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reuse reflected table generator #1

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Merged
merged 1 commit into from
Nov 17, 2021
Merged

reuse reflected table generator #1

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34 changes: 34 additions & 0 deletions src/libraries/Common/src/System/Numerics/Crc32ReflectedTable.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

namespace System.Numerics
{
internal class Crc32ReflectedTable
{
internal static uint[] Generate(uint reflectedPolynomial)
{
uint[] table = new uint[256];

for (int i = 0; i < 256; i++)
{
uint val = (uint)i;

for (int j = 0; j < 8; j++)
{
if ((val & 0b0000_0001) == 0)
{
val >>= 1;
}
else
{
val = (val >> 1) ^ reflectedPolynomial;
}
}

table[i] = val;
}

return table;
}
}
}
3 changes: 3 additions & 0 deletions src/libraries/System.IO.Hashing/src/System.IO.Hashing.csproj
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Expand Up @@ -22,6 +22,9 @@ System.IO.Hashing.XxHash32</PackageDescription>
<Compile Include="System\IO\Hashing\XxHash64.cs" />
<Compile Include="System\IO\Hashing\XxHash64.State.cs" />
<Compile Include="System\IO\Hashing\NonCryptographicHashAlgorithm.cs" />
<Compile Include="$(CommonPath)System\Numerics\Crc32ReflectedTable.cs">
<Link>Common\System\Numerics\Crc32ReflectedTable.cs</Link>
</Compile>
</ItemGroup>
<ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
<Reference Include="System.Buffers" />
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30 changes: 3 additions & 27 deletions src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32.Table.cs
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@@ -1,6 +1,8 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Numerics;

namespace System.IO.Hashing
{
public sealed partial class Crc32 : NonCryptographicHashAlgorithm
Expand All @@ -9,32 +11,6 @@ public sealed partial class Crc32 : NonCryptographicHashAlgorithm
// While this implementation is based on the standard CRC-32 polynomial,
// x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x1 + x0,
// this version uses reflected bit ordering, so 0x04C11DB7 becomes 0xEDB88320
private static readonly uint[] s_crcLookup = GenerateReflectedTable(0xEDB88320u);

private static uint[] GenerateReflectedTable(uint reflectedPolynomial)
{
uint[] table = new uint[256];

for (int i = 0; i < 256; i++)
{
uint val = (uint)i;

for (int j = 0; j < 8; j++)
{
if ((val & 0b0000_0001) == 0)
{
val >>= 1;
}
else
{
val = (val >> 1) ^ reflectedPolynomial;
}
}

table[i] = val;
}

return table;
}
private static readonly uint[] s_crcLookup = Crc32ReflectedTable.Generate(0xEDB88320u);
}
}
3 changes: 3 additions & 0 deletions src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
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Expand Up @@ -1197,6 +1197,9 @@
<Compile Include="$(CommonPath)System\NotImplemented.cs">
<Link>Common\System\NotImplemented.cs</Link>
</Compile>
<Compile Include="$(CommonPath)System\Numerics\Crc32ReflectedTable.cs">
<Link>Common\System\Numerics\Crc32ReflectedTable.cs</Link>
</Compile>
<Compile Include="$(CommonPath)System\Obsoletions.cs">
<Link>Common\System\Obsoletions.cs</Link>
</Compile>
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36 changes: 1 addition & 35 deletions src/libraries/System.Private.CoreLib/src/System/Numerics/BitOperations.cs
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Expand Up @@ -41,41 +41,7 @@ public static class BitOperations
19, 27, 23, 06, 26, 05, 04, 31
};

