mirror of
https://gitea.wildfiregames.com/0ad/0ad
synced 2026-06-16 13:23:56 -07:00
2ef4e7353e
- headerless: distinguish between allocation granularity and min size (hopefully fixes test failure on x64) - test_wdbg_sym: disable printf spew - hpet: use workaround when x64 MOVD isn't available due to processor or compiler - JSConversions: VC2005 x64 apparently distinguishes ssize_t from long int (as it does with size_t) This was SVN commit r7179.
94 lines
3.1 KiB
C++
94 lines
3.1 KiB
C++
/* Copyright (C) 2009 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* (header-less) pool-based heap allocator
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*/
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#ifndef INCLUDED_HEADERLESS
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#define INCLUDED_HEADERLESS
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/**
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* (header-less) pool-based heap allocator
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* provides Allocate and Deallocate without requiring in-band headers;
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* this is useful when allocating page-aligned I/O buffers
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* (headers would waste an entire page per buffer)
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*
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* policy:
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* - allocation: first exhaust the freelist, then allocate more
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* - freelist: address-ordered good fit, always split blocks
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* - coalescing: immediate
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* mechanism:
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* - coalescing: boundary tags in freed memory with distinct bit patterns
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* - freelist: segregated range lists of power-of-two size classes
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*
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* note: this module basically implements a (rather complex) freelist and
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* could be made independent of the Pool allocation scheme. however, reading
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* neighboring boundary tags may cause segmentation violations; knowing the
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* bounds of valid committed memory (i.e. Pool extents) avoids this.
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**/
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class HeaderlessAllocator
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{
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public:
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// allocators must 'naturally' align pointers, i.e. ensure they are
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// multiples of the largest native type (currently __m128).
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// since there are no headers, we can guarantee alignment by
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// requiring sizes to be multiples of allocationGranularity.
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static const size_t allocationGranularity = 16;
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// allocations must be large enough to hold our boundary tags
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// when freed. (see rationale above BoundaryTagManager)
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static const size_t minAllocationSize = 128;
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/**
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* @param poolSize maximum amount of memory that can be allocated.
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* this much virtual address space is reserved up-front (see Pool).
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**/
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HeaderlessAllocator(size_t poolSize);
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/**
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* restore the original state (as if newly constructed).
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* this includes reclaiming all extant allocations.
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**/
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void Reset();
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/**
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* @param size [bytes] (= minAllocationSize + i*allocationGranularity).
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* (this allocator is designed for requests on the order of several KiB)
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* @return allocated memory or 0 if the pool is too fragmented or full.
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**/
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void* Allocate(size_t size) throw();
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/**
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* deallocate memory.
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* @param p must be exactly as returned by Allocate (in particular,
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* evenly divisible by allocationGranularity)
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* @param size must be exactly as specified to Allocate.
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**/
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void Deallocate(void* p, size_t size);
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/**
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* perform sanity checks; ensure allocator state is consistent.
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**/
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void Validate() const;
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private:
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class Impl;
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shared_ptr<Impl> impl;
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};
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#endif // #ifndef INCLUDED_HEADERLESS
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