Source/WTF/wtf/BumpPointerAllocator.h - WebKit - Git at Google

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #pragma once

 #include <algorithm>
 #include <wtf/PageAllocation.h>
 #include <wtf/PageBlock.h>

 namespace WTF {

 #define MINIMUM_BUMP_POOL_SIZE 0x1000

 class BumpPointerPool {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     // ensureCapacity will check whether the current pool has capacity to
     // allocate 'size' bytes of memory  If it does not, it will attempt to
     // allocate a new pool (which will be added to this one in a chain).
     //
     // If allocation fails (out of memory) this method will return null.
     // If the return value is non-null, then callers should update any
     // references they have to this current (possibly full) BumpPointerPool
     // to instead point to the newly returned BumpPointerPool.
     BumpPointerPool* ensureCapacity(size_t size)
     {
         void* allocationEnd = static_cast<char*>(m_current) + size;
         ASSERT_WITH_SECURITY_IMPLICATION(allocationEnd > m_current); // check for overflow
         if (allocationEnd <= static_cast<void*>(this))
             return this;
         return ensureCapacityCrossPool(this, size);
     }

     // alloc should only be called after calling ensureCapacity; as such
     // alloc will never fail.
     void* alloc(size_t size)
     {
         void* current = m_current;
         void* allocationEnd = static_cast<char*>(current) + size;
         ASSERT_WITH_SECURITY_IMPLICATION(allocationEnd > current); // check for overflow
         ASSERT(allocationEnd <= static_cast<void*>(this));
         m_current = allocationEnd;
         return current;
     }

     // The dealloc method releases memory allocated using alloc.  Memory
     // must be released in a LIFO fashion, e.g. if the client calls alloc
     // four times, returning pointer A, B, C, D, then the only valid order
     // in which these may be deallocaed is D, C, B, A.
     //
     // The client may optionally skip some deallocations.  In the example
     // above, it would be valid to only explicitly dealloc C, A (D being
     // dealloced along with C, B along with A).
     //
     // If pointer was not allocated from this pool (or pools) then dealloc
     // will CRASH().  Callers should update any references they have to
     // this current BumpPointerPool to instead point to the returned
     // BumpPointerPool.
     BumpPointerPool* dealloc(void* position)
     {
         if ((position >= m_start) && (position <= static_cast<void*>(this))) {
             ASSERT(position <= m_current);
             m_current = position;
             return this;
         }
         return deallocCrossPool(this, position);
     }

 private:
     // Placement operator new, returns the last 'size' bytes of allocation for use as this.
     void* operator new(size_t size, const PageAllocation& allocation)
     {
         ASSERT(size < allocation.size());
         return reinterpret_cast<char*>(reinterpret_cast<intptr_t>(allocation.base()) + allocation.size()) - size;
     }

     BumpPointerPool(const PageAllocation& allocation)
         : m_current(allocation.base())
         , m_start(allocation.base())
         , m_next(0)
         , m_previous(0)
         , m_allocation(allocation)
     {
     }

     static BumpPointerPool* create(size_t minimumCapacity = 0)
     {
         // Add size of BumpPointerPool object, check for overflow.
         minimumCapacity += sizeof(BumpPointerPool);
         if (minimumCapacity < sizeof(BumpPointerPool))
             return 0;

         size_t poolSize = std::max(static_cast<size_t>(MINIMUM_BUMP_POOL_SIZE), WTF::pageSize());
         while (poolSize < minimumCapacity) {
             poolSize <<= 1;
             // The following if check relies on MINIMUM_BUMP_POOL_SIZE being a power of 2!
             ASSERT(!(MINIMUM_BUMP_POOL_SIZE & (MINIMUM_BUMP_POOL_SIZE - 1)));
             if (!poolSize)
                 return 0;
         }

         PageAllocation allocation = PageAllocation::allocate(poolSize);
         if (!!allocation)
             return new (allocation) BumpPointerPool(allocation);
         return 0;
     }

     void shrink()
     {
         ASSERT(!m_previous);
         m_current = m_start;
         while (m_next) {
             BumpPointerPool* nextNext = m_next->m_next;
             m_next->destroy();
             m_next = nextNext;
         }
     }

     void destroy()
     {
         m_allocation.deallocate();
     }

     static BumpPointerPool* ensureCapacityCrossPool(BumpPointerPool* previousPool, size_t size)
     {
         // The pool passed should not have capacity, so we'll start with the next one.
         ASSERT(previousPool);
         ASSERT((static_cast<char*>(previousPool->m_current) + size) > previousPool->m_current); // check for overflow
         ASSERT((static_cast<char*>(previousPool->m_current) + size) > static_cast<void*>(previousPool));
         BumpPointerPool* pool = previousPool->m_next;

         while (true) {
             if (!pool) {
                 // We've run to the end; allocate a new pool.
                 pool = BumpPointerPool::create(size);
                 previousPool->m_next = pool;
                 pool->m_previous = previousPool;
                 return pool;
             }

