@@ -59,6 +59,9 @@
# undef weak_alias
# define weak_alias(a, b)
# define WCSSTR c_wcsstr
+# define __wmemcmp wmemcmp
+# define __wcsnlen wcsnlen
+# define __wcslen wcslen
# include "wcsstr.c"
# define C_IMPL WCSSTR
#endif
@@ -217,6 +220,31 @@ check2 (void)
}
}
+static void
+check3 (void)
+{
+ /* Check that a long periodic needle does not cause false positives. */
+ {
+ const CHAR input[] = L("F_BD_CE_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+ "_C3_88_20_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+ "_C3_A7_20_EF_BF_BD");
+ const CHAR need[] = L("_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD");
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, input, need, NULL);
+ }
+
+ {
+ const CHAR input[] = L("F_BD_CE_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+ "_C3_88_20_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+ "_C3_A7_20_EF_BF_BD_DA_B5_C2_A6_20"
+ "_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD");
+ const CHAR need[] = L("_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD");
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, input, need, (CHAR *) input + 115);
+ }
+}
+
+
#define N 1024
static void
@@ -243,6 +271,148 @@ pr23637 (void)
check_result (impl, h, n, exp_result);
}
+static void
+pr23865 (void)
+{
+ /* Check that a very long haystack is handled quickly if the needle is
+ short and occurs near the beginning. */
+ {
+ size_t m = 1000000;
+ const CHAR *needle =
+ L("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+ "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+ CHAR *haystack = xmalloc ((m + 1) * sizeof (CHAR));
+ MEMSET (haystack, L('A'), m);
+ haystack[0] = L('B');
+ haystack[m] = L('\0');
+
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, haystack, needle, haystack + 1);
+
+ free (haystack);
+ }
+
+ /* Check that a very long needle is discarded quickly if the haystack is
+ short. */
+ {
+ size_t m = 1000000;
+ const CHAR *haystack =
+ L("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+ "ABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABAB");
+ CHAR *needle = xmalloc ((m + 1) * sizeof (CHAR));
+ MEMSET (needle, L'A', m);
+ needle[m] = L('\0');
+
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, haystack, needle, NULL);
+
+ free (needle);
+ }
+
+ /* Check that the asymptotic worst-case complexity is not quadratic. */
+ {
+ size_t m = 1000000;
+ CHAR *haystack = xmalloc ((2 * m + 2) * sizeof (CHAR));
+ CHAR *needle = xmalloc ((m + 2) * sizeof (CHAR));
+
+ MEMSET (haystack, L('A'), 2 * m);
+ haystack[2 * m] = L('B');
+ haystack[2 * m + 1] = L('\0');
+
+ MEMSET (needle, L('A'), m);
+ needle[m] = L('B');
+ needle[m + 1] = L('\0');
+
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, haystack, needle, haystack + m);
+
+ free (needle);
+ free (haystack);
+ }
+
+ {
+ /* Ensure that with a barely periodic "short" needle, STRSTR's
+ search does not mistakenly skip just past the match point. */
+ const CHAR *haystack =
+ L("\n"
+ "with_build_libsubdir\n"
+ "with_local_prefix\n"
+ "with_gxx_include_dir\n"
+ "with_cpp_install_dir\n"
+ "enable_generated_files_in_srcdir\n"
+ "with_gnu_ld\n"
+ "with_ld\n"
+ "with_demangler_in_ld\n"
+ "with_gnu_as\n"
+ "with_as\n"
+ "enable_largefile\n"
+ "enable_werror_always\n"
+ "enable_checking\n"
+ "enable_coverage\n"
+ "enable_gather_detailed_mem_stats\n"
+ "enable_build_with_cxx\n"
+ "with_stabs\n"
+ "enable_multilib\n"
+ "enable___cxa_atexit\n"
+ "enable_decimal_float\n"
+ "enable_fixed_point\n"
+ "enable_threads\n"
+ "enable_tls\n"
+ "enable_objc_gc\n"
+ "with_dwarf2\n"
+ "enable_shared\n"
+ "with_build_sysroot\n"
+ "with_sysroot\n"
+ "with_specs\n"
+ "with_pkgversion\n"
+ "with_bugurl\n"
+ "enable_languages\n"
+ "with_multilib_list\n");
+ const CHAR *needle =
+ L("\n"
+ "with_gnu_ld\n");
+
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, haystack, needle, (CHAR*) haystack + 114);
+ }
+
+ {
+ /* Same bug, shorter trigger. */
+ const CHAR *haystack = L("..wi.d.");
+ const CHAR *needle = L(".d.");
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, haystack, needle, (CHAR*) haystack + 4);
+ }
+
+ /* Test case from Yves Bastide.
