尾椎在，在源码的common/unicode/uvernum.h:77: #define U_ICU_VERSION_SUFFIX _48

g_lpfnUcnvConvert = (TUCNVCONVERT)dlsym(g_lpdlIcuuc, "ucnv_convert_3_8");

while (0 == g_lpfnUcnvConvert)

{

memset(szDLFnName, 0, 32*sizeof(char));

sprintf(szDLFnName, "ucnv_convert_%d%d", i, j);

g_lpfnUcnvConvert = (TUCNVCONVERT)dlsym(g_lpdlIcuuc, szDLFnName);

if (g_lpfnUcnvConvert != 0){

return 1;

}

sprintf(szDLFnName, "ucnv_convert_%d_%d", i, j);

g_lpfnUcnvConvert = (TUCNVCONVERT)dlsym(g_lpdlIcuuc, szDLFnName);

if (g_lpfnUcnvConvert != 0){

return 1;

}

j++;

if (j > 9){

j = 1;

i++;

if (i > 5){

break;

}

}

}

}

return 0;

}

int dl_icuuc_uninit()

{

if (g_lpdlIcuuc != 0)

{

dlclose(g_lpdlIcuuc);

g_lpdlIcuuc = 0;

}

return 1;

}

//utf-8,gb2312,ucs4

//utf-8: 一个英文字母或者是数字占用一个字节，汉字占3个字节

//gb2312: 一个英文字母或者是数字占用一个字节，汉字占2个字节

int32_t dl_icuuc_gbk2utf8(char *outbuf, int32_t buflen, const char *instring, int32_t inlen)

{

int32_t iret;

iret = 0;

if (outbuf != 0 && instring != 0)

{

if (g_lpfnUcnvConvert != 0)

{

int32_t err_code = 0;

iret = g_lpfnUcnvConvert("utf-8", "gb2312"

,outbuf, buflen

,instring, inlen

,&err_code);

}

}

return iret;

}

int32_t dl_icuuc_utf82gbk(char *outbuf, int32_t buflen, const char *instring, int32_t inlen)

{

int32_t iret;

iret = 0;

if (outbuf != 0 && instring != 0)

{

if (g_lpfnUcnvConvert != 0)

{

int32_t err_code = 0;

iret = g_lpfnUcnvConvert("gb2312", "utf-8"

,outbuf, buflen

,instring, inlen

,&err_code);

}

}

return iret;

}

int32_t dl_icuuc_unicode2utf8(char *outbuf, int32_t buflen, const unsigned short *instring, int32_t inlen)

{

int32_t iret;

iret = 0;

if (outbuf != 0 && instring != 0)

{

if (g_lpfnUcnvConvert != 0)

{

int32_t err_code = 0;

iret = g_lpfnUcnvConvert("utf-8", "ucs4"

,outbuf, buflen

,(const char *)instring, inlen*sizeof(unsigned short)/sizeof(char)

,&err_code);

}

}

return iret;

}

int32_t dl_icuuc_utf82unicode(unsigned short *outbuf, int32_t buflen, const char *instring, int32_t inlen)

{

int32_t iret;

iret = 0;

if (outbuf != 0 && instring != 0)

{

if (g_lpfnUcnvConvert != 0)

{

int32_t err_code = 0;

iret = g_lpfnUcnvConvert("ucs4", "utf-8"

,(char *)outbuf, buflen*sizeof(unsigned short)/sizeof(char)

,instring, inlen

,&err_code);

}

}

return iret;

}