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, 93 insertions, 0 deletions

diff --git a/absl/crc/internal/crc_non_temporal_memcpy.cc b/absl/crc/internal/crc_non_temporal_memcpy.cc
new file mode 100644
index 00000000..adc867f6
--- /dev/null
+++ b/absl/crc/internal/crc_non_temporal_memcpy.cc
@@ -0,0 +1,93 @@
+// 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 <cstdint>
+
+#include "absl/base/config.h"
+#include "absl/crc/crc32c.h"
+#include "absl/crc/internal/crc_memcpy.h"
+#include "absl/crc/internal/non_temporal_memcpy.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+crc32c_t CrcNonTemporalMemcpyEngine::Compute(void* __restrict dst,
+                                             const void* __restrict src,
+                                             std::size_t length,
+                                             crc32c_t initial_crc) const {
+  constexpr size_t kBlockSize = 8192;
+  crc32c_t crc = initial_crc;
+
+  const char* src_bytes = reinterpret_cast<const char*>(src);
+  char* dst_bytes = reinterpret_cast<char*>(dst);
+
+  // Copy + CRC loop - run 8k chunks until we are out of full chunks.
+  std::size_t offset = 0;
+  for (; offset + kBlockSize < length; offset += kBlockSize) {
+    crc = absl::ExtendCrc32c(crc,
+                             absl::string_view(src_bytes + offset, kBlockSize));
+    non_temporal_store_memcpy(dst_bytes + offset, src_bytes + offset,
+                              kBlockSize);
+  }
+
+  // Save some work if length is 0.
+  if (offset < length) {
+    std::size_t final_copy_size = length - offset;
+    crc = ExtendCrc32c(crc,
+                       absl::string_view(src_bytes + offset, final_copy_size));
+
+    non_temporal_store_memcpy(dst_bytes + offset, src_bytes + offset,
+                              final_copy_size);
+  }
+
+  return crc;
+}
+
+crc32c_t CrcNonTemporalMemcpyAVXEngine::Compute(void* __restrict dst,
+                                                const void* __restrict src,
+                                                std::size_t length,
+                                                crc32c_t initial_crc) const {
+  constexpr size_t kBlockSize = 8192;
+  crc32c_t crc = initial_crc;
+
+  const char* src_bytes = reinterpret_cast<const char*>(src);
+  char* dst_bytes = reinterpret_cast<char*>(dst);
+
+  // Copy + CRC loop - run 8k chunks until we are out of full chunks.
+  std::size_t offset = 0;
+  for (; offset + kBlockSize < length; offset += kBlockSize) {
+    crc = ExtendCrc32c(crc, absl::string_view(src_bytes + offset, kBlockSize));
+
+    non_temporal_store_memcpy_avx(dst_bytes + offset, src_bytes + offset,
+                                  kBlockSize);
+  }
+
+  // Save some work if length is 0.
+  if (offset < length) {
+    std::size_t final_copy_size = length - offset;
+    crc = ExtendCrc32c(crc,
+                       absl::string_view(src_bytes + offset, final_copy_size));
+
+    non_temporal_store_memcpy_avx(dst_bytes + offset, src_bytes + offset,
+                                  final_copy_size);
+  }
+
+  return crc;
+}
+
+}  // namespace crc_internal
+ABSL_NAMESPACE_END
+}  // namespace absl