+2008-01-14 Eric Blake <ebb9@byu.net>
+
+ Convert strcasestr module to use Two-Way algorithm.
+ * modules/strcasestr-simple: New module, based on the old
+ strcasestr, but with Two-Way rather than KMP.
+ * modules/strcasestr (Depends-on): Change to strcasestr-simple.
+ * 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.
+ * NEWS: Document new module.
+ * MODULES.html.sh (string handling): Likewise.
+ * doc/functions/strcasestr.texi: New file.
+ * doc/gnulib.texi (Function Substitutes): New node. Move memmem
+ here, since it is not a POSIX function.
+
2008-01-14 Colin Watson <cjwatson@debian.org>
Bruno Haible <bruno@clisp.org>
func_module c-strcaseeq
func_module c-strcasestr
func_module strcasestr
+ func_module strcasestr-simple
func_module strchrnul
func_module strdup
func_module streq
Date Modules Changes
+2008-01-14 strcasestr This module now replaces worst-case inefficient
+ implementations; clients that use controlled
+ needles and thus do not care about worst-case
+ efficiency should use the new strcasestr-simple
+ module instead for smaller code size.
+
2008-01-09 alloca-opt Now defines HAVE_ALLOCA_H only when the system
supplies an <alloca.h>. Gnulib-using code is now
expected to include <alloca.h> unconditionally.
--- /dev/null
+@node strcasestr
+@section @code{strcasestr}
+@findex strcasestr
+
+Unspecified by POSIX, but comparable to a mix of @code{strstr} and
+@code{strcasecmp}.
+
+Gnulib module: strcasestr or strcasestr-simple
+
+Portability problems fixed by either Gnulib module @code{strcasestr-simple}
+or @code{strcasestr}:
+@itemize
+@item
+This function is missing on some platforms:
+MacOS X 10.3, FreeBSD 5.2.1, OpenBSD 4.0, AIX 4.3.2, HP-UX 11, IRIX
+6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw, Interix 3.5, BeOS.
+@end itemize
+
+Portability problems fixed by Gnulib module @code{strcasestr}:
+@itemize
+@item
+This function has quadratic instead of linear worst-case complexity on some
+platforms:
+glibc 2.6.1, FreeBSD 6.2, NetBSD 3.0, AIX 5.1.
+@end itemize
+
+Portability problems not fixed by Gnulib:
+@itemize
+@end itemize
module providing a substitute for the function. When the list
``Portability problems not fixed by Gnulib'' is empty, such a module is
not needed: No portability problems are known. Otherwise, it indicates
-that such a module would be useful but is not available: Noone so far
+that such a module would be useful but is not available: No one so far
found this function important enough to contribute a substitute for it.
If you need this particular function, you may write to
@code{<bug-gnulib at gnu dot org>}.
* memchr::
* memcmp::
* memcpy::
-* memmem::
* memmove::
* memset::
* mkdir::
@include glibc-headers/sysexits.texi
@include glibc-headers/ttyent.texi
+@node Glibc Function Substitutes
+@chapter Glibc Function Substitutes
+
+This chapter describes which functions and function-like macros
+provided as extensions by at least glibc are also supported by Gnulib,
+which portability pitfalls are fixed by Gnulib, and which (known)
+portability problems are not worked around by Gnulib.
+
+The notation ``Gnulib module: ---'' means that Gnulib does not provide a
+module providing a substitute for the function. When the list
+``Portability problems not fixed by Gnulib'' is empty, such a module is
+not needed: No portability problems are known. Otherwise, it indicates
+that such a module would be useful but is not available: No one so far
+found this function important enough to contribute a substitute for it.
+If you need this particular function, you may write to
+@code{<bug-gnulib at gnu dot org>}.
+
+@menu
+* memmem::
+* strcasestr::
+@end menu
+
+@include functions/memmem.texi
+@include functions/strcasestr.texi
+
@node Particular Modules
@chapter Particular Modules
#undef AVAILABLE
#undef CANON_ELEMENT
+#undef CMP_FUNC
#undef MAX
#undef RETURN_TYPE
/* 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 <bruno@clisp.org>, 2005.
This program is free software; you can redistribute it and/or modify
#include <ctype.h>
#include <stdbool.h>
-#include <stddef.h> /* for NULL, in case a nonstandard string.h lacks it */
-
-#include "malloca.h"
+#include <strings.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(p1, p2, l) \
+ strncasecmp ((const char *) (p1), (const char *) (p2), l)
+#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 ((unsigned char) *haystack)
+ == TOLOWER ((unsigned char) *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;
+ 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_start,
+ needle_len);
+ return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
+ (const unsigned char *) needle_start,
+ needle_len);
}
+
+#undef LONG_NEEDLE_THRESHOLD
/* 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. */
-# 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.
-AC_DEFUN([gl_FUNC_STRCASESTR],
+dnl Check that strcasestr is present.
+AC_DEFUN([gl_FUNC_STRCASESTR_SIMPLE],
[
+ dnl Persuade glibc <string.h> to declare strcasestr().
+ AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
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
fi
-])
+]) # gl_FUNC_STRCASESTR_SIMPLE
+
+dnl Additionally, check that strcasestr is efficient.
+AC_DEFUN([gl_FUNC_STRCASESTR])
+[
+ AC_REQUIRE([gl_FUNC_STRCASESTR_SIMPLE])
+ if test $ac_cv_func_strcasestr = yes; then
+ AC_CACHE_CHECK([whether strcasestr works in linear time],
+ [gl_cv_func_strcasestr_linear],
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([
+#include <string.h> /* for memmem */
+#include <stdlib.h> /* for malloc */
+#include <unistd.h> /* for alarm */
+], [[size_t m = 1000000;
+ char *haystack = (char *) malloc (2 * m + 2);
+ char *needle = (char *) malloc (m + 2);
+ void *result = 0;
+ /* Failure to compile this test due to missing alarm is okay,
+ since all such platforms (mingw) also lack strcasestr. */
+ alarm (5);
+ /* Check for quadratic performance. */
+ if (haystack && needle)
+ {
+ memset (haystack, 'A', 2 * m);
+ haystack[2 * m] = 'B';
+ haystack[2 * m + 1] = 0;
+ memset (needle, 'A', m);
+ needle[m] = 'B';
+ needle[m + 1] = 0;
+ result = strcasestr (haystack, needle);
+ }
+ return !result;]])],
+ [gl_cv_func_strcasestr_linear=yes], [gl_cv_func_strcasestr_linear=no],
+ [dnl pessimistically assume the worst, since even glibc 2.6.1
+ dnl has quadratic complexity in its strcasestr
+ gl_cv_func_strcasestr_linear="guessing no"])])
+ if test "$gl_cv_func_strcasestr_linear" != yes; then
+ REPLACE_STRCASESTR=1
+ AC_LIBOBJ([strcasestr])
+ fi
+ fi
+]) # gl_FUNC_STRCASESTR
# Prerequisites of lib/strcasestr.c.
AC_DEFUN([gl_PREREQ_STRCASESTR], [
REPLACE_STRERROR=0; AC_SUBST([REPLACE_STRERROR])
REPLACE_STRSIGNAL=0; AC_SUBST([REPLACE_STRSIGNAL])
REPLACE_MEMMEM=0; AC_SUBST([REPLACE_MEMMEM])
+ REPLACE_STRCASESTR=0; AC_SUBST([REPLACE_STRCASESTR])
REPLACE_STRSTR=0; AC_SUBST([REPLACE_STRSTR])
])
Description:
-strcasestr() function: case-insensitive search for a substring in a string.
+strcasestr() function: efficient case-insensitive search for unibyte substring.
Files:
-lib/strcasestr.c
-lib/str-kmp.h
-m4/strcasestr.m4
Depends-on:
-string
-stdbool
-malloca
-strnlen
+strcasestr-simple
configure.ac:
gl_FUNC_STRCASESTR
-gl_STRING_MODULE_INDICATOR([strcasestr])
Makefile.am:
--- /dev/null
+Description:
+strcasestr() function: case-insensitive search for unibyte substring.
+
+Files:
+lib/strcasestr.c
+lib/str-two-way.h
+m4/strcasestr.m4
+
+Depends-on:
+string
+stdbool
+strcase
+
+configure.ac:
+gl_FUNC_STRCASESTR_SIMPLE
+gl_STRING_MODULE_INDICATOR([strcasestr])
+
+Makefile.am:
+
+Include:
+<string.h>
+
+License:
+LGPLv2+
+
+Maintainer:
+Bruno Haible
+
Depends-on:
configure.ac:
+AC_CHECK_DECLS_ONCE([alarm])
Makefile.am:
TESTS += test-strcasestr
-e 's|@''HAVE_DECL_STRERROR''@|$(HAVE_DECL_STRERROR)|g' \
-e 's|@''HAVE_DECL_STRSIGNAL''@|$(HAVE_DECL_STRSIGNAL)|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 's|@''REPLACE_STRSIGNAL''@|$(REPLACE_STRSIGNAL)|g' \
/* 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
#include <stdio.h>
#include <stdlib.h>
+#include <unistd.h>
#define ASSERT(expr) \
do \
int
main ()
{
+#if HAVE_DECL_ALARM
+ /* Declare failure if test takes too long, by using default abort
+ caused by SIGALRM. All known platforms that lack alarm also lack
+ memmem, and the replacement memmem is known to not take too
+ long. */
+ alarm (50);
+#endif
+
{
const char input[] = "foo";
const char *result = strcasestr (input, "");
ASSERT (result == NULL);
}
+ {
+ const char input[] = "ABC ABCDAB ABCDABCDABDE";
+ const char *result = strcasestr (input, "ABCDaBCD");
+ ASSERT (result == input + 11);
+ }
+
/* Check that a very long haystack is handled quickly if the needle is
short and occurs near the beginning. */
{
}
/* 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);
if (haystack != NULL)
free (haystack);
}
-#endif
return 0;
}
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