text: /*------------------------------------------------------------------
   * memcmp_s.c - Compares memory
   *
   * October 2008, Bo Berry
   *
   * Copyright (c) 2008-2011 Cisco Systems
   * All rights reserved.
   *
   * Permission is hereby granted, free of charge, to any person
   * obtaining a copy of this software and associated documentation
   * files (the "Software"), to deal in the Software without
   * restriction, including without limitation the rights to use,
   * copy, modify, merge, publish, distribute, sublicense, and/or
   * sell copies of the Software, and to permit persons to whom the
   * Software is furnished to do so, subject to the following
   * conditions:
   *
   * The above copyright notice and this permission notice shall be
   * included in all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
   * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
   * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
   * OTHER DEALINGS IN THE SOFTWARE.
   *------------------------------------------------------------------
   */
  
  #include "safeclib_private.h"
  #include "safe_mem_constraint.h"
  #include "safe_mem_lib.h"
  
  
  /**
   * NAME
   *    memcmp_s
   *
   * SYNOPSIS
   *    #include "safe_mem_lib.h"
   *    errno_t
   *    memcmp_s(const void *dest, rsize_t dmax,
   *             const void *src,  rsize_t smax, int *diff)
   *
   * DESCRIPTION
   *    Compares memory until they differ, and their difference is
   *    returned in diff.  If the block of memory is the same, diff=0.
   *
   * EXTENSION TO
   *    ISO/IEC JTC1 SC22 WG14 N1172, Programming languages, environments
   *    and system software interfaces, Extensions to the C Library,
   *    Part I: Bounds-checking interfaces
   *
   * INPUT PARAMETERS
   *    dest      pointer to memory to compare against
   *
   *    dmax      maximum length of dest, in bytess
   *
   *    src       pointer to the source memory to compare with dest
   *
   *    smax      length of the source memory block
   *
   *    *diff     pointer to the diff which is an integer greater
   *              than, equal to or less than zero according to
   *              whether the object pointed to by dest is
   *              greater than, equal to or less than the object
   *              pointed to by src.
   *
   *  OUTPUT PARAMETERS
   *    none
   *
   * RUNTIME CONSTRAINTS
   *    Neither dest nor src shall be a null pointer.
   *    Neither dmax nor smax shall be zero.
   *    dmax shall not be greater than RSIZE_MAX_MEM.
   *    smax shall not be greater than dmax.
   *
   * RETURN VALUE
   *    EOK        successful operation
   *    ESNULLP    NULL pointer
   *    ESZEROL    zero length
   *    ESLEMAX    length exceeds max limit
   *
   * ALSO SEE
   *    memcmp16_s(), memcmp32_s()
   *
   */
  errno_t
  memcmp_s (const void *dest, rsize_t dmax,
            const void *src,  rsize_t smax, int *diff)
  {
      const uint8_t *dp;
      const uint8_t *sp;
  
      dp = dest;
      sp = src;
  
      /*
       * must be able to return the diff
       */
      if (diff == NULL) {
          invoke_safe_mem_constraint_handler("memcmp_s: diff is null",
                     NULL, ESNULLP);
          return (RCNEGATE(ESNULLP));
      }
      *diff = -1;  /* default diff */
  
      if (dp == NULL) {
          invoke_safe_mem_constraint_handler("memcmp_s: dest is null",
                     NULL, ESNULLP);
          return (RCNEGATE(ESNULLP));
      }
  
      if (sp == NULL) {
          invoke_safe_mem_constraint_handler("memcmp_s: src is null",
                     NULL, ESNULLP);
          return (RCNEGATE(ESNULLP));
      }
  
      if (dmax == 0) {
          invoke_safe_mem_constraint_handler("memcmp_s: dmax is 0",
                     NULL, ESZEROL);
          return (RCNEGATE(ESZEROL));
      }
  
      if (dmax > RSIZE_MAX_MEM) {
          invoke_safe_mem_constraint_handler("memcmp_s: dmax exceeds max",
                     NULL, ESLEMAX);
          return (RCNEGATE(ESLEMAX));
      }
  
      if (smax == 0) {
          invoke_safe_mem_constraint_handler("memcmp_s: smax is 0",
                     NULL, ESZEROL);
          return (RCNEGATE(ESZEROL));
      }
  
      if (smax > dmax) {
          invoke_safe_mem_constraint_handler("memcmp_s: smax exceeds dmax",
                     NULL, ESLEMAX);
          return (RCNEGATE(ESLEMAX));
      }
  
      /*
       * no need to compare the same memory
       */
      if (dp == sp) {
          *diff = 0;
          return (RCNEGATE(EOK));
      }
  
      /*
       * now compare sp to dp
       */
      *diff = 0;
      while (dmax > 0 && smax > 0) {
          if (*dp != *sp) {
              /***  *diff = *dp - *sp; ***/
              *diff = *dp < *sp ? -1 : 1;
              break;
          }
  
          dmax--;
          smax--;
  
          dp++;
          sp++;
      }
  
      return (RCNEGATE(EOK));
  }
  EXPORT_SYMBOL(memcmp_s)
  