private static readonly uint[] s_crcTable = new uint[]
{
0x0, 0xF26B8303, 0xE13B70F7, 0x1350F3F4, 0xC79A971F, 0x35F1141C, 0x26A1E7E8, 0xD4CA64EB,
0x8AD958CF, 0x78B2DBCC, 0x6BE22838, 0x9989AB3B, 0x4D43CFD0, 0xBF284CD3, 0xAC78BF27, 0x5E133C24,
0x105EC76F, 0xE235446C, 0xF165B798, 0x30E349B, 0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384,
0x9A879FA0, 0x68EC1CA3, 0x7BBCEF57, 0x89D76C54, 0x5D1D08BF, 0xAF768BBC, 0xBC267848, 0x4E4DFB4B,
0x20BD8EDE, 0xD2D60DDD, 0xC186FE29, 0x33ED7D2A, 0xE72719C1, 0x154C9AC2, 0x61C6936, 0xF477EA35,
0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5, 0x6DFE410E, 0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA,
0x30E349B1, 0xC288CAB2, 0xD1D83946, 0x23B3BA45, 0xF779DEAE, 0x5125DAD, 0x1642AE59, 0xE4292D5A,
0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A, 0x7DA08661, 0x8FCB0562, 0x9C9BF696, 0x6EF07595,
0x417B1DBC, 0xB3109EBF, 0xA0406D4B, 0x522BEE48, 0x86E18AA3, 0x748A09A0, 0x67DAFA54, 0x95B17957,
0xCBA24573, 0x39C9C670, 0x2A993584, 0xD8F2B687, 0xC38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198,
0x5125DAD3, 0xA34E59D0, 0xB01EAA24, 0x42752927, 0x96BF4DCC, 0x64D4CECF, 0x77843D3B, 0x85EFBE38,
0xDBFC821C, 0x2997011F, 0x3AC7F2EB, 0xC8AC71E8, 0x1C661503, 0xEE0D9600, 0xFD5D65F4, 0xF36E6F7,
0x61C69362, 0x93AD1061, 0x80FDE395, 0x72966096, 0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789,
0xEB1FCBAD, 0x197448AE, 0xA24BB5A, 0xF84F3859, 0x2C855CB2, 0xDEEEDFB1, 0xCDBE2C45, 0x3FD5AF46,
0x7198540D, 0x83F3D70E, 0x90A324FA, 0x62C8A7F9, 0xB602C312, 0x44694011, 0x5739B3E5, 0xA55230E6,
0xFB410CC2, 0x92A8FC1, 0x1A7A7C35, 0xE811FF36, 0x3CDB9BDD, 0xCEB018DE, 0xDDE0EB2A, 0x2F8B6829,
0x82F63B78, 0x709DB87B, 0x63CD4B8F, 0x91A6C88C, 0x456CAC67, 0xB7072F64, 0xA457DC90, 0x563C5F93,
0x82F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043, 0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C,
0x92A8FC17, 0x60C37F14, 0x73938CE0, 0x81F80FE3, 0x55326B08, 0xA759E80B, 0xB4091BFF, 0x466298FC,
0x1871A4D8, 0xEA1A27DB, 0xF94AD42F, 0xB21572C, 0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033,
0xA24BB5A6, 0x502036A5, 0x4370C551, 0xB11B4652, 0x65D122B9, 0x97BAA1BA, 0x84EA524E, 0x7681D14D,
0x2892ED69, 0xDAF96E6A, 0xC9A99D9E, 0x3BC21E9D, 0xEF087A76, 0x1D63F975, 0xE330A81, 0xFC588982,
0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D, 0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622,
0x38CC2A06, 0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2, 0xFF56BD19, 0xD3D3E1A, 0x1E6DCDEE, 0xEC064EED,
0xC38D26C4, 0x31E6A5C7, 0x22B65633, 0xD0DDD530, 0x417B1DB, 0xF67C32D8, 0xE52CC12C, 0x1747422F,
0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF, 0x8ECEE914, 0x7CA56A17, 0x6FF599E3, 0x9D9E1AE0,
0xD3D3E1AB, 0x21B862A8, 0x32E8915C, 0xC083125F, 0x144976B4, 0xE622F5B7, 0xF5720643, 0x7198540,
0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90, 0x9E902E7B, 0x6CFBAD78, 0x7FAB5E8C, 0x8DC0DD8F,
0xE330A81A, 0x115B2B19, 0x20BD8ED, 0xF0605BEE, 0x24AA3F05, 0xD6C1BC06, 0xC5914FF2, 0x37FACCF1,
0x69E9F0D5, 0x9B8273D6, 0x88D28022, 0x7AB90321, 0xAE7367CA, 0x5C18E4C9, 0x4F48173D, 0xBD23943E,
0xF36E6F75, 0x105EC76, 0x12551F82, 0xE03E9C81, 0x34F4F86A, 0xC69F7B69, 0xD5CF889D, 0x27A40B9E,
0x79B737BA, 0x8BDCB4B9, 0x988C474D, 0x6AE7C44E, 0xBE2DA0A5, 0x4C4623A6, 0x5F16D052, 0xAD7D5351
};
private static readonly uint[] s_crcTable = Crc32ReflectedTable.Generate(0x82F63B78u);

/// <summary>
/// Evaluate whether a given integral value is a power of 2.
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