POOLMEM.C

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