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rocksdb/util/file_reader_writer.h

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same 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 "util/aligned_buffer.h"
namespace rocksdb {
class Statistics;
class HistogramImpl;
std::unique_ptr<RandomAccessFile> NewReadaheadRandomAccessFile(
std::unique_ptr<RandomAccessFile>&& file, size_t readahead_size);
class SequentialFileReader {
private:
std::unique_ptr<SequentialFile> file_;
std::atomic<size_t> offset_; // read offset
public:
explicit SequentialFileReader(std::unique_ptr<SequentialFile>&& _file)
: file_(std::move(_file)), offset_(0) {}
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);
SequentialFile* file() { return file_.get(); }
bool use_direct_io() const { return file_->use_direct_io(); }
protected:
Status DirectRead(size_t n, Slice* result, char* scratch);
};
class RandomAccessFileReader {
private:
std::unique_ptr<RandomAccessFile> file_;
Env* env_;
Statistics* stats_;
uint32_t hist_type_;
HistogramImpl* file_read_hist_;
public:
explicit RandomAccessFileReader(std::unique_ptr<RandomAccessFile>&& raf,
Env* env = nullptr,
Statistics* stats = nullptr,
uint32_t hist_type = 0,
HistogramImpl* file_read_hist = nullptr)
: file_(std::move(raf)),
env_(env),
stats_(stats),
hist_type_(hist_type),
file_read_hist_(file_read_hist) {}
RandomAccessFileReader(RandomAccessFileReader&& o) ROCKSDB_NOEXCEPT {
*this = std::move(o);
}
RandomAccessFileReader& operator=(RandomAccessFileReader&& o) ROCKSDB_NOEXCEPT{
file_ = std::move(o.file_);
env_ = std::move(o.env_);
stats_ = std::move(o.stats_);
hist_type_ = std::move(o.hist_type_);
file_read_hist_ = std::move(o.file_read_hist_);
return *this;
}
RandomAccessFileReader(const RandomAccessFileReader&) = delete;
RandomAccessFileReader& operator=(const RandomAccessFileReader&) = delete;
Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const;
Status Prefetch(uint64_t offset, size_t n) const {
return file_->Prefetch(offset, n);
}
RandomAccessFile* file() { return file_.get(); }
bool use_direct_io() const { return file_->use_direct_io(); }
protected:
Status DirectRead(uint64_t offset, size_t n, Slice* result,
char* scratch) const;
};
// Use posix write to write data to a file.
class WritableFileWriter {
private:
std::unique_ptr<WritableFile> writable_file_;
AlignedBuffer buf_;
size_t max_buffer_size_;
// Actually written data size can be used for truncate
// not counting padding data
uint64_t filesize_;
// This is necessary when we use unbuffered access
// and writes must happen on aligned offsets
// so we need to go back and write that page again
uint64_t next_write_offset_;
bool pending_sync_;
uint64_t last_sync_size_;
uint64_t bytes_per_sync_;
RateLimiter* rate_limiter_;
Statistics* stats_;
public:
WritableFileWriter(std::unique_ptr<WritableFile>&& file,
const EnvOptions& options, Statistics* stats = nullptr)
: writable_file_(std::move(file)),
buf_(),
max_buffer_size_(options.writable_file_max_buffer_size),
filesize_(0),
next_write_offset_(0),
pending_sync_(false),
last_sync_size_(0),
bytes_per_sync_(options.bytes_per_sync),
rate_limiter_(options.rate_limiter),
stats_(stats) {
buf_.Alignment(writable_file_->GetRequiredBufferAlignment());
buf_.AllocateNewBuffer(std::min((size_t)65536, max_buffer_size_));
}
WritableFileWriter(const WritableFileWriter&) = delete;
WritableFileWriter& operator=(const WritableFileWriter&) = delete;
~WritableFileWriter() { Close(); }
Status Append(const Slice& data);
Status Flush();
Status Close();
Status Sync(bool use_fsync);
// Sync only the data that was already Flush()ed. Safe to call concurrently
// with Append() and Flush(). If !writable_file_->IsSyncThreadSafe(),
// returns NotSupported status.
Status SyncWithoutFlush(bool use_fsync);
uint64_t GetFileSize() { return filesize_; }
Status InvalidateCache(size_t offset, size_t length) {
return writable_file_->InvalidateCache(offset, length);
}
WritableFile* writable_file() const { return writable_file_.get(); }
bool use_direct_io() { return writable_file_->use_direct_io(); }
private:
// Used when os buffering is OFF and we are writing
// DMA such as in Direct I/O mode
#ifndef ROCKSDB_LITE
Status WriteDirect();
#endif // !ROCKSDB_LITE
// Normal write
Status WriteBuffered(const char* data, size_t size);
Status RangeSync(uint64_t offset, uint64_t nbytes);
size_t RequestToken(size_t bytes, bool align);
Status SyncInternal(bool use_fsync);
};
extern Status NewWritableFile(Env* env, const std::string& fname,
unique_ptr<WritableFile>* result,
const EnvOptions& options);
} // namespace rocksdb