feat(cpp-object-oriented-modular-refactoring): step 23 - hdf5-writer-modules

src/fesa/io/hdf5/hdf5_atomic_file.cpp

@@ -0,0 +1,88 @@
+#define NOMINMAX
+#include "io/hdf5/hdf5_atomic_file.h"
+
+#include <Windows.h>
+
+#include <atomic>
+#include <cstddef>
+#include <cstdint>
+#include <filesystem>
+#include <string>
+#include <utility>
+
+#include "io/hdf5/hdf5_primitives.h"
+#include "io/hdf5/hdf5_raii.h"
+
+namespace fesa::hdf5_internal {
+namespace {
+
+bool AtomicReplace(const std::filesystem::path& candidate_path,
+                   const std::filesystem::path& output_path) {
+  const DWORD attributes = GetFileAttributesW(output_path.c_str());
+  if (attributes != INVALID_FILE_ATTRIBUTES) {
+    return ReplaceFileW(output_path.c_str(), candidate_path.c_str(), nullptr,
+                        0U, nullptr, nullptr) != FALSE;
+  }
+  const DWORD error = GetLastError();
+  if (error != ERROR_FILE_NOT_FOUND && error != ERROR_PATH_NOT_FOUND) {
+    return false;
+  }
+  return MoveFileExW(candidate_path.c_str(), output_path.c_str(),
+                     MOVEFILE_WRITE_THROUGH) != FALSE;
+}
+
+}  // namespace
+
+CandidateFileGuard::CandidateFileGuard(std::filesystem::path path)
+    : path_{std::move(path)} {}
+
+CandidateFileGuard::~CandidateFileGuard() {
+  if (active_) {
+    std::error_code ignored;
+    (void)std::filesystem::remove(path_, ignored);
+  }
+}
+
+void CandidateFileGuard::Release() noexcept { active_ = false; }
+
+std::filesystem::path MakeCandidatePath(
+    const std::filesystem::path& output_path) {
+  static std::atomic<std::uint64_t> sequence{0U};
+  const std::filesystem::path parent = output_path.parent_path();
+  for (std::size_t attempt = 0U; attempt < 1024U; ++attempt) {
+    const std::wstring filename =
+        L"." + output_path.filename().wstring() + L".tmp." +
+        std::to_wstring(GetCurrentProcessId()) + L"." +
+        std::to_wstring(sequence.fetch_add(1U));
+    const std::filesystem::path candidate = parent / filename;
+    std::error_code error;
+    const bool exists = std::filesystem::exists(candidate, error);
+    if (error) {
+      throw Hdf5Failure{"Unable to inspect the temporary output path."};
+    }
+    if (!exists) {
+      return candidate;
+    }
+  }
+  throw Hdf5Failure{"Unable to allocate a unique temporary output path."};
+}
+
+Status AtomicFinalizeValidatedCandidate(
+    const std::filesystem::path& candidate_path,
+    const std::filesystem::path& output_path, const Status& validation) {
+  if (!validation.IsOk()) {
+    std::error_code ignored;
+    (void)std::filesystem::remove(candidate_path, ignored);
+    return validation;
+  }
+  if (!AtomicReplace(candidate_path, output_path)) {
+    std::error_code ignored;
+    (void)std::filesystem::remove(candidate_path, ignored);
+    return OutputFailure("hdf5-finalization-failure",
+                         "The checked temporary HDF5 file could not replace "
+                         "the final output.");
+  }
+  return Status::Ok();
+}
+
+}  // namespace fesa::hdf5_internal