1 files changed, 117 insertions, 0 deletions
diff --git a/src/buildtool/execution_api/serve/utils.cpp b/src/buildtool/execution_api/serve/utils.cpp
new file mode 100644
index 00000000..2796d3b1
--- /dev/null
+++ b/src/buildtool/execution_api/serve/utils.cpp
@@ -0,0 +1,117 @@
+// Copyright 2024 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/execution_api/serve/utils.hpp"
+
+#include <cstddef>  // std::size_t
+#include <filesystem>
+#include <system_error>
+#include <utility>  // std::move
+
+#include "fmt/core.h"
+#include "src/buildtool/file_system/file_system_manager.hpp"
+#include "src/buildtool/storage/fs_utils.hpp"
+
+namespace MRApiUtils {
+
+auto ReadRehashedDigest(ArtifactDigest const& digest,
+                        StorageConfig const& source_config,
+                        StorageConfig const& target_config,
+                        bool from_git) noexcept
+    -> expected<std::optional<Artifact::ObjectInfo>, std::string> {
+    // check for mapping file in all generations
+    std::size_t generation = 0;
+    std::optional<std::filesystem::path> rehash_id_file = std::nullopt;
+    auto const compat_hash_type = target_config.hash_function.GetType();
+    for (; generation < source_config.num_generations; ++generation) {
+        auto path = StorageUtils::GetRehashIDFile(source_config,
+                                                  compat_hash_type,
+                                                  digest.hash(),
+                                                  from_git,
+                                                  generation);
+        if (FileSystemManager::Exists(path)) {
+            rehash_id_file = std::move(path);
+            break;  // found the generation
+        }
+    }
+    if (rehash_id_file) {
+        // read id file
+        auto compat_obj_str = FileSystemManager::ReadFile(*rehash_id_file);
+        if (not compat_obj_str) {
+            return unexpected{fmt::format("failed to read rehash id file {}",
+                                          rehash_id_file->string())};
+        }
+        // get artifact object from content
+        auto compat_obj =
+            Artifact::ObjectInfo::FromString(compat_hash_type, *compat_obj_str);
+        if (not compat_obj) {
+            // handle nullopt value explicitly
+            return unexpected{
+                fmt::format("failed to read rehashed artifact from id file {}",
+                            rehash_id_file->string())};
+        }
+        // ensure the id file is in generation 0 for future calls
+        if (generation != 0) {
+            auto dest_id_file = StorageUtils::GetRehashIDFile(
+                source_config, compat_hash_type, digest.hash(), from_git);
+            auto ok = FileSystemManager::CreateFileHardlink(*rehash_id_file,
+                                                            dest_id_file);
+            if (not ok) {
+                auto const& err = ok.error();
+                if (err != std::errc::too_many_links) {
+                    return unexpected{
+                        fmt::format("failed to link rehash id file {}:\n{} {}",
+                                    dest_id_file.string(),
+                                    err.value(),
+                                    err.message())};
+                }
+                // if too many links reported, write id file ourselves
+                if (not StorageUtils::WriteTreeIDFile(dest_id_file,
+                                                      *compat_obj_str)) {
+                    return unexpected{
+                        fmt::format("failed to write rehash id file {}",
+                                    dest_id_file.string())};
+                }
+            }
+        }
+        return std::move(compat_obj);  // not dereferenced to assist type
+                                       // deduction in variant
+    }
+    // no mapping file found
+    return std::optional<Artifact::ObjectInfo>{std::nullopt};
+}
+
+auto StoreRehashedDigest(ArtifactDigest const& source_digest,
+                         ArtifactDigest const& target_digest,
+                         ObjectType obj_type,
+                         StorageConfig const& source_config,
+                         StorageConfig const& target_config,
+                         bool from_git) noexcept -> std::optional<std::string> {
+    // write mapping
+    auto const rehash_id_file =
+        StorageUtils::GetRehashIDFile(source_config,
+                                      target_config.hash_function.GetType(),
+                                      source_digest.hash(),
+                                      from_git);
+    if (not StorageUtils::WriteTreeIDFile(
+            rehash_id_file,
+            Artifact::ObjectInfo{.digest = target_digest, .type = obj_type}
+                .ToString())) {
+        return fmt::format("failed to write rehash id to file {}",
+                           rehash_id_file.string());
+    }
+    return std::nullopt;  // a-ok
+}
+
+}  // namespace MRApiUtils