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3rdparty/c-ares-1.18.1/src/lib/bitncmp.c 1.59 KB
73ef4ff3   Hu Chunming   提交三方库
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  /*
   * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   * Copyright (c) 1996,1999 by Internet Software Consortium.
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
   * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #ifndef HAVE_BITNCMP
  
  #include "ares_setup.h"
  #include "bitncmp.h"
  
  /*
   * int
   * bitncmp(l, r, n)
   *	compare bit masks l and r, for n bits.
   * return:
   *	<0, >0, or 0 in the libc tradition.
   * note:
   *	network byte order assumed.  this means 192.5.5.240/28 has
   *	0x11110000 in its fourth octet.
   * author:
   *	Paul Vixie (ISC), June 1996
   */
  int ares__bitncmp(const void *l, const void *r, int n)
  {
    unsigned int lb, rb;
    int x, b;
  
    b = n / 8;
    x = memcmp(l, r, b);
    if (x || (n % 8) == 0)
      return (x);
  
    lb = ((const unsigned char *)l)[b];
    rb = ((const unsigned char *)r)[b];
    for (b = n % 8; b > 0; b--) {
      if ((lb & 0x80) != (rb & 0x80)) {
        if (lb & 0x80)
          return (1);
        return (-1);
      }
      lb <<= 1;
      rb <<= 1;
    }
    return (0);
  }
  #endif