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418 lines
11 KiB
C++
418 lines
11 KiB
C++
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/*
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** memarena.cpp
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** Implements memory arenas.
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**
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**---------------------------------------------------------------------------
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** Copyright 2010 Randy Heit
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** All rights reserved.
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**
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** Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions
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** are met:
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**
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** 1. Redistributions of source code must retain the above copyright
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** notice, this list of conditions and the following disclaimer.
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** 2. Redistributions in binary form must reproduce the above copyright
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** notice, this list of conditions and the following disclaimer in the
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** documentation and/or other materials provided with the distribution.
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** 3. The name of the author may not be used to endorse or promote products
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** derived from this software without specific prior written permission.
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**
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** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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**---------------------------------------------------------------------------
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**
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** A memory arena is used for efficient allocation of many small objects that
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** will all be freed at once. Note that since individual destructors are not
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** called, you must not use an arena to allocate any objects that use a
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** destructor, either explicitly or implicitly (because they have members
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** with destructors).
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*/
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#include "basics.h"
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#include "memarena.h"
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#include "printf.h"
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struct FMemArena::Block
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{
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Block *NextBlock;
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void *Limit; // End of this block
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void *Avail; // Start of free space in this block
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void *alignme; // align to 16 bytes.
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void Reset();
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void *Alloc(size_t size);
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};
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//==========================================================================
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//
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// RoundPointer
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//
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// Rounds a pointer up to a pointer-sized boundary.
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//
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//==========================================================================
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static inline void *RoundPointer(void *ptr)
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{
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return (void *)(((size_t)ptr + sizeof(void*) - 1) & ~(sizeof(void*) - 1));
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}
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//==========================================================================
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//
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// FMemArena Constructor
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//
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//==========================================================================
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FMemArena::FMemArena(size_t blocksize)
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{
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TopBlock = NULL;
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FreeBlocks = NULL;
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BlockSize = blocksize;
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}
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//==========================================================================
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//
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// FMemArena Destructor
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//
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//==========================================================================
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FMemArena::~FMemArena()
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{
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FreeAllBlocks();
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}
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//==========================================================================
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//
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// FMemArena :: Alloc
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//
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//==========================================================================
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void *FMemArena::iAlloc(size_t size)
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{
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Block *block;
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for (block = TopBlock; block != NULL; block = block->NextBlock)
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{
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void *res = block->Alloc(size);
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if (res != NULL)
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{
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return res;
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}
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}
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block = AddBlock(size);
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return block->Alloc(size);
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}
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void *FMemArena::Alloc(size_t size)
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{
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return iAlloc((size + 15) & ~15);
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}
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//==========================================================================
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//
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// FMemArena :: FreeAll
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//
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// Moves all blocks to the free list. No system-level deallocation occurs.
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//
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//==========================================================================
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void FMemArena::FreeAll()
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{
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for (Block *next, *block = TopBlock; block != NULL; block = next)
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{
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next = block->NextBlock;
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block->Reset();
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block->NextBlock = FreeBlocks;
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FreeBlocks = block;
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}
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TopBlock = NULL;
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}
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//==========================================================================
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//
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// FMemArena :: FreeAllBlocks
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//
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// Frees all blocks used by this arena.
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//
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//==========================================================================
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void FMemArena::FreeAllBlocks()
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{
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FreeBlockChain(TopBlock);
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FreeBlockChain(FreeBlocks);
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}
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//==========================================================================
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//
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// FMemArena :: DumpInfo
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//
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// Prints some info about this arena
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//
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//==========================================================================
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void FMemArena::DumpInfo()
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{
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size_t allocated = 0;
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size_t used = 0;
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for (auto block = TopBlock; block != NULL; block = block->NextBlock)
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{
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allocated += BlockSize;
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used += BlockSize - ((char*)block->Limit - (char*)block->Avail);
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}
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Printf("%zu bytes allocated, %zu bytes in use\n", allocated, used);
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}
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//==========================================================================
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//
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// FMemArena :: DumpInfo
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//
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// Dumps the arena to a file (for debugging)
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//
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//==========================================================================
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void FMemArena::DumpData(FILE *f)
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{
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for (auto block = TopBlock; block != NULL; block = block->NextBlock)
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{
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auto used = BlockSize - ((char*)block->Limit - (char*)block->Avail);
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fwrite(block, 1, used, f);
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}
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}
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//==========================================================================
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//
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// FMemArena :: FreeBlockChain
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//
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// Frees a chain of blocks.
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//
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//==========================================================================
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void FMemArena::FreeBlockChain(Block *&top)
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{
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for (Block *next, *block = top; block != NULL; block = next)
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{
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next = block->NextBlock;
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free(block);
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}
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top = NULL;
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}
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//==========================================================================
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//
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// FMemArena :: AddBlock
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//
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// Allocates a block large enough to hold at least <size> bytes and adds it
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// to the TopBlock chain.