             //
             void* current = pool->m_current;
             void* allocationEnd = static_cast<char*>(current) + size;
             ASSERT_WITH_SECURITY_IMPLICATION(allocationEnd > current); // check for overflow
             if (allocationEnd <= static_cast<void*>(pool))
                 return pool;

             previousPool = pool;
             pool = pool->m_next;
         }
     }

     static BumpPointerPool* deallocCrossPool(BumpPointerPool* pool, void* position)
     {
         // Should only be called if position is not in the current pool.
         ASSERT((position < pool->m_start) || (position > static_cast<void*>(pool)));

         while (true) {
             // Unwind the current pool to the start, move back in the chain to the previous pool.
             pool->m_current = pool->m_start;
             pool = pool->m_previous;

             // position was nowhere in the chain!
             if (!pool)
                 CRASH();

             if ((position >= pool->m_start) && (position <= static_cast<void*>(pool))) {
                 ASSERT(position <= pool->m_current);
                 pool->m_current = position;
                 return pool;
             }
         }
     }

     void* m_current;
     void* m_start;
     BumpPointerPool* m_next;
     BumpPointerPool* m_previous;
     PageAllocation m_allocation;

     friend class BumpPointerAllocator;
 };

 // A BumpPointerAllocator manages a set of BumpPointerPool objects, which
 // can be used for LIFO (stack like) allocation.
 //
 // To begin allocating using this class call startAllocator().  The result
 // of this method will be null if the initial pool allocation fails, or a
 // pointer to a BumpPointerPool object that can be used to perform
 // allocations.  Whilst running no memory will be released until
 // stopAllocator() is called.  At this point all allocations made through
 // this allocator will be reaped, and underlying memory may be freed.
 //
 // (In practice we will still hold on to the initial pool to allow allocation
 // to be quickly restared, but aditional pools will be freed).
 //
 // This allocator is non-renetrant, it is encumbant on the clients to ensure
 // startAllocator() is not called again until stopAllocator() has been called.
 class BumpPointerAllocator {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     BumpPointerAllocator()
         : m_head(0)
     {
     }

     ~BumpPointerAllocator()
     {
         if (m_head)
             m_head->destroy();
     }

     BumpPointerPool* startAllocator()
     {
         if (!m_head)
             m_head = BumpPointerPool::create();
         return m_head;
     }

     void stopAllocator()
     {
         if (m_head)
             m_head->shrink();
     }

 private:
     BumpPointerPool* m_head;
 };

 }

 using WTF::BumpPointerAllocator;
	/*
	* Copyright (C) 2010 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#pragma once

	#include <algorithm>
	#include <wtf/PageAllocation.h>
	#include <wtf/PageBlock.h>

	namespace WTF {

	#define MINIMUM_BUMP_POOL_SIZE 0x1000

	class BumpPointerPool {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	// ensureCapacity will check whether the current pool has capacity to
	// allocate 'size' bytes of memory If it does not, it will attempt to
	// allocate a new pool (which will be added to this one in a chain).
	//
	// If allocation fails (out of memory) this method will return null.
	// If the return value is non-null, then callers should update any
	// references they have to this current (possibly full) BumpPointerPool
	// to instead point to the newly returned BumpPointerPool.
	BumpPointerPool* ensureCapacity(size_t size)
	{
	void* allocationEnd = static_cast<char*>(m_current) + size;
	ASSERT_WITH_SECURITY_IMPLICATION(allocationEnd > m_current); // check for overflow
	if (allocationEnd <= static_cast<void*>(this))
	return this;
	return ensureCapacityCrossPool(this, size);
	}

	// alloc should only be called after calling ensureCapacity; as such
	// alloc will never fail.
	void* alloc(size_t size)
	{
	void* current = m_current;
	void* allocationEnd = static_cast<char*>(current) + size;
	ASSERT_WITH_SECURITY_IMPLICATION(allocationEnd > current); // check for overflow
	ASSERT(allocationEnd <= static_cast<void*>(this));
	m_current = allocationEnd;
	return current;
	}

	// The dealloc method releases memory allocated using alloc. Memory
	// must be released in a LIFO fashion, e.g. if the client calls alloc
	// four times, returning pointer A, B, C, D, then the only valid order
	// in which these may be deallocaed is D, C, B, A.
	//
	// The client may optionally skip some deallocations. In the example
	// above, it would be valid to only explicitly dealloc C, A (D being
	// dealloced along with C, B along with A).
	//
	// If pointer was not allocated from this pool (or pools) then dealloc
	// will CRASH(). Callers should update any references they have to
	// this current BumpPointerPool to instead point to the returned
	// BumpPointerPool.
	BumpPointerPool* dealloc(void* position)
	{
	if ((position >= m_start) && (position <= static_cast<void*>(this))) {
	ASSERT(position <= m_current);
	m_current = position;
	return this;
	}
	return deallocCrossPool(this, position);
	}

	private:
	// Placement operator new, returns the last 'size' bytes of allocation for use as this.
	void* operator new(size_t size, const PageAllocation& allocation)
	{
	ASSERT(size < allocation.size());
	return reinterpret_cast<char*>(reinterpret_cast<intptr_t>(allocation.base()) + allocation.size()) - size;
	}

