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According to Eric Blake on 1/10/2008 8:33 PM:
| should I go ahead and prepare a patch for strcasestr, c-strcasestr, and
| memcasecmp to utilize str-two-way.h?
How's this for strcasestr? Glibc's strcasestr is quadratic (no surprise
there, given our track record); cygwin 1.5.x does not have strcasestr but
CVS cygwin does, and it is quadratic (as of today, although I've posted a
similar patch there). We could add a strcasestr-simple, to parallel
memmem-simple, if desired.
- --
Don't work too hard, make some time for fun as well!
Eric Blake [EMAIL PROTECTED]
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>From 7051f3d9bab2bed584317204ce41c5dedc1f1b60 Mon Sep 17 00:00:00 2001
From: Eric Blake <[EMAIL PROTECTED]>
Date: Thu, 10 Jan 2008 22:22:51 -0700
Subject: [PATCH] Convert strcasestr module to use Two-Way algorithm.
* modules/strcasestr (Depends-on): Remove malloca, strnlen.
(Files): Use str-two-way.h, not str-kmp.h.
* lib/string.in.h (rpl_strcasestr): Declare.
* m4/strcasestr.m4 (gl_FUNC_STRCASESTR): Check for linear
performance.
* lib/strcasestr.c (strcasestr): Simplify, and avoid malloc.
* modules/string (Makefile.am): Support strcasestr.
* m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): Likewise.
* modules/strcasestr-tests (Depends-on): Check for alarm.
* tests/test-strcasestr.c: Augment test.
* lib/str-two-way.h: Clean up stray macro.
Signed-off-by: Eric Blake <[EMAIL PROTECTED]>
---
ChangeLog | 15 +++++
lib/str-two-way.h | 1 +
lib/strcasestr.c | 140 ++++++++++++++-------------------------------
lib/string.in.h | 10 ++-
m4/strcasestr.m4 | 40 ++++++++++++-
m4/string_h.m4 | 1 +
modules/strcasestr | 4 +-
modules/strcasestr-tests | 1 +
modules/string | 1 +
tests/test-strcasestr.c | 4 +-
10 files changed, 109 insertions(+), 108 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 1f1cb43..b36c3e8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2008-01-11 Eric Blake <[EMAIL PROTECTED]>
+
+ Convert strcasestr module to use Two-Way algorithm.
+ * modules/strcasestr (Depends-on): Remove malloca, strnlen.
+ (Files): Use str-two-way.h, not str-kmp.h.
+ * lib/string.in.h (rpl_strcasestr): Declare.
+ * m4/strcasestr.m4 (gl_FUNC_STRCASESTR): Check for linear
+ performance.
+ * lib/strcasestr.c (strcasestr): Simplify, and avoid malloc.
+ * modules/string (Makefile.am): Support strcasestr.
+ * m4/string_h.m4 (gl_HEADER_STRING_H_DEFAULTS): Likewise.
+ * modules/strcasestr-tests (Depends-on): Check for alarm.
+ * tests/test-strcasestr.c: Augment test.
+ * lib/str-two-way.h: Clean up stray macro.
+
2008-01-10 Eric Blake <[EMAIL PROTECTED]>
* m4/strstr.m4: Delete cruft from copy-n-paste.
diff --git a/lib/str-two-way.h b/lib/str-two-way.h
index 3aa3a1b..d144ac9 100644
--- a/lib/str-two-way.h
+++ b/lib/str-two-way.h
@@ -422,5 +422,6 @@ two_way_long_needle (const unsigned char *haystack, size_t
haystack_len,
#undef AVAILABLE
#undef CANON_ELEMENT
+#undef CMP_FUNC
#undef MAX
#undef RETURN_TYPE
diff --git a/lib/strcasestr.c b/lib/strcasestr.c
index 34f36a7..9a2db9b 100644
--- a/lib/strcasestr.c
+++ b/lib/strcasestr.c
@@ -1,5 +1,5 @@
/* Case-insensitive searching in a string.
- Copyright (C) 2005-2007 Free Software Foundation, Inc.
+ Copyright (C) 2005-2008 Free Software Foundation, Inc.
Written by Bruno Haible <[EMAIL PROTECTED]>, 2005.
This program is free software; you can redistribute it and/or modify
@@ -23,109 +23,57 @@
#include <ctype.h>
#include <stdbool.h>
-#include <stddef.h> /* for NULL, in case a nonstandard string.h lacks it */
-
-#include "malloca.h"
#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
-/* Knuth-Morris-Pratt algorithm. */
+/* Two-Way algorithm. */
+#define RETURN_TYPE char *
+#define AVAILABLE(h, h_l, j, n_l) \
+ (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
+ && ((h_l) = (j) + (n_l)))
#define CANON_ELEMENT(c) TOLOWER (c)
-#include "str-kmp.h"
+#define CMP_FUNC strncasecmp
+#include "str-two-way.h"
-/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive
- comparison.
