57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
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/* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <ansidecl.h>
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#include <stddef.h>
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#include <string.h>
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/* Return the first ocurrence of NEEDLE in HAYSTACK. */
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char *
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DEFUN(strstr, (haystack, needle),
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CONST char *CONST haystack AND
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CONST char *CONST needle)
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{
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register CONST char *CONST needle_end = strchr(needle, '\0');
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register CONST char *CONST haystack_end = strchr(haystack, '\0');
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register CONST size_t needle_len = needle_end - needle;
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register CONST size_t needle_last = needle_len - 1;
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register CONST char *begin;
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if (needle_len == 0)
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return (char *) haystack; /* ANSI 4.11.5.7, line 25. */
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if ((size_t) (haystack_end - haystack) < needle_len)
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return NULL;
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for (begin = &haystack[needle_last]; begin < haystack_end; ++begin)
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{
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register CONST char *n = &needle[needle_last];
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register CONST char *h = begin;
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do
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if (*h != *n)
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goto loop; /* continue for loop */
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while (--n >= needle && --h >= haystack);
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return (char *) h;
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loop:;
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}
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return NULL;
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}
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