From 5def0429f82c795d820b2307a0301b78dfb1e6b7 Mon Sep 17 00:00:00 2001
From: jhorv <38920027+jhorv@users.noreply.github.com>
Date: Thu, 4 Apr 2024 21:23:03 -0400
Subject: Add support to IVirtualMemoryManager for zero-copy reads (#6251)

* - WritableRegion: enable wrapping IMemoryOwner<byte>
- IVirtualMemoryManager impls of GetWritableRegion() use pooled memory when region is non-contiguous.
- IVirtualMemoryManager: add GetReadOnlySequence() and impls
- ByteMemoryPool: add new method RentCopy()
- ByteMemoryPool: make class static, remove ctor and singleton field from earlier impl

* - BytesReadOnlySequenceSegment: move from Ryujinx.Common.Memory to Ryujinx.Memory
- BytesReadOnlySequenceSegment: add IsContiguousWith() and Replace() methods
- VirtualMemoryManagerBase:
  - remove generic type parameters, instead use ulong for virtual addresses and nuint for host/physical addresses
  - implement IWritableBlock
  - add virtual GetReadOnlySequence() with coalescing of contiguous segments
  - add virtual GetSpan()
  - add virtual GetWritableRegion()
  - add abstract IsMapped()
  - add virtual MapForeign(ulong, nuint, ulong)
  - add virtual Read<T>()
  - add virtual Read(ulong, Span<byte>)
  - add virtual ReadTracked<T>()
  - add virtual SignalMemoryTracking()
  - add virtual Write()
  - add virtual Write<T>()
  - add virtual WriteUntracked()
  - add virtual WriteWithRedundancyCheck()
- VirtualMemoryManagerRefCountedBase: remove generic type parameters
- AddressSpaceManager: remove redundant methods, add required overrides
- HvMemoryManager: remove redundant methods, add required overrides, add overrides for _invalidAccessHandler handling
- MemoryManager: remove redundant methods, add required overrides, add overrides for _invalidAccessHandler handling
- MemoryManagerHostMapped: remove redundant methods, add required overrides, add overrides for _invalidAccessHandler handling
- NativeMemoryManager: add get properties for Pointer and Length
- throughout: removed invalid <inheritdoc/> comments

* make HvMemoryManager class sealed

* remove unused method

* adjust MemoryManagerHostTracked

* let MemoryManagerHostTracked override WriteImpl()
---
 src/Ryujinx.Memory/BytesReadOnlySequenceSegment.cs | 60 ++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 src/Ryujinx.Memory/BytesReadOnlySequenceSegment.cs

(limited to 'src/Ryujinx.Memory/BytesReadOnlySequenceSegment.cs')

diff --git a/src/Ryujinx.Memory/BytesReadOnlySequenceSegment.cs b/src/Ryujinx.Memory/BytesReadOnlySequenceSegment.cs
new file mode 100644
index 00000000..5fe8d936
--- /dev/null
+++ b/src/Ryujinx.Memory/BytesReadOnlySequenceSegment.cs
@@ -0,0 +1,60 @@
+using System;
+using System.Buffers;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Memory
+{
+    /// <summary>
+    /// A concrete implementation of <seealso cref="ReadOnlySequence{Byte}"/>,
+    /// with methods to help build a full sequence.
+    /// </summary>
+    public sealed class BytesReadOnlySequenceSegment : ReadOnlySequenceSegment<byte>
+    {
+        public BytesReadOnlySequenceSegment(Memory<byte> memory) => Memory = memory;
+
+        public BytesReadOnlySequenceSegment Append(Memory<byte> memory)
+        {
+            var nextSegment = new BytesReadOnlySequenceSegment(memory)
+            {
+                RunningIndex = RunningIndex + Memory.Length
+            };
+
+            Next = nextSegment;
+
+            return nextSegment;
+        }
+
+        /// <summary>
+        /// Attempts to determine if the current <seealso cref="Memory{Byte}"/> and <paramref name="other"/> are contiguous.
+        /// Only works if both were created by a <seealso cref="NativeMemoryManager{Byte}"/>.
+        /// </summary>
+        /// <param name="other">The segment to check if continuous with the current one</param>
+        /// <param name="contiguousStart">The starting address of the contiguous segment</param>
+        /// <param name="contiguousSize">The size of the contiguous segment</param>
+        /// <returns>True if the segments are contiguous, otherwise false</returns>
+        public unsafe bool IsContiguousWith(Memory<byte> other, out nuint contiguousStart, out int contiguousSize)
+        {
+            if (MemoryMarshal.TryGetMemoryManager<byte, NativeMemoryManager<byte>>(Memory, out var thisMemoryManager) &&
+                MemoryMarshal.TryGetMemoryManager<byte, NativeMemoryManager<byte>>(other, out var otherMemoryManager) &&
+                thisMemoryManager.Pointer + thisMemoryManager.Length == otherMemoryManager.Pointer)
+            {
+                contiguousStart = (nuint)thisMemoryManager.Pointer;
+                contiguousSize = thisMemoryManager.Length + otherMemoryManager.Length;
+                return true;
+            }
+            else
+            {
+                contiguousStart = 0;
+                contiguousSize = 0;
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Replaces the current <seealso cref="Memory{Byte}"/> value with the one provided.
+        /// </summary>
+        /// <param name="memory">The new segment to hold in this <seealso cref="BytesReadOnlySequenceSegment"/></param>
+        public void Replace(Memory<byte> memory)
+            => Memory = memory;
+    }
+}
-- 
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