Summary: This diff simplifies EnvOptions by treating it as POD, similar to Options. - virtual functions are removed and member fields are accessed directly. - StorageOptions is removed. - Options.allow_readahead and Options.allow_readahead_compactions are deprecated. - Unused global variables are removed: useOsBuffer, useFsReadAhead, useMmapRead, useMmapWrite Test Plan: make check; db_stress Reviewers: dhruba CC: leveldb Differential Revision: https://reviews.facebook.net/D11175
519 lines
18 KiB
C++
519 lines
18 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// An Env is an interface used by the leveldb implementation to access
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// operating system functionality like the filesystem etc. Callers
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// may wish to provide a custom Env object when opening a database to
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// get fine gain control; e.g., to rate limit file system operations.
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//
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// All Env implementations are safe for concurrent access from
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// multiple threads without any external synchronization.
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#ifndef STORAGE_LEVELDB_INCLUDE_ENV_H_
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#define STORAGE_LEVELDB_INCLUDE_ENV_H_
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#include <cstdarg>
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#include <string>
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#include <memory>
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#include <vector>
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#include <stdint.h>
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#include "leveldb/status.h"
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namespace leveldb {
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class FileLock;
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class Logger;
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class RandomAccessFile;
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class SequentialFile;
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class Slice;
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class WritableFile;
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class Options;
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using std::unique_ptr;
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using std::shared_ptr;
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// Options while opening a file to read/write
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struct EnvOptions {
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// construct with default Options
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EnvOptions();
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// construct from Options
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EnvOptions(const Options& options);
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// If true, then allow caching of data in environment buffers
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bool use_os_buffer;
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// If true, then use mmap to read data
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bool use_mmap_reads;
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// If true, then use mmap to write data
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bool use_mmap_writes;
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// If true, set the FD_CLOEXEC on open fd.
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bool set_fd_cloexec;
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};
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class Env {
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public:
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Env() { }
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virtual ~Env();
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// Return a default environment suitable for the current operating
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// system. Sophisticated users may wish to provide their own Env
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// implementation instead of relying on this default environment.
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//
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// The result of Default() belongs to leveldb and must never be deleted.
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static Env* Default();
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// Create a brand new sequentially-readable file with the specified name.
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// On success, stores a pointer to the new file in *result and returns OK.
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// On failure stores nullptr in *result and returns non-OK. If the file does
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// not exist, returns a non-OK status.
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//
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// The returned file will only be accessed by one thread at a time.
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virtual Status NewSequentialFile(const std::string& fname,
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unique_ptr<SequentialFile>* result,
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const EnvOptions& options)
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= 0;
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// Create a brand new random access read-only file with the
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// specified name. On success, stores a pointer to the new file in
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// *result and returns OK. On failure stores nullptr in *result and
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// returns non-OK. If the file does not exist, returns a non-OK
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// status.
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//
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// The returned file may be concurrently accessed by multiple threads.
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virtual Status NewRandomAccessFile(const std::string& fname,
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unique_ptr<RandomAccessFile>* result,
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const EnvOptions& options)
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= 0;
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// Create an object that writes to a new file with the specified
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// name. Deletes any existing file with the same name and creates a
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// new file. On success, stores a pointer to the new file in
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// *result and returns OK. On failure stores nullptr in *result and
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// returns non-OK.
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//
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// The returned file will only be accessed by one thread at a time.
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virtual Status NewWritableFile(const std::string& fname,
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unique_ptr<WritableFile>* result,
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const EnvOptions& options) = 0;
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// Returns true iff the named file exists.
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virtual bool FileExists(const std::string& fname) = 0;
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// Store in *result the names of the children of the specified directory.
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// The names are relative to "dir".
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// Original contents of *results are dropped.
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virtual Status GetChildren(const std::string& dir,
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std::vector<std::string>* result) = 0;
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// Delete the named file.
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virtual Status DeleteFile(const std::string& fname) = 0;
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// Create the specified directory. Returns error if directory exists.
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virtual Status CreateDir(const std::string& dirname) = 0;
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// Creates directory if missing. Return Ok if it exists, or successful in
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// Creating.
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virtual Status CreateDirIfMissing(const std::string& dirname) = 0;
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// Delete the specified directory.
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virtual Status DeleteDir(const std::string& dirname) = 0;
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// Store the size of fname in *file_size.
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virtual Status GetFileSize(const std::string& fname, uint64_t* file_size) = 0;
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// Store the last modification time of fname in *file_mtime.
