Squashed 'src/crc32c/' content from commit 224988680f7673cd7c769963d4035cb315aa3388

git-subtree-dir: src/crc32c
git-subtree-split: 224988680f7673cd7c769963d4035cb315aa3388

24 files changed, 1754 insertions, 0 deletions

diff --git a/src/crc32c.cc b/src/crc32c.cc
new file mode 100644
index 0000000000..4d3018af47
--- /dev/null
+++ b/src/crc32c.cc
@@ -0,0 +1,39 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "crc32c/crc32c.h"
+
+#include <cstddef>
+#include <cstdint>
+
+#include "./crc32c_arm64.h"
+#include "./crc32c_arm64_linux_check.h"
+#include "./crc32c_internal.h"
+#include "./crc32c_sse42.h"
+#include "./crc32c_sse42_check.h"
+
+namespace crc32c {
+
+uint32_t Extend(uint32_t crc, const uint8_t* data, size_t count) {
+#if HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+  static bool can_use_sse42 = CanUseSse42();
+  if (can_use_sse42) return ExtendSse42(crc, data, count);
+#elif HAVE_ARM64_CRC32C
+  static bool can_use_arm_linux = CanUseArm64Linux();
+  if (can_use_arm_linux) return ExtendArm64(crc, data, count);
+#endif  // HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+  return ExtendPortable(crc, data, count);
+}
+
+extern "C" uint32_t crc32c_extend(uint32_t crc, const uint8_t* data,
+                                  size_t count) {
+  return crc32c::Extend(crc, data, count);
+}
+
+extern "C" uint32_t crc32c_value(const uint8_t* data, size_t count) {
+  return crc32c::Crc32c(data, count);
+}
+
+}  // namespace crc32c
diff --git a/src/crc32c_arm64.cc b/src/crc32c_arm64.cc
new file mode 100644
index 0000000000..b872245f95
--- /dev/null
+++ b/src/crc32c_arm64.cc
@@ -0,0 +1,126 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "./crc32c_arm64.h"
+
+// In a separate source file to allow this accelerated CRC32C function to be
+// compiled with the appropriate compiler flags to enable ARM NEON CRC32C
+// instructions.
+
+// This implementation is based on https://github.com/google/leveldb/pull/490.
+
+#include <cstddef>
+#include <cstdint>
+
+#include "./crc32c_internal.h"
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#if HAVE_ARM64_CRC32C
+
+#include <arm_acle.h>
+#include <arm_neon.h>
+
+#define KBYTES 1032
+#define SEGMENTBYTES 256
+
+// compute 8bytes for each segment parallelly
+#define CRC32C32BYTES(P, IND)                                             \
+  do {                                                                    \
+    crc1 = __crc32cd(                                                     \
+        crc1, *((const uint64_t *)(P) + (SEGMENTBYTES / 8) * 1 + (IND))); \
+    crc2 = __crc32cd(                                                     \
+        crc2, *((const uint64_t *)(P) + (SEGMENTBYTES / 8) * 2 + (IND))); \
+    crc3 = __crc32cd(                                                     \
+        crc3, *((const uint64_t *)(P) + (SEGMENTBYTES / 8) * 3 + (IND))); \
+    crc0 = __crc32cd(                                                     \
+        crc0, *((const uint64_t *)(P) + (SEGMENTBYTES / 8) * 0 + (IND))); \
+  } while (0);
+
+// compute 8*8 bytes for each segment parallelly
+#define CRC32C256BYTES(P, IND)      \
+  do {                              \
+    CRC32C32BYTES((P), (IND)*8 + 0) \
+    CRC32C32BYTES((P), (IND)*8 + 1) \
+    CRC32C32BYTES((P), (IND)*8 + 2) \
+    CRC32C32BYTES((P), (IND)*8 + 3) \
+    CRC32C32BYTES((P), (IND)*8 + 4) \
+    CRC32C32BYTES((P), (IND)*8 + 5) \
+    CRC32C32BYTES((P), (IND)*8 + 6) \
+    CRC32C32BYTES((P), (IND)*8 + 7) \
+  } while (0);
+
+// compute 4*8*8 bytes for each segment parallelly
+#define CRC32C1024BYTES(P)   \
+  do {                       \
+    CRC32C256BYTES((P), 0)   \
+    CRC32C256BYTES((P), 1)   \
+    CRC32C256BYTES((P), 2)   \
+    CRC32C256BYTES((P), 3)   \
+    (P) += 4 * SEGMENTBYTES; \
+  } while (0)
+
+namespace crc32c {
+
+uint32_t ExtendArm64(uint32_t crc, const uint8_t *buf, size_t size) {
+  int64_t length = size;
+  uint32_t crc0, crc1, crc2, crc3;
+  uint64_t t0, t1, t2;
+
+  // k0=CRC(x^(3*SEGMENTBYTES*8)), k1=CRC(x^(2*SEGMENTBYTES*8)),
+  // k2=CRC(x^(SEGMENTBYTES*8))
+  const poly64_t k0 = 0x8d96551c, k1 = 0xbd6f81f8, k2 = 0xdcb17aa4;
+
+  crc = crc ^ kCRC32Xor;
+  const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
+
+  while (length >= KBYTES) {
+    crc0 = crc;
+    crc1 = 0;
+    crc2 = 0;
+    crc3 = 0;
+
+    // Process 1024 bytes in parallel.
+    CRC32C1024BYTES(p);
+
+    // Merge the 4 partial CRC32C values.
+    t2 = (uint64_t)vmull_p64(crc2, k2);
+    t1 = (uint64_t)vmull_p64(crc1, k1);
+    t0 = (uint64_t)vmull_p64(crc0, k0);
+    crc = __crc32cd(crc3, *(uint64_t *)p);
+    p += sizeof(uint64_t);
+    crc ^= __crc32cd(0, t2);
+    crc ^= __crc32cd(0, t1);
+    crc ^= __crc32cd(0, t0);
+
+    length -= KBYTES;
+  }
+
+  while (length >= 8) {
+    crc = __crc32cd(crc, *(uint64_t *)p);
+    p += 8;
+    length -= 8;
+  }
+
+  if (length & 4) {
+    crc = __crc32cw(crc, *(uint32_t *)p);
+    p += 4;
+  }
+
+  if (length & 2) {
+    crc = __crc32ch(crc, *(uint16_t *)p);
+    p += 2;
+  }
+
+  if (length & 1) {
+    crc = __crc32cb(crc, *p);
+  }
+
+  return crc ^ kCRC32Xor;
+}
+
+}  // namespace crc32c
+
+#endif  // HAVE_ARM64_CRC32C
diff --git a/src/crc32c_arm64.h b/src/crc32c_arm64.h
new file mode 100644
index 0000000000..100cd56ec8
--- /dev/null
+++ b/src/crc32c_arm64.h
@@ -0,0 +1,27 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+// Linux-specific code checking the availability for ARM CRC32C instructions.
+
+#ifndef CRC32C_CRC32C_ARM_LINUX_H_
+#define CRC32C_CRC32C_ARM_LINUX_H_
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#if HAVE_ARM64_CRC32C
+
+namespace crc32c {
+
+uint32_t ExtendArm64(uint32_t crc, const uint8_t* data, size_t count);
+
+}  // namespace crc32c
+
+#endif  // HAVE_ARM64_CRC32C
+
+#endif  // CRC32C_CRC32C_ARM_LINUX_H_
diff --git a/src/crc32c_arm64_linux_check.h b/src/crc32c_arm64_linux_check.h
new file mode 100644
index 0000000000..1a20a757bb
--- /dev/null
+++ b/src/crc32c_arm64_linux_check.h
@@ -0,0 +1,50 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+// ARM Linux-specific code checking for the availability of CRC32C instructions.
+
+#ifndef CRC32C_CRC32C_ARM_LINUX_CHECK_H_
+#define CRC32C_CRC32C_ARM_LINUX_CHECK_H_
+
+// X86-specific code checking for the availability of SSE4.2 instructions.
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#if HAVE_ARM64_CRC32C
+
+#if HAVE_STRONG_GETAUXVAL
+#include <sys/auxv.h>
+#elif HAVE_WEAK_GETAUXVAL
+// getauxval() is not available on Android until API level 20. Link it as a weak
+// symbol.
+extern "C" unsigned long getauxval(unsigned long type) __attribute__((weak));
+
+#define AT_HWCAP 16
+#endif  // HAVE_STRONG_GETAUXVAL || HAVE_WEAK_GETAUXVAL
+
+namespace crc32c {
+
+inline bool CanUseArm64Linux() {
+#if HAVE_STRONG_GETAUXVAL || HAVE_WEAK_GETAUXVAL
+  // From 'arch/arm64/include/uapi/asm/hwcap.h' in Linux kernel source code.
+  constexpr unsigned long kHWCAP_PMULL = 1 << 4;
+  constexpr unsigned long kHWCAP_CRC32 = 1 << 7;
+  unsigned long hwcap = (&getauxval != nullptr) ? getauxval(AT_HWCAP) : 0;
+  return (hwcap & (kHWCAP_PMULL | kHWCAP_CRC32)) ==
+         (kHWCAP_PMULL | kHWCAP_CRC32);
+#else
+  return false;
+#endif  // HAVE_STRONG_GETAUXVAL || HAVE_WEAK_GETAUXVAL
+}
+
+}  // namespace crc32c
+
+#endif  // HAVE_ARM64_CRC32C
+
+#endif  // CRC32C_CRC32C_ARM_LINUX_CHECK_H_
diff --git a/src/crc32c_arm64_unittest.cc b/src/crc32c_arm64_unittest.cc
new file mode 100644
index 0000000000..6f917d9c0c
--- /dev/null
+++ b/src/crc32c_arm64_unittest.cc
@@ -0,0 +1,24 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+
+#include "./crc32c_arm64.h"
+#include "./crc32c_extend_unittests.h"
+
+namespace crc32c {
+
+#if HAVE_ARM64_CRC32C
+
+struct Arm64TestTraits {
+  static uint32_t Extend(uint32_t crc, const uint8_t* data, size_t count) {
+    return ExtendArm64(crc, data, count);
+  }
+};
+
+INSTANTIATE_TYPED_TEST_SUITE_P(Arm64, ExtendTest, Arm64TestTraits);
+
+#endif  // HAVE_ARM64_CRC32C
+
+}  // namespace crc32c
diff --git a/src/crc32c_benchmark.cc b/src/crc32c_benchmark.cc
new file mode 100644
index 0000000000..c464304b3f
--- /dev/null
+++ b/src/crc32c_benchmark.cc
@@ -0,0 +1,106 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#include "benchmark/benchmark.h"
+
+#if CRC32C_TESTS_BUILT_WITH_GLOG
+#include "glog/logging.h"
+#endif  // CRC32C_TESTS_BUILT_WITH_GLOG
+
+#include "./crc32c_arm64.h"
+#include "./crc32c_arm64_linux_check.h"
+#include "./crc32c_internal.h"
+#include "./crc32c_sse42.h"
+#include "./crc32c_sse42_check.h"
+#include "crc32c/crc32c.h"
+
+class CRC32CBenchmark : public benchmark::Fixture {
+ public:
+  void SetUp(const benchmark::State& state) override {
+    block_size_ = static_cast<size_t>(state.range(0));
+    block_data_ = std::string(block_size_, 'x');
+    block_buffer_ = reinterpret_cast<const uint8_t*>(block_data_.data());
+  }
+
+ protected:
+  std::string block_data_;
+  const uint8_t* block_buffer_;
+  size_t block_size_;
+};
+
+BENCHMARK_DEFINE_F(CRC32CBenchmark, Public)(benchmark::State& state) {
+  uint32_t crc = 0;
+  for (auto _ : state)
+    crc = crc32c::Extend(crc, block_buffer_, block_size_);
+  state.SetBytesProcessed(state.iterations() * block_size_);
+}
+BENCHMARK_REGISTER_F(CRC32CBenchmark, Public)
+    ->RangeMultiplier(16)
+    ->Range(256, 16777216);  // Block size.
