private static UIntPtr SpaceToAlign(UIntPtr data, UIntPtr size)
{
return(MemoryManager.Pad(data, size) - data);
}
public unsafe UIntPtr Allocate(UIntPtr limitAddr,
UIntPtr bytes,
UIntPtr alignment,
Process process)
{
ushort tag = process != null ? (ushort)process.ProcessId : KernelPage;
UIntPtr blockPtr;
bool iflag = Lock();
if (alignment < MemoryManager.PageSize)
{
alignment = MemoryManager.PageSize;
}
try {
CheckConsistency();
// Find an appropriately-sized block
FreeNode *foundNode = freeList.FindGoodFit(bytes, alignment);
if (foundNode == null)
{
return(UIntPtr.Zero);
}
DebugStub.Assert(MemoryManager.IsPageAligned((UIntPtr)foundNode));
// Respect alignment within the node
blockPtr = MemoryManager.Pad((UIntPtr)foundNode, alignment);
UIntPtr alignedSize = bytes + SpaceToAlign((UIntPtr)foundNode, alignment);
DebugStub.Assert(alignedSize == (blockPtr + bytes) - (UIntPtr)foundNode);
DebugStub.Assert(foundNode->bytes >= alignedSize);
// Give back any extra pages
UIntPtr numPages = MemoryManager.PagesFromBytes(MemoryManager.PagePad(alignedSize));
UIntPtr chunkPages = MemoryManager.PagesFromBytes(foundNode->bytes);
DebugStub.Assert(chunkPages >= numPages);
UIntPtr extraPages = chunkPages - numPages;
if (extraPages > 0)
{
// Give back the extra memory
UIntPtr remainderPtr = (UIntPtr)foundNode + (numPages * MemoryManager.PageSize);
fixed(PhysicalHeap *thisPtr = &this)
{
freeList.CreateAndInsert(thisPtr, remainderPtr, extraPages);
}
}
SetPages((UIntPtr)foundNode, numPages, tag);
CheckConsistency();
}
finally {
Unlock(iflag);
}
// TODO: Flexible limit specification not yet implemented
if (limitAddr > UIntPtr.Zero)
{
DebugStub.Assert(blockPtr < limitAddr);
}
return(blockPtr);
}