url编解码实现

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static unsigned char char_to_hex(unsigned char x)
{
    return (unsigned char)(x > 9 ? x + 55 : x + 48);
}

static int is_alpha_number_char(unsigned char c)
{
    if((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9'))
        return 1;
    return 0;
}

//url编码实现
void urlencode(unsigned char * src, int  src_len, unsigned char * dest, int  dest_len)
{
    unsigned char ch;
    int  len = 0;
    while(len < (dest_len - 4) && *src)
    {
        ch = (unsigned char) * src;
        if(*src == ' ')
        {
            *dest++ = '+';
        }
        else if(is_alpha_number_char(ch) || strchr("-_.!~*'()", ch))
        {
            *dest++ = *src;
        }
        else
        {
            *dest++ = '%';
            *dest++ = char_to_hex((unsigned char)(ch >> 4));
            *dest++ = char_to_hex((unsigned char)(ch % 16));
        }
        ++src;
        ++len;
    }
    *dest = 0;
    return ;
}


/**
* @param str 需要解码的url字符串
* @param len 需要解码的url的长度
* @return int 返回解码后的url长度
*/
int urldecode(char *str, int len)
{
    char *dest = str;
    char *data = str;

    int value;
    int c;

    while(len--)
    {
        if(*data == '+')
        {
            *dest = ' ';
        }
        else if(*data == '%' && len >= 2 && isxdigit((int) * (data + 1))
                && isxdigit((int) * (data + 2)))
        {

            c = ((unsigned char *)(data + 1))[0];
            if(isupper(c))
                c = tolower(c);
            value = (c >= '0' && c <= '9' ? c - '0' : c - 'a' + 10) * 16;
            c = ((unsigned char *)(data + 1))[1];
            if(isupper(c))
                c = tolower(c);
            value += c >= '0' && c <= '9' ? c - '0' : c - 'a' + 10;

            *dest = (char)value ;
            data += 2;
            len -= 2;
        }
        else
        {
            *dest = *data;
        }
        data++;
        dest++;
    }
    *dest = '\0';
    return dest - str;
}