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[C#] Improve Span<> utilization (#8588)

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There are a couple instances where the ByteBuffer's Span property was accessed in a loop.
 + Extracted the use of the property outside of the loop to save a few cpu cycles.

Access to the allocator's internal buffer isn't exposed as a ReadOnlySpan<byte> from the ByteBuffer
or the FlatBufferBuilder.
 + Added a few convenience functions to access the buffer using a ReadOnlySpan<byte>.

There are a few cases where built in Span extensions can be used to run optimized code.
 + Added the use of Span.Fill() and ReadOnlySpan.SequenceCompareTo to replace existing loops.

Co-authored-by: Björn Harrtell <bjornharrtell@users.noreply.github.com>
Co-authored-by: Wouter van Oortmerssen <aardappel@gmail.com>
This commit is contained in:
bigjt
2025-08-28 19:06:18 -04:00
committed by GitHub
parent a6b337f803
commit 82396fa0fe
3 changed files with 45 additions and 6 deletions
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23
net/FlatBuffers/ByteBuffer.cs
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@@ -275,6 +275,11 @@ namespace Google.FlatBuffers
}
#if ENABLE_SPAN_T && UNSAFE_BYTEBUFFER
public ReadOnlySpan<byte> ToSizedReadOnlySpan()
{
return _buffer.ReadOnlySpan.Slice(Position, Length - Position);
}
public ReadOnlyMemory<byte> ToReadOnlyMemory(int pos, int len)
{
return _buffer.ReadOnlyMemory.Slice(pos, len);
@@ -289,6 +294,11 @@ namespace Google.FlatBuffers
{
return _buffer.Span.Slice(pos, len);
}
public ReadOnlySpan<byte> ToReadOnlySpan(int pos, int len)
{
return _buffer.ReadOnlySpan.Slice(pos, len);
}
#else
public ArraySegment<byte> ToArraySegment(int pos, int len)
{
@@ -380,18 +390,19 @@ namespace Google.FlatBuffers
#elif ENABLE_SPAN_T
protected void WriteLittleEndian(int offset, int count, ulong data)
{
Span<byte> span = _buffer.Span.Slice(offset, count);
if (BitConverter.IsLittleEndian)
{
for (int i = 0; i < count; i++)
{
_buffer.Span[offset + i] = (byte)(data >> i * 8);
span[i] = (byte)(data >> i * 8);
}
}
else
{
for (int i = 0; i < count; i++)
{
_buffer.Span[offset + count - 1 - i] = (byte)(data >> i * 8);
span[count - 1 - i] = (byte)(data >> i * 8);
}
}
}
@@ -399,19 +410,20 @@ namespace Google.FlatBuffers
protected ulong ReadLittleEndian(int offset, int count)
{
AssertOffsetAndLength(offset, count);
ReadOnlySpan<byte> span = _buffer.ReadOnlySpan.Slice(offset, count);
ulong r = 0;
if (BitConverter.IsLittleEndian)
{
for (int i = 0; i < count; i++)
{
r |= (ulong)_buffer.Span[offset + i] << i * 8;
r |= (ulong)span[i] << i * 8;
}
}
else
{
for (int i = 0; i < count; i++)
{
r |= (ulong)_buffer.Span[offset + count - 1 - i] << i * 8;
r |= (ulong)span[count - 1 - i] << i * 8;
}
}
return r;
@@ -445,8 +457,7 @@ namespace Google.FlatBuffers
{
AssertOffsetAndLength(offset, sizeof(byte) * count);
Span<byte> span = _buffer.Span.Slice(offset, count);
for (var i = 0; i < span.Length; ++i)
span[i] = value;
span.Fill(value);
}
#else
public void PutSbyte(int offset, sbyte value)