1 files changed, 231 insertions, 0 deletions
diff --git a/sdch/open-vcdiff/src/rolling_hash_test.cc b/sdch/open-vcdiff/src/rolling_hash_test.cc
new file mode 100644
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+++ b/sdch/open-vcdiff/src/rolling_hash_test.cc
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+// Copyright 2007 Google Inc.
+// Authors: Jeff Dean, Lincoln Smith
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <config.h>
+#include "rolling_hash.h"
+#include <stdint.h>  // uint32_t
+#include <stdlib.h>  // rand, srand
+#include <vector>
+#include "testing.h"
+
+namespace open_vcdiff {
+namespace {
+
+static const uint32_t kBase = RollingHashUtil::kBase;
+
+class RollingHashSimpleTest : public testing::Test {
+ protected:
+  RollingHashSimpleTest() { }
+  virtual ~RollingHashSimpleTest() { }
+
+  void TestModBase(uint32_t operand) {
+    EXPECT_EQ(operand % kBase, RollingHashUtil::ModBase(operand));
+    EXPECT_EQ(static_cast<uint32_t>((-static_cast<int32_t>(operand)) % kBase),
+              RollingHashUtil::FindModBaseInverse(operand));
+    EXPECT_EQ(0U, RollingHashUtil::ModBase(
+        operand + RollingHashUtil::FindModBaseInverse(operand)));
+  }
+
+  void TestHashFirstTwoBytes(char first_value, char second_value) {
+    char buf[2];
+    buf[0] = first_value;
+    buf[1] = second_value;
+    EXPECT_EQ(RollingHashUtil::HashFirstTwoBytes(buf),
+              RollingHashUtil::HashStep(RollingHashUtil::HashStep(0,
+                                                                  first_value),
+                                        second_value));
+    EXPECT_EQ(RollingHashUtil::HashFirstTwoBytes(buf),
+              RollingHashUtil::HashStep(static_cast<unsigned char>(first_value),
+                                        second_value));
+  }
+};
+
+#ifdef GTEST_HAS_DEATH_TEST
+typedef RollingHashSimpleTest RollingHashDeathTest;
+#endif  // GTEST_HAS_DEATH_TEST
+
+TEST_F(RollingHashSimpleTest, KBaseIsAPowerOfTwo) {
+  EXPECT_EQ(0U, kBase & (kBase - 1));
+}
+
+TEST_F(RollingHashSimpleTest, TestModBaseForValues) {
+  TestModBase(0);
+  TestModBase(10);
+  TestModBase(static_cast<uint32_t>(-10));
+  TestModBase(kBase - 1);
+  TestModBase(kBase);
+  TestModBase(kBase + 1);
+  TestModBase(0x7FFFFFFF);
+  TestModBase(0x80000000);
+  TestModBase(0xFFFFFFFE);
+  TestModBase(0xFFFFFFFF);
+}
+
+TEST_F(RollingHashSimpleTest, VerifyHashFirstTwoBytes) {
+  TestHashFirstTwoBytes(0x00, 0x00);
+  TestHashFirstTwoBytes(0x00, 0xFF);
+  TestHashFirstTwoBytes(0xFF, 0x00);
+  TestHashFirstTwoBytes(0xFF, 0xFF);
+  TestHashFirstTwoBytes(0x00, 0x80);
+  TestHashFirstTwoBytes(0x7F, 0xFF);
+  TestHashFirstTwoBytes(0x7F, 0x80);
+  TestHashFirstTwoBytes(0x01, 0x8F);
+}
+
+#ifdef GTEST_HAS_DEATH_TEST
+TEST_F(RollingHashDeathTest, InstantiateRollingHashWithoutCallingInit) {
+  EXPECT_DEBUG_DEATH(RollingHash<16> bad_hash, "Init");
+}
+#endif  // GTEST_HAS_DEATH_TEST
+
+class RollingHashTest : public testing::Test {
+ public:
+  static const int kUpdateHashBlocks = 1000;
+  static const int kLargestBlockSize = 128;
+
+  static void MakeRandomBuffer(char* buffer, int buffer_size) {
+    for (int i = 0; i < buffer_size; ++i) {
+      buffer[i] = PortableRandomInRange<unsigned char>(0xFF);
+    }
+  }
+
+  template<int kBlockSize> static void BM_DefaultHash(int iterations,
+                                                      const char *buffer) {
+    RollingHash<kBlockSize> hasher;
+    static uint32_t result_array[kUpdateHashBlocks];
+    for (int iter = 0; iter < iterations; ++iter) {
+      for (int i = 0; i < kUpdateHashBlocks; ++i) {
+        result_array[i] = hasher.Hash(&buffer[i]);
+      }
+    }
+  }
+
+  template<int kBlockSize> static void BM_UpdateHash(int iterations,
+                                                     const char *buffer) {
+    RollingHash<kBlockSize> hasher;
+    static uint32_t result_array[kUpdateHashBlocks];
+    for (int iter = 0; iter < iterations; ++iter) {
+      uint32_t running_hash = hasher.Hash(buffer);
+      for (int i = 0; i < kUpdateHashBlocks; ++i) {
+        running_hash = hasher.UpdateHash(running_hash,
+                                         buffer[i],
+                                         buffer[i + kBlockSize]);
+        result_array[i] = running_hash;
+      }
+    }
+  }
+
+ protected:
+  static const int kUpdateHashTestIterations = 400;
+  static const int kTimingTestSize = 1 << 14;  // 16K iterations
+
+  RollingHashTest() { }
+  virtual ~RollingHashTest() { }
+
+  template<int kBlockSize> void UpdateHashMatchesHashForBlockSize() {
+    RollingHash<kBlockSize>::Init();
+    RollingHash<kBlockSize> hasher;
+    for (int x = 0; x < kUpdateHashTestIterations; ++x) {
+      int random_buffer_size =
+          PortableRandomInRange(kUpdateHashBlocks - 1) + kBlockSize;
+      MakeRandomBuffer(buffer_, random_buffer_size);
+      uint32_t running_hash = hasher.Hash(buffer_);
+      for (int i = kBlockSize; i < random_buffer_size; ++i) {
+        // UpdateHash() calculates the hash value incrementally.
