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// 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.
#include "helpers/memenv/memenv.h"
#include "leveldb/env.h"
#include "leveldb/status.h"
#include "port/port.h"
#include "util/mutexlock.h"
#include <map>
#include <string.h>
#include <string>
#include <vector>
namespace leveldb {
namespace {
class FileState {
public:
// FileStates are reference counted. The initial reference count is zero
// and the caller must call Ref() at least once.
FileState() : refs_(0), size_(0) {}
// Increase the reference count.
void Ref() {
MutexLock lock(&refs_mutex_);
++refs_;
}
// Decrease the reference count. Delete if this is the last reference.
void Unref() {
bool do_delete = false;
{
MutexLock lock(&refs_mutex_);
--refs_;
assert(refs_ >= 0);
if (refs_ <= 0) {
do_delete = true;
}
}
if (do_delete) {
delete this;
}
}
uint64_t Size() const { return size_; }
Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const {
if (offset > size_) {
return Status::IOError("Offset greater than file size.");
}
const uint64_t available = size_ - offset;
if (n > available) {
n = static_cast<size_t>(available);
}
if (n == 0) {
*result = Slice();
return Status::OK();
}
assert(offset / kBlockSize <= SIZE_MAX);
size_t block = static_cast<size_t>(offset / kBlockSize);
size_t block_offset = offset % kBlockSize;
if (n <= kBlockSize - block_offset) {
// The requested bytes are all in the first block.
*result = Slice(blocks_[block] + block_offset, n);
return Status::OK();
}
size_t bytes_to_copy = n;
char* dst = scratch;
while (bytes_to_copy > 0) {
size_t avail = kBlockSize - block_offset;
if (avail > bytes_to_copy) {
avail = bytes_to_copy;
}
memcpy(dst, blocks_[block] + block_offset, avail);
bytes_to_copy -= avail;
dst += avail;
block++;
block_offset = 0;
}
*result = Slice(scratch, n);
return Status::OK();
}
Status Append(const Slice& data) {
const char* src = data.data();
size_t src_len = data.size();
while (src_len > 0) {
size_t avail;
size_t offset = size_ % kBlockSize;
if (offset != 0) {
// There is some room in the last block.
avail = kBlockSize - offset;
} else {
// No room in the last block; push new one.
blocks_.push_back(new char[kBlockSize]);
avail = kBlockSize;
}
if (avail > src_len) {
avail = src_len;
}
memcpy(blocks_.back() + offset, src, avail);
src_len -= avail;
src += avail;
size_ += avail;
}
return Status::OK();
}
private:
// Private since only Unref() should be used to delete it.
~FileState() {
for (std::vector<char*>::iterator i = blocks_.begin(); i != blocks_.end();
++i) {
delete [] *i;
}
}
// No copying allowed.
FileState(const FileState&);
void operator=(const FileState&);
port::Mutex refs_mutex_;
int refs_; // Protected by refs_mutex_;
// The following fields are not protected by any mutex. They are only mutable
// while the file is being written, and concurrent access is not allowed
// to writable files.
std::vector<char*> blocks_;
uint64_t size_;
enum { kBlockSize = 8 * 1024 };
};
class SequentialFileImpl : public SequentialFile {
public:
explicit SequentialFileImpl(FileState* file) : file_(file), pos_(0) {
file_->Ref();
}
~SequentialFileImpl() {
file_->Unref();
}
virtual Status Read(size_t n, Slice* result, char* scratch) {
Status s = file_->Read(pos_, n, result, scratch);
if (s.ok()) {
pos_ += result->size();
}
return s;
}
virtual Status Skip(uint64_t n) {
if (pos_ > file_->Size()) {
return Status::IOError("pos_ > file_->Size()");
}
const uint64_t available = file_->Size() - pos_;
if (n > available) {
n = available;
}
pos_ += n;
return Status::OK();
}
private:
FileState* file_;
uint64_t pos_;
};
class RandomAccessFileImpl : public RandomAccessFile {
public:
explicit RandomAccessFileImpl(FileState* file) : file_(file) {
file_->Ref();
}
~RandomAccessFileImpl() {
file_->Unref();
}
virtual Status Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const {
return file_->Read(offset, n, result, scratch);
}
private:
FileState* file_;
};
class WritableFileImpl : public WritableFile {
public:
WritableFileImpl(FileState* file) : file_(file) {
file_->Ref();
}
~WritableFileImpl() {
file_->Unref();
}
virtual Status Append(const Slice& data) {
return file_->Append(data);
}
virtual Status Close() { return Status::OK(); }
virtual Status Flush() { return Status::OK(); }
virtual Status Sync() { return Status::OK(); }
private:
FileState* file_;
};
class NoOpLogger : public Logger {
public:
virtual void Logv(const char* format, va_list ap) { }
};
class InMemoryEnv : public EnvWrapper {
public:
explicit InMemoryEnv(Env* base_env) : EnvWrapper(base_env) { }
virtual ~InMemoryEnv() {
for (FileSystem::iterator i = file_map_.begin(); i != file_map_.end(); ++i){
i->second->Unref();
}
}
// Partial implementation of the Env interface.
