Faster (unsafe) BinaryReader in .NET

Question

I came across a situation where I have a pretty big file that I need to read binary data from.

Consequently, I realized that the default BinaryReader implementation in .

Answer 1

I ran into a similar performance issue with BinaryReader/FileStream, and after profiling, I discovered that the problem isn't with FileStream buffering, but instead with this line:

while (br.BaseStream.Position < br.BaseStream.Length) {

Specifically, the property br.BaseStream.Length on a FileStream makes a (relatively) slow system call to get the file size on each loop. After changing the code to this:

long length = br.BaseStream.Length;
while (br.BaseStream.Position < length) {

and using an appropriate buffer size for the FileStream, I achieved similar performance to the MemoryStream example.