Ryujinx/Ryujinx.Graphics.Nvdec/Image/SurfaceCache.cs

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using Ryujinx.Graphics.Gpu.Memory;
using Ryujinx.Graphics.Video;
using System;
using System.Diagnostics;
namespace Ryujinx.Graphics.Nvdec.Image
{
class SurfaceCache
{
// Must be equal to at least the maximum number of surfaces
// that can be in use simultaneously (which is 17, since H264
// can have up to 16 reference frames, and we need another one
// for the current frame).
// Realistically, most codecs won't ever use more than 4 simultaneously.
private const int MaxItems = 17;
private struct CacheItem
{
public int ReferenceCount;
public uint LumaOffset;
public uint ChromaOffset;
public int Width;
public int Height;
public CodecId CodecId;
public ISurface Surface;
}
private readonly CacheItem[] _pool = new CacheItem[MaxItems];
private readonly MemoryManager _gmm;
public SurfaceCache(MemoryManager gmm)
{
_gmm = gmm;
}
public ISurface Get(IDecoder decoder, CodecId codecId, uint lumaOffset, uint chromaOffset, int width, int height)
{
ISurface surface = null;
// Try to find a compatible surface with same parameters, and same offsets.
for (int i = 0; i < MaxItems; i++)
{
ref CacheItem item = ref _pool[i];
if (item.LumaOffset == lumaOffset &&
item.ChromaOffset == chromaOffset &&
item.CodecId == codecId &&
item.Width == width &&
item.Height == height)
{
item.ReferenceCount++;
surface = item.Surface;
MoveToFront(i);
break;
}
}
// If we failed to find a perfect match, now ignore the offsets.
// Search backwards to replace the oldest compatible surface,
// this avoids thrashing frquently used surfaces.
// Now we need to ensure that the surface is not in use, as we'll change the data.
if (surface == null)
{
for (int i = MaxItems - 1; i >= 0; i--)
{
ref CacheItem item = ref _pool[i];
if (item.ReferenceCount == 0 && item.CodecId == codecId && item.Width == width && item.Height == height)
{
item.ReferenceCount = 1;
item.LumaOffset = lumaOffset;
item.ChromaOffset = chromaOffset;
surface = item.Surface;
if ((lumaOffset | chromaOffset) != 0)
{
SurfaceReader.Read(_gmm, surface, lumaOffset, chromaOffset);
}
MoveToFront(i);
break;
}
}
}
// If everything else failed, we try to create a new surface,
// and insert it on the pool. We replace the oldest item on the
// pool to avoid thrashing frequently used surfaces.
// If even the oldest item is in use, that means that the entire pool
// is in use, in that case we throw as there's no place to insert
// the new surface.
if (surface == null)
{
if (_pool[MaxItems - 1].ReferenceCount == 0)
{
surface = decoder.CreateSurface(width, height);
if ((lumaOffset | chromaOffset) != 0)
{
SurfaceReader.Read(_gmm, surface, lumaOffset, chromaOffset);
}
MoveToFront(MaxItems - 1);
ref CacheItem item = ref _pool[0];
item.Surface?.Dispose();
item.ReferenceCount = 1;
item.LumaOffset = lumaOffset;
item.ChromaOffset = chromaOffset;
item.Width = width;
item.Height = height;
item.CodecId = codecId;
item.Surface = surface;
}
else
{
throw new InvalidOperationException("No free slot on the surface pool.");
}
}
return surface;
}
public void Put(ISurface surface)
{
for (int i = 0; i < MaxItems; i++)
{
ref CacheItem item = ref _pool[i];
if (item.Surface == surface)
{
item.ReferenceCount--;
Debug.Assert(item.ReferenceCount >= 0);
break;
}
}
}
private void MoveToFront(int index)
{
// If index is 0 we don't need to do anything,
// as it's already on the front.
if (index != 0)
{
CacheItem temp = _pool[index];
Array.Copy(_pool, 0, _pool, 1, index);
_pool[0] = temp;
}
}
}
}