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// Copyright (c) 2011-present, 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 <atomic>
#include "rocksdb/memory_allocator.h"
namespace ROCKSDB_NAMESPACE {
// A memory allocator using new/delete
class DefaultMemoryAllocator : public MemoryAllocator {
public:
static const char* kClassName() { return "DefaultMemoryAllocator"; }
const char* Name() const override { return kClassName(); }
void* Allocate(size_t size) override {
return static_cast<void*>(new char[size]);
}
void Deallocate(void* p) override { delete[] static_cast<char*>(p); }
};
// Base class for a MemoryAllocator. This implementation does nothing
// and implements the methods in failuse mode (assert if the methods are
// invoked). Implementations can extend this class and override these methods
// when they are enabled via compiler switches (e.g., the
// JeMallocMemoryAllocator can define these methods if ROCKSDB_JEMALLOC is
// defined at compile time. If compiled in "disabled" mode, this class provides
// default/failure implementations. If compiled in "enabled" mode, the derived
// class needs to provide the appopriate "enabled" methods for the "real"
// implementation. Failure of the "real" implementation to implement ovreride
// any of these methods will result in an assert failure.
class BaseMemoryAllocator : public MemoryAllocator {
public:
void* Allocate(size_t /*size*/) override {
assert(false);
return nullptr;
}
void Deallocate(void* /*p*/) override { assert(false); }
};
// A Wrapped MemoryAllocator. Delegates the memory allcator functions to the
// wrapped one.
class MemoryAllocatorWrapper : public MemoryAllocator {
public:
// Initialize an MemoryAllocatorWrapper that delegates all calls to *t
explicit MemoryAllocatorWrapper(const std::shared_ptr<MemoryAllocator>& t);
~MemoryAllocatorWrapper() override {}
// Return the target to which to forward all calls
MemoryAllocator* target() const { return target_.get(); }
// Allocate a block of at least size. Has to be thread-safe.
void* Allocate(size_t size) override { return target_->Allocate(size); }
// Deallocate previously allocated block. Has to be thread-safe.
void Deallocate(void* p) override { return target_->Deallocate(p); }
// Returns the memory size of the block allocated at p. The default
// implementation that just returns the original allocation_size is fine.
size_t UsableSize(void* p, size_t allocation_size) const override {
return target_->UsableSize(p, allocation_size);
}
const Customizable* Inner() const override { return target_.get(); }
protected:
std::shared_ptr<MemoryAllocator> target_;
};
// A memory allocator that counts the number of allocations and deallocations
// This class is useful if the number of memory allocations/dellocations is
// important.
class CountedMemoryAllocator : public MemoryAllocatorWrapper {
public:
CountedMemoryAllocator()
: MemoryAllocatorWrapper(std::make_shared<DefaultMemoryAllocator>()),
allocations_(0),
deallocations_(0) {}
explicit CountedMemoryAllocator(const std::shared_ptr<MemoryAllocator>& t)
: MemoryAllocatorWrapper(t), allocations_(0), deallocations_(0) {}
static const char* kClassName() { return "CountedMemoryAllocator"; }
const char* Name() const override { return kClassName(); }
std::string GetId() const override { return std::string(Name()); }
void* Allocate(size_t size) override {
allocations_++;
return MemoryAllocatorWrapper::Allocate(size);
}
void Deallocate(void* p) override {
deallocations_++;
MemoryAllocatorWrapper::Deallocate(p);
}
uint64_t GetNumAllocations() const { return allocations_; }
uint64_t GetNumDeallocations() const { return deallocations_; }
private:
std::atomic<uint64_t> allocations_;
std::atomic<uint64_t> deallocations_;
};
} // namespace ROCKSDB_NAMESPACE
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