	BumpPointerPool(const PageAllocation& allocation)
	: m_current(allocation.base())
	, m_start(allocation.base())
	, m_next(0)
	, m_previous(0)
	, m_allocation(allocation)
	{
	}

	static BumpPointerPool* create(size_t minimumCapacity = 0)
	{
	// Add size of BumpPointerPool object, check for overflow.
	minimumCapacity += sizeof(BumpPointerPool);
	if (minimumCapacity < sizeof(BumpPointerPool))
	return 0;

	size_t poolSize = std::max(static_cast<size_t>(MINIMUM_BUMP_POOL_SIZE), WTF::pageSize());
	while (poolSize < minimumCapacity) {
	poolSize <<= 1;
	// The following if check relies on MINIMUM_BUMP_POOL_SIZE being a power of 2!
	ASSERT(!(MINIMUM_BUMP_POOL_SIZE & (MINIMUM_BUMP_POOL_SIZE - 1)));
	if (!poolSize)
	return 0;
	}

	PageAllocation allocation = PageAllocation::allocate(poolSize);
	if (!!allocation)
	return new (allocation) BumpPointerPool(allocation);
	return 0;
	}

	void shrink()
	{
	ASSERT(!m_previous);
	m_current = m_start;
	while (m_next) {
	BumpPointerPool* nextNext = m_next->m_next;
	m_next->destroy();
	m_next = nextNext;
	}
	}

	void destroy()
	{
	m_allocation.deallocate();
	}

	static BumpPointerPool* ensureCapacityCrossPool(BumpPointerPool* previousPool, size_t size)
	{
	// The pool passed should not have capacity, so we'll start with the next one.
	ASSERT(previousPool);
	ASSERT((static_cast<char*>(previousPool->m_current) + size) > previousPool->m_current); // check for overflow
	ASSERT((static_cast<char>(previousPool->m_current) + size) > static_cast<void>(previousPool));
	BumpPointerPool* pool = previousPool->m_next;

	while (true) {
	if (!pool) {
	// We've run to the end; allocate a new pool.
	pool = BumpPointerPool::create(size);
	previousPool->m_next = pool;
	pool->m_previous = previousPool;
	return pool;
	}

	//
	void* current = pool->m_current;
	void* allocationEnd = static_cast<char*>(current) + size;
	ASSERT_WITH_SECURITY_IMPLICATION(allocationEnd > current); // check for overflow
	if (allocationEnd <= static_cast<void*>(pool))
	return pool;

	previousPool = pool;
	pool = pool->m_next;
	}
	}

	static BumpPointerPool* deallocCrossPool(BumpPointerPool* pool, void* position)
	{
	// Should only be called if position is not in the current pool.
	ASSERT((position < pool->m_start) \|\| (position > static_cast<void*>(pool)));

	while (true) {
	// Unwind the current pool to the start, move back in the chain to the previous pool.
	pool->m_current = pool->m_start;
	pool = pool->m_previous;

	// position was nowhere in the chain!
	if (!pool)
	CRASH();

	if ((position >= pool->m_start) && (position <= static_cast<void*>(pool))) {
	ASSERT(position <= pool->m_current);
	pool->m_current = position;
	return pool;
	}
	}
	}

	void* m_current;
	void* m_start;
	BumpPointerPool* m_next;
	BumpPointerPool* m_previous;
	PageAllocation m_allocation;

	friend class BumpPointerAllocator;
	};

	// A BumpPointerAllocator manages a set of BumpPointerPool objects, which
	// can be used for LIFO (stack like) allocation.
	//
	// To begin allocating using this class call startAllocator(). The result
	// of this method will be null if the initial pool allocation fails, or a
	// pointer to a BumpPointerPool object that can be used to perform
	// allocations. Whilst running no memory will be released until
	// stopAllocator() is called. At this point all allocations made through
	// this allocator will be reaped, and underlying memory may be freed.
	//
	// (In practice we will still hold on to the initial pool to allow allocation
	// to be quickly restared, but aditional pools will be freed).
	//
	// This allocator is non-renetrant, it is encumbant on the clients to ensure
	// startAllocator() is not called again until stopAllocator() has been called.
	class BumpPointerAllocator {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	BumpPointerAllocator()
	: m_head(0)
	{
	}

	~BumpPointerAllocator()
	{
	if (m_head)
	m_head->destroy();
	}

	BumpPointerPool* startAllocator()
	{
	if (!m_head)
	m_head = BumpPointerPool::create();
	return m_head;
	}

	void stopAllocator()
	{
	if (m_head)
	m_head->shrink();
	}

	private:
	BumpPointerPool* m_head;
	};

	}

	using WTF::BumpPointerAllocator;