- Note: This function may, in multibyte locales, return success even if
- strlen (haystack) < strlen (needle) ! */
+/* Find the first occurrence of NEEDLE in HAYSTACK, using
+ case-insensitive comparison. This function gives unspecified
+ results in multibyte locales. */
char *
-strcasestr (const char *haystack, const char *needle)
+strcasestr (const char *haystack_start, const char *needle_start)
{
- 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 = TOLOWER ((unsigned char) *needle);
+ const char *haystack = haystack_start;
+ const char *needle = needle_start;
+ size_t needle_len; /* Length of NEEDLE. */
+ size_t haystack_len; /* Known minimum length of HAYSTACK. */
+ bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
+ /* Determine length of NEEDLE, and in the process, make sure
+ HAYSTACK is at least as long (no point processing all of a long
+ NEEDLE if HAYSTACK is too short). */
+ while (*haystack && *needle)
+ {
+ ok &= TOLOWER (*haystack) == TOLOWER (*needle);
+ haystack++;
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 (TOLOWER ((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 (TOLOWER ((unsigned char) *rhaystack)
- != TOLOWER ((unsigned char) *rneedle))
- /* Nothing in this round. */
- break;
- }
- }
- }
}
- else
- return (char *) haystack;
+ if (*needle)
+ return NULL;
+ if (ok)
+ return (char *) haystack_start;
+ needle_len = needle - needle_start;
+ needle -= needle_len;
+ haystack = haystack_start + 1;
+ haystack_len = needle_len - 1;
+
+ /* Perform the search. Abstract memory is considered to be an array
+ of 'unsigned char' values, not an array of 'char' values. See
+ ISO C 99 section 6.2.6.1. */
+ if (needle_len < LONG_NEEDLE_THRESHOLD)
+ return two_way_short_needle ((const unsigned char *) haystack,
+ haystack_len,
+ (const unsigned char *) needle, needle_len);
+ return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
+ (const unsigned char *) needle, needle_len);
}
+
+#undef LONG_NEEDLE_THRESHOLD
diff --git a/lib/string.in.h b/lib/string.in.h
index 4d68cd9..e34645d 100644
--- a/lib/string.in.h
+++ b/lib/string.in.h
@@ -313,11 +313,15 @@ char *strstr (const char *haystack, const char *needle)
/* Find the first occurrence of NEEDLE in HAYSTACK, using case-insensitive
comparison. */
-#if ! @HAVE_STRCASESTR@
+#if @GNULIB_STRCASESTR@
+# if @REPLACE_STRCASESTR@
+# define strcasestr rpl_strcasestr
+# endif
+# if ! @HAVE_STRCASESTR@ || @REPLACE_STRCASESTR@
extern char *strcasestr (const char *haystack, const char *needle)
__attribute__ ((__pure__));
-#endif
-#if defined GNULIB_POSIXCHECK
+# endif
+#elif defined GNULIB_POSIXCHECK
/* strcasestr() does not work with multibyte strings:
It is a glibc extension, and glibc implements it only for unibyte
locales. */
diff --git a/m4/strcasestr.m4 b/m4/strcasestr.m4
index 52f3a58..9583b14 100644
--- a/m4/strcasestr.m4
+++ b/m4/strcasestr.m4
@@ -1,5 +1,5 @@
-# strcasestr.m4 serial 6
-dnl Copyright (C) 2005, 2007 Free Software Foundation, Inc.
+# strcasestr.m4 serial 7
+dnl Copyright (C) 2005, 2007, 2008 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
@@ -7,10 +7,44 @@ dnl with or without modifications, as long as this notice is
preserved.
