c - 如何使用iconv 进行utf8 转换？

Question

我想将其他编码的数据转换为 UTF-8。我遇到了以下问题:

1. 执行附加代码会得到:正在释放的指针未在 iconv() 中分配。为什么 iconv 会玩弄我的内存？
2. 当我不 free(dst) 时，它不会崩溃，但不会打印任何内容。甚至不是胡言乱语。怎么了？

---

void utf8(char **dst, char **src, const char *enc)
{
    iconv_t cd;
    size_t len_src,
           len_dst;

    len_src = strlen(*src);
    len_dst = len_src * 8; // is that enough for ASCII to UTF8?

    cd = iconv_open("UTF-8", enc);

    *dst = (char *)calloc(len_dst+1, 1);

    iconv(cd, src, &len_src, dst, &len_dst);
    iconv_close(cd);
}

int main(int argc, char **argv)
{
    char *src = "hello world";
    char *dst;

    utf8(&dst, &src, "ASCII");
    printf("%s\n", dst);

    free(dst);
    return 0;
}

Answer 1

引自 iconv() description at POSIX.1-2008

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

The variable pointed to by outbuf shall be updated to point to the byte following the last byte of converted output data.

您需要在 utf8() 函数中保存和恢复 *dst(可能还有 *src)。