Prepare for radical source tree reorganization.zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 527 insertions, 0 deletions

diff --git a/REORG.TODO/string/str-two-way.h b/REORG.TODO/string/str-two-way.h
new file mode 100644
index 0000000000..599c867ffd
--- /dev/null
+++ b/REORG.TODO/string/str-two-way.h
@@ -0,0 +1,527 @@
+/* Byte-wise substring search, using the Two-Way algorithm.
+   Copyright (C) 2008-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Written by Eric Blake <ebb9@byu.net>, 2008.
+
+   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
+   <http://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:
+     RETURN_TYPE             A macro that expands to the return type.
+     AVAILABLE(h, h_l, j, n_l)
+			     A macro that returns nonzero if there are
+			     at least N_L bytes left starting at H[J].
+			     H is 'unsigned char *', 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 'unsigned char'; the result
+			     must be an 'unsigned char' as well.
+
+  Other macros you may optionally define:
+     RET0_IF_0(a)            Documented below at default definition.
+     CHECK_EOL               Same.
+
+  This file undefines the macros listed above, and defines
+  LONG_NEEDLE_THRESHOLD.
+*/
+
+#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.  Additionally, for long
+   needles, we also use a bad character shift table similar to the
+   Boyer-Moore algorithm to achieve improved (potentially sub-linear)
+   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
+
+#ifndef CANON_ELEMENT
+# define CANON_ELEMENT(c) c
+#endif
+#ifndef CMP_FUNC
+# define CMP_FUNC memcmp
+#endif
+
+/* Check for end-of-line in strstr and strcasestr routines.
+   We piggy-back matching procedure for detecting EOL where possible,
+   and use AVAILABLE macro otherwise.  */
+#ifndef CHECK_EOL
+# define CHECK_EOL (0)
+#endif
+
+/* Return NULL if argument is '\0'.  */
+#ifndef RET0_IF_0
+# define RET0_IF_0(a) /* nothing */
+#endif
+
+/* 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 = 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 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 non-empty NEEDLE within HAYSTACK, or
+   NULL.  HAYSTACK_LEN is the minimum known length of HAYSTACK.  This
+   method is optimized for NEEDLE_LEN < LONG_NEEDLE_THRESHOLD.
+   Performance is guaranteed to be linear, with an initialization cost
+   of 2 * NEEDLE_LEN comparisons.
+
+   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 RETURN_TYPE
+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 (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 unsigned char *pneedle;
+	  const unsigned char *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 (RETURN_TYPE) (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 unsigned char *phaystack = &haystack[suffix];
+      /* The comparison always starts from needle[suffix], so cache it
+	 and use an optimized first-character loop.  */
+      unsigned char needle_suffix = CANON_ELEMENT (needle[suffix]);
+
+#if CHECK_EOL
+      /* We start matching from the SUFFIX'th element, so make sure we
+	 don't hit '\0' before that.  */
+      if (haystack_len < suffix + 1
+	  && !AVAILABLE (haystack, haystack_len, 0, suffix + 1))
+	return NULL;
+#endif
+
+      /* 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 (1
+#if !CHECK_EOL
+	     && AVAILABLE (haystack, haystack_len, j, needle_len)
+#endif
+	     )
+	{
+	  unsigned char haystack_char;
+	  const unsigned char *pneedle;
+
+	  /* TODO: The first-character loop can be sped up by adapting
+	     longword-at-a-time implementation of memchr/strchr.  */
+	  if (needle_suffix
+	      != (haystack_char = CANON_ELEMENT (*phaystack++)))
+	    {
+	      RET0_IF_0 (haystack_char);
+#if !CHECK_EOL
+	      ++j;
+#endif
+	      continue;
+	    }
+
+#if CHECK_EOL
+	  /* Calculate J if it wasn't kept up-to-date in the first-character
+	     loop.  */
+	  j = phaystack - &haystack[suffix] - 1;
+#endif
+
+	  /* 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++)))
+		{
+		  RET0_IF_0 (haystack_char);
+		  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--)))
+		    {
+		      RET0_IF_0 (haystack_char);
+		      break;
+		    }
+		  --i;
+		}
+	      if (i == SIZE_MAX)
+		return (RETURN_TYPE) (haystack + j);
+	      j += period;
+	    }
+	  else
+	    j += i - suffix + 1;
+
+#if CHECK_EOL
+	  if (!AVAILABLE (haystack, haystack_len, j, needle_len))
+	    break;
+#endif
+
+	  phaystack = &haystack[suffix + j];
+	}
+    }
+ ret0: __attribute__ ((unused))
+  return NULL;
+}
+
+/* Return the first location of non-empty NEEDLE within HAYSTACK, or
+   NULL.  HAYSTACK_LEN is the minimum known length of HAYSTACK.  This
+   method is optimized for LONG_NEEDLE_THRESHOLD <= NEEDLE_LEN.
