b2StackAllocator.cpp

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/*
* Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/

#include <Box2D/Common/b2StackAllocator.h>
#include <Box2D/Common/b2Math.h>

b2StackAllocator::b2StackAllocator()
{
        m_index = 0;
        m_allocation = 0;
        m_maxAllocation = 0;
        m_entryCount = 0;
}

b2StackAllocator::~b2StackAllocator()
{
        b2Assert(m_index == 0);
        b2Assert(m_entryCount == 0);
}

void* b2StackAllocator::Allocate(int32 size)
{
        b2Assert(m_entryCount < b2_maxStackEntries);

        b2StackEntry* entry = m_entries + m_entryCount;
        entry->size = size;
        if (m_index + size > b2_stackSize)
        {
                entry->data = (char*)b2Alloc(size);
                entry->usedMalloc = true;
        }
        else
        {
                entry->data = m_data + m_index;
                entry->usedMalloc = false;
                m_index += size;
        }

        m_allocation += size;
        m_maxAllocation = b2Max(m_maxAllocation, m_allocation);
        ++m_entryCount;

        return entry->data;
}

void b2StackAllocator::Free(void* p)
{
        b2Assert(m_entryCount > 0);
        b2StackEntry* entry = m_entries + m_entryCount - 1;
        b2Assert(p == entry->data);
        if (entry->usedMalloc)
        {
                b2Free(p);
        }
        else
        {
                m_index -= entry->size;
        }
        m_allocation -= entry->size;
        --m_entryCount;

        p = NULL;
}

int32 b2StackAllocator::GetMaxAllocation() const
{
        return m_maxAllocation;
}