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virtual Status GetFileModificationTime(const std::string& fname,
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uint64_t* file_mtime) = 0;
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// Rename file src to target.
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virtual Status RenameFile(const std::string& src,
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const std::string& target) = 0;
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// Lock the specified file. Used to prevent concurrent access to
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// the same db by multiple processes. On failure, stores nullptr in
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// *lock and returns non-OK.
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//
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// On success, stores a pointer to the object that represents the
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// acquired lock in *lock and returns OK. The caller should call
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// UnlockFile(*lock) to release the lock. If the process exits,
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// the lock will be automatically released.
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//
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// If somebody else already holds the lock, finishes immediately
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// with a failure. I.e., this call does not wait for existing locks
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// to go away.
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//
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// May create the named file if it does not already exist.
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virtual Status LockFile(const std::string& fname, FileLock** lock) = 0;
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// Release the lock acquired by a previous successful call to LockFile.
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// REQUIRES: lock was returned by a successful LockFile() call
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// REQUIRES: lock has not already been unlocked.
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virtual Status UnlockFile(FileLock* lock) = 0;
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// Arrange to run "(*function)(arg)" once in a background thread.
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//
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// "function" may run in an unspecified thread. Multiple functions
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// added to the same Env may run concurrently in different threads.
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// I.e., the caller may not assume that background work items are
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// serialized.
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virtual void Schedule(
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void (*function)(void* arg),
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void* arg) = 0;
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// Start a new thread, invoking "function(arg)" within the new thread.
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// When "function(arg)" returns, the thread will be destroyed.
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virtual void StartThread(void (*function)(void* arg), void* arg) = 0;
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// *path is set to a temporary directory that can be used for testing. It may
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// or many not have just been created. The directory may or may not differ
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// between runs of the same process, but subsequent calls will return the
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// same directory.
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virtual Status GetTestDirectory(std::string* path) = 0;
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// Create and return a log file for storing informational messages.
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virtual Status NewLogger(const std::string& fname,
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shared_ptr<Logger>* result) = 0;
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// Returns the number of micro-seconds since some fixed point in time. Only
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// useful for computing deltas of time.
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virtual uint64_t NowMicros() = 0;
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// Sleep/delay the thread for the perscribed number of micro-seconds.
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virtual void SleepForMicroseconds(int micros) = 0;
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// Get the current host name.
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virtual Status GetHostName(char* name, uint64_t len) = 0;
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// Get the number of seconds since the Epoch, 1970-01-01 00:00:00 (UTC).
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virtual Status GetCurrentTime(int64_t* unix_time) = 0;
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// Get full directory name for this db.
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virtual Status GetAbsolutePath(const std::string& db_path,
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std::string* output_path) = 0;
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// The number of background worker threads for this environment.
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// default: 1
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virtual void SetBackgroundThreads(int number) = 0;
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// Converts seconds-since-Jan-01-1970 to a printable string
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virtual std::string TimeToString(uint64_t time) = 0;
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private:
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// No copying allowed
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Env(const Env&);
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void operator=(const Env&);
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};
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// A file abstraction for reading sequentially through a file
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class SequentialFile {
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public:
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SequentialFile() { }
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virtual ~SequentialFile();
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// Read up to "n" bytes from the file. "scratch[0..n-1]" may be
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// written by this routine. Sets "*result" to the data that was
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// read (including if fewer than "n" bytes were successfully read).
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// May set "*result" to point at data in "scratch[0..n-1]", so
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// "scratch[0..n-1]" must be live when "*result" is used.
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// If an error was encountered, returns a non-OK status.
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//
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// REQUIRES: External synchronization
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virtual Status Read(size_t n, Slice* result, char* scratch) = 0;
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// Skip "n" bytes from the file. This is guaranteed to be no
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// slower that reading the same data, but may be faster.
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//
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// If end of file is reached, skipping will stop at the end of the
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// file, and Skip will return OK.
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//
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// REQUIRES: External synchronization
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virtual Status Skip(uint64_t n) = 0;
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};
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// A file abstraction for randomly reading the contents of a file.
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class RandomAccessFile {
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public:
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RandomAccessFile() { }
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virtual ~RandomAccessFile();
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// Read up to "n" bytes from the file starting at "offset".
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// "scratch[0..n-1]" may be written by this routine. Sets "*result"
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// to the data that was read (including if fewer than "n" bytes were
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// successfully read). May set "*result" to point at data in
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// "scratch[0..n-1]", so "scratch[0..n-1]" must be live when
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// "*result" is used. If an error was encountered, returns a non-OK
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// status.
