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.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/buildtool/crypto/hash_function.hpp b/src/buildtool/crypto/hash_function.hpp
index 44341777..fa141ed2 100644
--- a/src/buildtool/crypto/hash_function.hpp
+++ b/src/buildtool/crypto/hash_function.hpp
@@ -16,9 +16,11 @@
 #define INCLUDED_SRC_BUILDTOOL_CRYPTO_HASH_FUNCTION_HPP
 
 #include <cstdint>
+#include <filesystem>
 #include <functional>
 #include <optional>
 #include <string>
+#include <utility>
 
 #include "src/buildtool/crypto/hasher.hpp"
 
@@ -53,6 +55,12 @@ class HashFunction {
         return ComputeTaggedHash(data, kBlobTagCreator);
     }
 
+    /// \brief Compute the blob hash of a file or std::nullopt on IO error.
+    [[nodiscard]] static auto ComputeHashFile(
+        const std::filesystem::path& file_path,
+        bool as_tree) noexcept
+        -> std::optional<std::pair<Hasher::HashDigest, std::uintmax_t>>;
+
     /// \brief Compute a tree hash.
     [[nodiscard]] static auto ComputeTreeHash(std::string const& data) noexcept
         -> Hasher::HashDigest {