25'ten fazla konu seçemezsiniz
Konular bir harf veya rakamla başlamalı, kısa çizgiler ('-') içerebilir ve en fazla 35 karakter uzunluğunda olabilir.
387 satır
14 KiB
387 satır
14 KiB
// 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 <stdarg.h>
|
|
#include <stdint.h>
|
|
|
|
#include <string>
|
|
#include <vector>
|
|
|
|
#include "leveldb/export.h"
|
|
#include "leveldb/status.h"
|
|
|
|
#if defined(_WIN32)
|
|
// The leveldb::Env class below contains a DeleteFile method.
|
|
// At the same time, <windows.h>, a fairly popular header
|
|
// file for Windows applications, defines a DeleteFile macro.
|
|
//
|
|
// Without any intervention on our part, the result of this
|
|
// unfortunate coincidence is that the name of the
|
|
// leveldb::Env::DeleteFile method seen by the compiler depends on
|
|
// whether <windows.h> was included before or after the LevelDB
|
|
// headers.
|
|
//
|
|
// To avoid headaches, we undefined DeleteFile (if defined) and
|
|
// redefine it at the bottom of this file. This way <windows.h>
|
|
// can be included before this file (or not at all) and the
|
|
// exported method will always be leveldb::Env::DeleteFile.
|
|
#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 {
|
|
public:
|
|
Env() = default;
|
|
|
|
Env(const Env&) = delete;
|
|
Env& operator=(const Env&) = delete;
|
|
|
|
virtual ~Env();
|
|
|
|
// Return a default environment suitable for the current operating
|
|
// system. Sophisticated users may wish to provide their own Env
|
|
// implementation instead of relying on this default environment.
|
|
//
|
|
// The result of Default() belongs to leveldb and must never be deleted.
|
|
static Env* Default();
|
|
|
|
// Create an object that sequentially reads the file with the specified name.
|
|
// On success, stores a pointer to the new file in *result and returns OK.
|
|
// On failure stores nullptr in *result and returns non-OK. If the file does
|
|
// not exist, returns a non-OK status. Implementations should return a
|
|
// NotFound status when the file does not exist.
|
|
//
|
|
// The returned file will only be accessed by one thread at a time.
|
|
virtual Status NewSequentialFile(const std::string& fname,
|
|
SequentialFile** result) = 0;
|
|
|
|
// Create an object supporting random-access reads from the file with the
|
|
// specified name. On success, stores a pointer to the new file in
|
|
// *result and returns OK. On failure stores nullptr in *result and
|
|
// returns non-OK. If the file does not exist, returns a non-OK
|
|
// status. Implementations should return a NotFound status when the file does
|
|
// not exist.
|
|
//
|
|
// The returned file may be concurrently accessed by multiple threads.
|
|
virtual Status NewRandomAccessFile(const std::string& fname,
|
|
RandomAccessFile** result) = 0;
|
|
|
|
// Create an object that writes to a new file with the specified
|
|
// name. Deletes any existing file with the same name and creates a
|
|
// new file. On success, stores a pointer to the new file in
|
|
// *result and returns OK. On failure stores nullptr in *result and
|
|
// returns non-OK.
|
|
//
|
|
// The returned file will only be accessed by one thread at a time.
|
|
virtual Status NewWritableFile(const std::string& fname,
|
|
WritableFile** result) = 0;
|
|
|
|
// Create an object that either appends to an existing file, or
|
|
// writes to a new file (if the file does not exist to begin with).
|
|
// On success, stores a pointer to the new file in *result and
|
|
// returns OK. On failure stores nullptr in *result and returns
|
|
// non-OK.
|
|
//
|
|
// The returned file will only be accessed by one thread at a time.
|
|
//
|
|
// May return an IsNotSupportedError error if this Env does
|
|
// not allow appending to an existing file. Users of Env (including
|
|
// the leveldb implementation) must be prepared to deal with
|
|
// an Env that does not support appending.
|
|
virtual Status NewAppendableFile(const std::string& fname,
|
|
WritableFile** result);
|
|
|
|
// Returns true iff the named file exists.
|
|
virtual bool FileExists(const std::string& fname) = 0;
|
|
|
|
// Store in *result the names of the children of the specified directory.
|
|
// The names are relative to "dir".
|
|
// Original contents of *results are dropped.
|
|
virtual Status GetChildren(const std::string& dir,
|
|
std::vector<std::string>* result) = 0;
|
|
|
|
// Delete the named file.
|
|
virtual Status DeleteFile(const std::string& fname) = 0;
|
|
|
|
// Create the specified directory.
|
|
virtual Status CreateDir(const std::string& dirname) = 0;
|
|
|
|
// Delete the specified directory.
|
|
virtual Status DeleteDir(const std::string& dirname) = 0;
|
|
|
|
// Store the size of fname in *file_size.
|
|
virtual Status GetFileSize(const std::string& fname, uint64_t* file_size) = 0;
|
|
|
|
// Rename file src to target.
