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memstr - Dustfly的专栏 - 博客频道 - CSDN.NET

memstr

2011-04-01 12:45 1009人阅读 评论(0) 收藏 举报

libraryincludestringsearchcblog

好长时间没有写过Blog了，呵呵

在glibc里面有memchr,却没有memstr,发个memstr出来：

 

/* Return the offset of one string within another.
   Copyright (C) 1994,1996,1997,2000,2001,2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */


#if HAVE_CONFIG_H
# include <config.h>
#endif

#if defined _LIBC || defined HAVE_STRING_H
# include <string.h>
#endif

typedef unsigned chartype;

#undef memstr

/*
 memstr -- search string in memory range, by sunline lisunlin0@yahoo.com.cn
 memstr rewrite from strstr in glibc, which implement by
 Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
char *
memstr (phaystack, pend, pneedle)
     const char *phaystack;
    const char *pend;
     const char *pneedle;
{
  const unsigned char *haystack, *needle, *end;
  chartype b;
  const unsigned char *rneedle;

  haystack = (const unsigned char *) phaystack;
  end = pend - 1;

  if ((b = *(needle = (const unsigned char *) pneedle)))
    {
      chartype c;
      haystack--;        /* possible ANSI violation */

      {
    do
      if (++haystack >= end)
        goto ret0;
    while (*haystack != b);
      }

      if (!(c = *++needle))
    goto foundneedle;
      ++needle;
      goto jin;

      for (;;)
    {
      {
        chartype a;
        if (0)
        jin:{
        if ((a = *++haystack) == c)
          goto crest;
          }
        else
          a = *++haystack;
        do
          {
        for (; a != b; a = *++haystack)
          {
            if (haystack >= end)
              goto ret0;
            if ((a = *++haystack) == b)
              break;
            if (haystack >= end)
              goto ret0;
          }
          }
        while ((a = *++haystack) != c);
      }
    crest:
      {
        chartype a;
        {
          const unsigned char *rhaystack;
          if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
        do
          {
            if (!a)
              goto foundneedle;
            if (*++rhaystack != (a = *++needle))
              break;
            if (!a)
              goto foundneedle;
          }
        while (*++rhaystack == (a = *++needle));
          needle = rneedle;    /* took the register-poor aproach */
        }
        if (!a)
          break;
      }
    }
    }
foundneedle:
  return (char *) haystack;
ret0:
  return 0;
}
//libc_hidden_builtin_def (memstr)