+ <https://www.openwall.com/lists/musl/2014/04/18/2> */
+ {
+ const CHAR *input = L("playing play play play always");
+ const CHAR *needle = L("play play play");
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, input, needle, (CHAR*) input + 8);
+ }
+
+ /* Test long needles. */
+ {
+ size_t m = 1024;
+ CHAR *haystack = xmalloc ((2 * m + 1) * sizeof (CHAR));
+ CHAR *needle = xmalloc ((m + 1) * sizeof (CHAR));
+ haystack[0] = L('x');
+ MEMSET (haystack + 1, L(' '), m - 1);
+ MEMSET (haystack + m, L('x'), m);
+ haystack[2 * m] = L('\0');
+ MEMSET (needle, L('x'), m);
+ needle[m] = L('\0');
+
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, haystack, needle, haystack + m);
+
+ free (needle);
+ free (haystack);
+ }
+}
+
static int
test_main (void)
{
@@ -250,7 +420,9 @@ test_main (void)
check1 ();
check2 ();
+ check3 ();
pr23637 ();
+ pr23865 ();
printf ("%23s", "");
FOR_EACH_IMPL (impl, 0)
new file mode 100644
@@ -0,0 +1,312 @@
+/* Wide character substring search, using the Two-Way algorithm.
+ Copyright (C) 2008-2024 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* Before including this file, you need to include <string.h> (and
+ <config.h> before that, if not part of libc), and define:
+ AVAILABLE(h, h_l, j, n_l)
+ A macro that returns nonzero if there are
+ at least N_L characters left starting at H[J].
+ H is 'wchar_t *', H_L, J, and N_L are 'size_t';
+ H_L is an lvalue. For NUL-terminated searches,
+ H_L can be modified each iteration to avoid
+ having to compute the end of H up front.
+
+ For case-insensitivity, you may optionally define:
+ CMP_FUNC(p1, p2, l) A macro that returns 0 iff the first L
+ characters of P1 and P2 are equal.
+ CANON_ELEMENT(c) A macro that canonicalizes an element right after
+ it has been fetched from one of the two strings.
+ The argument is an 'wchar_t'; the result must
+ be an 'wchar_t' as well.
+*/
+
+#include <limits.h>
+#include <stdint.h>
+#include <sys/param.h> /* Defines MAX. */
+
+/* We use the Two-Way string matching algorithm, which guarantees
+ linear complexity with constant space.
+
+ See http://www-igm.univ-mlv.fr/~lecroq/string/node26.html#SECTION00260
+ and http://en.wikipedia.org/wiki/Boyer-Moore_string_search_algorithm
+*/
+
+#ifndef CANON_ELEMENT
+# define CANON_ELEMENT(c) c
+#endif
+#ifndef CMP_FUNC
+# define CMP_FUNC __wmemcmp
+#endif
+
+/* Perform a critical factorization of NEEDLE, of length NEEDLE_LEN.
+ Return the index of the first character in the right half, and set
+ *PERIOD to the global period of the right half.
+
+ The global period of a string is the smallest index (possibly its
+ length) at which all remaining bytes in the string are repetitions
+ of the prefix (the last repetition may be a subset of the prefix).
+
+ When NEEDLE is factored into two halves, a local period is the
+ length of the smallest word that shares a suffix with the left half
+ and shares a prefix with the right half. All factorizations of a
+ non-empty NEEDLE have a local period of at least 1 and no greater
+ than NEEDLE_LEN.
+
+ A critical factorization has the property that the local period
+ equals the global period. All strings have at least one critical
+ factorization with the left half smaller than the global period.