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//
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//==========================================================================
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FMemArena::Block *FMemArena::AddBlock(size_t size)
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{
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Block *mem, **last;
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size += sizeof(Block); // Account for header size
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// Search for a free block to use
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for (last = &FreeBlocks, mem = FreeBlocks; mem != NULL; last = &mem->NextBlock, mem = mem->NextBlock)
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{
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if ((uint8_t *)mem->Limit - (uint8_t *)mem >= (ptrdiff_t)size)
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{
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*last = mem->NextBlock;
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break;
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}
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}
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if (mem == NULL)
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{
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// Allocate a new block
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if (size < BlockSize)
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{
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size = BlockSize;
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}
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else
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{ // Stick some free space at the end so we can use this block for
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// other things.
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size += BlockSize/2;
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}
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mem = (Block *)malloc(size);
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mem->Limit = (uint8_t *)mem + size;
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}
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mem->Reset();
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mem->NextBlock = TopBlock;
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TopBlock = mem;
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return mem;
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}
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//==========================================================================
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//
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// FMemArena :: Block :: Reset
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//
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// Resets this block's Avail pointer.
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//
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//==========================================================================
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void FMemArena::Block::Reset()
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{
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Avail = RoundPointer(reinterpret_cast<char*>(this) + sizeof(*this));
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}
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//==========================================================================
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//
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// FMemArena :: Block :: Alloc
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//
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// Allocates memory from the block if it has space. Returns NULL if not.
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//
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//==========================================================================
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void *FMemArena::Block::Alloc(size_t size)
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{
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if ((char *)Avail + size > Limit)
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{
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return NULL;
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}
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void *res = Avail;
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Avail = RoundPointer((char *)Avail + size);
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return res;
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}
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//==========================================================================
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//
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// FSharedStringArena Constructor
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//
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//==========================================================================
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FSharedStringArena::FSharedStringArena()
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{
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memset(Buckets, 0, sizeof(Buckets));
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}
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//==========================================================================
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//
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// FSharedStringArena Destructor
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//
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//==========================================================================
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FSharedStringArena::~FSharedStringArena()
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{
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FreeAll();
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// FMemArena destructor will free the blocks.
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}
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//==========================================================================
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//
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// FSharedStringArena :: Alloc
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//
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// Allocates a new string and initializes it with the passed string. This
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// version takes an FString as a parameter, so it won't need to allocate any
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// memory for the string text if it already exists in the arena.
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//
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//==========================================================================
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FString *FSharedStringArena::Alloc(const FString &source)
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{
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unsigned int hash;
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Node *strnode;
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strnode = FindString(source, source.Len(), hash);
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if (strnode == NULL)
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{
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strnode = (Node *)iAlloc(sizeof(Node));
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::new(&strnode->String) FString(source);
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strnode->Hash = hash;
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hash %= Bucket_Count;
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strnode->Next = Buckets[hash];
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Buckets[hash] = strnode;
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}
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return &strnode->String;
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}
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//==========================================================================
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//
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// FSharedStringArena :: Alloc
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//
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//==========================================================================
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FString *FSharedStringArena::Alloc(const char *source)
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{
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return Alloc(source, strlen(source));
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}
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//==========================================================================
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//
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// FSharedStringArena :: Alloc
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//
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//==========================================================================
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FString *FSharedStringArena::Alloc(const char *source, size_t strlen)
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{
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unsigned int hash;
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Node *strnode;
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strnode = FindString(source, strlen, hash);
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if (strnode == NULL)
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{
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strnode = (Node *)iAlloc(sizeof(Node));
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::new(&strnode->String) FString(source, strlen);
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strnode->Hash = hash;
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hash %= Bucket_Count;
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strnode->Next = Buckets[hash];
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Buckets[hash] = strnode;
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}
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return &strnode->String;
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}
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//==========================================================================
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//
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// FSharedStringArena :: FindString
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//
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// Finds the string if it's already in the arena. Returns NULL if not.
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//
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//==========================================================================
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FSharedStringArena::Node *FSharedStringArena::FindString(const char *str, size_t strlen, unsigned int &hash)
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{
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hash = SuperFastHash(str, strlen);
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for (Node *node = Buckets[hash % Bucket_Count]; node != NULL; node = node->Next)
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{
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if (node->Hash == hash && node->String.Len() == strlen && memcmp(&node->String[0], str, strlen) == 0)
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{
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return node;
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}
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}
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return NULL;
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}
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//==========================================================================
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//
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// FSharedStringArena :: FreeAll
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//
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// In addition to moving all used blocks onto the free list, all FStrings
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// they contain will have their destructors called.
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//
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//==========================================================================
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void FSharedStringArena::FreeAll()
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{
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for (Block *next, *block = TopBlock; block != NULL; block = next)
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{
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next = block->NextBlock;
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void *limit = block->Avail;
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block->Reset();
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for (Node *string = (Node *)block->Avail; string < limit; ++string)
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{
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string->~Node();
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}
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block->NextBlock = FreeBlocks;
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FreeBlocks = block;
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}
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memset(Buckets, 0, sizeof(Buckets));
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TopBlock = NULL;
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}
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