/// <summary>
/// Unmaps mapped memory at a given range.
/// </summary>
/// <param name="location">Address of the range</param>
/// <param name="size">Size of the range in bytes</param>
public void UnmapRange(IntPtr location, IntPtr size)
{
ulong startAddress = (ulong)location;
ulong unmapSize = (ulong)size;
ulong endAddress = startAddress + unmapSize;
var overlaps = Array.Empty <IntervalTreeNode <ulong, byte> >();
int count = 0;
lock (_mappings)
{
count = _mappings.Get(startAddress, endAddress, ref overlaps);
}
for (int index = 0; index < count; index++)
{
var overlap = overlaps[index];
// Tree operations might modify the node start/end values, so save a copy before we modify the tree.
ulong unmapStart = Math.Max(overlap.Start, startAddress);
ulong unmapEnd = Math.Min(overlap.End, endAddress);
_mappings.Remove(overlap);
ulong currentAddress = unmapStart;
while (currentAddress < unmapEnd)
{
WindowsApi.UnmapViewOfFile2(WindowsApi.CurrentProcessHandle, (IntPtr)currentAddress, 2);
currentAddress += PageSize;
}
}
}
/// <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>
/// Maps a shared memory view on a previously reserved memory region.
/// </summary>
/// <param name="sharedMemory">Shared memory that will be the backing storage for the view</param>
/// <param name="srcOffset">Offset in the shared memory to map</param>
/// <param name="location">Address to map the view into</param>
/// <param name="size">Size of the view in bytes</param>
/// <exception cref="WindowsApiException">Thrown when the Windows API returns an error mapping the memory</exception>
private void MapViewInternal(IntPtr sharedMemory, ulong srcOffset, IntPtr location, IntPtr size)
{
SplitForMap((ulong)location, (ulong)size, srcOffset);
var ptr = WindowsApi.MapViewOfFile3(
sharedMemory,
WindowsApi.CurrentProcessHandle,
location,
srcOffset,
size,
0x4000,
MemoryProtection.ReadWrite,
IntPtr.Zero,
0);
if (ptr == IntPtr.Zero)
{
throw new WindowsApiException("MapViewOfFile3");
}
}
/// <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>
/// Reprotects a region of memory that has been mapped.
/// </summary>
/// <param name="address">Address of the region to reprotect</param>
/// <param name="size">Size of the region to reprotect in bytes</param>
/// <param name="permission">New permissions</param>
/// <param name="throwOnError">Throw an exception instead of returning an error if the operation fails</param>
/// <returns>True if the reprotection was successful or if <paramref name="throwOnError"/> is true, false otherwise</returns>
/// <exception cref="WindowsApiException">If <paramref name="throwOnError"/> is true, it is thrown when the Windows API returns an error reprotecting the memory</exception>
private bool ReprotectViewInternal(IntPtr address, IntPtr size, MemoryPermission permission, bool throwOnError)
{
ulong reprotectAddress = (ulong)address;
ulong reprotectSize = (ulong)size;
ulong endAddress = reprotectAddress + reprotectSize;
var overlaps = Array.Empty <IntervalTreeNode <ulong, ulong> >();
int count;
lock (_mappings)
{
count = _mappings.Get(reprotectAddress, endAddress, ref overlaps);
}
bool success = true;
for (int index = 0; index < count; index++)
{
var overlap = overlaps[index];
ulong mappedAddress = overlap.Start;
ulong mappedSize = overlap.End - overlap.Start;
if (mappedAddress < reprotectAddress)
{
ulong delta = reprotectAddress - mappedAddress;
mappedAddress = reprotectAddress;
mappedSize -= delta;
}
ulong mappedEndAddress = mappedAddress + mappedSize;
if (mappedEndAddress > endAddress)
{
ulong delta = mappedEndAddress - endAddress;
mappedSize -= delta;
}
if (!WindowsApi.VirtualProtect((IntPtr)mappedAddress, (IntPtr)mappedSize, WindowsApi.GetProtection(permission), out _))
{
if (throwOnError)
{
throw new WindowsApiException("VirtualProtect");
}
success = false;
}
// We only keep track of "non-standard" protections,
// that is, everything that is not just RW (which is the default when views are mapped).
if (permission == MemoryPermission.ReadAndWrite)
{
RemoveProtection(mappedAddress, mappedSize);
}
else
{
AddProtection(mappedAddress, mappedSize, permission);
}
}
return(success);
}
/// <summary>
/// Unmaps a view that has been previously mapped with <see cref="MapView"/>.
/// </summary>
/// <remarks>
/// For "partial unmaps" (when not the entire mapped range is being unmapped), it might be
/// necessary to unmap the whole range and then remap the sub-ranges that should remain mapped.
/// </remarks>
/// <param name="sharedMemory">Shared memory that the view being unmapped belongs to</param>
/// <param name="location">Address to unmap</param>
/// <param name="size">Size of the region to unmap in bytes</param>
/// <param name="owner">Memory block that owns the mapping</param>
/// <exception cref="WindowsApiException">Thrown when the Windows API returns an error unmapping or remapping the memory</exception>
private void UnmapViewInternal(IntPtr sharedMemory, IntPtr location, IntPtr size, MemoryBlock owner)
{
ulong startAddress = (ulong)location;
ulong unmapSize = (ulong)size;
ulong endAddress = startAddress + unmapSize;
var overlaps = Array.Empty <IntervalTreeNode <ulong, ulong> >();
int count;
lock (_mappings)
{
count = _mappings.Get(startAddress, 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");
}
// 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;
lock (_mappings)
{
_mappings.Remove(overlap);
_mappings.Add(overlapStart, overlapEnd, ulong.MaxValue);
}
bool overlapStartsBefore = overlapStart < startAddress;
bool overlapEndsAfter = overlapEnd > endAddress;
if (overlapStartsBefore || overlapEndsAfter)
{
// If the overlap extends beyond the region we are unmapping,
// then we need to re-map the regions that are supposed to remain mapped.
// This is necessary because Windows does not support partial view unmaps.
// That is, you can only fully unmap a view that was previously mapped, you can't just unmap a chunck of it.
LockCookie lockCookie = _partialUnmapLock.UpgradeToWriterLock(Timeout.Infinite);
_partialUnmapsCount++;
if (overlapStartsBefore)
{
ulong remapSize = startAddress - overlapStart;
MapViewInternal(sharedMemory, overlapValue, (IntPtr)overlapStart, (IntPtr)remapSize);
RestoreRangeProtection(overlapStart, remapSize);
}
if (overlapEndsAfter)
{
ulong overlappedSize = endAddress - overlapStart;
ulong remapBackingOffset = overlapValue + overlappedSize;
ulong remapAddress = overlapStart + overlappedSize;
ulong remapSize = overlapEnd - endAddress;
MapViewInternal(sharedMemory, remapBackingOffset, (IntPtr)remapAddress, (IntPtr)remapSize);
RestoreRangeProtection(remapAddress, remapSize);
}
_partialUnmapLock.DowngradeFromWriterLock(ref lockCookie);
}
}
}
CoalesceForUnmap(startAddress, unmapSize, owner);
RemoveProtection(startAddress, unmapSize);
}
/// <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);
}
}
private static string CreateMessage(string functionName)
{
return($"{functionName} returned error code 0x{WindowsApi.GetLastError():X}.");
}