--- /dev/null
+/* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2007,2008 Free Software
+ Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ 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
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+
+ This program 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along
+ with this program; if not, write to the Free Software Foundation,
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+
+/* This particular implementation was written by Eric Blake, 2008. */
+
+#ifndef _LIBC
+# include <config.h>
+#endif
+
+/* Specification of strstr. */
+#include <string.h>
+
+#include <limits.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#ifndef _LIBC
+# define __builtin_expect(expr, val) (expr)
+#endif
+
+/* We use the Two-Way string matching algorithm, which guarantees
+ linear complexity with constant space. Additionally, for long
+ needles, we also use a bad character shift table similar to the
+ Boyer-Moore algorithm to achieve better performance.
+
+ See http://www-igm.univ-mlv.fr/~lecroq/string/node26.html#SECTION00260
+ and http://en.wikipedia.org/wiki/Boyer-Moore_string_search_algorithm
+*/
+
+/* Point at which computing a bad-byte shift table is likely to be
+ worthwhile. Small needles should not compute a table, since it
+ adds (1 << CHAR_BIT) + NEEDLE_LEN computations of preparation for a
+ speedup no greater than a factor of NEEDLE_LEN. The larger the
+ needle, the better the potential performance gain. On the other
+ hand, on non-POSIX systems with CHAR_BIT larger than eight, the
+ memory required for the table is prohibitive. */
+#if CHAR_BIT < 10
+# define LONG_NEEDLE_THRESHOLD 32U
+#else
+# define LONG_NEEDLE_THRESHOLD SIZE_MAX
+#endif
+
+#define MAX(a, b) ((a < b) ? (b) : (a))
+
+/* Perform a critical factorization of NEEDLE, of length NEEDLE_LEN.
+ Return the index of the first byte 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 unsigned char *needle, size_t needle_len,
+ size_t *period)
+{
+ /* Index of last byte 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. */
+ unsigned char a, b; /* Current comparison bytes. */
+
+ /* 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 = needle[j + k];
+ b = 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 = needle[j + k];
+ b = 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 longer suffix. Return the first byte of the right
+ half, rather than the last byte 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 NEEDLE within HAYSTACK, or NULL. This
+ method requires 0 < NEEDLE_LEN <= HAYSTACK_LEN, and is optimized
+ for NEEDLE_LEN < LONG_NEEDLE_THRESHOLD. Performance is linear,
+ with 2 * NEEDLE_LEN comparisons in preparation, and at most 3 *
+ HAYSTACK_LEN - NEEDLE_LEN comparisons in searching. */
+static char *
+two_way_short_needle (const unsigned char *haystack, size_t haystack_len,
+ const unsigned char *needle, size_t needle_len)
+{
+ size_t i; /* Index into current byte 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 (memcmp (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 (!memchr (&haystack[haystack_len], '\0',
+ j + needle_len - haystack_len)
+ && (haystack_len = j + needle_len))
+ {
+ /* Scan for matches in right half. */
+ i = MAX (suffix, memory);
+ while (i < needle_len && needle[i] == haystack[i + j])
+ ++i;
+ if (needle_len <= i)
+ {
+ /* Scan for matches in left half. */
+ i = suffix - 1;
+ while (memory < i + 1 && needle[i] == haystack[i + j])
+ --i;
+ if (i + 1 < memory + 1)
+ return (char *) (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
+ {
+ /* 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 (!memchr (&haystack[haystack_len], '\0',
+ j + needle_len - haystack_len)
+ && (haystack_len = j + needle_len))
+ {
+ /* Scan for matches in right half. */
+ i = suffix;
+ while (i < needle_len && needle[i] == haystack[i + j])
+ ++i;
+ if (needle_len <= i)
+ {
+ /* Scan for matches in left half. */
+ i = suffix - 1;
+ while (i != SIZE_MAX && needle[i] == haystack[i + j])
+ --i;
+ if (i == SIZE_MAX)
+ return (char *) (haystack + j);
+ j += period;
+ }
+ else
+ j += i - suffix + 1;
+ }
+ }
+ return NULL;
+}
+
+/* Return the first location of NEEDLE within HAYSTACK, or NULL. This
+ method requires 0 < NEEDLE_LEN <= HAYSTACK_LEN, and is optimized
+ for LONG_NEEDLE_THRESHOLD <= NEEDLE_LEN. Performance is linear,
+ with 3 * NEEDLE_LEN + (1U << CHAR_BIT) operations in preparation,
+ and at most 3 * HAYSTACK_LEN - NEEDLE_LEN comparisons in searching.