+
+BENCHMARK_DEFINE_F(CRC32CBenchmark, Portable)(benchmark::State& state) {
+  uint32_t crc = 0;
+  for (auto _ : state)
+    crc = crc32c::ExtendPortable(crc, block_buffer_, block_size_);
+  state.SetBytesProcessed(state.iterations() * block_size_);
+}
+BENCHMARK_REGISTER_F(CRC32CBenchmark, Portable)
+    ->RangeMultiplier(16)
+    ->Range(256, 16777216);  // Block size.
+
+#if HAVE_ARM64_CRC32C
+
+BENCHMARK_DEFINE_F(CRC32CBenchmark, ArmLinux)(benchmark::State& state) {
+  if (!crc32c::CanUseArm64Linux()) {
+    state.SkipWithError("ARM CRC32C instructions not available or not enabled");
+    return;
+  }
+
+  uint32_t crc = 0;
+  for (auto _ : state)
+    crc = crc32c::ExtendArm64(crc, block_buffer_, block_size_);
+  state.SetBytesProcessed(state.iterations() * block_size_);
+}
+BENCHMARK_REGISTER_F(CRC32CBenchmark, ArmLinux)
+    ->RangeMultiplier(16)
+    ->Range(256, 16777216);  // Block size.
+
+#endif  // HAVE_ARM64_CRC32C
+
+#if HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+BENCHMARK_DEFINE_F(CRC32CBenchmark, Sse42)(benchmark::State& state) {
+  if (!crc32c::CanUseSse42()) {
+    state.SkipWithError("SSE4.2 instructions not available or not enabled");
+    return;
+  }
+
+  uint32_t crc = 0;
+  for (auto _ : state)
+    crc = crc32c::ExtendSse42(crc, block_buffer_, block_size_);
+  state.SetBytesProcessed(state.iterations() * block_size_);
+}
+BENCHMARK_REGISTER_F(CRC32CBenchmark, Sse42)
+    ->RangeMultiplier(16)
+    ->Range(256, 16777216);  // Block size.
+
+#endif  // HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+int main(int argc, char** argv) {
+#if CRC32C_TESTS_BUILT_WITH_GLOG
+  google::InitGoogleLogging(argv[0]);
+  google::InstallFailureSignalHandler();
+#endif  // CRC32C_TESTS_BUILT_WITH_GLOG
+
+  benchmark::Initialize(&argc, argv);
+  benchmark::RunSpecifiedBenchmarks();
+  return 0;
+}
diff --git a/src/crc32c_capi_unittest.c b/src/crc32c_capi_unittest.c
new file mode 100644
index 0000000000..c8993a0959
--- /dev/null
+++ b/src/crc32c_capi_unittest.c
@@ -0,0 +1,66 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "crc32c/crc32c.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+  /* From rfc3720 section B.4. */
+  uint8_t buf[32];
+
+  memset(buf, 0, sizeof(buf));
+  if ((uint32_t)0x8a9136aa != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(zeros) test failed\n");
+    return 1;
+  }
+
+  memset(buf, 0xff, sizeof(buf));
+  if ((uint32_t)0x62a8ab43 != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(0xff) test failed\n");
+    return 1;
+  }
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = (uint8_t)i;
+  if ((uint32_t)0x46dd794e != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(0..31) test failed\n");
+    return 1;
+  }
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = (uint8_t)(31 - i);
+  if ((uint32_t)0x113fdb5c != crc32c_value(buf, sizeof(buf))) {
+    printf("crc32c_value(31..0) test failed\n");
+    return 1;
+  }
+
+  uint8_t data[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  if ((uint32_t)0xd9963a56 != crc32c_value(data, sizeof(data))) {
+    printf("crc32c_value(31..0) test failed\n");
+    return 1;
+  }
+
+  const uint8_t* hello_space_world = (const uint8_t*)"hello world";
+  const uint8_t* hello_space = (const uint8_t*)"hello ";
+  const uint8_t* world = (const uint8_t*)"world";
+
+  if (crc32c_value(hello_space_world, 11) !=
+      crc32c_extend(crc32c_value(hello_space, 6), world, 5)) {
+    printf("crc32c_extend test failed\n");
+    return 1;
+  }
+
+  printf("All tests passed\n");
+  return 0;
+}
diff --git a/src/crc32c_config.h.in b/src/crc32c_config.h.in
new file mode 100644
index 0000000000..4034fa5644
--- /dev/null
+++ b/src/crc32c_config.h.in
@@ -0,0 +1,36 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_CONFIG_H_
+#define CRC32C_CRC32C_CONFIG_H_
+
+// Define to 1 if building for a big-endian platform.
+#cmakedefine01 BYTE_ORDER_BIG_ENDIAN
+
+// Define to 1 if the compiler has the __builtin_prefetch intrinsic.
+#cmakedefine01 HAVE_BUILTIN_PREFETCH
+
+// Define to 1 if targeting X86 and the compiler has the _mm_prefetch intrinsic.
+#cmakedefine01 HAVE_MM_PREFETCH
+
+// Define to 1 if targeting X86 and the compiler has the _mm_crc32_u{8,32,64}
+// intrinsics.
+#cmakedefine01 HAVE_SSE42
+
+// Define to 1 if targeting ARM and the compiler has the __crc32c{b,h,w,d} and
+// the vmull_p64 intrinsics.
+#cmakedefine01 HAVE_ARM64_CRC32C
+
+// Define to 1 if the system libraries have the getauxval function in the
+// <sys/auxv.h> header. Should be true on Linux and Android API level 20+.
+#cmakedefine01 HAVE_STRONG_GETAUXVAL
+
+// Define to 1 if the compiler supports defining getauxval as a weak symbol.
+// Should be true for any compiler that supports __attribute__((weak)).
+#cmakedefine01 HAVE_WEAK_GETAUXVAL
+
+// Define to 1 if CRC32C tests have been built with Google Logging.
+#cmakedefine01 CRC32C_TESTS_BUILT_WITH_GLOG
+
+#endif  // CRC32C_CRC32C_CONFIG_H_
diff --git a/src/crc32c_extend_unittests.h b/src/crc32c_extend_unittests.h
new file mode 100644
index 0000000000..0732973737
--- /dev/null
+++ b/src/crc32c_extend_unittests.h
@@ -0,0 +1,112 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_EXTEND_UNITTESTS_H_
+#define CRC32C_CRC32C_EXTEND_UNITTESTS_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+
+#include "gtest/gtest.h"
+
+// Common test cases for all implementations of CRC32C_Extend().
+
+namespace crc32c {
+
+template<typename TestTraits>
+class ExtendTest : public testing::Test {};
+
+TYPED_TEST_SUITE_P(ExtendTest);
+
+TYPED_TEST_P(ExtendTest, StandardResults) {
+  // From rfc3720 section B.4.
+  uint8_t buf[32];
+
+  std::memset(buf, 0, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x8a9136aa),
+            TypeParam::Extend(0, buf, sizeof(buf)));
+
+  std::memset(buf, 0xff, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x62a8ab43),
+            TypeParam::Extend(0, buf, sizeof(buf)));
+
+  for (int i = 0; i < 32; ++i)
+    buf[i] = static_cast<uint8_t>(i);
+  EXPECT_EQ(static_cast<uint32_t>(0x46dd794e),
+            TypeParam::Extend(0, buf, sizeof(buf)));
+
+  for (int i = 0; i < 32; ++i)
+    buf[i] = static_cast<uint8_t>(31 - i);
+  EXPECT_EQ(static_cast<uint32_t>(0x113fdb5c),
+            TypeParam::Extend(0, buf, sizeof(buf)));
+
+  uint8_t data[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  EXPECT_EQ(static_cast<uint32_t>(0xd9963a56),
+            TypeParam::Extend(0, data, sizeof(data)));
+}
+
+TYPED_TEST_P(ExtendTest, HelloWorld) {
+  const uint8_t* hello_space_world =
+      reinterpret_cast<const uint8_t*>("hello world");
+  const uint8_t* hello_space = reinterpret_cast<const uint8_t*>("hello ");
+  const uint8_t* world = reinterpret_cast<const uint8_t*>("world");
+
+  EXPECT_EQ(TypeParam::Extend(0, hello_space_world, 11),
+            TypeParam::Extend(TypeParam::Extend(0, hello_space, 6), world, 5));
+}
+
+TYPED_TEST_P(ExtendTest, BufferSlicing) {
+  uint8_t buffer[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+
+  for (size_t i = 0; i < 48; ++i) {
+    for (size_t j = i + 1; j <= 48; ++j) {
+      uint32_t crc = 0;
+
+      if (i > 0) crc = TypeParam::Extend(crc, buffer, i);
+      crc = TypeParam::Extend(crc, buffer + i, j - i);
+      if (j < 48) crc = TypeParam::Extend(crc, buffer + j, 48 - j);
+
+      EXPECT_EQ(static_cast<uint32_t>(0xd9963a56), crc);
+    }
+  }
+}
+
+TYPED_TEST_P(ExtendTest, LargeBufferSlicing) {
+  uint8_t buffer[2048];
+  for (size_t i = 0; i < 2048; i++)
+    buffer[i] = static_cast<uint8_t>(3 * i * i + 7 * i + 11);
+
+  for (size_t i = 0; i < 2048; ++i) {
+    for (size_t j = i + 1; j <= 2048; ++j) {
+      uint32_t crc = 0;
+
+      if (i > 0) crc = TypeParam::Extend(crc, buffer, i);
+      crc = TypeParam::Extend(crc, buffer + i, j - i);
+      if (j < 2048) crc = TypeParam::Extend(crc, buffer + j, 2048 - j);
+
+      EXPECT_EQ(static_cast<uint32_t>(0x36dcc753), crc);
+    }
+  }
+}
+
+REGISTER_TYPED_TEST_SUITE_P(ExtendTest,
+    StandardResults,
+    HelloWorld,
+    BufferSlicing,
+    LargeBufferSlicing);
+
+}  // namespace crc32c
+
+#endif  // CRC32C_CRC32C_EXTEND_UNITTESTS_H_
diff --git a/src/crc32c_internal.h b/src/crc32c_internal.h
new file mode 100644
index 0000000000..2bd23dea43
--- /dev/null
+++ b/src/crc32c_internal.h
@@ -0,0 +1,23 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_INTERNAL_H_
+#define CRC32C_CRC32C_INTERNAL_H_
+
+// Internal functions that may change between releases.
+
+#include <cstddef>
+#include <cstdint>
+
+namespace crc32c {
+
+// Un-accelerated implementation that works on all CPUs.