+
+ Given an ordered alphabet, a critical factorization can be computed
+ in linear time, with 2 * NEEDLE_LEN comparisons, by computing the
+ larger of two ordered maximal suffixes. The ordered maximal
+ suffixes are determined by lexicographic comparison of
+ periodicity. */
+static size_t
+critical_factorization (const wchar_t *needle, size_t needle_len,
+ size_t *period)
+{
+ /* Index of last character of left half, or SIZE_MAX. */
+ size_t max_suffix, max_suffix_rev;
+ size_t j; /* Index into NEEDLE for current candidate suffix. */
+ size_t k; /* Offset into current period. */
+ size_t p; /* Intermediate period. */
+ wchar_t a, b; /* Current comparison bytes. */
+
+ /* Special case NEEDLE_LEN of 1 or 2 (all callers already filtered
+ out 0-length needles. */
+ if (needle_len < 3)
+ {
+ *period = 1;
+ return needle_len - 1;
+ }
+
+ /* Invariants:
+ 0 <= j < NEEDLE_LEN - 1
+ -1 <= max_suffix{,_rev} < j (treating SIZE_MAX as if it were signed)
+ min(max_suffix, max_suffix_rev) < global period of NEEDLE
+ 1 <= p <= global period of NEEDLE
+ p == global period of the substring NEEDLE[max_suffix{,_rev}+1...j]
+ 1 <= k <= p
+ */
+
+ /* Perform lexicographic search. */
+ max_suffix = SIZE_MAX;
+ j = 0;
+ k = p = 1;
+ while (j + k < needle_len)
+ {
+ a = CANON_ELEMENT (needle[j + k]);
+ b = CANON_ELEMENT (needle[max_suffix + k]);
+ if (a < b)
+ {
+ /* Suffix is smaller, period is entire prefix so far. */
+ j += k;
+ k = 1;
+ p = j - max_suffix;
+ }
+ else if (a == b)
+ {
+ /* Advance through repetition of the current period. */
+ if (k != p)
+ ++k;
+ else
+ {
+ j += p;
+ k = 1;
+ }
+ }
+ else /* b < a */
+ {
+ /* Suffix is larger, start over from current location. */
+ max_suffix = j++;
+ k = p = 1;
+ }
+ }
+ *period = p;
+
+ /* Perform reverse lexicographic search. */
+ max_suffix_rev = SIZE_MAX;
+ j = 0;
+ k = p = 1;
+ while (j + k < needle_len)
+ {
+ a = CANON_ELEMENT (needle[j + k]);
+ b = CANON_ELEMENT (needle[max_suffix_rev + k]);
+ if (b < a)
+ {
+ /* Suffix is smaller, period is entire prefix so far. */
+ j += k;
+ k = 1;
+ p = j - max_suffix_rev;
+ }
+ else if (a == b)
+ {
+ /* Advance through repetition of the current period. */
+ if (k != p)
+ ++k;
+ else
+ {
+ j += p;
+ k = 1;
+ }
+ }
+ else /* a < b */
+ {
+ /* Suffix is larger, start over from current location. */
+ max_suffix_rev = j++;
+ k = p = 1;
+ }
+ }
+
+ /* Choose the shorter suffix. Return the first character of the right
+ half, rather than the last character of the left half. */
+ if (max_suffix_rev + 1 < max_suffix + 1)
+ return max_suffix + 1;
+ *period = p;
+ return max_suffix_rev + 1;
+}
+
+/* Return the first location of non-empty NEEDLE within HAYSTACK, or
+ NULL. HAYSTACK_LEN is the minimum known length of HAYSTACK.
+
+ If AVAILABLE does not modify HAYSTACK_LEN (as in memmem), then at
+ most 2 * HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching.
+ If AVAILABLE modifies HAYSTACK_LEN (as in strstr), then at most 3 *
+ HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching. */
+static inline wchar_t *
+two_way_short_needle (const wchar_t *haystack, size_t haystack_len,
+ const wchar_t *needle, size_t needle_len)
+{
+ size_t i; /* Index into current character of NEEDLE. */
+ size_t j; /* Index into current window of HAYSTACK. */
+ size_t period; /* The period of the right half of needle. */
+ size_t suffix; /* The index of the right half of needle. */
+
+ /* Factor the needle into two halves, such that the left half is
+ smaller than the global period, and the right half is
+ periodic (with a period as large as NEEDLE_LEN - suffix). */
+ suffix = critical_factorization (needle, needle_len, &period);
+
+ /* Perform the search. Each iteration compares the right half
+ first. */
+ if (CMP_FUNC (needle, needle + period, suffix) == 0)
+ {
+ /* Entire needle is periodic; a mismatch can only advance by the
+ period, so use memory to avoid rescanning known occurrences
+ of the period. */
+ size_t memory = 0;
+ j = 0;
+ while (AVAILABLE (haystack, haystack_len, j, needle_len))
+ {
+ const wchar_t *pneedle;
+ const wchar_t *phaystack;
+
+ /* Scan for matches in right half. */
+ i = MAX (suffix, memory);
+ pneedle = &needle[i];
+ phaystack = &haystack[i + j];
+ while (i < needle_len && (CANON_ELEMENT (*pneedle++)
+ == CANON_ELEMENT (*phaystack++)))
+ ++i;
+ if (needle_len <= i)
