[Zucchini] crc32 implementation and unittests.

This introduces a single function CalculateCrc32, adapted from LZMA SDK, with stl-like interface.

Bug: 729154
Change-Id: Ie15fb95b143e92b8e0a1650386ef01b7b2de5401
Reviewed-on: https://chromium-review.googlesource.com/563876
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485476}

chrome/installer/zucchini/BUILD.gn

@@ -8,6 +8,8 @@ import("//testing/test.gni")
 static_library("zucchini_lib") {
   sources = [
     "buffer_view.h",
+    "crc32.cc",
+    "crc32.h",
     "disassembler.cc",
     "disassembler.h",
     "image_utils.h",
@@ -41,6 +43,7 @@ if (is_win) {
 test("zucchini_unittests") {
   sources = [
     "buffer_view_unittest.cc",
+    "crc32_unittest.cc",
     "typed_value_unittest.cc",
   ]
 

chrome/installer/zucchini/crc32.cc

+// Copyright 2017 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.
+
+#include "chrome/installer/zucchini/crc32.h"
+
+#include <array>
+
+#include "base/logging.h"
+
+namespace zucchini {
+
+namespace {
+
+std::array<uint32_t, 256> MakeCrc32Table() {
+  constexpr uint32_t kCrc32Poly = 0xEDB88320;
+
+  std::array<uint32_t, 256> crc32Table;
+  for (uint32_t i = 0; i < 256; ++i) {
+    uint32_t r = i;
+    for (int j = 0; j < 8; ++j)
+      r = (r >> 1) ^ (kCrc32Poly & ~((r & 1) - 1));
+    crc32Table[i] = r;
+  }
+  return crc32Table;
+}
+
+}  // namespace
+
+// Minimalistic CRC-32 implementation for Zucchini usage. Adapted from LZMA SDK
+// (found at third_party/lzma_sdk/7zCrc.c), which is public domain.
+uint32_t CalculateCrc32(const uint8_t* first, const uint8_t* last) {
+  DCHECK_GE(last, first);
+
+  static const std::array<uint32_t, 256> kCrc32Table = MakeCrc32Table();
+
+  uint32_t ret = 0xFFFFFFFF;
+  for (; first != last; ++first)
+    ret = kCrc32Table[(ret ^ *first) & 0xFF] ^ (ret >> 8);
+  return ret ^ 0xFFFFFFFF;
+}
+
+}  // namespace zucchini

chrome/installer/zucchini/crc32.h

+// Copyright 2017 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 CHROME_INSTALLER_ZUCCHINI_CRC32_H_
+#define CHROME_INSTALLER_ZUCCHINI_CRC32_H_
+
+#include <cstdint>
+
+namespace zucchini {
+
+// Calculates CRC-32 of the given range [|first|, |last|).
+uint32_t CalculateCrc32(const uint8_t* first, const uint8_t* last);
+
+}  // namespace zucchini
+
+#endif  // CHROME_INSTALLER_ZUCCHINI_CRC32_H_

chrome/installer/zucchini/crc32_unittest.cc

+// Copyright 2017 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.
+
+#include "chrome/installer/zucchini/crc32.h"
+
+#include <cstdint>
+#include <iterator>
+
+#include "base/test/gtest_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace zucchini {
+
+constexpr uint8_t bytes[] = {0x10, 0x32, 0x54, 0x76, 0x98,
+                             0xBA, 0xDC, 0xFE, 0x10, 0x00};
+
+TEST(Crc32Test, All) {
+  // Results can be verified with any CRC-32 calculator found online.
+
+  // Empty region.
+  EXPECT_EQ(0x00000000U, CalculateCrc32(std::begin(bytes), std::begin(bytes)));
+
+  // Single byte.
+  EXPECT_EQ(0xCFB5FFE9U,
+            CalculateCrc32(std::begin(bytes), std::begin(bytes) + 1));
+
+  // Same byte (0x10) appearing at different location.
+  EXPECT_EQ(0xCFB5FFE9U,
+            CalculateCrc32(std::begin(bytes) + 8, std::begin(bytes) + 9));
+
+  // Single byte of 0.
+  EXPECT_EQ(0xD202EF8DU,
+            CalculateCrc32(std::begin(bytes) + 9, std::end(bytes)));
+
+  // Whole region.
+  EXPECT_EQ(0xA86FD7D6U, CalculateCrc32(std::begin(bytes), std::end(bytes)));
+
+  // Whole region excluding 0 at end.
+  EXPECT_EQ(0x0762F38BU,
+            CalculateCrc32(std::begin(bytes), std::begin(bytes) + 9));
+
+  EXPECT_DCHECK_DEATH(CalculateCrc32(std::begin(bytes) + 1, std::begin(bytes)));
+}
+
+}  // namespace zucchini