+ The extra initialization cost allows for as few as HAYSTACK_LEN +
+ HAYSTACK_LEN / NEEDLE_LEN. */
+static char *
+two_way_long_needle (const unsigned char *haystack, size_t haystack_len,
+ const unsigned char *needle, size_t needle_len)
+{
+ size_t i; /* Index into current byte 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. */
+ size_t shift_table[1U << CHAR_BIT]; /* See below. */
+
+ /* 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);
+
+ /* Populate shift_table. For each possible byte value c,
+ shift_table[c] is the distance from the last occurrence of c to
+ the end of NEEDLE, or NEEDLE_LEN if c is absent from the NEEDLE.
+ shift_table[NEEDLE[NEEDLE_LEN - 1]] contains the only 0. */
+ for (i = 0; i < 1U << CHAR_BIT; i++)
+ shift_table[i] = needle_len;
+ for (i = 0; i < needle_len; i++)
+ shift_table[needle[i]] = needle_len - i - 1;
+
+ /* Perform the search. Each iteration compares the right half
+ first. */
+ if (memcmp (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 (!memchr (&haystack[haystack_len], '\0',
+ j + needle_len - haystack_len)
+ && (haystack_len = j + needle_len))
+ {
+ /* Check the last byte first; if it does not match, then
+ shift to the next possible match location. */
+ size_t shift = shift_table[haystack[j + needle_len - 1]];
+ if (0 < shift)
+ {
+ if (memory && shift < period)
+ {
+ /* Since needle is periodic, but the last period has
+ a byte out of place, there can be no match until
+ after the mismatch. */
+ shift = needle_len - period;
+ memory = 0;
+ }
+ j += shift;
+ continue;
+ }
+ /* Scan for matches in right half. The last byte has
+ already been matched, by virtue of the shift table. */
+ i = MAX (suffix, memory);
+ while (i < needle_len - 1 && needle[i] == haystack[i + j])
+ ++i;
+ if (needle_len - 1 <= i)
+ {
+ /* Scan for matches in left half. */
+ i = suffix - 1;
+ while (memory < i + 1 && needle[i] == haystack[i + j])
+ --i;
+ if (i + 1 < memory + 1)
+ return (char *) (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
+ {
+ /* 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 (!memchr (&haystack[haystack_len], '\0',
+ j + needle_len - haystack_len)
+ && (haystack_len = j + needle_len))
+ {
+ /* Check the last byte first; if it does not match, then
+ shift to the next possible match location. */
+ size_t shift = shift_table[haystack[j + needle_len - 1]];
+ if (0 < shift)
+ {
+ j += shift;
+ continue;
+ }
+ /* Scan for matches in right half. The last byte has
+ already been matched, by virtue of the shift table. */
+ i = suffix;
+ while (i < needle_len - 1 && needle[i] == haystack[i + j])
+ ++i;
+ if (needle_len - 1 <= i)
+ {
+ /* Scan for matches in left half. */
+ i = suffix - 1;
+ while (i != SIZE_MAX && needle[i] == haystack[i + j])
+ --i;
+ if (i == SIZE_MAX)
+ return (char *) (haystack + j);
+ j += period;
+ }
+ else
+ j += i - suffix + 1;
+ }
+ }
+ return NULL;
+}
+
+/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
+ if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
+ HAYSTACK. */
+char *
+strstr (const char *haystack_start, const char *needle_start)
+{
+ 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 &= *haystack++ == *needle++;
+ if (*needle)
+ return NULL;
+ if (ok)
+ return (char *) haystack_start;
+
+ /* Reduce the size of haystack using strchr, since it has a smaller
