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| author | Steve Block <steveblock@google.com> | 2011-05-06 11:45:16 +0100 |
|---|---|---|
| committer | Steve Block <steveblock@google.com> | 2011-05-12 13:44:10 +0100 |
| commit | cad810f21b803229eb11403f9209855525a25d57 (patch) | |
| tree | 29a6fd0279be608e0fe9ffe9841f722f0f4e4269 /JavaScriptCore/wtf/BumpPointerAllocator.h | |
| parent | 121b0cf4517156d0ac5111caf9830c51b69bae8f (diff) | |
| download | external_webkit-cad810f21b803229eb11403f9209855525a25d57.zip external_webkit-cad810f21b803229eb11403f9209855525a25d57.tar.gz external_webkit-cad810f21b803229eb11403f9209855525a25d57.tar.bz2 | |
Merge WebKit at r75315: Initial merge by git.
Change-Id: I570314b346ce101c935ed22a626b48c2af266b84
Diffstat (limited to 'JavaScriptCore/wtf/BumpPointerAllocator.h')
| -rw-r--r-- | JavaScriptCore/wtf/BumpPointerAllocator.h | 250 |
1 files changed, 0 insertions, 250 deletions
diff --git a/JavaScriptCore/wtf/BumpPointerAllocator.h b/JavaScriptCore/wtf/BumpPointerAllocator.h deleted file mode 100644 index 682283c..0000000 --- a/JavaScriptCore/wtf/BumpPointerAllocator.h +++ /dev/null @@ -1,250 +0,0 @@ -/* - * 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. - */ - -#ifndef BumpPointerAllocator_h -#define BumpPointerAllocator_h - -#include <wtf/PageAllocation.h> - -namespace WTF { - -#define MINIMUM_BUMP_POOL_SIZE 0x1000 - -class BumpPointerPool { -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(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(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 = MINIMUM_BUMP_POOL_SIZE; - 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(allocationEnd > current); // check for overflow - if (allocationEnd <= static_cast<void*>(pool)) - return pool; - } - } - - 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 { -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; - -#endif // BumpPointerAllocator_h |
