Rework all the string handling. Make const stuff be constified.

 -Erik

1 files changed, 113 insertions, 42 deletions

diff --git a/libc/string/strstr.c b/libc/string/strstr.c
index 3c853ac52..03d6c8e5f 100644
--- a/libc/string/strstr.c
+++ b/libc/string/strstr.c
@@ -1,54 +1,125 @@
-/* Copyright (C) 1995,1996 Robert de Bath <rdebath@cix.compulink.co.uk>
- * This file is part of the Linux-8086 C library and is distributed
- * under the GNU Library General Public License.
- */
+/* Return the offset of one string within another.
+   Copyright (C) 1994, 1996, 1997 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
 
-#include <string.h>
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
 
-#if 1
-/* We've now got a nice fast strchr and memcmp use them */
+   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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  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(s1, s2)
-char *s1; char *s2;
+strstr (phaystack, pneedle)
+     const char *phaystack;
+     const char *pneedle;
 {
-   register int l = strlen(s2);
-   register char * p = s1;
-
-   if( l==0 ) return p;
-
-   while ((p = strchr(p, *s2)))
-   {
-      if( memcmp(p, s2, l) == 0 )
-         return p;
-      p++;
-   }
-   return (char *) 0;
-}
+  register const unsigned char *haystack, *needle;
+  register chartype b, c;
 
-#else
-/* This is a nice simple self contained strstr,
-   now go and work out why the GNU one is faster :-) */
+  haystack = (const unsigned char *) phaystack;
+  needle = (const unsigned char *) pneedle;
 
-char *strstr(str1, str2)
-char *str1, *str2;
-{
-    register char *Sptr, *Tptr;
-    int	len = strlen(str1) -strlen(str2) + 1;
+  b = *needle;
+  if (b != '\0')
+    {
+      haystack--;				/* possible ANSI violation */
+      do
+	{
+	  c = *++haystack;
+	  if (c == '\0')
+	    goto ret0;
+	}
+      while (c != b);
 
-    if (*str2)
-	for (; len > 0;	len--, str1++){
-	    if (*str1 != *str2)
-		continue;
+      c = *++needle;
+      if (c == '\0')
+	goto foundneedle;
+      ++needle;
+      goto jin;
 
-	    for	(Sptr =	str1, Tptr = str2; *Tptr != '\0'; Sptr++, Tptr++)
-		if (*Sptr != *Tptr)
-		    break;
+      for (;;)
+        {
+          register chartype a;
+	  register const unsigned char *rhaystack, *rneedle;
 
-	    if (*Tptr == '\0')
-		return (char*) str1;
-	}
+	  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;
 
-    return (char*)0;
+	  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;
 }
-#endif