+   Performance is guaranteed to be linear, with an initialization cost
+   of 3 * NEEDLE_LEN + (1 << CHAR_BIT) operations.
+
+   If AVAILABLE does not modify HAYSTACK_LEN (as in memmem), then at
+   most 2 * HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching,
+   and sublinear performance O(HAYSTACK_LEN / NEEDLE_LEN) is possible.
+   If AVAILABLE modifies HAYSTACK_LEN (as in strstr), then at most 3 *
+   HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching, and
+   sublinear performance is not possible.  */
+static RETURN_TYPE
+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[CANON_ELEMENT (needle[i])] = needle_len - i - 1;
+
+  /* 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;
+      size_t shift;
+      j = 0;
+      while (AVAILABLE (haystack, haystack_len, j, needle_len))
+	{
+	  const unsigned char *pneedle;
+	  const unsigned char *phaystack;
+
+	  /* Check the last byte first; if it does not match, then
+	     shift to the next possible match location.  */
+	  shift = shift_table[CANON_ELEMENT (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);
+	  pneedle = &needle[i];
+	  phaystack = &haystack[i + j];
+	  while (i < needle_len - 1 && (CANON_ELEMENT (*pneedle++)
+					== CANON_ELEMENT (*phaystack++)))
+	    ++i;
+	  if (needle_len - 1 <= 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 (RETURN_TYPE) (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.  */
+      size_t shift;
+      period = MAX (suffix, needle_len - suffix) + 1;
+      j = 0;
+      while (AVAILABLE (haystack, haystack_len, j, needle_len))
+	{
+	  const unsigned char *pneedle;
+	  const unsigned char *phaystack;
+
+	  /* Check the last byte first; if it does not match, then
+	     shift to the next possible match location.  */
+	  shift = shift_table[CANON_ELEMENT (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;
+	  pneedle = &needle[i];
+	  phaystack = &haystack[i + j];
+	  while (i < needle_len - 1 && (CANON_ELEMENT (*pneedle++)
+					== CANON_ELEMENT (*phaystack++)))
+	    ++i;
+	  if (needle_len - 1 <= i)
+	    {
+	      /* Scan for matches in left half.  */
+	      i = suffix - 1;
+	      pneedle = &needle[i];
+	      phaystack = &haystack[i + j];
+	      while (i != SIZE_MAX && (CANON_ELEMENT (*pneedle--)
+				       == CANON_ELEMENT (*phaystack--)))
+		--i;
+	      if (i == SIZE_MAX)
+		return (RETURN_TYPE) (haystack + j);
+	      j += period;
+	    }
+	  else
+	    j += i - suffix + 1;
+	}
+    }
+  return NULL;
+}
+
+#undef AVAILABLE
+#undef CANON_ELEMENT
+#undef CMP_FUNC
+#undef RET0_IF_0
+#undef RETURN_TYPE
+#undef CHECK_EOL