b2_stack_allocator.h

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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.

#ifndef B2_STACK_ALLOCATOR_H
#define B2_STACK_ALLOCATOR_H

#include "b2_api.h"
#include "b2_settings.h"

const int32 b2_stackSize = 100 * 1024;  // 100k
const int32 b2_maxStackEntries = 32;

struct B2_API b2StackEntry
{
        char* data;
        int32 size;
        bool usedMalloc;
};

// This is a stack allocator used for fast per step allocations.
// You must nest allocate/free pairs. The code will assert
// if you try to interleave multiple allocate/free pairs.
class B2_API b2StackAllocator
{
public:
        b2StackAllocator();
        ~b2StackAllocator();

        void* Allocate(int32 size);
        void Free(void* p);

        int32 GetMaxAllocation() const;

private:

        char m_data[b2_stackSize];
        int32 m_index;

        int32 m_allocation;
        int32 m_maxAllocation;

        b2StackEntry m_entries[b2_maxStackEntries];
        int32 m_entryCount;
};

#endif