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3party/bsdiff-courgette/bsdiff/bsdiff_search.h

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+// 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>
+// 2016-06-28 - Moved matchlen() and search() to a new file; format; changed
+//              search() use std::lexicographical_compare().
+// 2016-06-30 - Changed matchlen() input; changed search() to return struct.
+//                --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>
+
+namespace bsdiff {
+
+// Return values of search().
+struct SearchResult {
+  SearchResult(int pos_in, int size_in) : pos(pos_in), size(size_in) {}
+  int pos;
+  int size;
+};
+
+// Similar to ::memcmp(), but assumes equal |size| and returns match length.
+inline int matchlen(const unsigned char* buf1,
+                    const unsigned char* buf2,
+                    int size) {
+  for (int i = 0; i < size; ++i)
+    if (buf1[i] != buf2[i])
+      return i;
+  return size;
+}
+
+// Finds a suffix in |old| that has the longest common prefix with |keybuf|,
+// aided by suffix array |sa| 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>
+SearchResult search(const T & sa,
+                    const unsigned char* srcbuf,
+                    int srcsize,
+                    const unsigned char* keybuf,
+                    int keysize) {
+  int lo = 0;
+  int hi = srcsize;
+  while (hi - lo > 1) {
+    int mid = (lo + hi) / 2;
+    if (std::lexicographical_compare(
+            srcbuf + sa[mid], srcbuf + srcsize, keybuf, keybuf + keysize)) {
+      lo = mid;
+    } else {
+      hi = mid;
+    }
+  }
+  int x = matchlen(srcbuf + sa[lo], keybuf, std::min(srcsize - sa[lo], keysize));
+  int y = matchlen(srcbuf + sa[hi], keybuf, std::min(srcsize - sa[hi], keysize));
+  return (x > y) ? SearchResult(sa[lo], x) : SearchResult(sa[hi], y);
+}
+
+}  // namespace bsdiff
+
+#endif  // COURGETTE_THIRD_PARTY_BSDIFF_BSDIFF_SEARCH_H_