125 lines
2.7 KiB
C
125 lines
2.7 KiB
C
/* strstr - find a substring within a string */
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/* Copyright (C) 1994, 1999 Free Software Foundation, Inc.
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This file is part of GNU Bash, the Bourne Again SHell.
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Bash is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Bash 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Bash. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* My personal strstr() implementation that beats most other algorithms.
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* Until someone tells me otherwise, I assume that this is the
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* fastest implementation of strstr() in C.
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* I deliberately chose not to comment it. You should have at least
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* as much fun trying to understand it, as I had to write it :-).
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*
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* Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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#if defined _LIBC || defined HAVE_STRING_H
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# include <string.h>
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#endif
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#include <sys/types.h>
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typedef unsigned chartype;
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#undef strstr
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char *
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strstr (const char *phaystack, const char *pneedle)
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{
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register const unsigned char *haystack, *needle;
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register chartype b, c;
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haystack = (const unsigned char *) phaystack;
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needle = (const unsigned char *) pneedle;
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b = *needle;
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if (b != '\0')
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{
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haystack--; /* possible ANSI violation */
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do
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{
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c = *++haystack;
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if (c == '\0')
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goto ret0;
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}
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while (c != b);
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c = *++needle;
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if (c == '\0')
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goto foundneedle;
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++needle;
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goto jin;
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for (;;)
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{
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register chartype a;
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register const unsigned char *rhaystack, *rneedle;
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do
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{
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a = *++haystack;
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if (a == '\0')
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goto ret0;
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if (a == b)
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break;
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a = *++haystack;
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if (a == '\0')
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goto ret0;
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shloop:; }
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while (a != b);
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jin: a = *++haystack;
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if (a == '\0')
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goto ret0;
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if (a != c)
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goto shloop;
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rhaystack = haystack-- + 1;
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rneedle = needle;
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a = *rneedle;
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if (*rhaystack == a)
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do
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{
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if (a == '\0')
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goto foundneedle;
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++rhaystack;
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a = *++needle;
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if (*rhaystack != a)
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break;
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if (a == '\0')
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goto foundneedle;
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++rhaystack;
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a = *++needle;
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}
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while (*rhaystack == a);
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needle = rneedle; /* took the register-poor approach */
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if (a == '\0')
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break;
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}
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}
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foundneedle:
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return (char*) haystack;
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ret0:
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return 0;
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}
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