5d91b678bb
Also avoid ReadBytes calls that allocate a buffer by either updating the stream position (if not interested in the bytes), by reusing an input buffer (if interested in the bytes), or using a stackalloc buffer to avoid the allocation (for small reads).
87 lines
2.3 KiB
C#
87 lines
2.3 KiB
C#
#region Copyright & License Information
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/*
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* Copyright (c) The OpenRA Developers and Contributors
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* This file is part of OpenRA, which is free software. It is made
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* available to you under the terms of the GNU General Public License
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* as published by the Free Software Foundation, either version 3 of
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* the License, or (at your option) any later version. For more
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* information, see COPYING.
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*/
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#endregion
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using System;
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namespace OpenRA.Mods.Common.FileFormats
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{
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public static class WestwoodCompressedReader
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{
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static readonly int[] AudWsStepTable2 = { -2, -1, 0, 1 };
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static readonly int[] AudWsStepTable4 = { -9, -8, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 8 };
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public static void DecodeWestwoodCompressedSample(ReadOnlySpan<byte> input, Span<byte> output)
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{
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if (input.Length == output.Length)
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{
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input.CopyTo(output);
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return;
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}
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var sample = 0x80;
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var r = 0;
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var w = 0;
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while (r < input.Length)
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{
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var count = input[r++] & 0x3f;
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switch (input[r - 1] >> 6)
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{
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case 0:
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for (count++; count > 0; count--)
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{
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var code = input[r++];
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output[w++] = (byte)(sample = (sample + AudWsStepTable2[(code >> 0) & 0x03]).Clamp(byte.MinValue, byte.MaxValue));
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output[w++] = (byte)(sample = (sample + AudWsStepTable2[(code >> 2) & 0x03]).Clamp(byte.MinValue, byte.MaxValue));
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output[w++] = (byte)(sample = (sample + AudWsStepTable2[(code >> 4) & 0x03]).Clamp(byte.MinValue, byte.MaxValue));
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output[w++] = (byte)(sample = (sample + AudWsStepTable2[(code >> 6) & 0x03]).Clamp(byte.MinValue, byte.MaxValue));
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}
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break;
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case 1:
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for (count++; count > 0; count--)
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{
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var code = input[r++];
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output[w++] = (byte)(sample = (sample + AudWsStepTable4[(code >> 0) & 0x0f]).Clamp(byte.MinValue, byte.MaxValue));
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output[w++] = (byte)(sample = (sample + AudWsStepTable4[(code >> 4) & 0xff]).Clamp(byte.MinValue, byte.MaxValue));
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}
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break;
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case 2 when (count & 0x20) != 0:
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output[w++] = (byte)(sample += (sbyte)((sbyte)count << 3) >> 3);
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break;
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case 2:
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for (count++; count > 0; count--)
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output[w++] = input[r++];
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sample = input[r - 1];
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break;
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default:
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for (count++; count > 0; count--)
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output[w++] = (byte)sample;
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break;
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}
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}
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}
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}
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}
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