refactor: Extract file recompression code to a class

3 files changed, 138 insertions, 0 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 0a448b98..6eee59c8 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(
   sources
   CacheEntry.cpp
+  FileRecompressor.cpp
   Manifest.cpp
   MsvcShowIncludesOutput.cpp
   Result.cpp
diff --git a/src/core/FileRecompressor.cpp b/src/core/FileRecompressor.cpp
new file mode 100644
index 00000000..13272612
--- /dev/null
+++ b/src/core/FileRecompressor.cpp
@@ -0,0 +1,89 @@
+// Copyright (C) 2022 Joel Rosdahl and other contributors
+//
+// See doc/AUTHORS.adoc for a complete list of contributors.
+//
+// This program is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program; if not, write to the Free Software Foundation, Inc., 51
+// Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+#include "FileRecompressor.hpp"
+
+#include <AtomicFile.hpp>
+#include <Util.hpp>
+#include <core/CacheEntry.hpp>
+#include <core/exceptions.hpp>
+#include <util/expected.hpp>
+#include <util/file.hpp>
+
+namespace core {
+
+int64_t
+FileRecompressor::recompress(const std::string& cache_file,
+                             const std::optional<int8_t> level)
+{
+  core::CacheEntry::Header header(cache_file);
+
+  const int8_t wanted_level =
+    level ? (*level == 0 ? core::CacheEntry::default_compression_level : *level)
+          : 0;
+  const auto old_stat = Stat::lstat(cache_file, Stat::OnError::log);
+  Stat new_stat(old_stat);
+
+  if (header.compression_level != wanted_level) {
+    const auto cache_file_data = util::value_or_throw<core::Error>(
+      util::read_file<util::Bytes>(cache_file),
+      FMT("Failed to read {}: ", cache_file));
+    core::CacheEntry cache_entry(cache_file_data);
+    cache_entry.verify_checksum();
+
+    header.entry_format_version = core::CacheEntry::k_format_version;
+    header.compression_type =
+      level ? core::CompressionType::zstd : core::CompressionType::none;
+    header.compression_level = wanted_level;
+
+    AtomicFile new_cache_file(cache_file, AtomicFile::Mode::binary);
+    new_cache_file.write(
+      core::CacheEntry::serialize(header, cache_entry.payload()));
+    new_cache_file.commit();
+    new_stat = Stat::lstat(cache_file, Stat::OnError::log);
+
+    // Restore mtime/atime to keep cache LRU cleanup working as expected:
+    util::set_timestamps(cache_file, old_stat.mtime(), old_stat.atime());
+  }
+
+  m_content_size += header.entry_size;
+  m_old_size += old_stat.size_on_disk();
+  m_new_size += new_stat.size_on_disk();
+
+  return Util::size_change_kibibyte(old_stat, new_stat);
+}
+
+uint64_t
+FileRecompressor::content_size() const
+{
+  return m_content_size;
+}
+
+uint64_t
+FileRecompressor::old_size() const
+{
+  return m_old_size;
+}
+
+uint64_t
+FileRecompressor::new_size() const
+{
+  return m_new_size;
+}
+
+} // namespace core
diff --git a/src/core/FileRecompressor.hpp b/src/core/FileRecompressor.hpp
new file mode 100644
index 00000000..289b0d75
--- /dev/null
+++ b/src/core/FileRecompressor.hpp
@@ -0,0 +1,48 @@
+// Copyright (C) 2022 Joel Rosdahl and other contributors
+//
+// See doc/AUTHORS.adoc for a complete list of contributors.
+//
+// This program is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program; if not, write to the Free Software Foundation, Inc., 51
+// Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+#pragma once
+
+#include <atomic>
+#include <cstdint>
+#include <mutex>
+#include <optional>
+#include <string>
+
+namespace core {
+
+class FileRecompressor
+{
+public:
+  FileRecompressor() = default;
+
+  // Returns on-disk size change in KiB.
+  int64_t recompress(const std::string& cache_file,
+                     const std::optional<int8_t> level);
+
+  uint64_t content_size() const;
+  uint64_t old_size() const;
+  uint64_t new_size() const;
+
+private:
+  std::atomic<uint64_t> m_content_size = 0;
+  std::atomic<uint64_t> m_old_size = 0;
+  std::atomic<uint64_t> m_new_size = 0;
+};
+
+} // namespace core