BinaryWriter File File.Open FileStream int sizeof

`BinaryReader`

This C# class handles binary files. A binary file may have thousands of integers stored in it, or another simple data type. Many files can be treated as binary.

File details

If you do not have a binary file you are trying to open already, you can create one using the BinaryWriter type. BinaryReader makes using binary data easier.

Example

Here we open the same binary file and then read in the bytes. BinaryReader here provides some useful properties. When you run the next program, you will see all the ints recovered.

Note We see that BinaryReader receives a FileStream. This is returned by File.Open.

Info The program calls ReadInt32. This method consumes 4 bytes in the binary file and turns it into an int.

Also The method advances the file read. It increments our position. This line adds 4 bytes to our position.

Here We use sizeof int. This evaluates to the integer value 4 and always will, but it might be preferable for clarity.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        R();
    }

    static void R()
    {
        // 1.
        using (BinaryReader b = new BinaryReader(
            File.Open("file.bin", FileMode.Open)))
        {
            // 2.
            // Position and length variables.
            int pos = 0;
            // 2A.
            // Use BaseStream.
            int length = (int)b.BaseStream.Length;
            while (pos < length)
            {
                // 3.
                // Read integer.
                int v = b.ReadInt32();
                Console.WriteLine(v);

                // 4.
                // Advance our position variable.
                pos += sizeof(int);
            }
        }
    }
}1
4
6
7
11
55
777
23
266
44
82
93

Performance

Most programs read in much more data than they write. I found BinaryReader substantially faster than using plain text.

Info Looking into PeekChar indicates that it performs a separate read each time it is called.

Tip This can easily multiply the time required for the BinaryReader. PeekChar should thus be avoided.

using (BinaryReader b = new BinaryReader(File.Open("file.bin", FileMode.Open)))
{
    // Do not do this.
    while (b.PeekChar() != -1)
    {
        int v = b.ReadInt32();
    }
}

Encoding

Sometimes you can fix an encoding problem by specifying Encoding.ASCII to File.Open. I do not understand why this works but it solved one of my problems.

//
// If all else fails, specify Encoding.ASCII to your File.Open call.
//
using (BinaryReader b = new BinaryReader(
    File.Open("file.bin", FileMode.Open, Encoding.ASCII)))
{
    // ...
}

Summary

This C# class is effective for reading binary files. Binary files have great advantages for performance, but they tend not to be standard and can be difficult to work with.