1 files changed, 390 insertions, 0 deletions
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 <cstring>
+#include <limits>
+#include <map>
+#include <string>
+#include <vector>
+
+#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<size_t>(available);
+    }
+    if (n == 0) {
+      *result = Slice();
+      return Status::OK();
+    }
+
+    assert(offset / kBlockSize <= std::numeric_limits<size_t>::max());
+    size_t block = static_cast<size_t>(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<char*> 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<std::string>* 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<std::string, FileState*> FileSystem;
+
+  port::Mutex mutex_;
+  FileSystem file_map_ GUARDED_BY(mutex_);
+};
+
+}  // namespace
+
+Env* NewMemEnv(Env* base_env) { return new InMemoryEnv(base_env); }
+
+}  // namespace leveldb