Rev | Line | |
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[25] | 1 | /* |
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| 2 | * strstr.c -- |
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| 3 | * |
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| 4 | * Source code for the "strstr" library routine. |
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| 5 | * |
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| 6 | * Copyright (c) 1988-1993 The Regents of the University of California. |
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| 7 | * Copyright (c) 1994 Sun Microsystems, Inc. |
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| 8 | * |
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| 9 | * See the file "license.terms" for information on usage and redistribution of |
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| 10 | * this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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| 11 | * |
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| 12 | * RCS: @(#) $Id: strstr.c,v 1.7 2007/04/16 13:36:34 dkf Exp $ |
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| 13 | */ |
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| 14 | |
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| 15 | #include "tcl.h" |
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| 16 | #ifndef NULL |
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| 17 | #define NULL 0 |
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| 18 | #endif |
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| 19 | |
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| 20 | /* |
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| 21 | *---------------------------------------------------------------------- |
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| 22 | * |
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| 23 | * strstr -- |
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| 24 | * |
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| 25 | * Locate the first instance of a substring in a string. |
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| 26 | * |
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| 27 | * Results: |
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| 28 | * If string contains substring, the return value is the location of the |
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| 29 | * first matching instance of substring in string. If string doesn't |
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| 30 | * contain substring, the return value is 0. Matching is done on an exact |
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| 31 | * character-for-character basis with no wildcards or special characters. |
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| 32 | * |
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| 33 | * Side effects: |
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| 34 | * None. |
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| 35 | * |
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| 36 | *---------------------------------------------------------------------- |
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| 37 | */ |
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| 38 | |
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| 39 | char * |
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| 40 | strstr( |
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| 41 | register char *string, /* String to search. */ |
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| 42 | char *substring) /* Substring to try to find in string. */ |
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| 43 | { |
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| 44 | register char *a, *b; |
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| 45 | |
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| 46 | /* |
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| 47 | * First scan quickly through the two strings looking for a |
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| 48 | * single-character match. When it's found, then compare the rest of the |
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| 49 | * substring. |
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| 50 | */ |
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| 51 | |
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| 52 | b = substring; |
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| 53 | if (*b == 0) { |
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| 54 | return string; |
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| 55 | } |
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| 56 | for ( ; *string != 0; string += 1) { |
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| 57 | if (*string != *b) { |
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| 58 | continue; |
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| 59 | } |
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| 60 | a = string; |
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| 61 | while (1) { |
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| 62 | if (*b == 0) { |
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| 63 | return string; |
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| 64 | } |
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| 65 | if (*a++ != *b++) { |
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| 66 | break; |
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| 67 | } |
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| 68 | } |
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| 69 | b = substring; |
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| 70 | } |
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| 71 | return NULL; |
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| 72 | } |
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