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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <list>
#include <memory>
#include <string>
#include "rocksdb/comparator.h"
#include "memory/arena.h"
#include "util/mutexlock.h"
namespace ROCKSDB_NAMESPACE {
//
// CacheWriteBuffer
//
// Buffer abstraction that can be manipulated via append
// (not thread safe)
class CacheWriteBuffer {
public:
explicit CacheWriteBuffer(const size_t size) : size_(size), pos_(0) {
buf_.reset(new char[size_]);
assert(!pos_);
assert(size_);
}
virtual ~CacheWriteBuffer() {}
void Append(const char* buf, const size_t size) {
assert(pos_ + size <= size_);
memcpy(buf_.get() + pos_, buf, size);
pos_ += size;
assert(pos_ <= size_);
}
void FillTrailingZeros() {
assert(pos_ <= size_);
memset(buf_.get() + pos_, '0', size_ - pos_);
pos_ = size_;
}
void Reset() { pos_ = 0; }
size_t Free() const { return size_ - pos_; }
size_t Capacity() const { return size_; }
size_t Used() const { return pos_; }
char* Data() const { return buf_.get(); }
private:
std::unique_ptr<char[]> buf_;
const size_t size_;
size_t pos_;
};
//
// CacheWriteBufferAllocator
//
// Buffer pool abstraction(not thread safe)
//
class CacheWriteBufferAllocator {
public:
explicit CacheWriteBufferAllocator(const size_t buffer_size,
const size_t buffer_count)
: cond_empty_(&lock_), buffer_size_(buffer_size) {
MutexLock _(&lock_);
buffer_size_ = buffer_size;
for (uint32_t i = 0; i < buffer_count; i++) {
auto* buf = new CacheWriteBuffer(buffer_size_);
assert(buf);
if (buf) {
bufs_.push_back(buf);
cond_empty_.Signal();
}
}
}
virtual ~CacheWriteBufferAllocator() {
MutexLock _(&lock_);
assert(bufs_.size() * buffer_size_ == Capacity());
for (auto* buf : bufs_) {
delete buf;
}
bufs_.clear();
}
CacheWriteBuffer* Allocate() {
MutexLock _(&lock_);
if (bufs_.empty()) {
return nullptr;
}
assert(!bufs_.empty());
CacheWriteBuffer* const buf = bufs_.front();
bufs_.pop_front();
return buf;
}
void Deallocate(CacheWriteBuffer* const buf) {
assert(buf);
MutexLock _(&lock_);
buf->Reset();
bufs_.push_back(buf);
cond_empty_.Signal();
}
void WaitUntilUsable() {
// We are asked to wait till we have buffers available
MutexLock _(&lock_);
while (bufs_.empty()) {
cond_empty_.Wait();
}
}
size_t Capacity() const { return bufs_.size() * buffer_size_; }
size_t Free() const { return bufs_.size() * buffer_size_; }
size_t BufferSize() const { return buffer_size_; }
private:
port::Mutex lock_; // Sync lock
port::CondVar cond_empty_; // Condition var for empty buffers
size_t buffer_size_; // Size of each buffer
std::list<CacheWriteBuffer*> bufs_; // Buffer stash
};
} // namespace ROCKSDB_NAMESPACE
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