url编码与解码

编码：

std::string urlencode ( char const *url )
{
    static unsigned char hexchars[] = "0123456789ABCDEF";
    register unsigned char c;
    unsigned char *to, *start;
    unsigned char const *from, *end;
    int len = strlen ( url );


    from = (unsigned char *)url;
    end = (unsigned char *)url + len;
    start = to = (unsigned char *) malloc ( 3 * len + 1 );


    while ( from < end )
    {
        c = *from++;
        if ( ' ' == c )
        {
            *to++ = '+';
#ifndef CHARSET_EBCDIC
        } 
        else if ( ( c < '0' && c != '-' && c != '.' ) 
            || ( c < 'A' && c > '9' ) 
            || ( c > 'Z' && c < 'a' && c != '_' ) 
            || ( c > 'z' ) )
        {
            to[0] = '%';
            to[1] = hexchars[c >> 4];
            to[2] = hexchars[c & 15];
            to += 3;
#else
        }
        else if ( !isalnum ( c ) && strchr ( "_-.", c ) == NULL )
        {
            to[0] = '%';
            to[1] = hexchars[os_toascii[c] >> 4];
            to[2] = hexchars[os_toascii[c] & 15];
            to += 3;
#endif
        }
        else
        {
            *to++ = c;
        }
    }


    *to = 0;


    return (char*)start;
}

解码：

static char x2c ( const char* what )
{
    register char digit;


    digit = ( ( what[0] >= 'A' ) ? ( ( what[0] & 0xdf ) - 'A' ) + 10 : ( what[0] - '0' ) );


    digit *= 16;
   
    digit += ( what[1] >= 'A' ? ( ( what[1] & 0xdf ) - 'A' ) + 10 : ( what[1] - '0' ) );


    return digit;
}


std::string urldecode ( const char* src )
{
    char* dest = (char*)malloc ( strlen ( src ) / 2 + 1 );


    char* cp = dest;


    while ( *src != '\0' )
    {
        if ( *src == '+' )
        {
            *dest++ = ' ';
        }
        else if ( *src == '%' )
        {
            int ch;
            ch = x2c ( src + 1 );
            *dest++ = ch;
            src += 2;
        }
        else
        {
            *dest++ = *src;
        }


        src++;
    }
    
    *dest = '\0';


    std::string str = cp;


    free ( cp );


    return str;
}