+ {
+ /* Scan for matches in left half. */
+ i = suffix - 1;
+ pneedle = &needle[i];
+ phaystack = &haystack[i + j];
+ while (memory < i + 1 && (CANON_ELEMENT (*pneedle--)
+ == CANON_ELEMENT (*phaystack--)))
+ --i;
+ if (i + 1 < memory + 1)
+ return (wchar_t *) (haystack + j);
+ /* No match, so remember how many repetitions of period
+ on the right half were scanned. */
+ j += period;
+ memory = needle_len - period;
+ }
+ else
+ {
+ j += i - suffix + 1;
+ memory = 0;
+ }
+ }
+ }
+ else
+ {
+ const wchar_t *phaystack;
+ /* The comparison always starts from needle[suffix], so cache it
+ and use an optimized first-character loop. */
+ wchar_t needle_suffix = CANON_ELEMENT (needle[suffix]);
+
+ /* The two halves of needle are distinct; no extra memory is
+ required, and any mismatch results in a maximal shift. */
+ period = MAX (suffix, needle_len - suffix) + 1;
+ j = 0;
+ while (AVAILABLE (haystack, haystack_len, j, needle_len))
+ {
+ wchar_t haystack_char;
+ const wchar_t *pneedle;
+
+ phaystack = &haystack[suffix + j];
+
+ while (needle_suffix
+ != (haystack_char = CANON_ELEMENT (*phaystack++)))
+ {
+ ++j;
+ if (!AVAILABLE (haystack, haystack_len, j, needle_len))
+ goto ret0;
+ }
+
+ /* Scan for matches in right half. */
+ i = suffix + 1;
+ pneedle = &needle[i];
+ while (i < needle_len)
+ {
+ if (CANON_ELEMENT (*pneedle++)
+ != (haystack_char = CANON_ELEMENT (*phaystack++)))
+ break;
+ ++i;
+ }
+ if (needle_len <= i)
+ {
+ /* Scan for matches in left half. */
+ i = suffix - 1;
+ pneedle = &needle[i];
+ phaystack = &haystack[i + j];
+ while (i != SIZE_MAX)
+ {
+ if (CANON_ELEMENT (*pneedle--)
+ != (haystack_char = CANON_ELEMENT (*phaystack--)))
+ break;
+ --i;
+ }
+ if (i == SIZE_MAX)
+ return (wchar_t *) (haystack + j);
+ j += period;
+ }
+ else
+ j += i - suffix + 1;
+ }
+ }
+ret0: __attribute__ ((unused))
+ return NULL;
+}
+
+#undef AVAILABLE
+#undef CANON_ELEMENT
+#undef CMP_FUNC
@@ -1,4 +1,5 @@
-/* Copyright (C) 1995-2024 Free Software Foundation, Inc.
+/* Locate a substring in a wide-character string.
+ Copyright (C) 1995-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -15,18 +16,14 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-/*
- * The original strstr() file contains the following comment:
- *
- * 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 */
-
#include <wchar.h>
+#include <string.h>
+
+#define AVAILABLE(h, h_l, j, n_l) \
+ (((j) + (n_l) <= (h_l)) \
+ || ((h_l) += __wcsnlen ((void*)((h) + (h_l)), (n_l) + 128), \
+ (j) + (n_l) <= (h_l)))
+#include "wcs-two-way.h"
#ifndef WCSSTR
# define WCSSTR wcsstr
@@ -35,66 +32,20 @@
wchar_t *
WCSSTR (const wchar_t *haystack, const wchar_t *needle)
{
- wchar_t b, c;
-
- if ((b = *needle) != L'\0')
- {
- haystack--; /* possible ANSI violation */
- do
- if ((c = *++haystack) == L'\0')
- goto ret0;
- while (c != b);
-
- if (!(c = *++needle))
- goto foundneedle;
- ++needle;
- goto jin;
-
- for (;;)
- {
- wchar_t a;
- const wchar_t *rhaystack, *rneedle;
-
- do
- {
- if (!(a = *++haystack))
- goto ret0;
- if (a == b)
- break;
- if ((a = *++haystack) == L'\0')
- goto ret0;
-shloop: ;
- }
- while (a != b);
-
-jin: if (!(a = *++haystack))
- goto ret0;
-
- if (a != c)
- goto shloop;
-
- if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
- do
- {
- if (a == L'\0')
- goto foundneedle;
- if (*++rhaystack != (a = *++needle))
- break;
- if (a == L'\0')
- goto foundneedle;
- }
- while (*++rhaystack == (a = *++needle));
-
- needle = rneedle; /* took the register-poor approach */
-
- if (a == L'\0')
- break;
- }
- }
-foundneedle:
- return (wchar_t*) haystack;
-ret0:
- return NULL;
+ /* Ensure haystack length is at least as long as needle length.
+ Since a match may occur early on in a huge haystack, use strnlen
+ and read ahead a few cachelines for improved performance. */
+ size_t ne_len = __wcslen (needle);
+ size_t hs_len = __wcsnlen (haystack, ne_len | 128);
+ if (hs_len < ne_len)
+ return NULL;
+
+ /* Check whether we have a match. This improves performance since we
+ avoid initialization overheads. */
+ if (__wmemcmp (haystack, needle, ne_len) == 0)
+ return (wchar_t *) haystack;
+
+ return two_way_short_needle (haystack, hs_len, needle, ne_len);
}
/* This alias is for backward compatibility with drafts of the ISO C
standard. Unfortunately the Unix(TM) standard requires this name. */