+uint32_t ExtendPortable(uint32_t crc, const uint8_t* data, size_t count);
+
+// CRCs are pre- and post- conditioned by xoring with all ones.
+static constexpr const uint32_t kCRC32Xor = static_cast<uint32_t>(0xffffffffU);
+
+}  // namespace crc32c
+
+#endif  // CRC32C_CRC32C_INTERNAL_H_
diff --git a/src/crc32c_portable.cc b/src/crc32c_portable.cc
new file mode 100644
index 0000000000..31ec6eac53
--- /dev/null
+++ b/src/crc32c_portable.cc
@@ -0,0 +1,351 @@
+// Copyright 2008 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "./crc32c_internal.h"
+
+#include <cstddef>
+#include <cstdint>
+
+#include "./crc32c_prefetch.h"
+#include "./crc32c_read_le.h"
+#include "./crc32c_round_up.h"
+
+namespace {
+
+const uint32_t kByteExtensionTable[256] = {
+    0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c,
+    0x26a1e7e8, 0xd4ca64eb, 0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
+    0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24, 0x105ec76f, 0xe235446c,
+    0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
+    0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc,
+    0xbc267848, 0x4e4dfb4b, 0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
+    0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35, 0xaa64d611, 0x580f5512,
+    0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
+    0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad,
+    0x1642ae59, 0xe4292d5a, 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
+    0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595, 0x417b1dbc, 0xb3109ebf,
+    0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
+    0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f,
+    0xed03a29b, 0x1f682198, 0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
+    0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38, 0xdbfc821c, 0x2997011f,
+    0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
+    0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e,
+    0x4767748a, 0xb50cf789, 0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
+    0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 0x7198540d, 0x83f3d70e,
+    0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
+    0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de,
+    0xdde0eb2a, 0x2f8b6829, 0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
+    0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 0x082f63b7, 0xfa44e0b4,
+    0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
+    0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b,
+    0xb4091bff, 0x466298fc, 0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
+    0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 0xa24bb5a6, 0x502036a5,
+    0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
+    0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975,
+    0x0e330a81, 0xfc588982, 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
+    0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 0x38cc2a06, 0xcaa7a905,
+    0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
+    0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8,
+    0xe52cc12c, 0x1747422f, 0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
+    0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0, 0xd3d3e1ab, 0x21b862a8,
+    0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
+    0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78,
+    0x7fab5e8c, 0x8dc0dd8f, 0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
+    0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 0x69e9f0d5, 0x9b8273d6,
+    0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
+    0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69,
+    0xd5cf889d, 0x27a40b9e, 0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
+    0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351};
+
+const uint32_t kStrideExtensionTable0[256] = {
+    0x00000000, 0x30d23865, 0x61a470ca, 0x517648af, 0xc348e194, 0xf39ad9f1,
+    0xa2ec915e, 0x923ea93b, 0x837db5d9, 0xb3af8dbc, 0xe2d9c513, 0xd20bfd76,
+    0x4035544d, 0x70e76c28, 0x21912487, 0x11431ce2, 0x03171d43, 0x33c52526,
+    0x62b36d89, 0x526155ec, 0xc05ffcd7, 0xf08dc4b2, 0xa1fb8c1d, 0x9129b478,
+    0x806aa89a, 0xb0b890ff, 0xe1ced850, 0xd11ce035, 0x4322490e, 0x73f0716b,
+    0x228639c4, 0x125401a1, 0x062e3a86, 0x36fc02e3, 0x678a4a4c, 0x57587229,
+    0xc566db12, 0xf5b4e377, 0xa4c2abd8, 0x941093bd, 0x85538f5f, 0xb581b73a,
+    0xe4f7ff95, 0xd425c7f0, 0x461b6ecb, 0x76c956ae, 0x27bf1e01, 0x176d2664,
+    0x053927c5, 0x35eb1fa0, 0x649d570f, 0x544f6f6a, 0xc671c651, 0xf6a3fe34,
+    0xa7d5b69b, 0x97078efe, 0x8644921c, 0xb696aa79, 0xe7e0e2d6, 0xd732dab3,
+    0x450c7388, 0x75de4bed, 0x24a80342, 0x147a3b27, 0x0c5c750c, 0x3c8e4d69,
+    0x6df805c6, 0x5d2a3da3, 0xcf149498, 0xffc6acfd, 0xaeb0e452, 0x9e62dc37,
+    0x8f21c0d5, 0xbff3f8b0, 0xee85b01f, 0xde57887a, 0x4c692141, 0x7cbb1924,
+    0x2dcd518b, 0x1d1f69ee, 0x0f4b684f, 0x3f99502a, 0x6eef1885, 0x5e3d20e0,
+    0xcc0389db, 0xfcd1b1be, 0xada7f911, 0x9d75c174, 0x8c36dd96, 0xbce4e5f3,
+    0xed92ad5c, 0xdd409539, 0x4f7e3c02, 0x7fac0467, 0x2eda4cc8, 0x1e0874ad,
+    0x0a724f8a, 0x3aa077ef, 0x6bd63f40, 0x5b040725, 0xc93aae1e, 0xf9e8967b,
+    0xa89eded4, 0x984ce6b1, 0x890ffa53, 0xb9ddc236, 0xe8ab8a99, 0xd879b2fc,
+    0x4a471bc7, 0x7a9523a2, 0x2be36b0d, 0x1b315368, 0x096552c9, 0x39b76aac,
+    0x68c12203, 0x58131a66, 0xca2db35d, 0xfaff8b38, 0xab89c397, 0x9b5bfbf2,
+    0x8a18e710, 0xbacadf75, 0xebbc97da, 0xdb6eafbf, 0x49500684, 0x79823ee1,
+    0x28f4764e, 0x18264e2b, 0x18b8ea18, 0x286ad27d, 0x791c9ad2, 0x49cea2b7,
+    0xdbf00b8c, 0xeb2233e9, 0xba547b46, 0x8a864323, 0x9bc55fc1, 0xab1767a4,
+    0xfa612f0b, 0xcab3176e, 0x588dbe55, 0x685f8630, 0x3929ce9f, 0x09fbf6fa,
+    0x1baff75b, 0x2b7dcf3e, 0x7a0b8791, 0x4ad9bff4, 0xd8e716cf, 0xe8352eaa,
+    0xb9436605, 0x89915e60, 0x98d24282, 0xa8007ae7, 0xf9763248, 0xc9a40a2d,
+    0x5b9aa316, 0x6b489b73, 0x3a3ed3dc, 0x0aecebb9, 0x1e96d09e, 0x2e44e8fb,
+    0x7f32a054, 0x4fe09831, 0xddde310a, 0xed0c096f, 0xbc7a41c0, 0x8ca879a5,
+    0x9deb6547, 0xad395d22, 0xfc4f158d, 0xcc9d2de8, 0x5ea384d3, 0x6e71bcb6,
+    0x3f07f419, 0x0fd5cc7c, 0x1d81cddd, 0x2d53f5b8, 0x7c25bd17, 0x4cf78572,
+    0xdec92c49, 0xee1b142c, 0xbf6d5c83, 0x8fbf64e6, 0x9efc7804, 0xae2e4061,
+    0xff5808ce, 0xcf8a30ab, 0x5db49990, 0x6d66a1f5, 0x3c10e95a, 0x0cc2d13f,
+    0x14e49f14, 0x2436a771, 0x7540efde, 0x4592d7bb, 0xd7ac7e80, 0xe77e46e5,
+    0xb6080e4a, 0x86da362f, 0x97992acd, 0xa74b12a8, 0xf63d5a07, 0xc6ef6262,
+    0x54d1cb59, 0x6403f33c, 0x3575bb93, 0x05a783f6, 0x17f38257, 0x2721ba32,
+    0x7657f29d, 0x4685caf8, 0xd4bb63c3, 0xe4695ba6, 0xb51f1309, 0x85cd2b6c,
+    0x948e378e, 0xa45c0feb, 0xf52a4744, 0xc5f87f21, 0x57c6d61a, 0x6714ee7f,
+    0x3662a6d0, 0x06b09eb5, 0x12caa592, 0x22189df7, 0x736ed558, 0x43bced3d,
+    0xd1824406, 0xe1507c63, 0xb02634cc, 0x80f40ca9, 0x91b7104b, 0xa165282e,
+    0xf0136081, 0xc0c158e4, 0x52fff1df, 0x622dc9ba, 0x335b8115, 0x0389b970,
+    0x11ddb8d1, 0x210f80b4, 0x7079c81b, 0x40abf07e, 0xd2955945, 0xe2476120,
+    0xb331298f, 0x83e311ea, 0x92a00d08, 0xa272356d, 0xf3047dc2, 0xc3d645a7,
+    0x51e8ec9c, 0x613ad4f9, 0x304c9c56, 0x009ea433};
+
+const uint32_t kStrideExtensionTable1[256] = {
+    0x00000000, 0x54075546, 0xa80eaa8c, 0xfc09ffca, 0x55f123e9, 0x01f676af,
+    0xfdff8965, 0xa9f8dc23, 0xabe247d2, 0xffe51294, 0x03eced5e, 0x57ebb818,
+    0xfe13643b, 0xaa14317d, 0x561dceb7, 0x021a9bf1, 0x5228f955, 0x062fac13,
+    0xfa2653d9, 0xae21069f, 0x07d9dabc, 0x53de8ffa, 0xafd77030, 0xfbd02576,
+    0xf9cabe87, 0xadcdebc1, 0x51c4140b, 0x05c3414d, 0xac3b9d6e, 0xf83cc828,
+    0x043537e2, 0x503262a4, 0xa451f2aa, 0xf056a7ec, 0x0c5f5826, 0x58580d60,
