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GH-45559: [C#] Increasing performance by avoiding array allocation everytime method gets used #45609

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GH-45559: [C#] Increasing performance by avoiding array allocation everytime method gets used #45609

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32 changes: 14 additions & 18 deletions csharp/src/Apache.Arrow/BitUtility.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ namespace Apache.Arrow
{
public static class BitUtility
{
private static ReadOnlySpan<byte> PopcountTable => new byte[] {
private static readonly byte[] s_popcountTable = [
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
Expand All @@ -31,35 +31,31 @@ public static class BitUtility
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
};
];

private static ReadOnlySpan<byte> BitMask => new byte[] {
private static readonly byte[] s_bitMask = [
1, 2, 4, 8, 16, 32, 64, 128
};
];

public static bool GetBit(byte data, int index) =>
((data >> index) & 1) != 0;

public static bool GetBit(ReadOnlySpan<byte> data, int index) =>
(data[index / 8] & BitMask[index % 8]) != 0;
(data[index / 8] & s_bitMask[index % 8]) != 0;

public static void ClearBit(Span<byte> data, int index)
{
data[index / 8] &= (byte) ~BitMask[index % 8];
}
public static void ClearBit(Span<byte> data, int index) =>
data[index / 8] &= (byte)~s_bitMask[index % 8];

public static void SetBit(Span<byte> data, int index)
{
data[index / 8] |= BitMask[index % 8];
}
public static void SetBit(Span<byte> data, int index) =>
data[index / 8] |= s_bitMask[index % 8];

public static void SetBit(Span<byte> data, int index, bool value)
{
int idx = index / 8;
int mod = index % 8;
data[idx] = value
? (byte)(data[idx] | BitMask[mod])
: (byte)(data[idx] & ~BitMask[mod]);
? (byte)(data[idx] | s_bitMask[mod])
: (byte)(data[idx] & ~s_bitMask[mod]);
}

/// <summary>
Expand Down Expand Up @@ -125,7 +121,7 @@ internal static void SetBits(Span<byte> data, int index, int length, bool value)

public static void ToggleBit(Span<byte> data, int index)
{
data[index / 8] ^= BitMask[index % 8];
data[index / 8] ^= s_bitMask[index % 8];
}

/// <summary>
Expand Down Expand Up @@ -210,7 +206,7 @@ public static int CountBits(ReadOnlySpan<byte> data)
{
int count = 0;
foreach (byte t in data)
count += PopcountTable[t];
count += s_popcountTable[t];
return count;
}

Expand Down Expand Up @@ -266,4 +262,4 @@ internal static int ReadInt32(ReadOnlyMemory<byte> value)
return Unsafe.ReadUnaligned<int>(ref MemoryMarshal.GetReference(value.Span));
}
}
}
}