summaryrefslogtreecommitdiffstats
path: root/lib/sh/strstr.c
diff options
context:
space:
mode:
Diffstat (limited to 'lib/sh/strstr.c')
-rw-r--r--lib/sh/strstr.c125
1 files changed, 125 insertions, 0 deletions
diff --git a/lib/sh/strstr.c b/lib/sh/strstr.c
new file mode 100644
index 0000000..c43b05e
--- /dev/null
+++ b/lib/sh/strstr.c
@@ -0,0 +1,125 @@
+/* strstr - find a substring within a string */
+
+/* Copyright (C) 1994, 1999 Free Software Foundation, Inc.
+
+ This file is part of GNU Bash, the Bourne Again SHell.
+
+ Bash is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ Bash 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Bash. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/*
+ * 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
+#include <sys/types.h>
+
+typedef unsigned chartype;
+
+#undef strstr
+
+char *
+strstr (const char *phaystack, const char *pneedle)
+{
+ register const unsigned char *haystack, *needle;
+ register chartype b, c;
+
+ haystack = (const unsigned char *) phaystack;
+ needle = (const unsigned char *) pneedle;
+
+ b = *needle;
+ if (b != '\0')
+ {
+ haystack--; /* possible ANSI violation */
+ do
+ {
+ c = *++haystack;
+ if (c == '\0')
+ goto ret0;
+ }
+ while (c != b);
+
+ c = *++needle;
+ if (c == '\0')
+ goto foundneedle;
+ ++needle;
+ goto jin;
+
+ for (;;)
+ {
+ register chartype a;
+ register const unsigned char *rhaystack, *rneedle;
+
+ do
+ {
+ a = *++haystack;
+ if (a == '\0')
+ goto ret0;
+ if (a == b)
+ break;
+ a = *++haystack;
+ if (a == '\0')
+ goto ret0;
+shloop:; }
+ while (a != b);
+
+jin: a = *++haystack;
+ if (a == '\0')
+ goto ret0;
+
+ if (a != c)
+ goto shloop;
+
+ rhaystack = haystack-- + 1;
+ rneedle = needle;
+ a = *rneedle;
+
+ if (*rhaystack == a)
+ do
+ {
+ if (a == '\0')
+ goto foundneedle;
+ ++rhaystack;
+ a = *++needle;
+ if (*rhaystack != a)
+ break;
+ if (a == '\0')
+ goto foundneedle;
+ ++rhaystack;
+ a = *++needle;
+ }
+ while (*rhaystack == a);
+
+ needle = rneedle; /* took the register-poor approach */
+
+ if (a == '\0')
+ break;
+ }
+ }
+foundneedle:
+ return (char*) haystack;
+ret0:
+ return 0;
+}