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//
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// Safe for concurrent use by multiple threads.
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virtual Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const = 0;
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// Tries to get an unique ID for this file that will be the same each time
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// the file is opened (and will stay the same while the file is open).
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// Furthermore, it tries to make this ID at most "max_size" bytes. If such an
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// ID can be created this function returns the length of the ID and places it
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// in "id"; otherwise, this function returns 0, in which case "id"
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// may not have been modified.
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//
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// This function guarantees, for IDs from a given environment, two unique ids
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// cannot be made equal to eachother by adding arbitrary bytes to one of
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// them. That is, no unique ID is the prefix of another.
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//
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// This function guarantees that the returned ID will not be interpretable as
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// a single varint.
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//
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// Note: these IDs are only valid for the duration of the process.
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virtual size_t GetUniqueId(char* id, size_t max_size) const {
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return 0; // Default implementation to prevent issues with backwards
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// compatibility.
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};
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enum AccessPattern { NORMAL, RANDOM, SEQUENTIAL, WILLNEED, DONTNEED };
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virtual void Hint(AccessPattern pattern) {}
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};
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// A file abstraction for sequential writing. The implementation
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// must provide buffering since callers may append small fragments
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// at a time to the file.
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class WritableFile {
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public:
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WritableFile() : last_preallocated_block_(0), preallocation_block_size_ (0) {
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}
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virtual ~WritableFile();
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virtual Status Append(const Slice& data) = 0;
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virtual Status Close() = 0;
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virtual Status Flush() = 0;
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virtual Status Sync() = 0; // sync data
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/*
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* Sync data and/or metadata as well.
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* By default, sync only metadata.
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* Override this method for environments where we need to sync
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* metadata as well.
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*/
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virtual Status Fsync() {
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return Sync();
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}
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/*
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* Get the size of valid data in the file.
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*/
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virtual uint64_t GetFileSize() {
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return 0;
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}
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/*
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* Get and set the default pre-allocation block size for writes to
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* this file. If non-zero, then Allocate will be used to extend the
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* underlying storage of a file (generally via fallocate) if the Env
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* instance supports it.
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*/
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void SetPreallocationBlockSize(size_t size) {
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preallocation_block_size_ = size;
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}
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virtual void GetPreallocationStatus(size_t* block_size,
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size_t* last_allocated_block) {
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*last_allocated_block = last_preallocated_block_;
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*block_size = preallocation_block_size_;
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}
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protected:
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// PrepareWrite performs any necessary preparation for a write
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// before the write actually occurs. This allows for pre-allocation
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// of space on devices where it can result in less file
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// fragmentation and/or less waste from over-zealous filesystem
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// pre-allocation.
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void PrepareWrite(size_t offset, size_t len) {
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if (preallocation_block_size_ == 0) {
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return;
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}
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// If this write would cross one or more preallocation blocks,
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// determine what the last preallocation block necesessary to
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// cover this write would be and Allocate to that point.
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const auto block_size = preallocation_block_size_;
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size_t new_last_preallocated_block =
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(offset + len + block_size - 1) / block_size;
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if (new_last_preallocated_block > last_preallocated_block_) {
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size_t num_spanned_blocks =
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new_last_preallocated_block - last_preallocated_block_;
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Allocate(block_size * last_preallocated_block_,
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block_size * num_spanned_blocks);
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last_preallocated_block_ = new_last_preallocated_block;
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}
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}
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/*
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* Pre-allocate space for a file.
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*/
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virtual Status Allocate(off_t offset, off_t len) {
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return Status::OK();
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}
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private:
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size_t last_preallocated_block_;
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size_t preallocation_block_size_;
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// No copying allowed
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WritableFile(const WritableFile&);
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void operator=(const WritableFile&);
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};
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// An interface for writing log messages.
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class Logger {
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public:
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enum { DO_NOT_SUPPORT_GET_LOG_FILE_SIZE = -1 };
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Logger() { }
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virtual ~Logger();
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// Write an entry to the log file with the specified format.
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virtual void Logv(const char* format, va_list ap) = 0;
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virtual size_t GetLogFileSize() const {
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return DO_NOT_SUPPORT_GET_LOG_FILE_SIZE;
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}
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private:
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// No copying allowed
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Logger(const Logger&);
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void operator=(const Logger&);
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};
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// Identifies a locked file.
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class FileLock {
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public:
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FileLock() { }
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virtual ~FileLock();
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private:
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// No copying allowed
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FileLock(const FileLock&);
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void operator=(const FileLock&);
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};
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// Log the specified data to *info_log if info_log is non-nullptr.
