Mercurial > hg > octave-kai > gnulib-hg
annotate lib/strstr.c @ 4682:90abbdf08583
Assume ANSI C.
| author | Bruno Haible <bruno@clisp.org> |
|---|---|
| date | Wed, 10 Sep 2003 14:07:55 +0000 (2003-09-10) |
| parents | e34e6bd35c66 |
| children | a48fb0e98c8c |
| rev | line source |
|---|---|
| 4682 | 1 /* Copyright (C) 1994, 1999, 2002-2003 Free Software Foundation, Inc. |
| 656 | 2 This file is part of the GNU C Library. |
| 5 | 3 |
| 656 | 4 This program is free software; you can redistribute it and/or modify |
| 5 it under the terms of the GNU General Public License as published by | |
| 6 the Free Software Foundation; either version 2, or (at your option) | |
| 7 any later version. | |
| 8 | |
| 9 This program is distributed in the hope that it will be useful, | |
| 10 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 12 GNU General Public License for more details. | |
| 5 | 13 |
| 656 | 14 You should have received a copy of the GNU General Public License |
| 15 along with this program; if not, write to the Free Software | |
| 16 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ | |
| 5 | 17 |
| 656 | 18 /* |
| 19 * My personal strstr() implementation that beats most other algorithms. | |
| 20 * Until someone tells me otherwise, I assume that this is the | |
| 21 * fastest implementation of strstr() in C. | |
| 22 * I deliberately chose not to comment it. You should have at least | |
| 23 * as much fun trying to understand it, as I had to write it :-). | |
| 24 * | |
| 25 * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */ | |
| 5 | 26 |
|
2020
989f1a5c1c0c
(strstr): Include config.h.
Jim Meyering <jim@meyering.net>
parents:
1557
diff
changeset
|
27 #if HAVE_CONFIG_H |
|
989f1a5c1c0c
(strstr): Include config.h.
Jim Meyering <jim@meyering.net>
parents:
1557
diff
changeset
|
28 # include <config.h> |
|
989f1a5c1c0c
(strstr): Include config.h.
Jim Meyering <jim@meyering.net>
parents:
1557
diff
changeset
|
29 #endif |
|
989f1a5c1c0c
(strstr): Include config.h.
Jim Meyering <jim@meyering.net>
parents:
1557
diff
changeset
|
30 |
| 4682 | 31 #include <string.h> |
| 5 | 32 |
| 656 | 33 typedef unsigned chartype; |
| 5 | 34 |
| 2988 | 35 #undef strstr |
| 36 | |
| 5 | 37 char * |
| 1557 | 38 strstr (const char *phaystack, const char *pneedle) |
| 5 | 39 { |
| 656 | 40 register const unsigned char *haystack, *needle; |
| 41 register chartype b, c; | |
| 42 | |
| 43 haystack = (const unsigned char *) phaystack; | |
| 44 needle = (const unsigned char *) pneedle; | |
| 45 | |
| 46 b = *needle; | |
| 47 if (b != '\0') | |
| 48 { | |
| 49 haystack--; /* possible ANSI violation */ | |
| 50 do | |
| 51 { | |
| 52 c = *++haystack; | |
| 53 if (c == '\0') | |
| 54 goto ret0; | |
| 55 } | |
| 56 while (c != b); | |
| 57 | |
| 58 c = *++needle; | |
| 59 if (c == '\0') | |
| 60 goto foundneedle; | |
| 61 ++needle; | |
| 62 goto jin; | |
| 63 | |
| 64 for (;;) | |
| 65 { | |
| 66 register chartype a; | |
| 67 register const unsigned char *rhaystack, *rneedle; | |
| 5 | 68 |
| 656 | 69 do |
| 70 { | |
| 71 a = *++haystack; | |
| 72 if (a == '\0') | |
| 73 goto ret0; | |
| 74 if (a == b) | |
| 75 break; | |
| 76 a = *++haystack; | |
| 77 if (a == '\0') | |
| 78 goto ret0; | |
|
2020
989f1a5c1c0c
(strstr): Include config.h.
Jim Meyering <jim@meyering.net>
parents:
1557
diff
changeset
|
79 shloop:; } |
| 656 | 80 while (a != b); |
| 81 | |
| 82 jin: a = *++haystack; | |
| 83 if (a == '\0') | |
| 84 goto ret0; | |
| 85 | |
| 86 if (a != c) | |
| 87 goto shloop; | |
| 88 | |
| 89 rhaystack = haystack-- + 1; | |
| 90 rneedle = needle; | |
| 91 a = *rneedle; | |
| 92 | |
| 93 if (*rhaystack == a) | |
| 94 do | |
| 95 { | |
| 96 if (a == '\0') | |
| 97 goto foundneedle; | |
| 98 ++rhaystack; | |
| 99 a = *++needle; | |
| 100 if (*rhaystack != a) | |
| 101 break; | |
| 102 if (a == '\0') | |
| 103 goto foundneedle; | |
| 104 ++rhaystack; | |
| 105 a = *++needle; | |
| 106 } | |
| 107 while (*rhaystack == a); | |
| 108 | |
| 2988 | 109 needle = rneedle; /* took the register-poor approach */ |
| 656 | 110 |
| 111 if (a == '\0') | |
| 112 break; | |
| 113 } | |
| 5 | 114 } |
| 656 | 115 foundneedle: |
| 116 return (char*) haystack; | |
| 117 ret0: | |
| 5 | 118 return 0; |
| 119 } |