env.h | Explore in Territory

// 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.
//
// An Env is an interface used by the leveldb implementation to access
// operating system functionality like the filesystem etc.  Callers
// may wish to provide a custom Env object when opening a database to
// get fine gain control; e.g., to rate limit file system operations.
//
// All Env implementations are safe for concurrent access from
// multiple threads without any external synchronization.

#ifndef STORAGE_LEVELDB_INCLUDE_ENV_H_
#define STORAGE_LEVELDB_INCLUDE_ENV_H_

#include <cstdarg>
#include <cstdint>
#include <string>
#include <vector>

#include "leveldb/export.h"
#include "leveldb/status.h"

// This workaround can be removed when leveldb::Env::DeleteFile is removed.
#if defined(_WIN32)
// On Windows, the method name DeleteFile (below) introduces the risk of
// triggering undefined behavior by exposing the compiler to different
// declarations of the Env class in different translation units.
//
// This is because <windows.h>, a fairly popular header file for Windows
// applications, defines a DeleteFile macro. So, files that include the Windows
// header before this header will contain an altered Env declaration.
//
// This workaround ensures that the compiler sees the same Env declaration,
// independently of whether <windows.h> was included.
#if defined(DeleteFile)
#undef DeleteFile
#define LEVELDB_DELETEFILE_UNDEFINED
#endif  // defined(DeleteFile)
#endif  // defined(_WIN32)

namespace leveldb {

class FileLock;
class Logger;
class RandomAccessFile;
class SequentialFile;
class Slice;
class WritableFile;

class LEVELDB_EXPORT Env { … };

// A file abstraction for reading sequentially through a file
class LEVELDB_EXPORT SequentialFile { … };

// A file abstraction for randomly reading the contents of a file.
class LEVELDB_EXPORT RandomAccessFile { … };

// A file abstraction for sequential writing.  The implementation
// must provide buffering since callers may append small fragments
// at a time to the file.
class LEVELDB_EXPORT WritableFile { … };

// An interface for writing log messages.
class LEVELDB_EXPORT Logger { … };

// Identifies a locked file.
class LEVELDB_EXPORT FileLock { … };

// Log the specified data to *info_log if info_log is non-null.
void Log(Logger* info_log, const char* format, ...)
#if defined(__GNUC__) || defined(__clang__)
    __attribute__((__format__(__printf__, 2, 3)))
#endif
    ;

// A utility routine: write "data" to the named file.
LEVELDB_EXPORT Status WriteStringToFile(Env* env, const Slice& data,
                                        const std::string& fname);

// A utility routine: read contents of named file into *data
LEVELDB_EXPORT Status ReadFileToString(Env* env, const std::string& fname,
                                       std::string* data);

// An implementation of Env that forwards all calls to another Env.
// May be useful to clients who wish to override just part of the
// functionality of another Env.
class LEVELDB_EXPORT EnvWrapper : public Env { … };

}  // namespace leveldb

// This workaround can be removed when leveldb::Env::DeleteFile is removed.
// Redefine DeleteFile if it was undefined earlier.
#if defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)
#if defined(UNICODE)
#define DeleteFile …
#else
#define DeleteFile …
#endif  // defined(UNICODE)
#endif  // defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)

#endif  // STORAGE_LEVELDB_INCLUDE_ENV_H_
chromium/third_party/leveldatabase/src/include/leveldb/env.h
