Efficient way to read big endian data in C#

BitConverter.ToInt32 isn't very fast in the first place. I'd simply use

public static int ToInt32BigEndian(byte[] buf, int i)
{
  return (buf[i]<<24) | (buf[i+1]<<16) | (buf[i+2]<<8) | buf[i+3];
}

You could also consider reading more than 4 bytes at a time.

As of 2019 (in fact, since .net core 2.1), there is now

byte[] buffer = ...;

BinaryPrimitives.ReadInt32BigEndian(buffer.AsSpan());

Documentation

Implementation

Related