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97 lines
3.1 KiB
C#
97 lines
3.1 KiB
C#
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using System;
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using System.Collections.Generic;
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namespace Ryujinx.Graphics.Gpu.Shader.HashTable
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{
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/// <summary>
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/// Smart data accessor that can cache data and hashes to avoid reading and re-hashing the same memory regions.
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/// </summary>
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ref struct SmartDataAccessor
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{
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private readonly IDataAccessor _dataAccessor;
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private ReadOnlySpan<byte> _data;
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private readonly SortedList<int, HashState> _cachedHashes;
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/// <summary>
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/// Creates a new smart data accessor.
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/// </summary>
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/// <param name="dataAccessor">Data accessor</param>
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public SmartDataAccessor(IDataAccessor dataAccessor)
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{
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_dataAccessor = dataAccessor;
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_data = ReadOnlySpan<byte>.Empty;
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_cachedHashes = new SortedList<int, HashState>();
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}
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/// <summary>
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/// Get a spans of a given size.
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/// </summary>
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/// <remarks>
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/// The actual length of the span returned depends on the <see cref="IDataAccessor"/>
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/// and might be less than requested.
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/// </remarks>
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/// <param name="length">Size in bytes</param>
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/// <returns>Span with the requested size</returns>
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public ReadOnlySpan<byte> GetSpan(int length)
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{
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if (_data.Length < length)
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{
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_data = _dataAccessor.GetSpan(0, length);
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}
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else if (_data.Length > length)
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{
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return _data.Slice(0, length);
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}
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return _data;
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}
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/// <summary>
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/// Gets a span of the requested size, and a hash of its data.
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/// </summary>
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/// <param name="length">Length of the span</param>
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/// <param name="hash">Hash of the span data</param>
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/// <returns>Span of data</returns>
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public ReadOnlySpan<byte> GetSpanAndHash(int length, out uint hash)
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{
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ReadOnlySpan<byte> data = GetSpan(length);
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hash = data.Length == length ? CalcHashCached(data) : 0;
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return data;
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}
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/// <summary>
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/// Calculates the hash for a requested span.
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/// This will try to use a cached hash if the data was already accessed before, to avoid re-hashing.
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/// </summary>
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/// <param name="data">Data to be hashed</param>
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/// <returns>Hash of the data</returns>
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private uint CalcHashCached(ReadOnlySpan<byte> data)
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{
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HashState state = default;
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bool found = false;
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for (int i = _cachedHashes.Count - 1; i >= 0; i--)
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{
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int cachedHashSize = _cachedHashes.Keys[i];
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if (cachedHashSize < data.Length)
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{
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state = _cachedHashes.Values[i];
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found = true;
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break;
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}
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}
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if (!found)
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{
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state = new HashState();
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state.Initialize();
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}
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state.Continue(data);
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_cachedHashes[data.Length & ~7] = state;
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return state.Finalize(data);
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}
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}
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}
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