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extern void Log(const shared_ptr<Logger>& info_log, const char* format, ...)
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# if defined(__GNUC__) || defined(__clang__)
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__attribute__((__format__ (__printf__, 2, 3)))
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# endif
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;
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extern void Log(Logger* info_log, const char* format, ...)
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# if defined(__GNUC__) || defined(__clang__)
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__attribute__((__format__ (__printf__, 2, 3)))
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# endif
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;
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// A utility routine: write "data" to the named file.
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extern Status WriteStringToFile(Env* env, const Slice& data,
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const std::string& fname);
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// A utility routine: read contents of named file into *data
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extern Status ReadFileToString(Env* env, const std::string& fname,
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std::string* data);
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// An implementation of Env that forwards all calls to another Env.
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// May be useful to clients who wish to override just part of the
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// functionality of another Env.
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class EnvWrapper : public Env {
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public:
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// Initialize an EnvWrapper that delegates all calls to *t
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explicit EnvWrapper(Env* t) : target_(t) { }
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virtual ~EnvWrapper();
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// Return the target to which this Env forwards all calls
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Env* target() const { return target_; }
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// The following text is boilerplate that forwards all methods to target()
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Status NewSequentialFile(const std::string& f,
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unique_ptr<SequentialFile>* r,
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const EnvOptions& options) {
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return target_->NewSequentialFile(f, r, options);
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}
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Status NewRandomAccessFile(const std::string& f,
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unique_ptr<RandomAccessFile>* r,
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const EnvOptions& options) {
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return target_->NewRandomAccessFile(f, r, options);
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}
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Status NewWritableFile(const std::string& f, unique_ptr<WritableFile>* r,
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const EnvOptions& options) {
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return target_->NewWritableFile(f, r, options);
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}
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bool FileExists(const std::string& f) { return target_->FileExists(f); }
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Status GetChildren(const std::string& dir, std::vector<std::string>* r) {
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return target_->GetChildren(dir, r);
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}
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Status DeleteFile(const std::string& f) { return target_->DeleteFile(f); }
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Status CreateDir(const std::string& d) { return target_->CreateDir(d); }
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Status CreateDirIfMissing(const std::string& d) {
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return target_->CreateDirIfMissing(d);
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}
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Status DeleteDir(const std::string& d) { return target_->DeleteDir(d); }
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Status GetFileSize(const std::string& f, uint64_t* s) {
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return target_->GetFileSize(f, s);
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}
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Status GetFileModificationTime(const std::string& fname,
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uint64_t* file_mtime) {
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return target_->GetFileModificationTime(fname, file_mtime);
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}
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Status RenameFile(const std::string& s, const std::string& t) {
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return target_->RenameFile(s, t);
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}
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Status LockFile(const std::string& f, FileLock** l) {
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return target_->LockFile(f, l);
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}
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Status UnlockFile(FileLock* l) { return target_->UnlockFile(l); }
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void Schedule(void (*f)(void*), void* a) {
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return target_->Schedule(f, a);
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}
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void StartThread(void (*f)(void*), void* a) {
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return target_->StartThread(f, a);
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}
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virtual Status GetTestDirectory(std::string* path) {
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return target_->GetTestDirectory(path);
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}
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virtual Status NewLogger(const std::string& fname,
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shared_ptr<Logger>* result) {
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return target_->NewLogger(fname, result);
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}
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uint64_t NowMicros() {
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return target_->NowMicros();
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}
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void SleepForMicroseconds(int micros) {
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target_->SleepForMicroseconds(micros);
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}
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Status GetHostName(char* name, uint64_t len) {
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return target_->GetHostName(name, len);
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}
|
|
Status GetCurrentTime(int64_t* unix_time) {
|
|
return target_->GetCurrentTime(unix_time);
|
|
}
|
|
Status GetAbsolutePath(const std::string& db_path,
|
|
std::string* output_path) {
|
|
return target_->GetAbsolutePath(db_path, output_path);
|
|
}
|
|
void SetBackgroundThreads(int num) {
|
|
return target_->SetBackgroundThreads(num);
|
|
}
|
|
std::string TimeToString(uint64_t time) {
|
|
return target_->TimeToString(time);
|
|
}
|
|
|
|
private:
|
|
Env* target_;
|
|
};
|
|
|
|
} // namespace leveldb
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|
|
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#endif // STORAGE_LEVELDB_INCLUDE_ENV_H_
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