src/common/MemoryBuffer.cpp

//
// Copyright (c) 2014 The ANGLE Project 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 "common/MemoryBuffer.h"

#include <algorithm>
#include <cstdlib>

#include "common/debug.h"

namespace angle
{

// MemoryBuffer implementation.
MemoryBuffer::MemoryBuffer() : mSize(0), mData(nullptr)
{
}

MemoryBuffer::~MemoryBuffer()
{
    free(mData);
    mData = nullptr;
}

bool MemoryBuffer::resize(size_t size)
{
    if (size == 0)
    {
        free(mData);
        mData = nullptr;
        mSize = 0;
        return true;
    }

    if (size == mSize)
    {
        return true;
    }

    // Only reallocate if the size has changed.
    uint8_t *newMemory = reinterpret_cast<uint8_t*>(malloc(sizeof(uint8_t) * size));
    if (newMemory == nullptr)
    {
        return false;
    }

    if (mData)
    {
        // Copy the intersection of the old data and the new data
        std::copy(mData, mData + std::min(mSize, size), newMemory);
        free(mData);
    }

    mData = newMemory;
    mSize = size;

    return true;
}

size_t MemoryBuffer::size() const
{
    return mSize;
}

const uint8_t *MemoryBuffer::data() const
{
    return mData;
}

uint8_t *MemoryBuffer::data()
{
    ASSERT(mData);
    return mData;
}

// ScratchBuffer implementation.

ScratchBuffer::ScratchBuffer(uint32_t lifetime) : mLifetime(lifetime), mResetCounter(lifetime)
{
}

ScratchBuffer::~ScratchBuffer()
{
}

bool ScratchBuffer::get(size_t requestedSize, MemoryBuffer **memoryBufferOut)
{
    if (mScratchMemory.size() == requestedSize)
    {
        mResetCounter    = mLifetime;
        *memoryBufferOut = &mScratchMemory;
        return true;
    }

    if (mScratchMemory.size() > requestedSize)
    {
        tick();
    }

    if (mResetCounter == 0 || mScratchMemory.size() < requestedSize)
    {
        mScratchMemory.resize(0);
        if (!mScratchMemory.resize(requestedSize))
        {
            return false;
        }
        mResetCounter = mLifetime;
    }

    ASSERT(mScratchMemory.size() >= requestedSize);

    *memoryBufferOut = &mScratchMemory;
    return true;
}

void ScratchBuffer::tick()
{
    if (mResetCounter > 0)
    {
        --mResetCounter;
    }
}

void ScratchBuffer::clear()
{
    mResetCounter = mLifetime;
    mScratchMemory.resize(0);
}

}  // namespace angle