b2_stack_allocator.cpp

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// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#include "box2d/b2_stack_allocator.h"
#include "box2d/b2_math.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 = nullptr;
}

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