virtual Status NewSequentialFile(const std::string& fname,
SequentialFile** result) {
MutexLock lock(&mutex_);
if (file_map_.find(fname) == file_map_.end()) {
*result = NULL;
return Status::IOError(fname, "File not found");
}
*result = new SequentialFileImpl(file_map_[fname]);
return Status::OK();
}
virtual Status NewRandomAccessFile(const std::string& fname,
RandomAccessFile** result) {
MutexLock lock(&mutex_);
if (file_map_.find(fname) == file_map_.end()) {
*result = NULL;
return Status::IOError(fname, "File not found");
}
*result = new RandomAccessFileImpl(file_map_[fname]);
return Status::OK();
}
virtual Status NewWritableFile(const std::string& fname,
WritableFile** result) {
MutexLock lock(&mutex_);
if (file_map_.find(fname) != file_map_.end()) {
DeleteFileInternal(fname);
}
FileState* file = new FileState();
file->Ref();
file_map_[fname] = file;
*result = new WritableFileImpl(file);
return Status::OK();
}
virtual Status NewAppendableFile(const std::string& fname,
WritableFile** result) {
MutexLock lock(&mutex_);
FileState** sptr = &file_map_[fname];
FileState* file = *sptr;
if (file == NULL) {
file = new FileState();
file->Ref();
}
*result = new WritableFileImpl(file);
return Status::OK();
}
virtual bool FileExists(const std::string& fname) {
MutexLock lock(&mutex_);
return file_map_.find(fname) != file_map_.end();
}
virtual Status GetChildren(const std::string& dir,
std::vector<std::string>* result) {
MutexLock lock(&mutex_);
result->clear();
for (FileSystem::iterator i = file_map_.begin(); i != file_map_.end(); ++i){
const std::string& filename = i->first;
if (filename.size() >= dir.size() + 1 && filename[dir.size()] == '/' &&
Slice(filename).starts_with(Slice(dir))) {
result->push_back(filename.substr(dir.size() + 1));
}
}
return Status::OK();
}
void DeleteFileInternal(const std::string& fname) {
if (file_map_.find(fname) == file_map_.end()) {
return;
}
file_map_[fname]->Unref();
file_map_.erase(fname);
}
virtual Status DeleteFile(const std::string& fname) {
MutexLock lock(&mutex_);
if (file_map_.find(fname) == file_map_.end()) {
return Status::IOError(fname, "File not found");
}
DeleteFileInternal(fname);
return Status::OK();
}
virtual Status CreateDir(const std::string& dirname) {
return Status::OK();
}
virtual Status DeleteDir(const std::string& dirname) {
return Status::OK();
}
virtual Status GetFileSize(const std::string& fname, uint64_t* file_size) {
MutexLock lock(&mutex_);
if (file_map_.find(fname) == file_map_.end()) {
return Status::IOError(fname, "File not found");
}
*file_size = file_map_[fname]->Size();
return Status::OK();
}
virtual Status RenameFile(const std::string& src,
const std::string& target) {
MutexLock lock(&mutex_);
if (file_map_.find(src) == file_map_.end()) {
return Status::IOError(src, "File not found");
}
DeleteFileInternal(target);
file_map_[target] = file_map_[src];
file_map_.erase(src);
return Status::OK();
}
virtual Status LockFile(const std::string& fname, FileLock** lock) {
*lock = new FileLock;
return Status::OK();
}
virtual Status UnlockFile(FileLock* lock) {
delete lock;
return Status::OK();
}
virtual Status GetTestDirectory(std::string* path) {
*path = "/test";
return Status::OK();
}
virtual Status NewLogger(const std::string& fname, Logger** result) {
*result = new NoOpLogger;
return Status::OK();
}
private:
// Map from filenames to FileState objects, representing a simple file system.
typedef std::map<std::string, FileState*> FileSystem;
port::Mutex mutex_;
FileSystem file_map_; // Protected by mutex_.
};
} // namespace
Env* NewMemEnv(Env* base_env) {
return new InMemoryEnv(base_env);
}
} // namespace leveldb