+    0xf1a0d143, 0xa5a78405, 0x59ae7bcf, 0x0da92e89, 0x0fb3b578, 0x5bb4e03e,
+    0xa7bd1ff4, 0xf3ba4ab2, 0x5a429691, 0x0e45c3d7, 0xf24c3c1d, 0xa64b695b,
+    0xf6790bff, 0xa27e5eb9, 0x5e77a173, 0x0a70f435, 0xa3882816, 0xf78f7d50,
+    0x0b86829a, 0x5f81d7dc, 0x5d9b4c2d, 0x099c196b, 0xf595e6a1, 0xa192b3e7,
+    0x086a6fc4, 0x5c6d3a82, 0xa064c548, 0xf463900e, 0x4d4f93a5, 0x1948c6e3,
+    0xe5413929, 0xb1466c6f, 0x18beb04c, 0x4cb9e50a, 0xb0b01ac0, 0xe4b74f86,
+    0xe6add477, 0xb2aa8131, 0x4ea37efb, 0x1aa42bbd, 0xb35cf79e, 0xe75ba2d8,
+    0x1b525d12, 0x4f550854, 0x1f676af0, 0x4b603fb6, 0xb769c07c, 0xe36e953a,
+    0x4a964919, 0x1e911c5f, 0xe298e395, 0xb69fb6d3, 0xb4852d22, 0xe0827864,
+    0x1c8b87ae, 0x488cd2e8, 0xe1740ecb, 0xb5735b8d, 0x497aa447, 0x1d7df101,
+    0xe91e610f, 0xbd193449, 0x4110cb83, 0x15179ec5, 0xbcef42e6, 0xe8e817a0,
+    0x14e1e86a, 0x40e6bd2c, 0x42fc26dd, 0x16fb739b, 0xeaf28c51, 0xbef5d917,
+    0x170d0534, 0x430a5072, 0xbf03afb8, 0xeb04fafe, 0xbb36985a, 0xef31cd1c,
+    0x133832d6, 0x473f6790, 0xeec7bbb3, 0xbac0eef5, 0x46c9113f, 0x12ce4479,
+    0x10d4df88, 0x44d38ace, 0xb8da7504, 0xecdd2042, 0x4525fc61, 0x1122a927,
+    0xed2b56ed, 0xb92c03ab, 0x9a9f274a, 0xce98720c, 0x32918dc6, 0x6696d880,
+    0xcf6e04a3, 0x9b6951e5, 0x6760ae2f, 0x3367fb69, 0x317d6098, 0x657a35de,
+    0x9973ca14, 0xcd749f52, 0x648c4371, 0x308b1637, 0xcc82e9fd, 0x9885bcbb,
+    0xc8b7de1f, 0x9cb08b59, 0x60b97493, 0x34be21d5, 0x9d46fdf6, 0xc941a8b0,
+    0x3548577a, 0x614f023c, 0x635599cd, 0x3752cc8b, 0xcb5b3341, 0x9f5c6607,
+    0x36a4ba24, 0x62a3ef62, 0x9eaa10a8, 0xcaad45ee, 0x3eced5e0, 0x6ac980a6,
+    0x96c07f6c, 0xc2c72a2a, 0x6b3ff609, 0x3f38a34f, 0xc3315c85, 0x973609c3,
+    0x952c9232, 0xc12bc774, 0x3d2238be, 0x69256df8, 0xc0ddb1db, 0x94dae49d,
+    0x68d31b57, 0x3cd44e11, 0x6ce62cb5, 0x38e179f3, 0xc4e88639, 0x90efd37f,
+    0x39170f5c, 0x6d105a1a, 0x9119a5d0, 0xc51ef096, 0xc7046b67, 0x93033e21,
+    0x6f0ac1eb, 0x3b0d94ad, 0x92f5488e, 0xc6f21dc8, 0x3afbe202, 0x6efcb744,
+    0xd7d0b4ef, 0x83d7e1a9, 0x7fde1e63, 0x2bd94b25, 0x82219706, 0xd626c240,
+    0x2a2f3d8a, 0x7e2868cc, 0x7c32f33d, 0x2835a67b, 0xd43c59b1, 0x803b0cf7,
+    0x29c3d0d4, 0x7dc48592, 0x81cd7a58, 0xd5ca2f1e, 0x85f84dba, 0xd1ff18fc,
+    0x2df6e736, 0x79f1b270, 0xd0096e53, 0x840e3b15, 0x7807c4df, 0x2c009199,
+    0x2e1a0a68, 0x7a1d5f2e, 0x8614a0e4, 0xd213f5a2, 0x7beb2981, 0x2fec7cc7,
+    0xd3e5830d, 0x87e2d64b, 0x73814645, 0x27861303, 0xdb8fecc9, 0x8f88b98f,
+    0x267065ac, 0x727730ea, 0x8e7ecf20, 0xda799a66, 0xd8630197, 0x8c6454d1,
+    0x706dab1b, 0x246afe5d, 0x8d92227e, 0xd9957738, 0x259c88f2, 0x719bddb4,
+    0x21a9bf10, 0x75aeea56, 0x89a7159c, 0xdda040da, 0x74589cf9, 0x205fc9bf,
+    0xdc563675, 0x88516333, 0x8a4bf8c2, 0xde4cad84, 0x2245524e, 0x76420708,
+    0xdfbadb2b, 0x8bbd8e6d, 0x77b471a7, 0x23b324e1};
+
+const uint32_t kStrideExtensionTable2[256] = {
+    0x00000000, 0x678efd01, 0xcf1dfa02, 0xa8930703, 0x9bd782f5, 0xfc597ff4,
+    0x54ca78f7, 0x334485f6, 0x3243731b, 0x55cd8e1a, 0xfd5e8919, 0x9ad07418,
+    0xa994f1ee, 0xce1a0cef, 0x66890bec, 0x0107f6ed, 0x6486e636, 0x03081b37,
+    0xab9b1c34, 0xcc15e135, 0xff5164c3, 0x98df99c2, 0x304c9ec1, 0x57c263c0,
+    0x56c5952d, 0x314b682c, 0x99d86f2f, 0xfe56922e, 0xcd1217d8, 0xaa9cead9,
+    0x020fedda, 0x658110db, 0xc90dcc6c, 0xae83316d, 0x0610366e, 0x619ecb6f,
+    0x52da4e99, 0x3554b398, 0x9dc7b49b, 0xfa49499a, 0xfb4ebf77, 0x9cc04276,
+    0x34534575, 0x53ddb874, 0x60993d82, 0x0717c083, 0xaf84c780, 0xc80a3a81,
+    0xad8b2a5a, 0xca05d75b, 0x6296d058, 0x05182d59, 0x365ca8af, 0x51d255ae,
+    0xf94152ad, 0x9ecfafac, 0x9fc85941, 0xf846a440, 0x50d5a343, 0x375b5e42,
+    0x041fdbb4, 0x639126b5, 0xcb0221b6, 0xac8cdcb7, 0x97f7ee29, 0xf0791328,
+    0x58ea142b, 0x3f64e92a, 0x0c206cdc, 0x6bae91dd, 0xc33d96de, 0xa4b36bdf,
+    0xa5b49d32, 0xc23a6033, 0x6aa96730, 0x0d279a31, 0x3e631fc7, 0x59ede2c6,
+    0xf17ee5c5, 0x96f018c4, 0xf371081f, 0x94fff51e, 0x3c6cf21d, 0x5be20f1c,
+    0x68a68aea, 0x0f2877eb, 0xa7bb70e8, 0xc0358de9, 0xc1327b04, 0xa6bc8605,
+    0x0e2f8106, 0x69a17c07, 0x5ae5f9f1, 0x3d6b04f0, 0x95f803f3, 0xf276fef2,
+    0x5efa2245, 0x3974df44, 0x91e7d847, 0xf6692546, 0xc52da0b0, 0xa2a35db1,
+    0x0a305ab2, 0x6dbea7b3, 0x6cb9515e, 0x0b37ac5f, 0xa3a4ab5c, 0xc42a565d,
+    0xf76ed3ab, 0x90e02eaa, 0x387329a9, 0x5ffdd4a8, 0x3a7cc473, 0x5df23972,
+    0xf5613e71, 0x92efc370, 0xa1ab4686, 0xc625bb87, 0x6eb6bc84, 0x09384185,
+    0x083fb768, 0x6fb14a69, 0xc7224d6a, 0xa0acb06b, 0x93e8359d, 0xf466c89c,
+    0x5cf5cf9f, 0x3b7b329e, 0x2a03aaa3, 0x4d8d57a2, 0xe51e50a1, 0x8290ada0,
+    0xb1d42856, 0xd65ad557, 0x7ec9d254, 0x19472f55, 0x1840d9b8, 0x7fce24b9,
+    0xd75d23ba, 0xb0d3debb, 0x83975b4d, 0xe419a64c, 0x4c8aa14f, 0x2b045c4e,
+    0x4e854c95, 0x290bb194, 0x8198b697, 0xe6164b96, 0xd552ce60, 0xb2dc3361,
+    0x1a4f3462, 0x7dc1c963, 0x7cc63f8e, 0x1b48c28f, 0xb3dbc58c, 0xd455388d,
+    0xe711bd7b, 0x809f407a, 0x280c4779, 0x4f82ba78, 0xe30e66cf, 0x84809bce,
+    0x2c139ccd, 0x4b9d61cc, 0x78d9e43a, 0x1f57193b, 0xb7c41e38, 0xd04ae339,
+    0xd14d15d4, 0xb6c3e8d5, 0x1e50efd6, 0x79de12d7, 0x4a9a9721, 0x2d146a20,
+    0x85876d23, 0xe2099022, 0x878880f9, 0xe0067df8, 0x48957afb, 0x2f1b87fa,
+    0x1c5f020c, 0x7bd1ff0d, 0xd342f80e, 0xb4cc050f, 0xb5cbf3e2, 0xd2450ee3,
+    0x7ad609e0, 0x1d58f4e1, 0x2e1c7117, 0x49928c16, 0xe1018b15, 0x868f7614,
+    0xbdf4448a, 0xda7ab98b, 0x72e9be88, 0x15674389, 0x2623c67f, 0x41ad3b7e,
+    0xe93e3c7d, 0x8eb0c17c, 0x8fb73791, 0xe839ca90, 0x40aacd93, 0x27243092,
+    0x1460b564, 0x73ee4865, 0xdb7d4f66, 0xbcf3b267, 0xd972a2bc, 0xbefc5fbd,
+    0x166f58be, 0x71e1a5bf, 0x42a52049, 0x252bdd48, 0x8db8da4b, 0xea36274a,
+    0xeb31d1a7, 0x8cbf2ca6, 0x242c2ba5, 0x43a2d6a4, 0x70e65352, 0x1768ae53,
+    0xbffba950, 0xd8755451, 0x74f988e6, 0x137775e7, 0xbbe472e4, 0xdc6a8fe5,
+    0xef2e0a13, 0x88a0f712, 0x2033f011, 0x47bd0d10, 0x46bafbfd, 0x213406fc,
+    0x89a701ff, 0xee29fcfe, 0xdd6d7908, 0xbae38409, 0x1270830a, 0x75fe7e0b,
+    0x107f6ed0, 0x77f193d1, 0xdf6294d2, 0xb8ec69d3, 0x8ba8ec25, 0xec261124,
+    0x44b51627, 0x233beb26, 0x223c1dcb, 0x45b2e0ca, 0xed21e7c9, 0x8aaf1ac8,
+    0xb9eb9f3e, 0xde65623f, 0x76f6653c, 0x1178983d};
+
+const uint32_t kStrideExtensionTable3[256] = {
+    0x00000000, 0xf20c0dfe, 0xe1f46d0d, 0x13f860f3, 0xc604aceb, 0x3408a115,
+    0x27f0c1e6, 0xd5fccc18, 0x89e52f27, 0x7be922d9, 0x6811422a, 0x9a1d4fd4,
+    0x4fe183cc, 0xbded8e32, 0xae15eec1, 0x5c19e33f, 0x162628bf, 0xe42a2541,
+    0xf7d245b2, 0x05de484c, 0xd0228454, 0x222e89aa, 0x31d6e959, 0xc3dae4a7,
+    0x9fc30798, 0x6dcf0a66, 0x7e376a95, 0x8c3b676b, 0x59c7ab73, 0xabcba68d,
+    0xb833c67e, 0x4a3fcb80, 0x2c4c517e, 0xde405c80, 0xcdb83c73, 0x3fb4318d,
+    0xea48fd95, 0x1844f06b, 0x0bbc9098, 0xf9b09d66, 0xa5a97e59, 0x57a573a7,
+    0x445d1354, 0xb6511eaa, 0x63add2b2, 0x91a1df4c, 0x8259bfbf, 0x7055b241,
+    0x3a6a79c1, 0xc866743f, 0xdb9e14cc, 0x29921932, 0xfc6ed52a, 0x0e62d8d4,
+    0x1d9ab827, 0xef96b5d9, 0xb38f56e6, 0x41835b18, 0x527b3beb, 0xa0773615,
+    0x758bfa0d, 0x8787f7f3, 0x947f9700, 0x66739afe, 0x5898a2fc, 0xaa94af02,
+    0xb96ccff1, 0x4b60c20f, 0x9e9c0e17, 0x6c9003e9, 0x7f68631a, 0x8d646ee4,
+    0xd17d8ddb, 0x23718025, 0x3089e0d6, 0xc285ed28, 0x17792130, 0xe5752cce,
+    0xf68d4c3d, 0x048141c3, 0x4ebe8a43, 0xbcb287bd, 0xaf4ae74e, 0x5d46eab0,
+    0x88ba26a8, 0x7ab62b56, 0x694e4ba5, 0x9b42465b, 0xc75ba564, 0x3557a89a,
+    0x26afc869, 0xd4a3c597, 0x015f098f, 0xf3530471, 0xe0ab6482, 0x12a7697c,
+    0x74d4f382, 0x86d8fe7c, 0x95209e8f, 0x672c9371, 0xb2d05f69, 0x40dc5297,
+    0x53243264, 0xa1283f9a, 0xfd31dca5, 0x0f3dd15b, 0x1cc5b1a8, 0xeec9bc56,
+    0x3b35704e, 0xc9397db0, 0xdac11d43, 0x28cd10bd, 0x62f2db3d, 0x90fed6c3,
+    0x8306b630, 0x710abbce, 0xa4f677d6, 0x56fa7a28, 0x45021adb, 0xb70e1725,
