maint: update copyright

[gnulib.git] / lib / c-strstr.c

diff --git a/lib/c-strstr.c b/lib/c-strstr.c
index 47226c3..c13cde2 100644 (file)
--- 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) 2005-2014 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);
 }