From 9907b61c574baf0747747f1c512f7cdd88ebed25 Mon Sep 17 00:00:00 2001 From: KunoiSayami Date: Tue, 9 Nov 2021 22:00:01 +0800 Subject: init --- helpers/memenv/memenv.cc | 390 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 390 insertions(+) create mode 100644 helpers/memenv/memenv.cc (limited to 'helpers/memenv/memenv.cc') diff --git a/helpers/memenv/memenv.cc b/helpers/memenv/memenv.cc new file mode 100644 index 0000000..e476613 --- /dev/null +++ b/helpers/memenv/memenv.cc @@ -0,0 +1,390 @@ +// 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 +#include +#include +#include +#include + +#include "leveldb/env.h" +#include "leveldb/status.h" +#include "port/port.h" +#include "port/thread_annotations.h" +#include "util/mutexlock.h" + +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) {} + + // No copying allowed. + FileState(const FileState&) = delete; + FileState& operator=(const FileState&) = delete; + + // 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 { + MutexLock lock(&blocks_mutex_); + return size_; + } + + void Truncate() { + MutexLock lock(&blocks_mutex_); + for (char*& block : blocks_) { + delete[] block; + } + blocks_.clear(); + size_ = 0; + } + + Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const { + MutexLock lock(&blocks_mutex_); + if (offset > size_) { + return Status::IOError("Offset greater than file size."); + } + const uint64_t available = size_ - offset; + if (n > available) { + n = static_cast(available); + } + if (n == 0) { + *result = Slice(); + return Status::OK(); + } + + assert(offset / kBlockSize <= std::numeric_limits::max()); + size_t block = static_cast(offset / kBlockSize); + size_t block_offset = offset % kBlockSize; + 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; + } + std::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(); + + MutexLock lock(&blocks_mutex_); + 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; + } + std::memcpy(blocks_.back() + offset, src, avail); + src_len -= avail; + src += avail; + size_ += avail; + } + + return Status::OK(); + } + + private: + enum { kBlockSize = 8 * 1024 }; + + // Private since only Unref() should be used to delete it. + ~FileState() { Truncate(); } + + port::Mutex refs_mutex_; + int refs_ GUARDED_BY(refs_mutex_); + + mutable port::Mutex blocks_mutex_; + std::vector blocks_ GUARDED_BY(blocks_mutex_); + uint64_t size_ GUARDED_BY(blocks_mutex_); +}; + +class SequentialFileImpl : public SequentialFile { + public: + explicit SequentialFileImpl(FileState* file) : file_(file), pos_(0) { + file_->Ref(); + } + + ~SequentialFileImpl() override { file_->Unref(); } + + Status Read(size_t n, Slice* result, char* scratch) override { + Status s = file_->Read(pos_, n, result, scratch); + if (s.ok()) { + pos_ += result->size(); + } + return s; + } + + Status Skip(uint64_t n) override { + 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() override { file_->Unref(); } + + Status Read(uint64_t offset, size_t n, Slice* result, + char* scratch) const override { + return file_->Read(offset, n, result, scratch); + } + + private: + FileState* file_; +}; + +class WritableFileImpl : public WritableFile { + public: + WritableFileImpl(FileState* file) : file_(file) { file_->Ref(); } + + ~WritableFileImpl() override { file_->Unref(); } + + Status Append(const Slice& data) override { return file_->Append(data); } + + Status Close() override { return Status::OK(); } + Status Flush() override { return Status::OK(); } + Status Sync() override { return Status::OK(); } + + private: + FileState* file_; +}; + +class NoOpLogger : public Logger { + public: + void Logv(const char* format, std::va_list ap) override {} +}; + +class InMemoryEnv : public EnvWrapper { + public: + explicit InMemoryEnv(Env* base_env) : EnvWrapper(base_env) {} + + ~InMemoryEnv() override { + for (const auto& kvp : file_map_) { + kvp.second->Unref(); + } + } + + // Partial implementation of the Env interface. + Status NewSequentialFile(const std::string& fname, + SequentialFile** result) override { + MutexLock lock(&mutex_); + if (file_map_.find(fname) == file_map_.end()) { + *result = nullptr; + return Status::IOError(fname, "File not found"); + } + + *result = new SequentialFileImpl(file_map_[fname]); + return Status::OK(); + } + + Status NewRandomAccessFile(const std::string& fname, + RandomAccessFile** result) override { + MutexLock lock(&mutex_); + if (file_map_.find(fname) == file_map_.end()) { + *result = nullptr; + return Status::IOError(fname, "File not found"); + } + + *result = new RandomAccessFileImpl(file_map_[fname]); + return Status::OK(); + } + + Status NewWritableFile(const std::string& fname, + WritableFile** result) override { + MutexLock lock(&mutex_); + FileSystem::iterator it = file_map_.find(fname); + + FileState* file; + if (it == file_map_.end()) { + // File is not currently open. + file = new FileState(); + file->Ref(); + file_map_[fname] = file; + } else { + file = it->second; + file->Truncate(); + } + + *result = new WritableFileImpl(file); + return Status::OK(); + } + + Status NewAppendableFile(const std::string& fname, + WritableFile** result) override { + MutexLock lock(&mutex_); + FileState** sptr = &file_map_[fname]; + FileState* file = *sptr; + if (file == nullptr) { + file = new FileState(); + file->Ref(); + } + *result = new WritableFileImpl(file); + return Status::OK(); + } + + bool FileExists(const std::string& fname) override { + MutexLock lock(&mutex_); + return file_map_.find(fname) != file_map_.end(); + } + + Status GetChildren(const std::string& dir, + std::vector* result) override { + MutexLock lock(&mutex_); + result->clear(); + + for (const auto& kvp : file_map_) { + const std::string& filename = kvp.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 RemoveFileInternal(const std::string& fname) + EXCLUSIVE_LOCKS_REQUIRED(mutex_) { + if (file_map_.find(fname) == file_map_.end()) { + return; + } + + file_map_[fname]->Unref(); + file_map_.erase(fname); + } + + Status RemoveFile(const std::string& fname) override { + MutexLock lock(&mutex_); + if (file_map_.find(fname) == file_map_.end()) { + return Status::IOError(fname, "File not found"); + } + + RemoveFileInternal(fname); + return Status::OK(); + } + + Status CreateDir(const std::string& dirname) override { return Status::OK(); } + + Status RemoveDir(const std::string& dirname) override { return Status::OK(); } + + Status GetFileSize(const std::string& fname, uint64_t* file_size) override { + 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(); + } + + Status RenameFile(const std::string& src, + const std::string& target) override { + MutexLock lock(&mutex_); + if (file_map_.find(src) == file_map_.end()) { + return Status::IOError(src, "File not found"); + } + + RemoveFileInternal(target); + file_map_[target] = file_map_[src]; + file_map_.erase(src); + return Status::OK(); + } + + Status LockFile(const std::string& fname, FileLock** lock) override { + *lock = new FileLock; + return Status::OK(); + } + + Status UnlockFile(FileLock* lock) override { + delete lock; + return Status::OK(); + } + + Status GetTestDirectory(std::string* path) override { + *path = "/test"; + return Status::OK(); + } + + Status NewLogger(const std::string& fname, Logger** result) override { + *result = new NoOpLogger; + return Status::OK(); + } + + private: + // Map from filenames to FileState objects, representing a simple file system. + typedef std::map FileSystem; + + port::Mutex mutex_; + FileSystem file_map_ GUARDED_BY(mutex_); +}; + +} // namespace + +Env* NewMemEnv(Env* base_env) { return new InMemoryEnv(base_env); } + +} // namespace leveldb -- cgit v1.3.1