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Avoid allocation in PackageEntry.HashFilename

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This is a very frequently called method during loading, and taking some care to avoid allocations improves performance noticeably.
This commit is contained in:
RoosterDragon
2021-10-09 13:47:19 +01:00
committed by abcdefg30
parent 2ed4cb8aff
commit 3bee524c6b
2 changed files with 40 additions and 45 deletions
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41
OpenRA.Mods.Cnc/FileFormats/CRC32.cs
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@@ -9,6 +9,8 @@
*/
#endregion
using System;
namespace OpenRA.Mods.Cnc.FileFormats
{
/// <summary>
@@ -20,7 +22,7 @@ namespace OpenRA.Mods.Cnc.FileFormats
/// <summary>
/// The CRC32 lookup table
/// </summary>
static uint[] lookUp = new uint[256]
static readonly uint[] LookUp = new uint[256]
{
0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
@@ -89,47 +91,32 @@ namespace OpenRA.Mods.Cnc.FileFormats
};
/// <summary>
/// A fast (native) CRC32 implementation that can be used on a regular byte arrays.
/// A CRC32 implementation that can be used on spans of bytes.
/// </summary>
/// <param name="data">The data from which to calculate the checksum.</param>
/// <param name="polynomial">The polynomial.</param>
/// <param name="polynomial">The polynomial to XOR with.</param>
/// <returns>
/// The calculated checksum.
/// </returns>
public static uint Calculate(byte[] data, uint polynomial)
public static uint Calculate(ReadOnlySpan<byte> data, uint polynomial)
{
var crc = polynomial;
for (var i = 0; i < data.Length; i++)
crc = (crc >> 8) ^ lookUp[(crc & 0xFF) ^ data[i]];
crc = (crc >> 8) ^ LookUp[(crc & 0xFF) ^ data[i]];
crc ^= polynomial;
return crc;
}
public static uint Calculate(byte[] data)
{
return Calculate(data, 0xFFFFFFFF);
}
/// <summary>
/// A fast (native) CRC32 implementation that can be used on a pinned byte array using
/// default polynomial.
/// A CRC32 implementation that can be used on spans of bytes, with default polynomial.
/// </summary>
/// <param name="data"> [in,out] If non-null, the.</param>
/// <param name="len"> The length of the data.</param>
/// <param name="polynomial">The polynomial to XOR with.</param>
/// <returns>The calculated checksum.</returns>
public static unsafe uint Calculate(byte* data, uint len, uint polynomial)
/// <param name="data">The data from which to calculate the checksum.</param>
/// <returns>
/// The calculated checksum.
/// </returns>
public static uint Calculate(ReadOnlySpan<byte> data)
{
var crc = polynomial;
for (var i = 0; i < len; i++)
crc = (crc >> 8) ^ lookUp[(crc & 0xFF) ^ *data++];
crc ^= polynomial;
return crc;
}
public static unsafe uint Calculate(byte* data, uint len)
{
return Calculate(data, len, 0xFFFFFFFF);
return Calculate(data, 0xFFFFFFFF);
}
}
}