escape.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2010, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

/* Escape and unescape URL encoding in strings. The functions return a new
 * allocated string or NULL if an error occurred.  */

#include <ctype.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* Portable character check (remember EBCDIC). Do not use isalnum() because
   its behavior is altered by the current locale.
   See http://tools.ietf.org/html/rfc3986#section-2.3
*/
static int Curl_isunreserved(unsigned char in)
{
  switch (in) {
    case '0': case '1': case '2': case '3': case '4':
    case '5': case '6': case '7': case '8': case '9':
    case 'a': case 'b': case 'c': case 'd': case 'e':
    case 'f': case 'g': case 'h': case 'i': case 'j':
    case 'k': case 'l': case 'm': case 'n': case 'o':
    case 'p': case 'q': case 'r': case 's': case 't':
    case 'u': case 'v': case 'w': case 'x': case 'y': case 'z':
    case 'A': case 'B': case 'C': case 'D': case 'E':
    case 'F': case 'G': case 'H': case 'I': case 'J':
    case 'K': case 'L': case 'M': case 'N': case 'O':
    case 'P': case 'Q': case 'R': case 'S': case 'T':
    case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z':
    case '-': case '.': case '_': case '~':
      return 1;
    default:
      break;
  }
  return 0;
}

char *uri_escape(const char *string, int inlength)
{
  size_t alloc = (inlength?(size_t)inlength:strlen(string))+1;
  char *ns;
  char *testing_ptr = NULL;
  unsigned char in; /* we need to treat the characters unsigned */
  size_t newlen = alloc;
  int strindex=0;
  size_t length;

  ns = malloc(alloc);
  if(!ns)
    return NULL;

  length = alloc-1;
  while(length--) {
    in = *string;

    if (Curl_isunreserved(in)) {
      /* just copy this */
      ns[strindex++]=in;
    }
    else {
      /* encode it */
      newlen += 2; /* the size grows with two, since this'll become a %XX */
      if(newlen > alloc) {
        alloc *= 2;
        testing_ptr = realloc(ns, alloc);
        if(!testing_ptr) {
          free( ns );
          return NULL;
        }
        else {
          ns = testing_ptr;
        }
      }

      snprintf(&ns[strindex], 4, "%%%02X", in);

      strindex+=3;
    }
    string++;
  }
  ns[strindex]=0; /* terminate it */
  return ns;
}

#define ISXDIGIT(x) (isxdigit((int) ((unsigned char)x)))
#define CURL_MASK_UCHAR  0xFF

/*
** unsigned long to unsigned char
*/

unsigned char curlx_ultouc(unsigned long ulnum)
{
#ifdef __INTEL_COMPILER
#  pragma warning(push)
#  pragma warning(disable:810) /* conversion may lose significant bits */
#endif

  return (unsigned char)(ulnum & (unsigned long) CURL_MASK_UCHAR);

#ifdef __INTEL_COMPILER
#  pragma warning(pop)
#endif
}

char *uri_unescape(const char *string, int length)
{
  int alloc = (length?length:(int)strlen(string))+1;
  char *ns = malloc(alloc);
  unsigned char in;
  int strindex=0;
  unsigned long hex;

  if( !ns )
    return NULL;

  while(--alloc > 0) {
    in = *string;
    if(('%' == in) && ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
      /* this is two hexadecimal digits following a '%' */
      char hexstr[3];
      char *ptr;
      hexstr[0] = string[1];
      hexstr[1] = string[2];
      hexstr[2] = 0;

      hex = strtoul(hexstr, &ptr, 16);

      in = curlx_ultouc(hex); /* this long is never bigger than 255 anyway */

#ifdef CURL_DOES_CONVERSIONS
/* escape sequences are always in ASCII so convert them on non-ASCII hosts */
      if(!handle ||
          (Curl_convert_from_network(handle, &in, 1) != CURLE_OK)) {
        /* Curl_convert_from_network calls failf if unsuccessful */
        free(ns);
        return NULL;
      }
#endif /* CURL_DOES_CONVERSIONS */

      string+=2;
      alloc-=2;
    }

    ns[strindex++] = in;
    string++;
  }
  ns[strindex]=0; /* terminate it */

  return ns;
}