+    0xeb17f41a, 0x191bf9e4, 0x0ae39917, 0xf8ef94e9, 0x2d1358f1, 0xdf1f550f,
+    0xcce735fc, 0x3eeb3802, 0xb13145f8, 0x433d4806, 0x50c528f5, 0xa2c9250b,
+    0x7735e913, 0x8539e4ed, 0x96c1841e, 0x64cd89e0, 0x38d46adf, 0xcad86721,
+    0xd92007d2, 0x2b2c0a2c, 0xfed0c634, 0x0cdccbca, 0x1f24ab39, 0xed28a6c7,
+    0xa7176d47, 0x551b60b9, 0x46e3004a, 0xb4ef0db4, 0x6113c1ac, 0x931fcc52,
+    0x80e7aca1, 0x72eba15f, 0x2ef24260, 0xdcfe4f9e, 0xcf062f6d, 0x3d0a2293,
+    0xe8f6ee8b, 0x1afae375, 0x09028386, 0xfb0e8e78, 0x9d7d1486, 0x6f711978,
+    0x7c89798b, 0x8e857475, 0x5b79b86d, 0xa975b593, 0xba8dd560, 0x4881d89e,
+    0x14983ba1, 0xe694365f, 0xf56c56ac, 0x07605b52, 0xd29c974a, 0x20909ab4,
+    0x3368fa47, 0xc164f7b9, 0x8b5b3c39, 0x795731c7, 0x6aaf5134, 0x98a35cca,
+    0x4d5f90d2, 0xbf539d2c, 0xacabfddf, 0x5ea7f021, 0x02be131e, 0xf0b21ee0,
+    0xe34a7e13, 0x114673ed, 0xc4babff5, 0x36b6b20b, 0x254ed2f8, 0xd742df06,
+    0xe9a9e704, 0x1ba5eafa, 0x085d8a09, 0xfa5187f7, 0x2fad4bef, 0xdda14611,
+    0xce5926e2, 0x3c552b1c, 0x604cc823, 0x9240c5dd, 0x81b8a52e, 0x73b4a8d0,
+    0xa64864c8, 0x54446936, 0x47bc09c5, 0xb5b0043b, 0xff8fcfbb, 0x0d83c245,
+    0x1e7ba2b6, 0xec77af48, 0x398b6350, 0xcb876eae, 0xd87f0e5d, 0x2a7303a3,
+    0x766ae09c, 0x8466ed62, 0x979e8d91, 0x6592806f, 0xb06e4c77, 0x42624189,
+    0x519a217a, 0xa3962c84, 0xc5e5b67a, 0x37e9bb84, 0x2411db77, 0xd61dd689,
+    0x03e11a91, 0xf1ed176f, 0xe215779c, 0x10197a62, 0x4c00995d, 0xbe0c94a3,
+    0xadf4f450, 0x5ff8f9ae, 0x8a0435b6, 0x78083848, 0x6bf058bb, 0x99fc5545,
+    0xd3c39ec5, 0x21cf933b, 0x3237f3c8, 0xc03bfe36, 0x15c7322e, 0xe7cb3fd0,
+    0xf4335f23, 0x063f52dd, 0x5a26b1e2, 0xa82abc1c, 0xbbd2dcef, 0x49ded111,
+    0x9c221d09, 0x6e2e10f7, 0x7dd67004, 0x8fda7dfa};
+
+constexpr const ptrdiff_t kPrefetchHorizon = 256;
+
+}  // namespace
+
+namespace crc32c {
+
+uint32_t ExtendPortable(uint32_t crc, const uint8_t* data, size_t size) {
+  const uint8_t* p = data;
+  const uint8_t* e = p + size;
+  uint32_t l = crc ^ kCRC32Xor;
+
+// Process one byte at a time.
+#define STEP1                              \
+  do {                                     \
+    int c = (l & 0xff) ^ *p++;             \
+    l = kByteExtensionTable[c] ^ (l >> 8); \
+  } while (0)
+
+// Process one of the 4 strides of 4-byte data.
+#define STEP4(s)                                                               \
+  do {                                                                         \
+    crc##s = ReadUint32LE(p + s * 4) ^ kStrideExtensionTable3[crc##s & 0xff] ^ \
+             kStrideExtensionTable2[(crc##s >> 8) & 0xff] ^                    \
+             kStrideExtensionTable1[(crc##s >> 16) & 0xff] ^                   \
+             kStrideExtensionTable0[crc##s >> 24];                             \
+  } while (0)
+
+// Process a 16-byte swath of 4 strides, each of which has 4 bytes of data.
+#define STEP16 \
+  do {         \
+    STEP4(0);  \
+    STEP4(1);  \
+    STEP4(2);  \
+    STEP4(3);  \
+    p += 16;   \
+  } while (0)
+
+// Process 4 bytes that were already loaded into a word.
+#define STEP4W(w)                                   \
+  do {                                              \
+    w ^= l;                                         \
+    for (size_t i = 0; i < 4; ++i) {                \
+      w = (w >> 8) ^ kByteExtensionTable[w & 0xff]; \
+    }                                               \
+    l = w;                                          \
+  } while (0)
+
+  // Point x at first 4-byte aligned byte in the buffer. This might be past the
+  // end of the buffer.
+  const uint8_t* x = RoundUp<4>(p);
+  if (x <= e) {
+    // Process bytes p is 4-byte aligned.
+    while (p != x) {
+      STEP1;
+    }
+  }
+
+  if ((e - p) >= 16) {
+    // Load a 16-byte swath into the stride partial results.
+    uint32_t crc0 = ReadUint32LE(p + 0 * 4) ^ l;
+    uint32_t crc1 = ReadUint32LE(p + 1 * 4);
+    uint32_t crc2 = ReadUint32LE(p + 2 * 4);
+    uint32_t crc3 = ReadUint32LE(p + 3 * 4);
+    p += 16;
+
+    while ((e - p) > kPrefetchHorizon) {
+      RequestPrefetch(p + kPrefetchHorizon);
+
+      // Process 64 bytes at a time.
+      STEP16;
+      STEP16;
+      STEP16;
+      STEP16;
+    }
+
+    // Process one 16-byte swath at a time.
+    while ((e - p) >= 16) {
+      STEP16;
+    }
+
+    // Advance one word at a time as far as possible.
+    while ((e - p) >= 4) {
+      STEP4(0);
+      uint32_t tmp = crc0;
+      crc0 = crc1;
+      crc1 = crc2;
+      crc2 = crc3;
+      crc3 = tmp;
+      p += 4;
+    }
+
+    // Combine the 4 partial stride results.
+    l = 0;
+    STEP4W(crc0);
+    STEP4W(crc1);
+    STEP4W(crc2);
+    STEP4W(crc3);
+  }
+
+  // Process the last few bytes.
+  while (p != e) {
+    STEP1;
+  }
+#undef STEP4W
+#undef STEP16
+#undef STEP4
+#undef STEP1
+  return l ^ kCRC32Xor;
+}
+
+}  // namespace crc32c
diff --git a/src/crc32c_portable_unittest.cc b/src/crc32c_portable_unittest.cc
new file mode 100644
index 0000000000..5098e2c373
--- /dev/null
+++ b/src/crc32c_portable_unittest.cc
@@ -0,0 +1,20 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+
+#include "./crc32c_extend_unittests.h"
+#include "./crc32c_internal.h"
+
+namespace crc32c {
+
+struct PortableTestTraits {
+  static uint32_t Extend(uint32_t crc, const uint8_t* data, size_t count) {
+    return ExtendPortable(crc, data, count);
+  }
+};
+
+INSTANTIATE_TYPED_TEST_SUITE_P(Portable, ExtendTest, PortableTestTraits);
+
+}  // namespace crc32c
diff --git a/src/crc32c_prefetch.h b/src/crc32c_prefetch.h
new file mode 100644
index 0000000000..aec7d54e84
--- /dev/null
+++ b/src/crc32c_prefetch.h
@@ -0,0 +1,46 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_PREFETCH_H_
+#define CRC32C_CRC32C_PREFETCH_H_
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#if HAVE_MM_PREFETCH
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#else  // !defined(_MSC_VER)
+#include <xmmintrin.h>
+#endif  // defined(_MSC_VER)
+
+#endif  // HAVE_MM_PREFETCH
+
+namespace crc32c {
+
+// Ask the hardware to prefetch the data at the given address into the L1 cache.
+inline void RequestPrefetch(const uint8_t* address) {
+#if HAVE_BUILTIN_PREFETCH
+  // Clang and GCC implement the __builtin_prefetch non-standard extension,
+  // which maps to the best instruction on the target architecture.
+  __builtin_prefetch(reinterpret_cast<const char*>(address), 0 /* Read only. */,
+                     0 /* No temporal locality. */);
+#elif HAVE_MM_PREFETCH
+  // Visual Studio doesn't implement __builtin_prefetch, but exposes the
+  // PREFETCHNTA instruction via the _mm_prefetch intrinsic.
+  _mm_prefetch(reinterpret_cast<const char*>(address), _MM_HINT_NTA);
+#else
+  // No prefetch support. Silence compiler warnings.
+  (void)address;
+#endif  // HAVE_BUILTIN_PREFETCH
+}
+
+}  // namespace crc32c
+
+#endif  // CRC32C_CRC32C_ROUND_UP_H_
diff --git a/src/crc32c_prefetch_unittest.cc b/src/crc32c_prefetch_unittest.cc
new file mode 100644
index 0000000000..b34ed2d5fe
--- /dev/null
+++ b/src/crc32c_prefetch_unittest.cc
@@ -0,0 +1,9 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "./crc32c_prefetch.h"
+
+// There is no easy way to test cache prefetching. We can only test that the
+// crc32c_prefetch.h header compiles on its own, so it doesn't have any unstated
+// dependencies.
diff --git a/src/crc32c_read_le.h b/src/crc32c_read_le.h
new file mode 100644
index 0000000000..3bd45fe3aa
--- /dev/null
+++ b/src/crc32c_read_le.h
@@ -0,0 +1,53 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_READ_LE_H_
+#define CRC32C_CRC32C_READ_LE_H_
+
+#include <cstdint>
+#include <cstring>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+namespace crc32c {
+
+// Reads a little-endian 32-bit integer from a 32-bit-aligned buffer.