|
|
virtual Status RenameFile(const std::string& src,
|
|
const std::string& target) = 0;
|
|
|
|
// Lock the specified file. Used to prevent concurrent access to
|
|
// the same db by multiple processes. On failure, stores nullptr in
|
|
// *lock and returns non-OK.
|
|
//
|
|
// On success, stores a pointer to the object that represents the
|
|
// acquired lock in *lock and returns OK. The caller should call
|
|
// UnlockFile(*lock) to release the lock. If the process exits,
|
|
// the lock will be automatically released.
|
|
//
|
|
// If somebody else already holds the lock, finishes immediately
|
|
// with a failure. I.e., this call does not wait for existing locks
|
|
// to go away.
|
|
//
|
|
// May create the named file if it does not already exist.
|
|
virtual Status LockFile(const std::string& fname, FileLock** lock) = 0;
|
|
|
|
// Release the lock acquired by a previous successful call to LockFile.
|
|
// REQUIRES: lock was returned by a successful LockFile() call
|
|
// REQUIRES: lock has not already been unlocked.
|
|
virtual Status UnlockFile(FileLock* lock) = 0;
|
|
|
|
// Arrange to run "(*function)(arg)" once in a background thread.
|
|
//
|
|
// "function" may run in an unspecified thread. Multiple functions
|
|
// added to the same Env may run concurrently in different threads.
|
|
// I.e., the caller may not assume that background work items are
|
|
// serialized.
|
|
virtual void Schedule(void (*function)(void* arg), void* arg) = 0;
|
|
|
|
// Start a new thread, invoking "function(arg)" within the new thread.
|
|
// When "function(arg)" returns, the thread will be destroyed.
|
|
virtual void StartThread(void (*function)(void* arg), void* arg) = 0;
|
|
|
|
// *path is set to a temporary directory that can be used for testing. It may
|
|
// or may not have just been created. The directory may or may not differ
|
|
// between runs of the same process, but subsequent calls will return the
|
|
// same directory.
|
|
virtual Status GetTestDirectory(std::string* path) = 0;
|
|
|
|
// Create and return a log file for storing informational messages.
|
|
virtual Status NewLogger(const std::string& fname, Logger** result) = 0;
|
|
|
|
// Returns the number of micro-seconds since some fixed point in time. Only
|
|
// useful for computing deltas of time.
|
|
virtual uint64_t NowMicros() = 0;
|
|
|
|
// Sleep/delay the thread for the prescribed number of micro-seconds.
|
|
virtual void SleepForMicroseconds(int micros) = 0;
|
|
};
|
|
|
|
// A file abstraction for reading sequentially through a file
|
|
class LEVELDB_EXPORT SequentialFile {
|
|
public:
|
|
SequentialFile() = default;
|
|
|
|
SequentialFile(const SequentialFile&) = delete;
|
|
SequentialFile& operator=(const SequentialFile&) = delete;
|
|
|
|
virtual ~SequentialFile();
|
|
|
|
// Read up to "n" bytes from the file. "scratch[0..n-1]" may be
|
|
// written by this routine. Sets "*result" to the data that was
|
|
// read (including if fewer than "n" bytes were successfully read).
|
|
// May set "*result" to point at data in "scratch[0..n-1]", so
|
|
// "scratch[0..n-1]" must be live when "*result" is used.
|
|
// If an error was encountered, returns a non-OK status.
|
|
//
|
|
// REQUIRES: External synchronization
|
|
virtual Status Read(size_t n, Slice* result, char* scratch) = 0;
|
|
|
|
// Skip "n" bytes from the file. This is guaranteed to be no
|
|
// slower that reading the same data, but may be faster.
|
|
//
|
|
// If end of file is reached, skipping will stop at the end of the
|
|
// file, and Skip will return OK.
|
|
//
|
|
// REQUIRES: External synchronization
|
|
virtual Status Skip(uint64_t n) = 0;
|
|
};
|
|
|
|
// A file abstraction for randomly reading the contents of a file.
|
|
class LEVELDB_EXPORT RandomAccessFile {
|
|
public:
|
|
RandomAccessFile() = default;
|
|
|
|
RandomAccessFile(const RandomAccessFile&) = delete;
|
|
RandomAccessFile& operator=(const RandomAccessFile&) = delete;
|
|
|
|
virtual ~RandomAccessFile();
|
|
|
|
// Read up to "n" bytes from the file starting at "offset".
|
|
// "scratch[0..n-1]" may be written by this routine. Sets "*result"
|
|
// to the data that was read (including if fewer than "n" bytes were
|
|
// successfully read). May set "*result" to point at data in
|
|
// "scratch[0..n-1]", so "scratch[0..n-1]" must be live when
|
|
// "*result" is used. If an error was encountered, returns a non-OK
|
|
// status.
|
|
//
|
|
// Safe for concurrent use by multiple threads.