+        running_hash = hasher.UpdateHash(running_hash,
+                                         buffer_[i - kBlockSize],
+                                         buffer_[i]);
+        // Hash() calculates the hash value from scratch.  Verify that both
+        // methods return the same hash value.
+        EXPECT_EQ(running_hash, hasher.Hash(&buffer_[i + 1 - kBlockSize]));
+      }
+    }
+  }
+
+  template<int kBlockSize> double DefaultHashTimingTest() {
+    // Execution time is expected to be O(kBlockSize) per hash operation,
+    // so scale the number of iterations accordingly
+    const int kTimingTestIterations = kTimingTestSize / kBlockSize;
+    CycleTimer timer;
+    timer.Start();
+    BM_DefaultHash<kBlockSize>(kTimingTestIterations, buffer_);
+    timer.Stop();
+    return static_cast<double>(timer.GetInUsec())
+        / (kTimingTestIterations * kUpdateHashBlocks);
+  }
+
+  template<int kBlockSize> double RollingTimingTest() {
+    // Execution time is expected to be O(1) per hash operation,
+    // so leave the number of iterations constant
+    const int kTimingTestIterations = kTimingTestSize;
+    CycleTimer timer;
+    timer.Start();
+    BM_UpdateHash<kBlockSize>(kTimingTestIterations, buffer_);
+    timer.Stop();
+    return static_cast<double>(timer.GetInUsec())
+        / (kTimingTestIterations * kUpdateHashBlocks);
+  }
+
+  double FindPercentage(double original, double modified) {
+    if (original < 0.0001) {
+      return 0.0;
+    } else {
+      return ((modified - original) / original) * 100.0;
+    }
+  }
+
+  template<int kBlockSize> void RunTimingTestForBlockSize() {
+    RollingHash<kBlockSize>::Init();
+    MakeRandomBuffer(buffer_, sizeof(buffer_));
+    const double time_for_default_hash = DefaultHashTimingTest<kBlockSize>();
+    const double time_for_rolling_hash = RollingTimingTest<kBlockSize>();
+    printf("%d\t%f\t%f (%f%%)\n",
+           kBlockSize,
+           time_for_default_hash,
+           time_for_rolling_hash,
+           FindPercentage(time_for_default_hash, time_for_rolling_hash));
+    CHECK_GT(time_for_default_hash, 0.0);
+    CHECK_GT(time_for_rolling_hash, 0.0);
+    if (kBlockSize > 16) {
+      EXPECT_GT(time_for_default_hash, time_for_rolling_hash);
+    }
+  }
+
+  char buffer_[kUpdateHashBlocks + kLargestBlockSize];
+};
+
+TEST_F(RollingHashTest, UpdateHashMatchesHashFromScratch) {
+  srand(1);  // test should be deterministic, including calls to rand()
+  UpdateHashMatchesHashForBlockSize<4>();
+  UpdateHashMatchesHashForBlockSize<8>();
+  UpdateHashMatchesHashForBlockSize<16>();
+  UpdateHashMatchesHashForBlockSize<32>();
+  UpdateHashMatchesHashForBlockSize<64>();
+  UpdateHashMatchesHashForBlockSize<128>();
+}
+
+TEST_F(RollingHashTest, TimingTests) {
+  srand(1);  // test should be deterministic, including calls to rand()
+  printf("BlkSize\tHash (us)\tUpdateHash (us)\n");
+  RunTimingTestForBlockSize<4>();
+  RunTimingTestForBlockSize<8>();
+  RunTimingTestForBlockSize<16>();
+  RunTimingTestForBlockSize<32>();
+  RunTimingTestForBlockSize<64>();
+  RunTimingTestForBlockSize<128>();
+}
+
+}  // anonymous namespace
+}  // namespace open_vcdiff