Sync with upstream repo.

Changes include:
* CPU check has been broken up into a number of small libraries
* BoringSSL option has been removed
* Better abseil integration

hasher.h

@@ -0,0 +1,96 @@
+// Copyright 2020 Google LLC
+//
+// 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.
+
+#ifndef THIRD_PARTY_CPU_CHECK_HASH_H_
+#define THIRD_PARTY_CPU_CHECK_HASH_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "malign_buffer.h"
+
+namespace cpu_check {
+
+class Hasher {
+ public:
+  virtual ~Hasher() {}
+  virtual std::string Name() const = 0;
+  virtual std::string Hash(const MalignBuffer &b) const = 0;
+};
+
+class Md5 : public Hasher {
+ public:
+  std::string Name() const override { return "MD5"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Sha1 : public Hasher {
+ public:
+  std::string Name() const override { return "SHA1"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Sha256 : public Hasher {
+ public:
+  std::string Name() const override { return "SHA256"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Sha512 : public Hasher {
+ public:
+  std::string Name() const override { return "SHA512"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Adler32 : public Hasher {
+ public:
+  std::string Name() const override { return "ADLER32"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Crc32 : public Hasher {
+ public:
+  std::string Name() const override { return "CRC32"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Crc32C : public Hasher {
+ public:
+  std::string Name() const override { return "CRC32C"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class FarmHash64 : public Hasher {
+ public:
+  std::string Name() const override { return "FarmHash64"; }
+  std::string Hash(const MalignBuffer &b) const override;
+};
+
+class Hashers {
+ public:
+  Hashers();
+
+  // Returns a randomly selected hasher.
+  const Hasher &RandomHasher(uint64_t seed) const;
+
+  const std::vector<std::unique_ptr<Hasher>> &hashers() const {
+    return hashers_;
+  }
+
+ private:
+  std::vector<std::unique_ptr<Hasher>> hashers_;
+};
+}  // namespace cpu_check
+#endif  // THIRD_PARTY_CPU_CHECK_HASH_H_