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-rw-r--r--string/strstr.c123
1 files changed, 123 insertions, 0 deletions
diff --git a/string/strstr.c b/string/strstr.c
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+++ b/string/strstr.c
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+/* Return the offset of one string within another.
+ Copyright (C) 1994,1996,1997,2000,2001,2003 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+/*
+ * My personal strstr() implementation that beats most other algorithms.
+ * Until someone tells me otherwise, I assume that this is the
+ * fastest implementation of strstr() in C.
+ * I deliberately chose not to comment it. You should have at least
+ * as much fun trying to understand it, as I had to write it :-).
+ *
+ * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#if defined _LIBC || defined HAVE_STRING_H
+# include <string.h>
+#endif
+
+typedef unsigned chartype;
+
+#undef strstr
+
+char *
+strstr (phaystack, pneedle)
+ const char *phaystack;
+ const char *pneedle;
+{
+ const unsigned char *haystack, *needle;
+ chartype b;
+ const unsigned char *rneedle;
+
+ haystack = (const unsigned char *) phaystack;
+
+ if ((b = *(needle = (const unsigned char *) pneedle)))
+ {
+ chartype c;
+ haystack--; /* possible ANSI violation */
+
+ {
+ chartype a;
+ do
+ if (!(a = *++haystack))
+ goto ret0;
+ while (a != b);
+ }
+
+ if (!(c = *++needle))
+ goto foundneedle;
+ ++needle;
+ goto jin;
+
+ for (;;)
+ {
+ {
+ chartype a;
+ if (0)
+ jin:{
+ if ((a = *++haystack) == c)
+ goto crest;
+ }
+ else
+ a = *++haystack;
+ do
+ {
+ for (; a != b; a = *++haystack)
+ {
+ if (!a)
+ goto ret0;
+ if ((a = *++haystack) == b)
+ break;
+ if (!a)
+ goto ret0;
+ }
+ }
+ while ((a = *++haystack) != c);
+ }
+ crest:
+ {
+ chartype a;
+ {
+ const unsigned char *rhaystack;
+ if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
+ do
+ {
+ if (!a)
+ goto foundneedle;
+ if (*++rhaystack != (a = *++needle))
+ break;
+ if (!a)
+ goto foundneedle;
+ }
+ while (*++rhaystack == (a = *++needle));
+ needle = rneedle; /* took the register-poor aproach */
+ }
+ if (!a)
+ break;
+ }
+ }
+ }
+foundneedle:
+ return (char *) haystack;
+ret0:
+ return 0;
+}
+libc_hidden_builtin_def (strstr)