|
|
virtual Status Read(uint64_t offset, size_t n, Slice* result,
|
|
char* scratch) const = 0;
|
|
};
|
|
|
|
// 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 {
|
|
public:
|
|
WritableFile() = default;
|
|
|
|
WritableFile(const WritableFile&) = delete;
|
|
WritableFile& operator=(const WritableFile&) = delete;
|
|
|
|
virtual ~WritableFile();
|
|
|
|
virtual Status Append(const Slice& data) = 0;
|
|
virtual Status Close() = 0;
|
|
virtual Status Flush() = 0;
|
|
virtual Status Sync() = 0;
|
|
};
|
|
|
|
// An interface for writing log messages.
|
|
class LEVELDB_EXPORT Logger {
|
|
public:
|
|
Logger() = default;
|
|
|
|
Logger(const Logger&) = delete;
|
|
Logger& operator=(const Logger&) = delete;
|
|
|
|
virtual ~Logger();
|
|
|
|
// Write an entry to the log file with the specified format.
|
|
virtual void Logv(const char* format, va_list ap) = 0;
|
|
};
|
|
|
|
// Identifies a locked file.
|
|
class LEVELDB_EXPORT FileLock {
|
|
public:
|
|
FileLock() = default;
|
|
|
|
FileLock(const FileLock&) = delete;
|
|
FileLock& operator=(const FileLock&) = delete;
|
|
|
|
virtual ~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 {
|
|
public:
|
|
// Initialize an EnvWrapper that delegates all calls to *t.
|
|
explicit EnvWrapper(Env* t) : target_(t) {}
|
|
virtual ~EnvWrapper();
|
|
|
|
// Return the target to which this Env forwards all calls.
|
|
Env* target() const { return target_; }
|
|
|
|
// The following text is boilerplate that forwards all methods to target().
|
|
Status NewSequentialFile(const std::string& f, SequentialFile** r) override {
|
|
return target_->NewSequentialFile(f, r);
|
|
}
|
|
Status NewRandomAccessFile(const std::string& f,
|
|
RandomAccessFile** r) override {
|
|
return target_->NewRandomAccessFile(f, r);
|
|
}
|
|
Status NewWritableFile(const std::string& f, WritableFile** r) override {
|
|
return target_->NewWritableFile(f, r);
|
|
}
|
|
Status NewAppendableFile(const std::string& f, WritableFile** r) override {
|
|
return target_->NewAppendableFile(f, r);
|
|
}
|
|
bool FileExists(const std::string& f) override {
|
|
return target_->FileExists(f);
|
|
}
|
|
Status GetChildren(const std::string& dir,
|
|
std::vector<std::string>* r) override {
|
|
return target_->GetChildren(dir, r);
|
|
}
|
|
Status DeleteFile(const std::string& f) override {
|
|
return target_->DeleteFile(f);
|
|
}
|
|
Status CreateDir(const std::string& d) override {
|
|
return target_->CreateDir(d);
|
|
}
|
|
Status DeleteDir(const std::string& d) override {
|
|
return target_->DeleteDir(d);
|
|
}
|
|
Status GetFileSize(const std::string& f, uint64_t* s) override {
|
|
return target_->GetFileSize(f, s);
|
|
}
|
|
Status RenameFile(const std::string& s, const std::string& t) override {
|
|
return target_->RenameFile(s, t);
|
|
}
|
|
Status LockFile(const std::string& f, FileLock** l) override {
|
|
return target_->LockFile(f, l);
|
|
}
|
|
Status UnlockFile(FileLock* l) override { return target_->UnlockFile(l); }
|
|
void Schedule(void (*f)(void*), void* a) override {
|
|
return target_->Schedule(f, a);
|
|
}
|
|
void StartThread(void (*f)(void*), void* a) override {
|
|
return target_->StartThread(f, a);
|
|
}
|
|
Status GetTestDirectory(std::string* path) override {
|
|
return target_->GetTestDirectory(path);
|
|
}
|
|
Status NewLogger(const std::string& fname, Logger** result) override {
|
|
return target_->NewLogger(fname, result);
|
|
}
|
|
uint64_t NowMicros() override { return target_->NowMicros(); }
|
|
void SleepForMicroseconds(int micros) override {
|
|
target_->SleepForMicroseconds(micros);
|
|
}
|
|
|
|
private:
|
|
Env* target_;
|
|
};
|
|
|
|
} // namespace leveldb
|
|
|
|
// Redefine DeleteFile if necessary.
|
|
#if defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)
|
|
#if defined(UNICODE)
|
|
#define DeleteFile DeleteFileW
|
|
#else
|
|
#define DeleteFile DeleteFileA
|
|
#endif // defined(UNICODE)
|
|
#endif // defined(_WIN32) && defined(LEVELDB_DELETEFILE_UNDEFINED)
|
|
|
|
#endif // STORAGE_LEVELDB_INCLUDE_ENV_H_
|