/// <summary>
/// Coalesces adjacent placeholders after unmap.
/// </summary>
/// <param name="address">Address of the region that was unmapped</param>
/// <param name="size">Size of the region that was unmapped in bytes</param>
/// <param name="owner">Memory block that owns the mapping</param>
private void CoalesceForUnmap(ulong address, ulong size, MemoryBlock owner)
{
ulong endAddress = address + size;
ulong blockAddress = (ulong)owner.Pointer;
ulong blockEnd = blockAddress + owner.Size;
var overlaps = Array.Empty <IntervalTreeNode <ulong, ulong> >();
int unmappedCount = 0;
lock (_mappings)
{
int count = _mappings.Get(
Math.Max(address - MinimumPageSize, blockAddress),
Math.Min(endAddress + MinimumPageSize, blockEnd), ref overlaps);
if (count < 2)
{
// Nothing to coalesce if we only have 1 or no overlaps.
return;
}
for (int index = 0; index < count; index++)
{
var overlap = overlaps[index];
if (!IsMapped(overlap.Value))
{
if (address > overlap.Start)
{
address = overlap.Start;
}
if (endAddress < overlap.End)
{
endAddress = overlap.End;
}
_mappings.Remove(overlap);
unmappedCount++;
}
}
_mappings.Add(address, endAddress, ulong.MaxValue);
}
if (unmappedCount > 1)
{
size = endAddress - address;
CheckFreeResult(WindowsApi.VirtualFree(
(IntPtr)address,
(IntPtr)size,
AllocationType.Release | AllocationType.CoalescePlaceholders));
}
}
/// <summary>
/// Unreserves a range of memory that has been previously reserved with <see cref="ReserveRange"/>.
/// </summary>
/// <param name="address">Start address of the region to unreserve</param>
/// <param name="size">Size in bytes of the region to unreserve</param>
/// <exception cref="WindowsApiException">Thrown when the Windows API returns an error unreserving the memory</exception>
public void UnreserveRange(ulong address, ulong size)
{
ulong endAddress = address + size;
var overlaps = Array.Empty <IntervalTreeNode <ulong, ulong> >();
int count;
lock (_mappings)
{
count = _mappings.Get(address, endAddress, ref overlaps);
for (int index = 0; index < count; index++)
{
var overlap = overlaps[index];
if (IsMapped(overlap.Value))
{
if (!WindowsApi.UnmapViewOfFile2(WindowsApi.CurrentProcessHandle, (IntPtr)overlap.Start, 2))
{
throw new WindowsApiException("UnmapViewOfFile2");
}
}
_mappings.Remove(overlap);
}
}
if (count > 1)
{
CheckFreeResult(WindowsApi.VirtualFree(
(IntPtr)address,
(IntPtr)size,
AllocationType.Release | AllocationType.CoalescePlaceholders));
}
RemoveProtection(address, size);
}
/// <summary>
/// Splits a larger placeholder, slicing at the start and end address, for a new memory mapping.
/// </summary>
/// <param name="address">Address to split</param>
/// <param name="size">Size of the new region</param>
/// <param name="backingOffset">Offset in the shared memory that will be mapped</param>
private void SplitForMap(ulong address, ulong size, ulong backingOffset)
{
ulong endAddress = address + size;
var overlaps = Array.Empty <IntervalTreeNode <ulong, ulong> >();
lock (_mappings)
{
int count = _mappings.Get(address, endAddress, ref overlaps);
Debug.Assert(count == 1);
Debug.Assert(!IsMapped(overlaps[0].Value));
var overlap = overlaps[0];
// Tree operations might modify the node start/end values, so save a copy before we modify the tree.
ulong overlapStart = overlap.Start;
ulong overlapEnd = overlap.End;
ulong overlapValue = overlap.Value;
_mappings.Remove(overlap);
bool overlapStartsBefore = overlapStart < address;
bool overlapEndsAfter = overlapEnd > endAddress;
if (overlapStartsBefore && overlapEndsAfter)
{
CheckFreeResult(WindowsApi.VirtualFree(
(IntPtr)address,
(IntPtr)size,
AllocationType.Release | AllocationType.PreservePlaceholder));
_mappings.Add(overlapStart, address, overlapValue);
_mappings.Add(endAddress, overlapEnd, AddBackingOffset(overlapValue, endAddress - overlapStart));
}
else if (overlapStartsBefore)
{
ulong overlappedSize = overlapEnd - address;
CheckFreeResult(WindowsApi.VirtualFree(
(IntPtr)address,
(IntPtr)overlappedSize,
AllocationType.Release | AllocationType.PreservePlaceholder));
_mappings.Add(overlapStart, address, overlapValue);
}
else if (overlapEndsAfter)
{
ulong overlappedSize = endAddress - overlapStart;
CheckFreeResult(WindowsApi.VirtualFree(
(IntPtr)overlapStart,
(IntPtr)overlappedSize,
AllocationType.Release | AllocationType.PreservePlaceholder));
_mappings.Add(endAddress, overlapEnd, AddBackingOffset(overlapValue, overlappedSize));
}
_mappings.Add(address, endAddress, backingOffset);
}
}
