forked from Mirror/Ryujinx
93 lines
3 KiB
C#
93 lines
3 KiB
C#
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using System.Runtime.InteropServices;
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using System.Threading;
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using static Ryujinx.Common.Memory.PartialUnmaps.PartialUnmapHelpers;
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namespace Ryujinx.Common.Memory.PartialUnmaps
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{
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/// <summary>
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/// A simple fixed size thread safe map that can be used from native code.
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/// Integer thread IDs map to corresponding structs.
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/// </summary>
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/// <typeparam name="T">The value type for the map</typeparam>
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[StructLayout(LayoutKind.Sequential, Pack = 1)]
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public struct ThreadLocalMap<T> where T : unmanaged
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{
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public const int MapSize = 20;
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public Array20<int> ThreadIds;
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public Array20<T> Structs;
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public static int ThreadIdsOffset;
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public static int StructsOffset;
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/// <summary>
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/// Populates the field offsets for use when emitting native code.
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/// </summary>
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static ThreadLocalMap()
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{
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ThreadLocalMap<T> instance = new ThreadLocalMap<T>();
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ThreadIdsOffset = OffsetOf(ref instance, ref instance.ThreadIds);
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StructsOffset = OffsetOf(ref instance, ref instance.Structs);
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}
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/// <summary>
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/// Gets the index of a given thread ID in the map, or reserves one.
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/// When reserving a struct, its value is set to the given initial value.
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/// Returns -1 when there is no space to reserve a new entry.
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/// </summary>
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/// <param name="threadId">Thread ID to use as a key</param>
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/// <param name="initial">Initial value of the associated struct.</param>
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/// <returns>The index of the entry, or -1 if none</returns>
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public int GetOrReserve(int threadId, T initial)
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{
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// Try get a match first.
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for (int i = 0; i < MapSize; i++)
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{
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int compare = Interlocked.CompareExchange(ref ThreadIds[i], threadId, threadId);
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if (compare == threadId)
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{
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return i;
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}
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}
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// Try get a free entry. Since the id is assumed to be unique to this thread, we know it doesn't exist yet.
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for (int i = 0; i < MapSize; i++)
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{
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int compare = Interlocked.CompareExchange(ref ThreadIds[i], threadId, 0);
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if (compare == 0)
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{
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Structs[i] = initial;
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return i;
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}
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}
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return -1;
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}
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/// <summary>
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/// Gets the struct value for a given map entry.
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/// </summary>
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/// <param name="index">Index of the entry</param>
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/// <returns>A reference to the struct value</returns>
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public ref T GetValue(int index)
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{
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return ref Structs[index];
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}
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/// <summary>
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/// Releases an entry from the map.
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/// </summary>
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/// <param name="index">Index of the entry to release</param>
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public void Release(int index)
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{
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Interlocked.Exchange(ref ThreadIds[index], 0);
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}
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}
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}
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