C实现urlencode&urldecode

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 ;
}



//解url编码实现

unsigned char* urldecode(unsigned char* encd,unsigned char* decd)
{
    int j,i;
    char *cd = encd;
    char p[2];
    unsigned int num;
j=0;

    for( i = 0; i < strlen(cd); i++ )
    {
        memset( p, '/0', 2 );
        if( cd[i] != '%' )
        {
            decd[j++] = cd[i];
            continue;
        }
 
  p[0] = cd[++i];
        p[1] = cd[++i];

        p[0] = p[0] - 48 - ((p[0] >= 'A') ? 7 : 0) - ((p[0] >= 'a') ? 32 : 0);
        p[1] = p[1] - 48 - ((p[1] >= 'A') ? 7 : 0) - ((p[1] >= 'a') ? 32 : 0);
        decd[j++] = (unsigned char)(p[0] * 16 + p[1]);
 
    }
    decd[j] = '/0';

    return decd;
}