Release the CRC library

This implementation can advantage of hardware acceleration available
on common CPUs when using GCC and Clang. A future update may enable
this on MSVC as well.

PiperOrigin-RevId: 487327024
Change-Id: I99a8f1bcbdf25297e776537e23bd0a902e0818a1

1 files changed, 186 insertions, 0 deletions

diff --git a/absl/crc/crc32c_test.cc b/absl/crc/crc32c_test.cc
new file mode 100644
index 00000000..98e5fea3
--- /dev/null
+++ b/absl/crc/crc32c_test.cc
@@ -0,0 +1,186 @@
+// Copyright 2022 The Abseil Authors
+//
+// 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
+//
+//     https://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 "absl/crc/crc32c.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "absl/crc/internal/crc32c.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+namespace {
+
+TEST(CRC32C, RFC3720) {
+  // Test the results of the vectors from
+  // https://www.rfc-editor.org/rfc/rfc3720#appendix-B.4
+  char data[32];
+
+  // 32 bytes of ones.
+  memset(data, 0, sizeof(data));
+  EXPECT_EQ(absl::ComputeCrc32c(absl::string_view(data, sizeof(data))),
+            absl::ToCrc32c(0x8a9136aa));
+
+  // 32 bytes of ones.
+  memset(data, 0xff, sizeof(data));
+  EXPECT_EQ(absl::ComputeCrc32c(absl::string_view(data, sizeof(data))),
+            absl::ToCrc32c(0x62a8ab43));
+
+  // 32 incrementing bytes.
+  for (int i = 0; i < 32; ++i) data[i] = static_cast<char>(i);
+  EXPECT_EQ(absl::ComputeCrc32c(absl::string_view(data, sizeof(data))),
+            absl::ToCrc32c(0x46dd794e));
+
+  // 32 decrementing bytes.
+  for (int i = 0; i < 32; ++i) data[i] = static_cast<char>(31 - i);
+  EXPECT_EQ(absl::ComputeCrc32c(absl::string_view(data, sizeof(data))),
+            absl::ToCrc32c(0x113fdb5c));
+
+  // An iSCSI - SCSI Read (10) Command PDU.
+  constexpr uint8_t cmd[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(absl::ComputeCrc32c(absl::string_view(
+                reinterpret_cast<const char*>(cmd), sizeof(cmd))),
+            absl::ToCrc32c(0xd9963a56));
+}
+
+std::string TestString(size_t len) {
+  std::string result;
+  result.reserve(len);
+  for (size_t i = 0; i < len; ++i) {
+    result.push_back(static_cast<char>(i % 256));
+  }
+  return result;
+}
+
+TEST(CRC32C, Compute) {
+  EXPECT_EQ(absl::ComputeCrc32c(""), absl::ToCrc32c(0));
+  EXPECT_EQ(absl::ComputeCrc32c("hello world"), absl::ToCrc32c(0xc99465aa));
+}
+
+TEST(CRC32C, Extend) {
+  uint32_t base = 0xC99465AA;  // CRC32C of "Hello World"
+  std::string extension = "Extension String";
+
+  EXPECT_EQ(
+      absl::ExtendCrc32c(absl::ToCrc32c(base), extension),
+      absl::ToCrc32c(0xD2F65090));  // CRC32C of "Hello WorldExtension String"
+}
+
+TEST(CRC32C, ExtendByZeroes) {
+  std::string base = "hello world";
+  absl::crc32c_t base_crc = absl::ToCrc32c(0xc99465aa);
+
+  for (const size_t extend_by : {100, 10000, 100000}) {
+    SCOPED_TRACE(extend_by);
+    absl::crc32c_t crc2 = absl::ExtendCrc32cByZeroes(base_crc, extend_by);
+    EXPECT_EQ(crc2, absl::ComputeCrc32c(base + std::string(extend_by, '\0')));
+  }
+}
+
+TEST(CRC32C, UnextendByZeroes) {
