SabreTools/SabreTools.Hashing
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Consolidate cases in fast transform

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This commit is contained in:
Matt Nadareski
2024-11-07 02:29:51 -05:00
parent aced21c9f0
commit 16d3472fc6
1 changed files with 18 additions and 31 deletions
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49
SabreTools.Hashing/Crc/CrcTable.cs
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@@ -168,25 +168,21 @@ namespace SabreTools.Hashing.Crc
if (_processBitwise)
return false;
// Check for optimizable transformations
if (_definition.Width == 16 && _definition.ReflectIn)
{
TransformBlockFastReflect(ref hash, data, offset, length);
return true;
}
if (_definition.Width == 32 && _definition.ReflectIn)
// Only certain widths can be optimized
if (System.Array.IndexOf([16, 32, 64], _definition.Width) == -1)
return false;
// All reflection-in implementations share an optimized path
if (_definition.ReflectIn)
{
TransformBlockFastReflect(ref hash, data, offset, length);
return true;
}
// CRC-32 with no reflection-in has can be optimized
if (_definition.Width == 32 && !_definition.ReflectIn)
{
TransformBlockFast32NoReflect(ref hash, data, offset, length);
return true;
}
if (_definition.Width == 64 && _definition.ReflectIn)
{
TransformBlockFastReflect(ref hash, data, offset, length);
TransformBlockFastNoReflect(ref hash, data, offset, length);
return true;
}
@@ -237,16 +233,16 @@ namespace SabreTools.Hashing.Crc
/// <summary>
/// Optimized transformation for 32-bit CRC with no reflection
/// </summary>
private void TransformBlockFast32NoReflect(ref ulong hash, byte[] data, int offset, int length)
private void TransformBlockFastNoReflect(ref ulong hash, byte[] data, int offset, int length)
{
// Process on a copy of the hash
ulong local = hash;
// Process aligned data
if (length > 8)
if (length > 4)
{
long end = offset + (length & ~(uint)7);
length &= 7;
long end = offset + (length & ~(uint)3);
length &= 3;
while (offset < end)
{
@@ -255,21 +251,12 @@ namespace SabreTools.Hashing.Crc
+ (data[offset + 2] << 8 )
+ (data[offset + 1] << 16)
+ (data[offset + 0] << 24));
ulong high = (uint)(
+ (data[offset + 7] << 32)
+ (data[offset + 6] << 40)
+ (data[offset + 5] << 48)
+ (data[offset + 4] << 56));
offset += 8;
offset += 4;
local = _table[4, (byte)(low )]
^ _table[5, (byte)(low >> 8 )]
^ _table[6, (byte)(low >> 16 )]
^ _table[7, (byte)(low >> 24 )]
^ _table[0, (byte)(high )]
^ _table[1, (byte)(high >> 8 )]
^ _table[2, (byte)(high >> 16)]
^ _table[3, (byte)(high >> 24)];
local = _table[0, (byte)(low )]
^ _table[1, (byte)(low >> 8 )]
^ _table[2, (byte)(low >> 16)]
^ _table[3, (byte)(low >> 24)];
}
}