74 lines
1.8 KiB
C
74 lines
1.8 KiB
C
/*
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* strstr.c --
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*
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* Source code for the "strstr" library routine.
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*
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* Copyright 1988-1991 Regents of the University of California
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* Permission to use, copy, modify, and distribute this
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* software and its documentation for any purpose and without
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* fee is hereby granted, provided that the above copyright
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* notice appears in all copies. The University of California
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* makes no representations about the suitability of this
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* software for any purpose. It is provided "as is" without
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* express or implied warranty.
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*/
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#ifndef lint
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static char rcsid[] = "$Header$ SPRITE (Berkeley)";
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#endif /* not lint */
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/*
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*----------------------------------------------------------------------
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*
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* strstr --
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*
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* Locate the first instance of a substring in a string.
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*
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* Results:
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* If string contains substring, the return value is the
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* location of the first matching instance of substring
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* in string. If string doesn't contain substring, the
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* return value is 0. Matching is done on an exact
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* character-for-character basis with no wildcards or special
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* characters.
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*
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* Side effects:
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* None.
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*
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*----------------------------------------------------------------------
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*/
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char *
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strstr(string, substring)
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register char *string; /* String to search. */
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char *substring; /* Substring to try to find in string. */
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{
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register char *a, *b;
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/* First scan quickly through the two strings looking for a
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* single-character match. When it's found, then compare the
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* rest of the substring.
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*/
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b = substring;
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if (*b == 0) {
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return string;
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}
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for ( ; *string != 0; string += 1) {
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if (*string != *b) {
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continue;
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}
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a = string;
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while (1) {
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if (*b == 0) {
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return string;
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}
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if (*a++ != *b++) {
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break;
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}
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}
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b = substring;
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}
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return (char *) 0;
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}
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