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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "cc/base/contiguous_container.h"
#include <stddef.h>
#include <algorithm>
#include <utility>
namespace cc {
// Default number of max-sized elements to allocate space for, if there is no
// initial buffer.
static const unsigned kDefaultInitialBufferSize = 32;
class ContiguousContainerBase::Buffer {
public:
explicit Buffer(size_t buffer_size) : end_(nullptr), capacity_(buffer_size) {}
~Buffer() {}
size_t Capacity() const { return capacity_; }
size_t UsedCapacity() const { return end_ - begin(); }
size_t UnusedCapacity() const { return Capacity() - UsedCapacity(); }
size_t MemoryUsage() const { return begin() ? capacity_ : 0; }
bool empty() const { return UsedCapacity() == 0; }
void* Allocate(size_t object_size) {
DCHECK_GE(UnusedCapacity(), object_size);
if (!data_) {
data_.reset(new char[capacity_]);
end_ = begin();
}
void* result = end_;
end_ += object_size;
return result;
}
void DeallocateLastObject(void* object) {
DCHECK_LE(begin(), object);
DCHECK_LT(object, end_);
end_ = static_cast<char*>(object);
}
private:
char* begin() { return data_.get(); }
const char* begin() const { return data_.get(); }
// begin() <= end_ <= begin() + capacity_
std::unique_ptr<char[]> data_;
char* end_;
size_t capacity_;
};
ContiguousContainerBase::ContiguousContainerBase(size_t max_object_size)
: end_index_(0), max_object_size_(max_object_size) {}
ContiguousContainerBase::ContiguousContainerBase(size_t max_object_size,
size_t initial_size_bytes)
: ContiguousContainerBase(max_object_size) {
AllocateNewBufferForNextAllocation(
std::max(max_object_size, initial_size_bytes));
}
ContiguousContainerBase::~ContiguousContainerBase() {}
size_t ContiguousContainerBase::GetCapacityInBytes() const {
size_t capacity = 0;
for (const auto& buffer : buffers_)
capacity += buffer->Capacity();
return capacity;
}
size_t ContiguousContainerBase::UsedCapacityInBytes() const {
size_t used_capacity = 0;
for (const auto& buffer : buffers_)
used_capacity += buffer->UsedCapacity();
return used_capacity;
}
size_t ContiguousContainerBase::MemoryUsageInBytes() const {
size_t memory_usage = 0;
for (const auto& buffer : buffers_)
memory_usage += buffer->MemoryUsage();
return sizeof(*this) + memory_usage +
elements_.capacity() * sizeof(elements_[0]);
}
void* ContiguousContainerBase::Allocate(size_t object_size) {
DCHECK_LE(object_size, max_object_size_);
Buffer* buffer_for_alloc = nullptr;
if (!buffers_.empty()) {
Buffer* end_buffer = buffers_[end_index_].get();
if (end_buffer->UnusedCapacity() >= object_size)
buffer_for_alloc = end_buffer;
else if (end_index_ + 1 < buffers_.size())
buffer_for_alloc = buffers_[++end_index_].get();
}
if (!buffer_for_alloc) {
size_t new_buffer_size = buffers_.empty()
? kDefaultInitialBufferSize * max_object_size_
: 2 * buffers_.back()->Capacity();
buffer_for_alloc = AllocateNewBufferForNextAllocation(new_buffer_size);
}
void* element = buffer_for_alloc->Allocate(object_size);
elements_.push_back(element);
return element;
}
void ContiguousContainerBase::RemoveLast() {
void* object = elements_.back();
elements_.pop_back();
Buffer* end_buffer = buffers_[end_index_].get();
end_buffer->DeallocateLastObject(object);
if (end_buffer->empty()) {
if (end_index_ > 0)
end_index_--;
if (end_index_ + 2 < buffers_.size())
buffers_.pop_back();
}
}
void ContiguousContainerBase::Clear() {
elements_.clear();
buffers_.clear();
end_index_ = 0;
}
void ContiguousContainerBase::Swap(ContiguousContainerBase& other) {
elements_.swap(other.elements_);
buffers_.swap(other.buffers_);
std::swap(end_index_, other.end_index_);
std::swap(max_object_size_, other.max_object_size_);
}
ContiguousContainerBase::Buffer*
ContiguousContainerBase::AllocateNewBufferForNextAllocation(
size_t buffer_size) {
DCHECK(buffers_.empty() || end_index_ == buffers_.size() - 1);
std::unique_ptr<Buffer> new_buffer(new Buffer(buffer_size));
Buffer* buffer_to_return = new_buffer.get();
buffers_.push_back(std::move(new_buffer));
end_index_ = buffers_.size() - 1;
return buffer_to_return;
}
} // namespace cc
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