71 lines
1.6 KiB
C
71 lines
1.6 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 (c) 1988-1993 The Regents of the University of California.
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* Copyright (c) 1994 Sun Microsystems, Inc.
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*
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* See the file "license.terms" for information on usage and redistribution of
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* this file, and for a DISCLAIMER OF ALL WARRANTIES.
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*/
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#include "tcl.h"
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#ifndef NULL
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#define NULL 0
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#endif
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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 location of the
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* first matching instance of substring in string. If string doesn't
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* contain substring, the return value is 0. Matching is done on an exact
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* character-for-character basis with no wildcards or special 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(
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const char *string, /* String to search. */
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const char *substring) /* Substring to try to find in string. */
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{
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const char *a, *b;
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/*
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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 rest of the
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* substring.
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*/
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b = substring;
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if (*b == 0) {
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return (char *)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 (char *)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 NULL;
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}
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