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// Copyright 2022 Huawei Cloud Computing Technology Co., Ltd.
//
// 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 INCLUDED_SRC_BUILDTOOL_CRYPTO_HASH_FUNCTION_HPP
#define INCLUDED_SRC_BUILDTOOL_CRYPTO_HASH_FUNCTION_HPP
#include <cstdint>
#include <functional>
#include <optional>
#include <string>
#include "src/buildtool/crypto/hasher.hpp"
#include <gsl/gsl>
/// \brief Hash function used for the entire buildtool.
class HashFunction {
public:
enum class JustHash : std::uint8_t {
Native, ///< SHA1 for plain hashes, and Git for blobs and trees.
Compatible ///< SHA256 for all hashes.
};
/// \brief Set globally used hash type.
static void SetHashType(JustHash type) {
[[maybe_unused]] auto _ = HashType(type);
}
/// \brief Compute a plain hash.
[[nodiscard]] static auto ComputeHash(std::string const& data) noexcept
-> Hasher::HashDigest {
return ComputeTaggedHash(data);
}
/// \brief Compute a blob hash.
[[nodiscard]] static auto ComputeBlobHash(std::string const& data) noexcept
-> Hasher::HashDigest {
static auto const kBlobTagCreator =
[](std::string const& data) -> std::string {
return {"blob " + std::to_string(data.size()) + '\0'};
};
return ComputeTaggedHash(data, kBlobTagCreator);
}
/// \brief Compute a tree hash.
[[nodiscard]] static auto ComputeTreeHash(std::string const& data) noexcept
-> Hasher::HashDigest {
static auto const kTreeTagCreator =
[](std::string const& data) -> std::string {
return {"tree " + std::to_string(data.size()) + '\0'};
};
return ComputeTaggedHash(data, kTreeTagCreator);
}
/// \brief Obtain incremental hasher for computing plain hashes.
[[nodiscard]] static auto Hasher() noexcept -> ::Hasher {
switch (HashType()) {
case JustHash::Native:
return ::Hasher{Hasher::HashType::SHA1};
case JustHash::Compatible:
return ::Hasher{Hasher::HashType::SHA256};
}
Ensures(false); // unreachable
}
private:
static constexpr auto kDefaultType = JustHash::Native;
[[nodiscard]] static auto HashType(
std::optional<JustHash> type = std::nullopt) -> JustHash {
static JustHash type_{kDefaultType};
if (type) {
type_ = *type;
}
return type_;
}
[[nodiscard]] static auto ComputeTaggedHash(
std::string const& data,
std::function<std::string(std::string const&)> const& tag_creator =
{}) noexcept -> Hasher::HashDigest {
auto hasher = Hasher();
if (tag_creator and HashType() == JustHash::Native) {
hasher.Update(tag_creator(data));
}
hasher.Update(data);
return std::move(hasher).Finalize();
}
};
#endif // INCLUDED_SRC_BUILDTOOL_CRYPTO_HASH_FUNCTION_HPP
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