[Courgette] Replace QSufSort with libdivsufsort.

courgette/third_party/bsdiff/qsufsort.h

-// Copyright 2003, 2004 Colin Percival
-// All rights reserved
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted providing that the following conditions
-// are met:
-// 1. Redistributions of source code must retain the above copyright
-//    notice, this list of conditions and the following disclaimer.
-// 2. Redistributions in binary form must reproduce the above copyright
-//    notice, this list of conditions and the following disclaimer in the
-//    documentation and/or other materials provided with the distribution.
-//
-// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
-// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
-// ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
-// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
-// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
-// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
-// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
-// IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-// POSSIBILITY OF SUCH DAMAGE.
-//
-// For the terms under which this work may be distributed, please see
-// the adjoining file "LICENSE".
-//
-// ChangeLog:
-// 2005-05-05 - Use the modified header struct from bspatch.h; use 32-bit
-//              values throughout.
-//                --Benjamin Smedberg <benjamin@smedbergs.us>
-// 2010-05-26 - Use a paged array for V and I. The address space may be too
-//              fragmented for these big arrays to be contiguous.
-//                --Stephen Adams <sra@chromium.org>
-// 2015-08-03 - Extract QSufSort to a separate file as template.
-//                --Samuel Huang <huangs@chromium.org>
-// 2015-08-19 - Optimize split(), add comments.
-//                --Samuel Huang <huangs@chromium.org>
-// 2016-04-27 - Change split() to use Bentley & McIlroy's pivot selection
-//              algorithm, which QSufSort originally used. Reference:
-//              http://www.larsson.dogma.net/qsufsort.c
-//                --Samuel Huang <huangs@chromium.org>
-
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef COURGETTE_THIRD_PARTY_BSDIFF_QSUFSORT_H_
-#define COURGETTE_THIRD_PARTY_BSDIFF_QSUFSORT_H_
-
-namespace qsuf {
-
-// ------------------------------------------------------------------------
-//
-// The following code is taken verbatim from 'bsdiff.c'. Please keep all the
-// code formatting and variable names.  The changes from the original are:
-// (1) replacing tabs with spaces,
-// (2) indentation and spacing,
-// (3) using 'const',
-// (4) changing the V and I parameters from int* to template <typename T>.
-// (5) optimizing split(); fix styles.
-// (6) moving matchlen() and search() to a separate file.
-//
-// The code appears to be a rewritten version of the suffix array algorithm
-// presented in "Faster Suffix Sorting" by N. Jesper Larsson and Kunihiko
-// Sadakane, special cased for bytes.
-
-namespace {
-
-template <typename T>
-T median3(const T& a, const T& b, const T& c) {
-  if (a < b)
-    return b < c ? b : (a < c ? c : a);
-  return b > c ? b : (a > c ? c : a);
-}
-
-}  // namespace
-
-template <typename T>
-void split(T I, T V, int start, int end, int h) {
-  // For small interval, apply selection sort.
-  if (end - start < 16) {
-    for (int i = start; i < end;) {
-      int skip = 1;
-      int best = V[I[i] + h];
-      for (int j = i + 1; j < end; j++) {
-        int cur = V[I[j] + h];
-        if (best > cur) {
-          best = cur;
-          int tmp = I[i];
-          I[i] = I[j];
-          I[j] = tmp;
-          skip = 1;
-        } else if (best == cur) {
-          int tmp = I[i + skip];
-          I[i + skip] = I[j];
-          I[j] = tmp;
-          ++skip;
-        }
-      }
-      if (skip == 1) {
-        V[I[i]] = i;
-        I[i] = -1;
-      } else {
-        for (int j = i, jend = i + skip; j < jend; j++)
-          V[I[j]] = jend - 1;
-      }
-      i += skip;
-    }
-    return;
-  }
-
-  // Select pivot, algorithm by Bentley & McIlroy.
-  int n = end - start;
-  int mid = start + (n >> 1);
-  int pivot = V[I[mid] + h];
-  int p1 = V[I[start] + h];
-  int p2 = V[I[end - 1] + h];
-  if (n > 40) {  // Big array: Pseudomedian of 9.
-    int s = n >> 3;
-    pivot = median3(pivot, V[I[mid - s] + h], V[I[mid + s] + h]);
-    p1 = median3(p1, V[I[start + s] + h], V[I[start + s + s] + h]);
-    p2 = median3(p2, V[I[end - 1 - s] + h], V[I[end - 1 - s - s] + h]);
-  }  // Else medium array: Pseudomedian of 3.
-  pivot = median3(pivot, p1, p2);
-
-  // Split [start, end) into 3 intervals:
-  //   [start, j) with secondary keys < pivot,
-  //   [j, k) with secondary keys == pivot,
-  //   [k, end) with secondary keys > pivot.
-  int j = start;
-  int k = end;
-  for (int i = start; i < k;) {
-    int cur = V[I[i] + h];
-    if (cur < pivot) {
-      if (i != j) {
-        int tmp = I[i];
-        I[i] = I[j];
-        I[j] = tmp;
-      }
-      ++i;
-      ++j;
-    } else if (cur > pivot) {
-      --k;
-      int tmp = I[i];
-      I[i] = I[k];
-      I[k] = tmp;
-    } else {
-      ++i;
-    }
-  }
-
-  // Recurse on the "< pivot" piece.
-  if (start < j)
-    split<T>(I, V, start, j, h);
-
-  // Update the "== pivot" piece.
-  if (j == k - 1) {
-    V[I[j]] = j;
-    I[j] = -1;
-  } else {
-    for (int i = j; i < k; ++i)
-      V[I[i]] = k - 1;
-  }
-
-  // Recurse on the "> pivot" piece.
-  if (k < end)
-    split<T>(I, V, k, end, h);
-}
-
-template <class T>
-static void qsufsort(T I, T V, const unsigned char* old, int oldsize) {
-  int buckets[256];
-  int i, h, len;
-
-  for (i = 0; i < 256; i++)
-    buckets[i] = 0;
-  for (i = 0; i < oldsize; i++)
-    buckets[old[i]]++;
-  for (i = 1; i < 256; i++)
-    buckets[i] += buckets[i - 1];
-  for (i = 255; i > 0; i--)
-    buckets[i] = buckets[i - 1];
-  buckets[0] = 0;
-
-  for (i = 0; i < oldsize; i++)
-    I[++buckets[old[i]]] = i;
-  I[0] = oldsize;
-  for (i = 0; i < oldsize; i++)
-    V[i] = buckets[old[i]];
-  V[oldsize] = 0;
-  for (i = 1; i < 256; i++)
-    if (buckets[i] == buckets[i - 1] + 1)
-      I[buckets[i]] = -1;
-  I[0] = -1;
-
-  for (h = 1; I[0] != -(oldsize + 1); h += h) {
-    len = 0;
-    for (i = 0; i < oldsize + 1;) {
-      if (I[i] < 0) {
-        len -= I[i];
-        i -= I[i];
-      } else {
-        if (len)
-          I[i - len] = -len;
-        len = V[I[i]] + 1 - i;
-        split<T>(I, V, i, i + len, h);
-        i += len;
-        len = 0;
-      };
-    };
-    if (len)
-      I[i - len] = -len;
-  };
-
-  for (i = 0; i < oldsize + 1; i++)
-    I[V[i]] = i;
-}
-
-//  End of 'verbatim' code.
-// ------------------------------------------------------------------------
-
-}  // namespace qsuf
-
-#endif  // COURGETTE_THIRD_PARTY_BSDIFF_QSUFSORT_H_