Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/src/rocksdb/file/sequence_file_reader.h b/src/rocksdb/file/sequence_file_reader.h
new file mode 100644
index 000000000..2f0898b42
--- /dev/null
+++ b/src/rocksdb/file/sequence_file_reader.h
@@ -0,0 +1,67 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#pragma once
+#include <atomic>
+#include <string>
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "rocksdb/file_system.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// SequentialFileReader is a wrapper on top of Env::SequentialFile. It handles
+// Buffered (i.e when page cache is enabled) and Direct (with O_DIRECT / page
+// cache disabled) reads appropriately, and also updates the IO stats.
+class SequentialFileReader {
+ private:
+  std::unique_ptr<FSSequentialFile> file_;
+  std::string file_name_;
+  std::atomic<size_t> offset_{0};  // read offset
+
+ public:
+  explicit SequentialFileReader(std::unique_ptr<FSSequentialFile>&& _file,
+                                const std::string& _file_name)
+      : file_(std::move(_file)), file_name_(_file_name) {}
+
+  explicit SequentialFileReader(std::unique_ptr<FSSequentialFile>&& _file,
+                                const std::string& _file_name,
+                                size_t _readahead_size)
+      : file_(NewReadaheadSequentialFile(std::move(_file), _readahead_size)),
+        file_name_(_file_name) {}
+
+  SequentialFileReader(SequentialFileReader&& o) ROCKSDB_NOEXCEPT {
+    *this = std::move(o);
+  }
+
+  SequentialFileReader& operator=(SequentialFileReader&& o) ROCKSDB_NOEXCEPT {
+    file_ = std::move(o.file_);
+    return *this;
+  }
+
+  SequentialFileReader(const SequentialFileReader&) = delete;
+  SequentialFileReader& operator=(const SequentialFileReader&) = delete;
+
+  Status Read(size_t n, Slice* result, char* scratch);
+
+  Status Skip(uint64_t n);
+
+  FSSequentialFile* file() { return file_.get(); }
+
+  std::string file_name() { return file_name_; }
+
+  bool use_direct_io() const { return file_->use_direct_io(); }
+
+ private:
+  // NewReadaheadSequentialFile provides a wrapper over SequentialFile to
+  // always prefetch additional data with every read.
+  static std::unique_ptr<FSSequentialFile> NewReadaheadSequentialFile(
+      std::unique_ptr<FSSequentialFile>&& file, size_t readahead_size);
+};
+}  // namespace ROCKSDB_NAMESPACE