ovska opened a new issue, #34636:
URL: https://github.com/apache/arrow/issues/34636
### Describe the enhancement requested
Quick single-use buffers are rented using [helper
methods](/apache/arrow/blob/main/csharp/src/Apache.Arrow/Extensions/ArrayPoolExtensions.cs)
that cause a (small) allocation on every invocation due to the delegate
capturing references to the reader/writer and other related variables. This
somewhat defeats the purpose of using pooled arrays, especially small ones for
quick operations such as reading the message length.
Here's a reference implementation for achieving roughly the same convenience
without any allocations (outside the ones the pool might make):
```csharp
public readonly struct ArrayLease : IDisposable
{
private readonly byte[] _array;
private readonly ArrayPool<byte> _pool;
public ArrayLease(byte[] array, ArrayPool<byte> pool)
{
_array = array;
_pool = pool;
}
public void Dispose()
{
_pool.Return(_array);
}
}
public static ArrayLease RentReturn(this ArrayPool<byte> pool, int length,
out Memory<byte> buffer)
{
byte[] array = pool.Rent(length);
buffer = array.AsMemory(0, length);
return new ArrayLease(array, pool);
}
```
Example usage:
```diff
- await Buffers.RentReturnAsync(4, async (buffer) =>
+ using (Buffers.RentReturn(4, out Memory<byte> buffer))
{
int footerLength;
checked
{
footerLength = (int)(BaseStream.Position - offset);
}
BinaryPrimitives.WriteInt32LittleEndian(buffer.Span, footerLength);
await BaseStream.WriteAsync(buffer,
cancellationToken).ConfigureAwait(false);
- }).ConfigureAwait(false);
+ }
```
### Component(s)
C#
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