AC_DEFUN([gl_FUNC_STRCASESTR],
[
AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
- AC_REPLACE_FUNCS(strcasestr)
+ AC_REPLACE_FUNCS([strcasestr])
if test $ac_cv_func_strcasestr = no; then
HAVE_STRCASESTR=0
gl_PREREQ_STRCASESTR
+ else
+ AC_CACHE_CHECK([whether strcasestr works in linear time],
+ [gl_cv_func_strcasestr_linear],
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([
+#include <string.h> /* for memmem */
+#include <stdlib.h> /* for malloc */
+#include <unistd.h> /* for alarm */
+], [[size_t m = 1000000;
+ char *haystack = (char *) malloc (2 * m + 2);
+ char *needle = (char *) malloc (m + 2);
+ void *result = 0;
+ /* Failure to compile this test due to missing alarm is okay,
+ since all such platforms (mingw) also lack strcasestr. */
+ alarm (5);
+ /* Check for quadratic performance. */
+ if (haystack && needle)
+ {
+ memset (haystack, 'A', 2 * m);
+ haystack[2 * m] = 'B';
+ haystack[2 * m + 1] = 0;
+ memset (needle, 'A', m);
+ needle[m] = 'B';
+ needle[m + 1] = 0;
+ result = strcasestr (haystack, needle);
+ }
+ return !result;]])],
+ [gl_cv_func_strcasestr_linear=yes], [gl_cv_func_strcasestr_linear=no],
+ [dnl pessimistically assume the worst, since even glibc 2.6.1
+ dnl has quadratic complexity in its strcasestr
+ gl_cv_func_strcasestr_linear="guessing no"])])
+ if test "$gl_cv_func_strcasestr_linear" != yes; then
+ REPLACE_STRCASESTR=1
+ AC_LIBOBJ([strcasestr])
+ fi
fi
])
diff --git a/m4/string_h.m4 b/m4/string_h.m4
index 1598c39..a50b3e3 100644
--- a/m4/string_h.m4
+++ b/m4/string_h.m4
@@ -79,5 +79,6 @@ AC_DEFUN([gl_HEADER_STRING_H_DEFAULTS],
HAVE_DECL_STRERROR=1; AC_SUBST([HAVE_DECL_STRERROR])
REPLACE_STRERROR=0; AC_SUBST([REPLACE_STRERROR])
REPLACE_MEMMEM=0; AC_SUBST([REPLACE_MEMMEM])
+ REPLACE_STRCASESTR=0; AC_SUBST([REPLACE_STRCASESTR])
REPLACE_STRSTR=0; AC_SUBST([REPLACE_STRSTR])
])
diff --git a/modules/strcasestr b/modules/strcasestr
index 884edfd..5be4ad9 100644
--- a/modules/strcasestr
+++ b/modules/strcasestr
@@ -3,14 +3,12 @@ strcasestr() function: case-insensitive search for a
substring in a string.
Files:
lib/strcasestr.c
-lib/str-kmp.h
+lib/str-two-way.h
m4/strcasestr.m4
Depends-on:
string
stdbool
-malloca
-strnlen
configure.ac:
gl_FUNC_STRCASESTR
diff --git a/modules/strcasestr-tests b/modules/strcasestr-tests
index e472d5b..e5262cc 100644
--- a/modules/strcasestr-tests
+++ b/modules/strcasestr-tests
@@ -4,6 +4,7 @@ tests/test-strcasestr.c
Depends-on:
configure.ac:
+AC_CHECK_DECLS_ONCE([alarm])
Makefile.am:
TESTS += test-strcasestr
diff --git a/modules/string b/modules/string
index 431a322..3e82431 100644
--- a/modules/string
+++ b/modules/string
@@ -68,6 +68,7 @@ string.h: string.in.h
-e 's|@''HAVE_DECL_STRTOK_R''@|$(HAVE_DECL_STRTOK_R)|g' \
-e 's|@''HAVE_DECL_STRERROR''@|$(HAVE_DECL_STRERROR)|g' \
-e 's|@''REPLACE_MEMMEM''@|$(REPLACE_MEMMEM)|g' \
+ -e 's|@''REPLACE_STRCASESTR''@|$(REPLACE_STRCASESTR)|g' \
-e 's|@''REPLACE_STRSTR''@|$(REPLACE_STRSTR)|g' \
-e 's|@''REPLACE_STRERROR''@|$(REPLACE_STRERROR)|g' \
-e '/definition of GL_LINK_WARNING/r $(LINK_WARNING_H)' \
diff --git a/tests/test-strcasestr.c b/tests/test-strcasestr.c
index ceaab79..64a09f2 100644
--- a/tests/test-strcasestr.c
+++ b/tests/test-strcasestr.c
@@ -1,5 +1,5 @@
/* Test of case-insensitive searching in a string.
- Copyright (C) 2007 Free Software Foundation, Inc.
+ Copyright (C) 2007, 2008 Free Software Foundation, Inc.
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
@@ -110,7 +110,6 @@ main ()
}
/* Check that the asymptotic worst-case complexity is not quadratic. */
-#if !HAVE_STRCASESTR /* The system's strcasestr() function fails this test. */
{
size_t m = 1000000;
char *haystack = (char *) malloc (2 * m + 2);
@@ -135,7 +134,6 @@ main ()
if (haystack != NULL)
free (haystack);
}
-#endif
return 0;
}
--
1.5.3.5
