/// <summary>
/// Creates a new buffer for the specified range, if needed.
/// If a buffer where this range can be fully contained already exists,
/// then the creation of a new buffer is not necessary.
/// </summary>
/// <param name="address">Address of the buffer in guest memory</param>
/// <param name="size">Size in bytes of the buffer</param>
private void CreateBufferAligned(ulong address, ulong size)
{
int overlapsCount;
lock (_buffers)
{
overlapsCount = _buffers.FindOverlapsNonOverlapping(address, size, ref _bufferOverlaps);
}
if (overlapsCount != 0)
{
// The buffer already exists. We can just return the existing buffer
// if the buffer we need is fully contained inside the overlapping buffer.
// Otherwise, we must delete the overlapping buffers and create a bigger buffer
// that fits all the data we need. We also need to copy the contents from the
// old buffer(s) to the new buffer.
ulong endAddress = address + size;
if (_bufferOverlaps[0].Address > address || _bufferOverlaps[0].EndAddress < endAddress)
{
for (int index = 0; index < overlapsCount; index++)
{
Buffer buffer = _bufferOverlaps[index];
address = Math.Min(address, buffer.Address);
endAddress = Math.Max(endAddress, buffer.EndAddress);
lock (_buffers)
{
_buffers.Remove(buffer);
}
}
Buffer newBuffer = new Buffer(_context, _physicalMemory, address, endAddress - address, _bufferOverlaps.Take(overlapsCount));
lock (_buffers)
{
_buffers.Add(newBuffer);
}
for (int index = 0; index < overlapsCount; index++)
{
Buffer buffer = _bufferOverlaps[index];
int dstOffset = (int)(buffer.Address - newBuffer.Address);
buffer.CopyTo(newBuffer, dstOffset);
newBuffer.InheritModifiedRanges(buffer);
buffer.DisposeData();
}
newBuffer.SynchronizeMemory(address, endAddress - address);
// Existing buffers were modified, we need to rebind everything.
NotifyBuffersModified?.Invoke();
}
}
else
{
// No overlap, just create a new buffer.
Buffer buffer = new Buffer(_context, _physicalMemory, address, size);
lock (_buffers)
{
_buffers.Add(buffer);
}
}
ShrinkOverlapsBufferIfNeeded();
}
/// <summary>
/// Creates a new buffer for the specified range, if needed.
/// If a buffer where this range can be fully contained already exists,
/// then the creation of a new buffer is not necessary.
/// </summary>
/// <param name="address">Address of the buffer in guest memory</param>
/// <param name="size">Size in bytes of the buffer</param>
private void CreateBufferAligned(ulong address, ulong size)
{
int overlapsCount;
lock (_buffers)
{
overlapsCount = _buffers.FindOverlapsNonOverlapping(address, size, ref _bufferOverlaps);
}
if (overlapsCount != 0)
{
// The buffer already exists. We can just return the existing buffer
// if the buffer we need is fully contained inside the overlapping buffer.
// Otherwise, we must delete the overlapping buffers and create a bigger buffer
// that fits all the data we need. We also need to copy the contents from the
// old buffer(s) to the new buffer.
ulong endAddress = address + size;
if (_bufferOverlaps[0].Address > address || _bufferOverlaps[0].EndAddress < endAddress)
{
// Check if the following conditions are met:
// - We have a single overlap.
// - The overlap starts at or before the requested range. That is, the overlap happens at the end.
// - The size delta between the new, merged buffer and the old one is of at most 2 pages.
// In this case, we attempt to extend the buffer further than the requested range,
// this can potentially avoid future resizes if the application keeps using overlapping
// sequential memory.
// Allowing for 2 pages (rather than just one) is necessary to catch cases where the
// range crosses a page, and after alignment, ends having a size of 2 pages.
if (overlapsCount == 1 &&
address >= _bufferOverlaps[0].Address &&
endAddress - _bufferOverlaps[0].EndAddress <= BufferAlignmentSize * 2)
{
// Try to grow the buffer by 1.5x of its current size.
// This improves performance in the cases where the buffer is resized often by small amounts.
ulong existingSize = _bufferOverlaps[0].Size;
ulong growthSize = (existingSize + Math.Min(existingSize >> 1, MaxDynamicGrowthSize)) & ~BufferAlignmentMask;
size = Math.Max(size, growthSize);
endAddress = address + size;
overlapsCount = _buffers.FindOverlapsNonOverlapping(address, size, ref _bufferOverlaps);
}
for (int index = 0; index < overlapsCount; index++)
{
Buffer buffer = _bufferOverlaps[index];
address = Math.Min(address, buffer.Address);
endAddress = Math.Max(endAddress, buffer.EndAddress);
lock (_buffers)
{
_buffers.Remove(buffer);
}
}
ulong newSize = endAddress - address;
Buffer newBuffer = new Buffer(_context, _physicalMemory, address, newSize, _bufferOverlaps.Take(overlapsCount));
lock (_buffers)
{
_buffers.Add(newBuffer);
}
for (int index = 0; index < overlapsCount; index++)
{
Buffer buffer = _bufferOverlaps[index];
int dstOffset = (int)(buffer.Address - newBuffer.Address);
buffer.CopyTo(newBuffer, dstOffset);
newBuffer.InheritModifiedRanges(buffer);
buffer.DisposeData();
}
newBuffer.SynchronizeMemory(address, newSize);
// Existing buffers were modified, we need to rebind everything.
NotifyBuffersModified?.Invoke();
}
}
else
{
// No overlap, just create a new buffer.
Buffer buffer = new Buffer(_context, _physicalMemory, address, size);
lock (_buffers)
{
_buffers.Add(buffer);
}
}
ShrinkOverlapsBufferIfNeeded();
}
