方法一：使用如下两个函数
mbstowcs将多字节编码转换为宽字节编码
wcstombs将宽字节编码转换为多字节编码
注意， 需要系统编码的支持， 可以通过locale -a 查看系统支持的。若不支持zh_CN.gbk, 需要安装，
#include <stdlib.h>
#include <stdio.h>#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <locale.h>
/******************************************************************************
* DESCRIPTION: 实现由utf8编码到gbk编码的转换
* Input: gbkStr,转换后的字符串;
* srcStr,待转换的字符串;
* maxGbkStrlen, gbkStr的最大长度
* Output: gbkStr
* Returns: -1,fail;>0,success
******************************************************************************/
int utf82gbk(char *gbkStr, const char *srcStr, int maxGbkStrlen)
{
if (NULL == srcStr)
{
printf("Bad Parameter\n");
return -1;
}
//首先先将utf8编码转换为unicode编码
if (NULL == setlocale(LC_ALL, "zh_CN.utf8")) //设置转换为unicode前的码,当前为utf8编码
{
printf("Bad Parameter\n");
return -1;
}
int unicodeLen = mbstowcs(NULL, srcStr, 0);
//计算转换后的长度
if (unicodeLen <= 0)
{
printf("Can not Transfer!!!\n");
return -1;
}
wchar_t *unicodeStr = (wchar_t *) calloc(sizeof(wchar_t), unicodeLen + 1);
mbstowcs(unicodeStr, srcStr, strlen(srcStr));
//将utf8转换为unicode
//将unicode编码转换为gbk编码
if (NULL == setlocale(LC_ALL, "zh_CN.gbk")) //设置unicode转换后的码,当前为gbk
{
printf("Bad Parameter\n");
return -1;
}
int gbkLen = wcstombs(NULL, unicodeStr, 0);
//计算转换后的长度
if (gbkLen <= 0)
{
printf("Can not Transfer!!!\n");
return -1;
} else if (gbkLen >= maxGbkStrlen) //判断空间是否足够
{
printf("Dst Str memory not enough\n");
return -1;
}
wcstombs(gbkStr, unicodeStr, gbkLen);
gbkStr[gbkLen] = 0; //添加结束符
free(unicodeStr);
return gbkLen;
}
/******************************************************************************
* function: gbk2utf8
* description: 实现由gbk编码到utf8编码的转换
*
* input: utfstr,转换后的字符串; srcstr,待转换的字符串; maxutfstrlen, utfstr的最大长度
* output: utfstr
* returns: -1,fail;>0,success
*
******************************************************************************/
int gbk2utf8(char *utfstr,const char *srcstr,int maxutfstrlen)
{
if(NULL==srcstr)
{
printf(" bad parameter\n");
return -1;
}
//首先先将gbk编码转换为unicode编码
if(NULL==setlocale(LC_ALL,"zh_cn.gbk"))//设置转换为unicode前的码,当前为gbk编码
{
printf("setlocale bad parameter\n");
return -1;
}
int unicodelen=mbstowcs(NULL,srcstr,0);//计算转换后的长度
if(unicodelen<=0)
{
printf("can not transfer!!!\n");
return -1;
}
wchar_t *unicodestr=(wchar_t *)calloc(sizeof(wchar_t),unicodelen+1);
mbstowcs(unicodestr,srcstr,strlen(srcstr));//将gbk转换为unicode
//将unicode编码转换为utf8编码
if(NULL==setlocale(LC_ALL,"zh_cn.utf8"))//设置unicode转换后的码,当前为utf8
{
printf("bad parameter\n");
return -1;
}
int utflen=wcstombs(NULL,unicodestr,0);//计算转换后的长度
if(utflen<=0)
{
printf("can not transfer!!!\n");
return -1;
}
else if(utflen>=maxutfstrlen)//判断空间是否足够
{
printf("dst str memory not enough\n");
return -1;
}
wcstombs(utfstr,unicodestr,utflen);
utfstr[utflen]=0;//添加结束符
free(unicodestr);
return utflen;
}
int main(void)
{
char *s = "中国";
int fd , res;
if ((fd= open("test.txt", O_WRONLY | O_CREAT | O_TRUNC,S_IREAD | S_IWRITE)) == -1)
{
printf("Error opening file.\n");
exit(1);
}
char bufgbk[10];
utf82gbk(bufgbk, s, sizeof(bufgbk));
int gbk_length = strlen(bufgbk);
if ((res = write(fd, bufgbk, gbk_length)) != gbk_length)
{
printf("Error gbk writing to the file.\n");
exit(1);
}
close(fd);
return 1;
}
方法二：使用iconv函数
#include <iconv.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
int code_convert(char *from_charset, char *to_charset, char *inbuf, size_t inlen,
char *outbuf, size_t outlen) {
iconv_t cd;
char **pin = &inbuf;
char **pout = &outbuf;
cd = iconv_open(to_charset, from_charset);
if (cd == 0)
return -1;
memset(outbuf, 0, outlen);
if (iconv(cd, pin, &inlen, pout, &outlen) == -1)
return -1;
iconv_close(cd);
*pout = '\0';
return 0;
}
int u2g(char *inbuf, size_t inlen, char *outbuf, size_t outlen) {
return code_convert("utf-8", "gb2312", inbuf, inlen, outbuf, outlen);
}
int g2u(char *inbuf, size_t inlen, char *outbuf, size_t outlen) {
return code_convert("gb2312", "utf-8", inbuf, inlen, outbuf, outlen);
}
int main(void) {
char *s = "中国";
int fd = open("test.txt", O_RDWR|O_CREAT, S_IRUSR | S_IWUSR);
char buf[10];
u2g(s, strlen(s), buf, sizeof(buf));
write(fd, buf, strlen(buf));
close(fd);
fd = open("test.txt2", O_RDWR|O_CREAT, S_IRUSR | S_IWUSR);
char buf2[10];
g2u(buf, strlen(buf), buf2, sizeof(buf2));
write(fd, buf2, strlen(buf2));
close(fd);
return 1;
}