Platob commented on code in PR #35299:
URL: https://github.com/apache/arrow/pull/35299#discussion_r1186649052
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csharp/src/Apache.Arrow/Builder/BufferBuilder.cs:
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@@ -0,0 +1,356 @@
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Apache.Arrow.Memory;
+
+namespace Apache.Arrow.Builder
+{
+ public class BufferBuilder : IBufferBuilder
+ {
+ public class BitBuffer
+ {
+ private readonly bool[] _bits;
+
+ public int Length { get; private set; }
+ public int AvailableLength => Capacity - Length;
+
+ public int Capacity;
+
+ public bool IsFull => Length == Capacity;
+ public byte ToByte(ref byte data) => BitUtility.ToByte(ref data,
_bits);
+
+ public BitBuffer(int capacity = 8)
+ {
+ Capacity = capacity;
+ _bits = new bool[capacity];
+ Length = 0;
+ }
+
+ public void Append(bool bit) => _bits[Length++] = bit;
+ public void Fill(ReadOnlySpan<bool> bits)
+ {
+ bits.CopyTo(_bits.AsSpan().Slice(Length, bits.Length));
+ Length += bits.Length;
+ }
+
+ public void Reset()
+ {
+ for (int i = 0; i < _bits.Length; i++)
+ {
+ _bits[i] = false;
+ }
+ Length = 0;
+ }
+ }
+
+ private const int DefaultCapacity = 64;
+ public int ByteLength { get; private set; }
+
+ public Memory<byte> Memory { get; private set; }
+ public BitBuffer BitOverhead { get; }
Review Comment:
Same for sequential append it looks better, thus it scales good with larger
value range
Old was in mean 1183 Ticks vs 938 Ticks for the new
```csharp
[Fact]
public void Bench()
{
output.WriteLine($"Elapsed {ElapsedTicks(100000, MakeOld)}");
output.WriteLine($"Elapsed {ElapsedTicks(100000, MakeNew)}");
}
private static void MakeNew()
{
var builder = new BufferBuilder(64);
for (int i = 0; i < 1000; i++)
builder.AppendBit(true);
builder.Build();
}
private static void MakeOld()
{
var builder = new ArrowBuffer.BitmapBuilder(64);
for (int i = 0; i < 1000; i++)
builder.Append(true);
builder.Build();
}
```
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