How to write/read bits from/to a Stream? (C#)

c#

Solution

You could create an extension method on Stream that enumerates the bits, like this:

public static class StreamExtensions
{
    public static IEnumerable<bool> ReadBits(this Stream input)
    {
        if (input == null) throw new ArgumentNullException("input");
        if (!input.CanRead) throw new ArgumentException("Cannot read from input", "input");
        return ReadBitsCore(input);
    }

    private static IEnumerable<bool> ReadBitsCore(Stream input)
    {
        int readByte;
        while((readByte = input.ReadByte()) >= 0)
        {
            for(int i = 7; i >= 0; i--)
                yield return ((readByte >> i) & 1) == 1;
        }
    }
}

Using this extension method is easy:

foreach(bool bit in stream.ReadBits())
{
    // do something with the bit
}

Attention: you should not call ReadBits multiple times on the same Stream, otherwise the subsequent calls will forget the current bit position and will just start reading the next byte.

Problem

Original source