201 lines
4.6 KiB
C++
201 lines
4.6 KiB
C++
#include "stdafx.h"
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// Tree Memory Allocation structure.
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typedef struct _POOLMEMORYBLOCK POOLMEMORYBLOCK, *PPOOLMEMORYBLOCK;
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struct _POOLMEMORYBLOCK {
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DWORD_PTR Index;
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DWORD_PTR Size;
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PPOOLMEMORYBLOCK NextBlock;
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PPOOLMEMORYBLOCK PrevBlock;
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PBYTE RawMemory;
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};
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typedef struct _POOLHEADER {
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PPOOLMEMORYBLOCK PoolHead;
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HANDLE Heap;
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} POOLHEADER, *PPOOLHEADER;
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BOOL
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PoolMemAddMemory (
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IN POOLHANDLE Handle,
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IN DWORD_PTR Size
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)
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{
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PBYTE allocedMemory;
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PPOOLMEMORYBLOCK newBlock;
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PPOOLHEADER poolHeader = (PPOOLHEADER) Handle;
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DWORD_PTR sizeNeeded;
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assert(poolHeader != NULL);
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//
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// Determine size needed and attempt to allocate memory.
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//
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if (Size + sizeof(POOLMEMORYBLOCK) > POOLMEMORYBLOCKSIZE) {
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sizeNeeded = Size + sizeof(POOLMEMORYBLOCK);
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}
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else {
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sizeNeeded = POOLMEMORYBLOCKSIZE;
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}
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allocedMemory = (unsigned char *) HeapAlloc(poolHeader -> Heap,0,sizeNeeded);
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if (allocedMemory) {
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//
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// Use the beginning of the alloc'ed block as the poolblock structure.
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//
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newBlock = (PPOOLMEMORYBLOCK) allocedMemory;
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newBlock -> Size = sizeNeeded - sizeof(POOLMEMORYBLOCK);
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newBlock -> RawMemory = allocedMemory + sizeof(POOLMEMORYBLOCK);
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newBlock -> Index = 0;
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//
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// Link the block into the list.
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//
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if (poolHeader -> PoolHead) {
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poolHeader -> PoolHead -> PrevBlock = newBlock;
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}
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newBlock -> NextBlock = poolHeader -> PoolHead;
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newBlock -> PrevBlock = NULL;
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poolHeader -> PoolHead = newBlock;
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}
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//
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// Assuming allocedMemory is non-NULL, we have succeeded.
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//
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return allocedMemory != NULL;
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}
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POOLHANDLE
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WINAPI
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PoolMemInitPool (
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)
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{
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BOOL ableToAddMemory;
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PPOOLHEADER header = NULL;
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HANDLE procHeap;
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procHeap = GetProcessHeap();
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//
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// Allocate the header of this pool.
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//
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header = (PPOOLHEADER) HeapAlloc(procHeap,0,sizeof(POOLHEADER));
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if (header) {
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//
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// Allocation was successful. Now, initialize the pool.
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//
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header -> PoolHead = NULL;
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header -> Heap = procHeap;
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//
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// Actually add some memory to the pool.
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//
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ableToAddMemory = PoolMemAddMemory(header,0);
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if (!ableToAddMemory) {
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//
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// Unable to add memory to the pool.
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//
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HeapFree(header -> Heap,0,header);
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header = NULL;
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}
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}
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return (POOLHANDLE) header;
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}
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VOID
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WINAPI
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PoolMemDestroyPool (
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POOLHANDLE Handle
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)
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{
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PPOOLMEMORYBLOCK nextBlock;
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PPOOLMEMORYBLOCK blockToFree;
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PPOOLHEADER poolHeader;
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assert(Handle != NULL);
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poolHeader = (PPOOLHEADER) Handle;
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//
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// Walk the list, freeing as we go.
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//
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blockToFree = poolHeader -> PoolHead;
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while (blockToFree != NULL) {
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nextBlock = blockToFree->NextBlock;
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HeapFree(poolHeader -> Heap,0,blockToFree);
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blockToFree = nextBlock;
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}
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//
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// Also, deallocate the poolheader itself.
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//
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HeapFree(poolHeader -> Heap,0,poolHeader);
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}
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PVOID
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WINAPI
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PoolMemGetAlignedMemory (
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IN POOLHANDLE Handle,
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IN DWORD_PTR Size,
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IN DWORD_PTR AlignSize
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)
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{
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BOOL haveEnoughMemory = TRUE;
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PVOID rMemory = NULL;
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PPOOLHEADER poolHeader = (PPOOLHEADER) Handle;
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PPOOLMEMORYBLOCK currentBlock;
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DWORD_PTR sizeNeeded;
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DWORD_PTR padLength;
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assert(poolHeader != NULL);
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currentBlock = poolHeader -> PoolHead;
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// Determine if more memory is needed, attempt to add if needed.
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sizeNeeded = Size;
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if (currentBlock -> Size - currentBlock -> Index < sizeNeeded + AlignSize) {
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haveEnoughMemory = PoolMemAddMemory(poolHeader,sizeNeeded + AlignSize);
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currentBlock = poolHeader -> PoolHead;
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}
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// If there is enough memory available, return it.
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if (haveEnoughMemory) {
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if (AlignSize) {
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padLength = (DWORD_PTR) currentBlock + sizeof(POOLMEMORYBLOCK)
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+ currentBlock -> Index;
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currentBlock -> Index += (AlignSize - (padLength % AlignSize)) % AlignSize;
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}
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//Now, get the address of the memory to return.
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rMemory = (PVOID)
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&(currentBlock->RawMemory[currentBlock -> Index]);
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currentBlock->Index += sizeNeeded;
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}
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return rMemory;
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}
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