+inline uint32_t ReadUint32LE(const uint8_t* buffer) {
+#if BYTE_ORDER_BIG_ENDIAN
+  return ((static_cast<uint32_t>(static_cast<uint8_t>(buffer[0]))) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[1])) << 8) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[2])) << 16) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[3])) << 24));
+#else   // !BYTE_ORDER_BIG_ENDIAN
+  uint32_t result;
+  // This should be optimized to a single instruction.
+  std::memcpy(&result, buffer, sizeof(result));
+  return result;
+#endif  // BYTE_ORDER_BIG_ENDIAN
+}
+
+// Reads a little-endian 64-bit integer from a 64-bit-aligned buffer.
+inline uint64_t ReadUint64LE(const uint8_t* buffer) {
+#if BYTE_ORDER_BIG_ENDIAN
+  return ((static_cast<uint32_t>(static_cast<uint8_t>(buffer[0]))) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[1])) << 8) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[2])) << 16) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[3])) << 24) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[4])) << 32) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[5])) << 40) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[6])) << 48) |
+          (static_cast<uint32_t>(static_cast<uint8_t>(buffer[7])) << 56));
+#else   // !BYTE_ORDER_BIG_ENDIAN
+  uint64_t result;
+  // This should be optimized to a single instruction.
+  std::memcpy(&result, buffer, sizeof(result));
+  return result;
+#endif  // BYTE_ORDER_BIG_ENDIAN
+}
+
+}  // namespace crc32c
+
+#endif  // CRC32C_CRC32C_READ_LE_H_
diff --git a/src/crc32c_read_le_unittest.cc b/src/crc32c_read_le_unittest.cc
new file mode 100644
index 0000000000..2a30302adf
--- /dev/null
+++ b/src/crc32c_read_le_unittest.cc
@@ -0,0 +1,32 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "./crc32c_read_le.h"
+
+#include <cstddef>
+#include <cstdint>
+
+#include "gtest/gtest.h"
+
+#include "./crc32c_round_up.h"
+
+namespace crc32c {
+
+TEST(Crc32CReadLETest, ReadUint32LE) {
+  // little-endian 0x12345678
+  alignas(4) uint8_t bytes[] = {0x78, 0x56, 0x34, 0x12};
+
+  ASSERT_EQ(RoundUp<4>(bytes), bytes) << "Stack array is not aligned";
+  EXPECT_EQ(static_cast<uint32_t>(0x12345678), ReadUint32LE(bytes));
+}
+
+TEST(Crc32CReadLETest, ReadUint64LE) {
+  // little-endian 0x123456789ABCDEF0
+  alignas(8) uint8_t bytes[] = {0xF0, 0xDE, 0xBC, 0x9A, 0x78, 0x56, 0x34, 0x12};
+
+  ASSERT_EQ(RoundUp<8>(bytes), bytes) << "Stack array is not aligned";
+  EXPECT_EQ(static_cast<uint64_t>(0x123456789ABCDEF0), ReadUint64LE(bytes));
+}
+
+}  // namespace crc32c
diff --git a/src/crc32c_round_up.h b/src/crc32c_round_up.h
new file mode 100644
index 0000000000..d3b922beb9
--- /dev/null
+++ b/src/crc32c_round_up.h
@@ -0,0 +1,34 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_ROUND_UP_H_
+#define CRC32C_CRC32C_ROUND_UP_H_
+
+#include <cstddef>
+#include <cstdint>
+
+namespace crc32c {
+
+// Returns the smallest number >= the given number that is evenly divided by N.
+//
+// N must be a power of two.
+template <int N>
+constexpr inline uintptr_t RoundUp(uintptr_t pointer) {
+  static_assert((N & (N - 1)) == 0, "N must be a power of two");
+  return (pointer + (N - 1)) & ~(N - 1);
+}
+
+// Returns the smallest address >= the given address that is aligned to N bytes.
+//
+// N must be a power of two.
+template <int N>
+constexpr inline const uint8_t* RoundUp(const uint8_t* pointer) {
+  static_assert((N & (N - 1)) == 0, "N must be a power of two");
+  return reinterpret_cast<uint8_t*>(
+      RoundUp<N>(reinterpret_cast<uintptr_t>(pointer)));
+}
+
+}  // namespace crc32c
+
+#endif  // CRC32C_CRC32C_ROUND_UP_H_
diff --git a/src/crc32c_round_up_unittest.cc b/src/crc32c_round_up_unittest.cc
new file mode 100644
index 0000000000..5ff657bb5c
--- /dev/null
+++ b/src/crc32c_round_up_unittest.cc
@@ -0,0 +1,84 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "./crc32c_round_up.h"
+
+#include <cstddef>
+#include <cstdint>
+
+#include "gtest/gtest.h"
+
+namespace crc32c {
+
+TEST(CRC32CRoundUpTest, RoundUpUintptr) {
+  uintptr_t zero = 0;
+
+  ASSERT_EQ(zero, RoundUp<1>(zero));
+  ASSERT_EQ(1U, RoundUp<1>(1U));
+  ASSERT_EQ(2U, RoundUp<1>(2U));
+  ASSERT_EQ(3U, RoundUp<1>(3U));
+  ASSERT_EQ(~static_cast<uintptr_t>(0), RoundUp<1>(~static_cast<uintptr_t>(0)));
+  ASSERT_EQ(~static_cast<uintptr_t>(1), RoundUp<1>(~static_cast<uintptr_t>(1)));
+  ASSERT_EQ(~static_cast<uintptr_t>(2), RoundUp<1>(~static_cast<uintptr_t>(2)));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<1>(~static_cast<uintptr_t>(3)));
+
+  ASSERT_EQ(zero, RoundUp<2>(zero));
+  ASSERT_EQ(2U, RoundUp<2>(1U));
+  ASSERT_EQ(2U, RoundUp<2>(2U));
+  ASSERT_EQ(4U, RoundUp<2>(3U));
+  ASSERT_EQ(4U, RoundUp<2>(4U));
+  ASSERT_EQ(6U, RoundUp<2>(5U));
+  ASSERT_EQ(6U, RoundUp<2>(6U));
+  ASSERT_EQ(8U, RoundUp<2>(7U));
+  ASSERT_EQ(8U, RoundUp<2>(8U));
+  ASSERT_EQ(~static_cast<uintptr_t>(1), RoundUp<2>(~static_cast<uintptr_t>(1)));
+  ASSERT_EQ(~static_cast<uintptr_t>(1), RoundUp<2>(~static_cast<uintptr_t>(2)));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<2>(~static_cast<uintptr_t>(3)));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<2>(~static_cast<uintptr_t>(4)));
+
+  ASSERT_EQ(zero, RoundUp<4>(zero));
+  ASSERT_EQ(4U, RoundUp<4>(1U));
+  ASSERT_EQ(4U, RoundUp<4>(2U));
+  ASSERT_EQ(4U, RoundUp<4>(3U));
+  ASSERT_EQ(4U, RoundUp<4>(4U));
+  ASSERT_EQ(8U, RoundUp<4>(5U));
+  ASSERT_EQ(8U, RoundUp<4>(6U));
+  ASSERT_EQ(8U, RoundUp<4>(7U));
+  ASSERT_EQ(8U, RoundUp<4>(8U));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<4>(~static_cast<uintptr_t>(3)));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<4>(~static_cast<uintptr_t>(4)));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<4>(~static_cast<uintptr_t>(5)));
+  ASSERT_EQ(~static_cast<uintptr_t>(3), RoundUp<4>(~static_cast<uintptr_t>(6)));
+  ASSERT_EQ(~static_cast<uintptr_t>(7), RoundUp<4>(~static_cast<uintptr_t>(7)));
+  ASSERT_EQ(~static_cast<uintptr_t>(7), RoundUp<4>(~static_cast<uintptr_t>(8)));
+  ASSERT_EQ(~static_cast<uintptr_t>(7), RoundUp<4>(~static_cast<uintptr_t>(9)));
+}
+
+TEST(CRC32CRoundUpTest, RoundUpPointer) {
+  uintptr_t zero = 0, three = 3, four = 4, seven = 7, eight = 8;
+
+  const uint8_t* zero_ptr = reinterpret_cast<const uint8_t*>(zero);
+  const uint8_t* three_ptr = reinterpret_cast<const uint8_t*>(three);
+  const uint8_t* four_ptr = reinterpret_cast<const uint8_t*>(four);
+  const uint8_t* seven_ptr = reinterpret_cast<const uint8_t*>(seven);
+  const uint8_t* eight_ptr = reinterpret_cast<uint8_t*>(eight);
+
+  ASSERT_EQ(zero_ptr, RoundUp<1>(zero_ptr));
+  ASSERT_EQ(zero_ptr, RoundUp<4>(zero_ptr));
+  ASSERT_EQ(zero_ptr, RoundUp<8>(zero_ptr));
+
+  ASSERT_EQ(three_ptr, RoundUp<1>(three_ptr));
+  ASSERT_EQ(four_ptr, RoundUp<4>(three_ptr));
+  ASSERT_EQ(eight_ptr, RoundUp<8>(three_ptr));
+
+  ASSERT_EQ(four_ptr, RoundUp<1>(four_ptr));
+  ASSERT_EQ(four_ptr, RoundUp<4>(four_ptr));
+  ASSERT_EQ(eight_ptr, RoundUp<8>(four_ptr));
+
+  ASSERT_EQ(seven_ptr, RoundUp<1>(seven_ptr));
+  ASSERT_EQ(eight_ptr, RoundUp<4>(seven_ptr));
+  ASSERT_EQ(eight_ptr, RoundUp<8>(four_ptr));
+}
+
+}  // namespace crc32c
diff --git a/src/crc32c_sse42.cc b/src/crc32c_sse42.cc
new file mode 100644
index 0000000000..139520428e
--- /dev/null
+++ b/src/crc32c_sse42.cc
@@ -0,0 +1,258 @@
+// Copyright 2008 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "./crc32c_sse42.h"
+
+// In a separate source file to allow this accelerated CRC32C function to be
+// compiled with the appropriate compiler flags to enable SSE4.2 instructions.
+
+// This implementation is loosely based on Intel Pub 323405 from April 2011,
+// "Fast CRC Computation for iSCSI Polynomial Using CRC32 Instruction".
