From 4838f42df1843ec9f5058d74c8114c1fcb332a89 Mon Sep 17 00:00:00 2001
From: Jim Meyering <jim@meyering.net>
Date: Tue, 16 Jul 1996 04:47:23 +0000
Subject: [PATCH] Update from libit.

---
 lib/strstr.c | 134 +++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 103 insertions(+), 31 deletions(-)

diff --git a/lib/strstr.c b/lib/strstr.c
index 77f24cbc9..cdee62117 100644
--- a/lib/strstr.c
+++ b/lib/strstr.c
@@ -1,44 +1,116 @@
-/* strstr.c -- return the offset of one string within another
-   Copyright (C) 1989, 1990 Free Software Foundation, Inc.
+/* Copyright (C) 1994 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
 
-   This program 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 2, or (at your option)
-   any later version.
+This program 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 2, or (at your option)
+any later version.
 
-   This program 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.
+This program 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 this program; if not, write to the Free Software Foundation,
-   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
 
-/* Written by Mike Rendell <michael@cs.mun.ca>.  */
+/*
+ * 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	*/
 
-/* Return the starting address of string S2 in S1;
-   return 0 if it is not found. */
+#include <string.h>
+#include <sys/types.h>
+
+typedef unsigned chartype;
 
 char *
-strstr (s1, s2)
-     char *s1;
-     char *s2;
+strstr (phaystack, pneedle)
+     const char *phaystack;
+     const char *pneedle;
 {
-  int i;
-  char *p1;
-  char *p2;
-  char *s = s1;
+  register const unsigned char *haystack, *needle;
+  register chartype b, c;
+
+  haystack = (const unsigned char *) phaystack;
+  needle = (const unsigned char *) pneedle;
 
-  for (p2 = s2, i = 0; *s; p2 = s2, i++, s++)
+  b = *needle;
+  if (b != '\0')
     {
-      for (p1 = s; *p1 && *p2 && *p1 == *p2; p1++, p2++)
-	;
-      if (!*p2)
-	break;
-    }
-  if (!*p2)
-    return s1 + i;
+      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 aproach */
+
+	  if (a == '\0')
+	    break;
+        }
+    }
+foundneedle:
+  return (char*) haystack;
+ret0:
   return 0;
 }
-- 
2.11.0