chromium/third_party/glslang/src/glslang/Include/PoolAlloc.h

//
// Copyright (C) 2002-2005  3Dlabs Inc. Ltd.
// Copyright (C) 2012-2013 LunarG, Inc.
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#ifndef _POOLALLOC_INCLUDED_
#define _POOLALLOC_INCLUDED_

#ifndef NDEBUG
#define GUARD_BLOCKS …
#endif

//
// This header defines an allocator that can be used to efficiently
// allocate a large number of small requests for heap memory, with the
// intention that they are not individually deallocated, but rather
// collectively deallocated at one time.
//
// This simultaneously
//
// * Makes each individual allocation much more efficient; the
//     typical allocation is trivial.
// * Completely avoids the cost of doing individual deallocation.
// * Saves the trouble of tracking down and plugging a large class of leaks.
//
// Individual classes can use this allocator by supplying their own
// new and delete methods.
//
// STL containers can use this allocator by using the pool_allocator
// class as the allocator (second) template argument.
//

#include <cstddef>
#include <cstring>
#include <vector>

namespace glslang {

// If we are using guard blocks, we must track each individual
// allocation.  If we aren't using guard blocks, these
// never get instantiated, so won't have any impact.
//

class TAllocation { … };

//
// There are several stacks.  One is to track the pushing and popping
// of the user, and not yet implemented.  The others are simply a
// repositories of free pages or used pages.
//
// Page stacks are linked together with a simple header at the beginning
// of each allocation obtained from the underlying OS.  Multi-page allocations
// are returned to the OS.  Individual page allocations are kept for future
// re-use.
//
// The "page size" used is not, nor must it match, the underlying OS
// page size.  But, having it be about that size or equal to a set of
// pages is likely most optimal.
//
class TPoolAllocator { … };

//
// There could potentially be many pools with pops happening at
// different times.  But a simple use is to have a global pop
// with everyone using the same global allocator.
//
extern TPoolAllocator& GetThreadPoolAllocator();
void SetThreadPoolAllocator(TPoolAllocator* poolAllocator);

//
// This STL compatible allocator is intended to be used as the allocator
// parameter to templatized STL containers, like vector and map.
//
// It will use the pools for allocation, and not
// do any deallocation, but will still do destruction.
//
template<class T>
class pool_allocator { … };

} // end namespace glslang

#endif // _POOLALLOC_INCLUDED_