+
+#include <cstddef>
+#include <cstdint>
+
+#include "./crc32c_internal.h"
+#include "./crc32c_prefetch.h"
+#include "./crc32c_read_le.h"
+#include "./crc32c_round_up.h"
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#if HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#else  // !defined(_MSC_VER)
+#include <nmmintrin.h>
+#endif  // defined(_MSC_VER)
+
+namespace crc32c {
+
+namespace {
+
+constexpr const ptrdiff_t kGroups = 3;
+constexpr const ptrdiff_t kBlock0Size = 16 * 1024 / kGroups / 64 * 64;
+constexpr const ptrdiff_t kBlock1Size = 4 * 1024 / kGroups / 8 * 8;
+constexpr const ptrdiff_t kBlock2Size = 1024 / kGroups / 8 * 8;
+
+const uint32_t kBlock0SkipTable[8][16] = {
+    {0x00000000, 0xff770459, 0xfb027e43, 0x04757a1a, 0xf3e88a77, 0x0c9f8e2e,
+     0x08eaf434, 0xf79df06d, 0xe23d621f, 0x1d4a6646, 0x193f1c5c, 0xe6481805,
+     0x11d5e868, 0xeea2ec31, 0xead7962b, 0x15a09272},
+    {0x00000000, 0xc196b2cf, 0x86c1136f, 0x4757a1a0, 0x086e502f, 0xc9f8e2e0,
+     0x8eaf4340, 0x4f39f18f, 0x10dca05e, 0xd14a1291, 0x961db331, 0x578b01fe,
+     0x18b2f071, 0xd92442be, 0x9e73e31e, 0x5fe551d1},
+    {0x00000000, 0x21b940bc, 0x43728178, 0x62cbc1c4, 0x86e502f0, 0xa75c424c,
+     0xc5978388, 0xe42ec334, 0x08267311, 0x299f33ad, 0x4b54f269, 0x6aedb2d5,
+     0x8ec371e1, 0xaf7a315d, 0xcdb1f099, 0xec08b025},
+    {0x00000000, 0x104ce622, 0x2099cc44, 0x30d52a66, 0x41339888, 0x517f7eaa,
+     0x61aa54cc, 0x71e6b2ee, 0x82673110, 0x922bd732, 0xa2fefd54, 0xb2b21b76,
+     0xc354a998, 0xd3184fba, 0xe3cd65dc, 0xf38183fe},
+    {0x00000000, 0x012214d1, 0x024429a2, 0x03663d73, 0x04885344, 0x05aa4795,
+     0x06cc7ae6, 0x07ee6e37, 0x0910a688, 0x0832b259, 0x0b548f2a, 0x0a769bfb,
+     0x0d98f5cc, 0x0cbae11d, 0x0fdcdc6e, 0x0efec8bf},
+    {0x00000000, 0x12214d10, 0x24429a20, 0x3663d730, 0x48853440, 0x5aa47950,
+     0x6cc7ae60, 0x7ee6e370, 0x910a6880, 0x832b2590, 0xb548f2a0, 0xa769bfb0,
+     0xd98f5cc0, 0xcbae11d0, 0xfdcdc6e0, 0xefec8bf0},
+    {0x00000000, 0x27f8a7f1, 0x4ff14fe2, 0x6809e813, 0x9fe29fc4, 0xb81a3835,
+     0xd013d026, 0xf7eb77d7, 0x3a294979, 0x1dd1ee88, 0x75d8069b, 0x5220a16a,
+     0xa5cbd6bd, 0x8233714c, 0xea3a995f, 0xcdc23eae},
+    {0x00000000, 0x745292f2, 0xe8a525e4, 0x9cf7b716, 0xd4a63d39, 0xa0f4afcb,
+     0x3c0318dd, 0x48518a2f, 0xaca00c83, 0xd8f29e71, 0x44052967, 0x3057bb95,
+     0x780631ba, 0x0c54a348, 0x90a3145e, 0xe4f186ac},
+};
+const uint32_t kBlock1SkipTable[8][16] = {
+    {0x00000000, 0x79113270, 0xf22264e0, 0x8b335690, 0xe1a8bf31, 0x98b98d41,
+     0x138adbd1, 0x6a9be9a1, 0xc6bd0893, 0xbfac3ae3, 0x349f6c73, 0x4d8e5e03,
+     0x2715b7a2, 0x5e0485d2, 0xd537d342, 0xac26e132},
+    {0x00000000, 0x889667d7, 0x14c0b95f, 0x9c56de88, 0x298172be, 0xa1171569,
+     0x3d41cbe1, 0xb5d7ac36, 0x5302e57c, 0xdb9482ab, 0x47c25c23, 0xcf543bf4,
+     0x7a8397c2, 0xf215f015, 0x6e432e9d, 0xe6d5494a},
+    {0x00000000, 0xa605caf8, 0x49e7e301, 0xefe229f9, 0x93cfc602, 0x35ca0cfa,
+     0xda282503, 0x7c2deffb, 0x2273faf5, 0x8476300d, 0x6b9419f4, 0xcd91d30c,
+     0xb1bc3cf7, 0x17b9f60f, 0xf85bdff6, 0x5e5e150e},
+    {0x00000000, 0x44e7f5ea, 0x89cfebd4, 0xcd281e3e, 0x1673a159, 0x529454b3,
+     0x9fbc4a8d, 0xdb5bbf67, 0x2ce742b2, 0x6800b758, 0xa528a966, 0xe1cf5c8c,
+     0x3a94e3eb, 0x7e731601, 0xb35b083f, 0xf7bcfdd5},
+    {0x00000000, 0x59ce8564, 0xb39d0ac8, 0xea538fac, 0x62d66361, 0x3b18e605,
+     0xd14b69a9, 0x8885eccd, 0xc5acc6c2, 0x9c6243a6, 0x7631cc0a, 0x2fff496e,
+     0xa77aa5a3, 0xfeb420c7, 0x14e7af6b, 0x4d292a0f},
+    {0x00000000, 0x8eb5fb75, 0x1887801b, 0x96327b6e, 0x310f0036, 0xbfbafb43,
+     0x2988802d, 0xa73d7b58, 0x621e006c, 0xecabfb19, 0x7a998077, 0xf42c7b02,
+     0x5311005a, 0xdda4fb2f, 0x4b968041, 0xc5237b34},
+    {0x00000000, 0xc43c00d8, 0x8d947741, 0x49a87799, 0x1ec49873, 0xdaf898ab,
+     0x9350ef32, 0x576cefea, 0x3d8930e6, 0xf9b5303e, 0xb01d47a7, 0x7421477f,
+     0x234da895, 0xe771a84d, 0xaed9dfd4, 0x6ae5df0c},
+    {0x00000000, 0x7b1261cc, 0xf624c398, 0x8d36a254, 0xe9a5f1c1, 0x92b7900d,
+     0x1f813259, 0x64935395, 0xd6a79573, 0xadb5f4bf, 0x208356eb, 0x5b913727,
+     0x3f0264b2, 0x4410057e, 0xc926a72a, 0xb234c6e6},
+};
+const uint32_t kBlock2SkipTable[8][16] = {
+    {0x00000000, 0x8f158014, 0x1bc776d9, 0x94d2f6cd, 0x378eedb2, 0xb89b6da6,
+     0x2c499b6b, 0xa35c1b7f, 0x6f1ddb64, 0xe0085b70, 0x74daadbd, 0xfbcf2da9,
+     0x589336d6, 0xd786b6c2, 0x4354400f, 0xcc41c01b},
+    {0x00000000, 0xde3bb6c8, 0xb99b1b61, 0x67a0ada9, 0x76da4033, 0xa8e1f6fb,
+     0xcf415b52, 0x117aed9a, 0xedb48066, 0x338f36ae, 0x542f9b07, 0x8a142dcf,
+     0x9b6ec055, 0x4555769d, 0x22f5db34, 0xfcce6dfc},
+    {0x00000000, 0xde85763d, 0xb8e69a8b, 0x6663ecb6, 0x742143e7, 0xaaa435da,
+     0xccc7d96c, 0x1242af51, 0xe84287ce, 0x36c7f1f3, 0x50a41d45, 0x8e216b78,
+     0x9c63c429, 0x42e6b214, 0x24855ea2, 0xfa00289f},
+    {0x00000000, 0xd569796d, 0xaf3e842b, 0x7a57fd46, 0x5b917ea7, 0x8ef807ca,
+     0xf4affa8c, 0x21c683e1, 0xb722fd4e, 0x624b8423, 0x181c7965, 0xcd750008,
+     0xecb383e9, 0x39dafa84, 0x438d07c2, 0x96e47eaf},
+    {0x00000000, 0x6ba98c6d, 0xd75318da, 0xbcfa94b7, 0xab4a4745, 0xc0e3cb28,
+     0x7c195f9f, 0x17b0d3f2, 0x5378f87b, 0x38d17416, 0x842be0a1, 0xef826ccc,
+     0xf832bf3e, 0x939b3353, 0x2f61a7e4, 0x44c82b89},
+    {0x00000000, 0xa6f1f0f6, 0x480f971d, 0xeefe67eb, 0x901f2e3a, 0x36eedecc,
+     0xd810b927, 0x7ee149d1, 0x25d22a85, 0x8323da73, 0x6dddbd98, 0xcb2c4d6e,
+     0xb5cd04bf, 0x133cf449, 0xfdc293a2, 0x5b336354},
+    {0x00000000, 0x4ba4550a, 0x9748aa14, 0xdcecff1e, 0x2b7d22d9, 0x60d977d3,
+     0xbc3588cd, 0xf791ddc7, 0x56fa45b2, 0x1d5e10b8, 0xc1b2efa6, 0x8a16baac,
+     0x7d87676b, 0x36233261, 0xeacfcd7f, 0xa16b9875},
+    {0x00000000, 0xadf48b64, 0x5e056039, 0xf3f1eb5d, 0xbc0ac072, 0x11fe4b16,
+     0xe20fa04b, 0x4ffb2b2f, 0x7df9f615, 0xd00d7d71, 0x23fc962c, 0x8e081d48,
+     0xc1f33667, 0x6c07bd03, 0x9ff6565e, 0x3202dd3a},
+};
+
+constexpr const ptrdiff_t kPrefetchHorizon = 256;
+
+}  // namespace
+
+uint32_t ExtendSse42(uint32_t crc, const uint8_t* data, size_t size) {
+  const uint8_t* p = data;
+  const uint8_t* e = data + size;
+  uint32_t l = crc ^ kCRC32Xor;
+
+#define STEP1                  \
+  do {                         \
+    l = _mm_crc32_u8(l, *p++); \
+  } while (0)
+
+#define STEP4(crc)                             \
+  do {                                         \
+    crc = _mm_crc32_u32(crc, ReadUint32LE(p)); \
+    p += 4;                                    \
+  } while (0)
+
+#define STEP8(crc, data)                          \
+  do {                                            \
+    crc = _mm_crc32_u64(crc, ReadUint64LE(data)); \
+    data += 8;                                    \
+  } while (0)
+
+#define STEP8BY3(crc0, crc1, crc2, p0, p1, p2) \
+  do {                                         \
+    STEP8(crc0, p0);                           \
+    STEP8(crc1, p1);                           \
+    STEP8(crc2, p2);                           \
+  } while (0)
+
+#define STEP8X3(crc0, crc1, crc2, bs)                     \
+  do {                                                    \
+    crc0 = _mm_crc32_u64(crc0, ReadUint64LE(p));          \
+    crc1 = _mm_crc32_u64(crc1, ReadUint64LE(p + bs));     \
+    crc2 = _mm_crc32_u64(crc2, ReadUint64LE(p + 2 * bs)); \
+    p += 8;                                               \
+  } while (0)
+
+#define SKIP_BLOCK(crc, tab)                                      \
+  do {                                                            \
+    crc = tab[0][crc & 0xf] ^ tab[1][(crc >> 4) & 0xf] ^          \
+          tab[2][(crc >> 8) & 0xf] ^ tab[3][(crc >> 12) & 0xf] ^  \
+          tab[4][(crc >> 16) & 0xf] ^ tab[5][(crc >> 20) & 0xf] ^ \
+          tab[6][(crc >> 24) & 0xf] ^ tab[7][(crc >> 28) & 0xf];  \
+  } while (0)
+
+  // Point x at first 8-byte aligned byte in the buffer. This might be past the
+  // end of the buffer.
