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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 = available;
- }
- if (n == 0) {
- *result = Slice();
- return Status::OK();
- }
-
- size_t block = 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 size_t available = file_->Size() - pos_;
- if (n > available) {
- n = available;
- }
- pos_ += n;
- return Status::OK();
- }
-
- private:
- FileState* file_;
- size_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 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 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();
- }
-
- 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
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