public unsafe void Free(UIntPtr addr, UIntPtr bytes, Process process)
{
if (addr == UIntPtr.Zero)
{
// Silently accept freeing null
return;
}
// We always hand out memory in page-size chunks, so round up what
// the caller thinks their block size is
bytes = MemoryManager.PagePad(bytes);
// Our blocks always start on page boundaries
DebugStub.Assert(MemoryManager.IsPageAligned(addr));
ushort tag = process != null ? (ushort)process.ProcessId : KernelPage;
bool iflag = Lock();
try {
CheckConsistency();
UIntPtr numPages = MemoryManager.PagesFromBytes(bytes);
VerifyOwner(addr, numPages, tag);
FreeNode *nextBlock = null;
FreeNode *prevBlock = null;
if ((addr + bytes) < heapLimit)
{
fixed(PhysicalHeap *thisPtr = &this)
{
nextBlock = FreeNode.GetNodeAt(thisPtr, addr + bytes);
}
}
if (addr > startAddr)
{
fixed(PhysicalHeap *thisPtr = &this)
{
prevBlock = LastNode.GetNodeFromLast(thisPtr, addr - MemoryManager.PageSize);
}
}
// Don't mark pages as free until we're done discovering the
// previous and next blocks, or the attempt to discover
// the previous and next blocks gets confused to find itself
// adjacent to a free block.
SetPages(addr, numPages, FreePage);
// Coalesce with the preceding region
if (prevBlock != null)
{
addr = (UIntPtr)prevBlock;
bytes += prevBlock->bytes;
freeList.Remove(prevBlock);
}
// Coalesce with the following region
if (nextBlock != null)
{
bytes += nextBlock->bytes;
freeList.Remove(nextBlock);
}
// Blocks should always be integral numbers of pages
DebugStub.Assert(MemoryManager.IsPageAligned(bytes));
// Create the free node.
fixed(PhysicalHeap *thisPtr = &this)
{
freeList.CreateAndInsert(thisPtr, addr, bytes / MemoryManager.PageSize);
}
CheckConsistency();
}
finally {
Unlock(iflag);
}
}