+  const uint8_t* x = RoundUp<8>(p);
+  if (x <= e) {
+    // Process bytes p is 8-byte aligned.
+    while (p != x) {
+      STEP1;
+    }
+  }
+
+  // Proccess the data in predetermined block sizes with tables for quickly
+  // combining the checksum. Experimentally it's better to use larger block
+  // sizes where possible so use a hierarchy of decreasing block sizes.
+  uint64_t l64 = l;
+  while ((e - p) >= kGroups * kBlock0Size) {
+    uint64_t l641 = 0;
+    uint64_t l642 = 0;
+    for (int i = 0; i < kBlock0Size; i += 8 * 8) {
+      // Prefetch ahead to hide latency.
+      RequestPrefetch(p + kPrefetchHorizon);
+      RequestPrefetch(p + kBlock0Size + kPrefetchHorizon);
+      RequestPrefetch(p + 2 * kBlock0Size + kPrefetchHorizon);
+
+      // Process 64 bytes at a time.
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+      STEP8X3(l64, l641, l642, kBlock0Size);
+    }
+
+    // Combine results.
+    SKIP_BLOCK(l64, kBlock0SkipTable);
+    l64 ^= l641;
+    SKIP_BLOCK(l64, kBlock0SkipTable);
+    l64 ^= l642;
+    p += (kGroups - 1) * kBlock0Size;
+  }
+  while ((e - p) >= kGroups * kBlock1Size) {
+    uint64_t l641 = 0;
+    uint64_t l642 = 0;
+    for (int i = 0; i < kBlock1Size; i += 8) {
+      STEP8X3(l64, l641, l642, kBlock1Size);
+    }
+    SKIP_BLOCK(l64, kBlock1SkipTable);
+    l64 ^= l641;
+    SKIP_BLOCK(l64, kBlock1SkipTable);
+    l64 ^= l642;
+    p += (kGroups - 1) * kBlock1Size;
+  }
+  while ((e - p) >= kGroups * kBlock2Size) {
+    uint64_t l641 = 0;
+    uint64_t l642 = 0;
+    for (int i = 0; i < kBlock2Size; i += 8) {
+      STEP8X3(l64, l641, l642, kBlock2Size);
+    }
+    SKIP_BLOCK(l64, kBlock2SkipTable);
+    l64 ^= l641;
+    SKIP_BLOCK(l64, kBlock2SkipTable);
+    l64 ^= l642;
+    p += (kGroups - 1) * kBlock2Size;
+  }
+
+  // Process bytes 16 at a time
+  while ((e - p) >= 16) {
+    STEP8(l64, p);
+    STEP8(l64, p);
+  }
+
+  l = static_cast<uint32_t>(l64);
+  // Process the last few bytes.
+  while (p != e) {
+    STEP1;
+  }
+#undef SKIP_BLOCK
+#undef STEP8X3
+#undef STEP8BY3
+#undef STEP8
+#undef STEP4
+#undef STEP1
+
+  return l ^ kCRC32Xor;
+}
+
+}  // namespace crc32c
+
+#endif  // HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
diff --git a/src/crc32c_sse42.h b/src/crc32c_sse42.h
new file mode 100644
index 0000000000..95da926632
--- /dev/null
+++ b/src/crc32c_sse42.h
@@ -0,0 +1,33 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_SSE42_H_
+#define CRC32C_CRC32C_SSE42_H_
+
+// X86-specific code.
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+// The hardware-accelerated implementation is only enabled for 64-bit builds,
+// because a straightforward 32-bit implementation actually runs slower than the
+// portable version. Most X86 machines are 64-bit nowadays, so it doesn't make
+// much sense to spend time building an optimized hardware-accelerated
+// implementation.
+#if HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+namespace crc32c {
+
+// SSE4.2-accelerated implementation in crc32c_sse42.cc
+uint32_t ExtendSse42(uint32_t crc, const uint8_t* data, size_t count);
+
+}  // namespace crc32c
+
+#endif  // HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+#endif  // CRC32C_CRC32C_SSE42_H_
diff --git a/src/crc32c_sse42_check.h b/src/crc32c_sse42_check.h
new file mode 100644
index 0000000000..e7528912a6
--- /dev/null
+++ b/src/crc32c_sse42_check.h
@@ -0,0 +1,50 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef CRC32C_CRC32C_SSE42_CHECK_H_
+#define CRC32C_CRC32C_SSE42_CHECK_H_
+
+// X86-specific code checking the availability of SSE4.2 instructions.
+
+#include <cstddef>
+#include <cstdint>
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#if HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+// If the compiler supports SSE4.2, it definitely supports X86.
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+
+namespace crc32c {
+
+inline bool CanUseSse42() {
+  int cpu_info[4];
+  __cpuid(cpu_info, 1);
+  return (cpu_info[2] & (1 << 20)) != 0;
+}
+
+}  // namespace crc32c
+
+#else  // !defined(_MSC_VER)
+#include <cpuid.h>
+
+namespace crc32c {
+
+inline bool CanUseSse42() {
+  unsigned int eax, ebx, ecx, edx;
+  return __get_cpuid(1, &eax, &ebx, &ecx, &edx) && ((ecx & (1 << 20)) != 0);
+}
+
+}  // namespace crc32c
+
+#endif  // defined(_MSC_VER)
+
+#endif  // HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+#endif  // CRC32C_CRC32C_SSE42_CHECK_H_
diff --git a/src/crc32c_sse42_unittest.cc b/src/crc32c_sse42_unittest.cc
new file mode 100644
index 0000000000..c73ad8ddd1
--- /dev/null
+++ b/src/crc32c_sse42_unittest.cc
@@ -0,0 +1,24 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "gtest/gtest.h"
+
+#include "./crc32c_extend_unittests.h"
+#include "./crc32c_sse42.h"
+
+namespace crc32c {
+
+#if HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+struct Sse42TestTraits {
+  static uint32_t Extend(uint32_t crc, const uint8_t* data, size_t count) {
+    return ExtendSse42(crc, data, count);
+  }
+};
+
+INSTANTIATE_TYPED_TEST_SUITE_P(Sse42, ExtendTest, Sse42TestTraits);
+
+#endif  // HAVE_SSE42 && (defined(_M_X64) || defined(__x86_64__))
+
+}  // namespace crc32c
diff --git a/src/crc32c_test_main.cc b/src/crc32c_test_main.cc
new file mode 100644
index 0000000000..275ee380c6
--- /dev/null
+++ b/src/crc32c_test_main.cc
@@ -0,0 +1,22 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifdef CRC32C_HAVE_CONFIG_H
+#include "crc32c/crc32c_config.h"
+#endif
+
+#include "gtest/gtest.h"
+
+#if CRC32C_TESTS_BUILT_WITH_GLOG
+#include "glog/logging.h"
+#endif  // CRC32C_TESTS_BUILT_WITH_GLOG
+
+int main(int argc, char** argv) {
+#if CRC32C_TESTS_BUILT_WITH_GLOG
+  google::InitGoogleLogging(argv[0]);
+  google::InstallFailureSignalHandler();
+#endif  // CRC32C_TESTS_BUILT_WITH_GLOG
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}
diff --git a/src/crc32c_unittest.cc b/src/crc32c_unittest.cc
new file mode 100644
index 0000000000..d6c6af680c
--- /dev/null
+++ b/src/crc32c_unittest.cc
@@ -0,0 +1,129 @@
+// Copyright 2017 The CRC32C Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "crc32c/crc32c.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+
+#include "gtest/gtest.h"
+
+#include "./crc32c_extend_unittests.h"
+
+TEST(Crc32CTest, Crc32c) {
+  // From rfc3720 section B.4.
+  uint8_t buf[32];
+
+  std::memset(buf, 0, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x8a9136aa),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  std::memset(buf, 0xff, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x62a8ab43),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<uint8_t>(i);
+  EXPECT_EQ(static_cast<uint32_t>(0x46dd794e),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<uint8_t>(31 - i);
+  EXPECT_EQ(static_cast<uint32_t>(0x113fdb5c),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  uint8_t data[48] = {
+      0x01, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
+      0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x18, 0x28, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  EXPECT_EQ(static_cast<uint32_t>(0xd9963a56),
+            crc32c::Crc32c(data, sizeof(data)));
+}
+
+namespace crc32c {
+
+struct ApiTestTraits {
+  static uint32_t Extend(uint32_t crc, const uint8_t* data, size_t count) {
+    return ::crc32c::Extend(crc, data, count);
+  }
+};
+
+INSTANTIATE_TYPED_TEST_SUITE_P(Api, ExtendTest, ApiTestTraits);
+
+}  // namespace crc32c
+
+TEST(CRC32CTest, Crc32cCharPointer) {
+  char buf[32];
+
+  std::memset(buf, 0, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x8a9136aa),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  std::memset(buf, 0xff, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x62a8ab43),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<char>(i);
+  EXPECT_EQ(static_cast<uint32_t>(0x46dd794e),
+            crc32c::Crc32c(buf, sizeof(buf)));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<char>(31 - i);
+  EXPECT_EQ(static_cast<uint32_t>(0x113fdb5c),
+            crc32c::Crc32c(buf, sizeof(buf)));
+}
+
+TEST(CRC32CTest, Crc32cStdString) {
+  std::string buf;
+  buf.resize(32);
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<char>(0x00);
+  EXPECT_EQ(static_cast<uint32_t>(0x8a9136aa), crc32c::Crc32c(buf));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = '\xff';
+  EXPECT_EQ(static_cast<uint32_t>(0x62a8ab43), crc32c::Crc32c(buf));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<char>(i);
+  EXPECT_EQ(static_cast<uint32_t>(0x46dd794e), crc32c::Crc32c(buf));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<char>(31 - i);
+  EXPECT_EQ(static_cast<uint32_t>(0x113fdb5c), crc32c::Crc32c(buf));
+}
+
+#if __cplusplus > 201402L
+#if __has_include(<string_view>)
+
+TEST(CRC32CTest, Crc32cStdStringView) {
+  uint8_t buf[32];
+  std::string_view view(reinterpret_cast<const char*>(buf), sizeof(buf));
+
+  std::memset(buf, 0, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x8a9136aa), crc32c::Crc32c(view));
+
+  std::memset(buf, 0xff, sizeof(buf));
+  EXPECT_EQ(static_cast<uint32_t>(0x62a8ab43), crc32c::Crc32c(view));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<uint8_t>(i);
+  EXPECT_EQ(static_cast<uint32_t>(0x46dd794e), crc32c::Crc32c(view));
+
+  for (size_t i = 0; i < 32; ++i)
+    buf[i] = static_cast<uint8_t>(31 - i);
+  EXPECT_EQ(static_cast<uint32_t>(0x113fdb5c), crc32c::Crc32c(view));
+}
+
+#endif  // __has_include(<string_view>)
+#endif  // __cplusplus > 201402L
+
+#define TESTED_EXTEND Extend
+#include "./crc32c_extend_unittests.h"
+#undef TESTED_EXTEND