+ linear coefficient than the Two-Way algorithm. */
+ needle_len = needle - needle_start;
+ haystack = strchr (haystack_start + 1, *needle_start);
+ if (!haystack || __builtin_expect (needle_len == 1, 0))
+ return (char *) haystack;
+ needle -= needle_len;
+ haystack_len = (haystack > haystack_start + needle_len ? 1
+ : needle_len + haystack_start - haystack);
+
+ /* 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
+#undef MAX
--- /dev/null
+/*
+ * Copyright (C) 2004, 2007, 2008 Free Software Foundation
+ * Written by Bruno Haible and Eric Blake
+ *
+ * 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
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+#include <string.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define ASSERT(expr) \
+ do \
+ { \
+ if (!(expr)) \
+ { \
+ fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+ abort (); \
+ } \
+ } \
+ while (0)
+
+int
+main (int argc, char *argv[])
+{
+#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 have
+ a quadratic strstr, and the replacement strstr is known to not
+ take too long. */
+ alarm (10);
+#endif
+
+ {
+ const char input[] = "foo";
+ const char *result = strstr (input, "");
+ ASSERT (result == input);
+ }
+
+ {
+ const char input[] = "foo";
+ const char *result = strstr (input, "o");
+ ASSERT (result == input + 1);
+ }
+
+ {
+ const char input[] = "ABC ABCDAB ABCDABCDABDE";
+ const char *result = strstr (input, "ABCDABD");
+ ASSERT (result == input + 15);
+ }
+
+ {
+ const char input[] = "ABC ABCDAB ABCDABCDABDE";
+ const char *result = strstr (input, "ABCDABE");
+ ASSERT (result == NULL);
+ }
+
+ {
+ const char input[] = "ABC ABCDAB ABCDABCDABDE";
+ const char *result = strstr (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. */
+ {
+ size_t repeat = 10000;
+ size_t m = 1000000;
+ char *needle =
+ "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+ "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+ char *haystack = (char *) malloc (m + 1);
+ if (haystack != NULL)
+ {
+ memset (haystack, 'A', m);
+ haystack[0] = 'B';
+ haystack[m] = '\0';
+
+ for (; repeat > 0; repeat--)
+ {
+ ASSERT (strstr (haystack, needle) == haystack + 1);
+ }
+
+ free (haystack);
+ }
+ }
+
+ /* Check that a very long needle is discarded quickly if the haystack is
+ short. */
+ {
+ size_t repeat = 10000;
+ size_t m = 1000000;
+ char *haystack =
+ "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+ "ABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABAB";
+ char *needle = (char *) malloc (m + 1);
+ if (needle != NULL)
+ {
+ memset (needle, 'A', m);
+ needle[m] = '\0';
+
+ for (; repeat > 0; repeat--)
+ {
+ ASSERT (strstr (haystack, needle) == NULL);
+ }
+
+ free (needle);
+ }
+ }
+
+ /* Check that the asymptotic worst-case complexity is not quadratic. */
+ {
+ size_t m = 1000000;
+ char *haystack = (char *) malloc (2 * m + 2);
+ char *needle = (char *) malloc (m + 2);
+ if (haystack != NULL && needle != NULL)
+ {
+ const char *result;
+
+ 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 = strstr (haystack, needle);
+ ASSERT (result == haystack + m);
+ }
+ if (needle != NULL)
+ free (needle);
+ if (haystack != NULL)
+ free (haystack);
+ }
+
+ /* Sublinear speed is only possible in memmem; strstr must examine
+ every character of haystack to find its length. */
+
+ return 0;
+}
projects / pspp / commitdiff