Make c-strstr rely on strstr.

1 files changed, 4 insertions, 101 deletions

diff --git a/lib/c-strstr.c b/lib/c-strstr.c
index 47226c3d47..d903ec3ebf 100644
--- a/lib/c-strstr.c
+++ b/lib/c-strstr.c
@@ -1,5 +1,5 @@
 /* c-strstr.c -- substring search in C locale
-   Copyright (C) 2005-2007 Free Software Foundation, Inc.
+   Copyright (C) 2005-2008 Free Software Foundation, Inc.
    Written by Bruno Haible <bruno@clisp.org>, 2005, 2007.
 
    This program is free software: you can redistribute it and/or modify
@@ -20,110 +20,13 @@
 /* Specification.  */
 #include "c-strstr.h"
 
-#include <stdbool.h>
-#include <stdlib.h>
 #include <string.h>
 
-#include "malloca.h"
-
-/* Knuth-Morris-Pratt algorithm.  */
-#define CANON_ELEMENT(c) c
-#include "str-kmp.h"
-
 /* Find the first occurrence of NEEDLE in HAYSTACK.  */
 char *
 c_strstr (const char *haystack, const char *needle)
 {
-  /* Be careful not to look at the entire extent of haystack or needle
-     until needed.  This is useful because of these two cases:
-       - haystack may be very long, and a match of needle found early,
-       - needle may be very long, and not even a short initial segment of
-         needle may be found in haystack.  */
-  if (*needle != '\0')
-    {
-      /* Minimizing the worst-case complexity:
-	 Let n = strlen(haystack), m = strlen(needle).
-	 The naïve algorithm is O(n*m) worst-case.
-	 The Knuth-Morris-Pratt algorithm is O(n) worst-case but it needs a
-	 memory allocation.
-	 To achieve linear complexity and yet amortize the cost of the memory
-	 allocation, we activate the Knuth-Morris-Pratt algorithm only once
-	 the naïve algorithm has already run for some time; more precisely,
-	 when
-	   - the outer loop count is >= 10,
-	   - the average number of comparisons per outer loop is >= 5,
-	   - the total number of comparisons is >= m.
-	 But we try it only once.  If the memory allocation attempt failed,
-	 we don't retry it.  */
-      bool try_kmp = true;
-      size_t outer_loop_count = 0;
-      size_t comparison_count = 0;
-      size_t last_ccount = 0;			/* last comparison count */
-      const char *needle_last_ccount = needle;	/* = needle + last_ccount */
-
-      /* Speed up the following searches of needle by caching its first
-	 character.  */
-      unsigned char b = (unsigned char) *needle;
-
-      needle++;
-      for (;; haystack++)
-	{
-	  if (*haystack == '\0')
-	    /* No match.  */
-	    return NULL;
-
-	  /* See whether it's advisable to use an asymptotically faster
-	     algorithm.  */
-	  if (try_kmp
-	      && outer_loop_count >= 10
-	      && comparison_count >= 5 * outer_loop_count)
-	    {
-	      /* See if needle + comparison_count now reaches the end of
-		 needle.  */
-	      if (needle_last_ccount != NULL)
-		{
-		  needle_last_ccount +=
-		    strnlen (needle_last_ccount, comparison_count - last_ccount);
-		  if (*needle_last_ccount == '\0')
-		    needle_last_ccount = NULL;
-		  last_ccount = comparison_count;
-		}
-	      if (needle_last_ccount == NULL)
-		{
-		  /* Try the Knuth-Morris-Pratt algorithm.  */
-		  const char *result;
-		  bool success =
-		    knuth_morris_pratt_unibyte (haystack, needle - 1, &result);
-		  if (success)
-		    return (char *) result;
-		  try_kmp = false;
-		}
-	    }
-
-	  outer_loop_count++;
-	  comparison_count++;
-	  if ((unsigned char) *haystack == b)
-	    /* The first character matches.  */
-	    {
-	      const char *rhaystack = haystack + 1;
-	      const char *rneedle = needle;
-
-	      for (;; rhaystack++, rneedle++)
-		{
-		  if (*rneedle == '\0')
-		    /* Found a match.  */
-		    return (char *) haystack;
-		  if (*rhaystack == '\0')
-		    /* No match.  */
-		    return NULL;
-		  comparison_count++;
-		  if ((unsigned char) *rhaystack != (unsigned char) *rneedle)
-		    /* Nothing in this round.  */
-		    break;
-		}
-	    }
-	}
-    }
-  else
-    return (char *) haystack;
+  /* POSIX says that strstr() interprets the strings as byte sequences, not
+     as character sequences in the current locale.  */
+  return strstr (haystack, needle);
 }