From cd66c1f47fbfc53d60d37d883c9c709c93e54a36 Mon Sep 17 00:00:00 2001
From: Klaus Aehlig <klaus.aehlig@huawei.com>
Date: Mon, 27 Nov 2023 16:17:08 +0100
Subject: hash_function: support hashing of files

Extend our internal hash-function abstraction to support hashing
of files. In this way, we can provide a way to compute the hash of
a potentially large file without having to fully read it to memory
first, while still keeping the details of the used hash function
abstracted away.
---
 src/buildtool/crypto/hash_function.cpp | 56 ++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 src/buildtool/crypto/hash_function.cpp

(limited to 'src/buildtool/crypto/hash_function.cpp')

diff --git a/src/buildtool/crypto/hash_function.cpp b/src/buildtool/crypto/hash_function.cpp
new file mode 100644
index 00000000..89bb0cb8
--- /dev/null
+++ b/src/buildtool/crypto/hash_function.cpp
@@ -0,0 +1,56 @@
+// Copyright 2023 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.
+
+#include "src/buildtool/crypto/hash_function.hpp"
+
+#include <fstream>
+#include <string>
+
+#include "src/buildtool/logging/log_level.hpp"
+#include "src/buildtool/logging/logger.hpp"
+
+[[nodiscard]] auto HashFunction::ComputeHashFile(
+    const std::filesystem::path& file_path,
+    bool as_tree) noexcept
+    -> std::optional<std::pair<Hasher::HashDigest, std::uintmax_t>> {
+    static constexpr std::size_t kChunkSize{4048};
+    try {
+        auto hasher = Hasher();
+        auto size = std::filesystem::file_size(file_path);
+        if (HashType() == JustHash::Native) {
+            hasher.Update(
+                (as_tree ? std::string{"tree "} : std::string{"blob "}) +
+                std::to_string(size) + '\0');
+        }
+        std::string chunk{};
+        chunk.resize(kChunkSize);
+        std::ifstream file_reader(file_path.string(), std::ios::binary);
+        if (file_reader.is_open()) {
+            auto chunk_size = gsl::narrow<std::streamsize>(chunk.size());
+            do {
+                file_reader.read(chunk.data(), chunk_size);
+                auto count = file_reader.gcount();
+                hasher.Update(chunk.substr(0, gsl::narrow<std::size_t>(count)));
+            } while (file_reader.good());
+            file_reader.close();
+            return std::make_pair(std::move(hasher).Finalize(), size);
+        }
+    } catch (std::exception const& e) {
+        Logger::Log(LogLevel::Debug,
+                    "Error while trying to hash {}: {}",
+                    file_path.string(),
+                    e.what());
+    }
+    return std::nullopt;
+}
-- 
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