[Courgette] Make BSDiff search() use lexicographical_compare().

courgette/third_party/bsdiff/bsdiff_search.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>
+// 2015-08-03 - Change search() to template to allow PagedArray usage.
+//                --Samuel Huang <huangs@chromium.org>
+// 2015-08-19 - Optimized search() to be non-recursive.
+//                --Samuel Huang <huangs@chromium.org>
+// 2016-06-17 - Moved matchlen() and search() to a new file; format; changed
+//              search() use std::lexicographical_compare().
+//                --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_BSDIFF_SEARCH_H_
+#define COURGETTE_THIRD_PARTY_BSDIFF_BSDIFF_SEARCH_H_
+
+#include <algorithm>
+#include <cstring>
+
+namespace courgette {
+
+// Similar to ::memcmp(), but returns match length instead.
+inline int matchlen(const unsigned char* old,
+                    int oldsize,
+                    const unsigned char* newbuf,
+                    int newsize) {
+  int i;
+
+  for (i = 0; (i < oldsize) && (i < newsize); i++)
+    if (old[i] != newbuf[i])
+      break;
+
+  return i;
+}
+
+// Finds a suffix in |old| that has the longest common prefix with |newbuf|,
+// aided by suffix array |I| of |old|. Returns the match length, and writes to
+// |pos| a position of best match in |old|. If multiple such positions exist,
+// |pos| would take an arbitrary one.
+template <class T>
+int search(T I,
+           const unsigned char* old,
+           int oldsize,
+           const unsigned char* newbuf,
+           int newsize,
+           int* pos) {
+  int lo = 0;
+  int hi = oldsize;
+  while (hi - lo >= 2) {
+    int mid = (lo + hi) / 2;
+    if (std::lexicographical_compare(old + I[mid], old + oldsize, newbuf,
+                                     newbuf + newsize)) {
+      lo = mid;
+    } else {
+      hi = mid;
+    }
+  }
+
+  int x = matchlen(old + I[lo], oldsize - I[lo], newbuf, newsize);
+  int y = matchlen(old + I[hi], oldsize - I[hi], newbuf, newsize);
+  if (x > y) {
+    *pos = I[lo];
+    return x;
+  }
+  *pos = I[hi];
+  return y;
+}
+
+}  // namespace courgette
+
+#endif  // COURGETTE_THIRD_PARTY_BSDIFF_BSDIFF_SEARCH_H_