+  for (auto seed_crc : {absl::ToCrc32c(0), absl::ToCrc32c(0xc99465aa)}) {
+    SCOPED_TRACE(seed_crc);
+    for (const size_t size_1 : {2, 200, 20000, 200000, 20000000}) {
+      for (const size_t size_2 : {0, 100, 10000, 100000, 10000000}) {
+        size_t extend_size = std::max(size_1, size_2);
+        size_t unextend_size = std::min(size_1, size_2);
+        SCOPED_TRACE(extend_size);
+        SCOPED_TRACE(unextend_size);
+
+        // Extending by A zeroes an unextending by B<A zeros should be identical
+        // to extending by A-B zeroes.
+        absl::crc32c_t crc1 = seed_crc;
+        crc1 = absl::ExtendCrc32cByZeroes(crc1, extend_size);
+        crc1 = absl::crc_internal::UnextendCrc32cByZeroes(crc1, unextend_size);
+
+        absl::crc32c_t crc2 = seed_crc;
+        crc2 = absl::ExtendCrc32cByZeroes(crc2, extend_size - unextend_size);
+
+        EXPECT_EQ(crc1, crc2);
+      }
+    }
+  }
+  for (const size_t size : {0, 1, 100, 10000}) {
+    SCOPED_TRACE(size);
+    std::string string_before = TestString(size);
+    std::string string_after = string_before + std::string(size, '\0');
+
+    absl::crc32c_t crc_before = absl::ComputeCrc32c(string_before);
+    absl::crc32c_t crc_after = absl::ComputeCrc32c(string_after);
+
+    EXPECT_EQ(crc_before,
+              absl::crc_internal::UnextendCrc32cByZeroes(crc_after, size));
+  }
+}
+
+TEST(CRC32C, Concat) {
+  std::string hello = "Hello, ";
+  std::string world = "world!";
+  std::string hello_world = absl::StrCat(hello, world);
+
+  absl::crc32c_t crc_a = absl::ComputeCrc32c(hello);
+  absl::crc32c_t crc_b = absl::ComputeCrc32c(world);
+  absl::crc32c_t crc_ab = absl::ComputeCrc32c(hello_world);
+
+  EXPECT_EQ(absl::ConcatCrc32c(crc_a, crc_b, world.size()), crc_ab);
+}
+
+TEST(CRC32C, Memcpy) {
+  for (size_t bytes : {0, 1, 20, 500, 100000}) {
+    SCOPED_TRACE(bytes);
+    std::string sample_string = TestString(bytes);
+    std::string target_buffer = std::string(bytes, '\0');
+
+    absl::crc32c_t memcpy_crc =
+        absl::MemcpyCrc32c(&(target_buffer[0]), sample_string.data(), bytes);
+    absl::crc32c_t compute_crc = absl::ComputeCrc32c(sample_string);
+
+    EXPECT_EQ(memcpy_crc, compute_crc);
+    EXPECT_EQ(sample_string, target_buffer);
+  }
+}
+
+TEST(CRC32C, RemovePrefix) {
+  std::string hello = "Hello, ";
+  std::string world = "world!";
+  std::string hello_world = absl::StrCat(hello, world);
+
+  absl::crc32c_t crc_a = absl::ComputeCrc32c(hello);
+  absl::crc32c_t crc_b = absl::ComputeCrc32c(world);
+  absl::crc32c_t crc_ab = absl::ComputeCrc32c(hello_world);
+
+  EXPECT_EQ(absl::RemoveCrc32cPrefix(crc_a, crc_ab, world.size()), crc_b);
+}
+
+TEST(CRC32C, RemoveSuffix) {
+  std::string hello = "Hello, ";
+  std::string world = "world!";
+  std::string hello_world = absl::StrCat(hello, world);
+
+  absl::crc32c_t crc_a = absl::ComputeCrc32c(hello);
+  absl::crc32c_t crc_b = absl::ComputeCrc32c(world);
+  absl::crc32c_t crc_ab = absl::ComputeCrc32c(hello_world);
+
+  EXPECT_EQ(absl::RemoveCrc32cSuffix(crc_ab, crc_b, world.size()), crc_a);
+}
+}  // namespace