Unpack a bit from a binary string with Ruby

Question

I'm using String::unpack to unpack a bunch of ints and double from a binary stream. How can I unpack a single bit from that bitstream? I cannot find a specific directive for decoding single bits with unpack.

bandi · Accepted Answer · 2011-04-22 08:26:02Z

3

Unpacking can go down to the byte level. You could read an unsigned byte by using the 'C' format and then you can use bitmasks to query individual maps.

answered Apr 22, 2011 at 8:26

bandi

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2 Comments

Anthony Liekens Over a year ago

Do I risk going out of bounds when the bit is at the end of the stream and reading 7 more bits using the 'C' directive?

bandi Over a year ago

@aliekens I don't think so. By the time the stream gets into to ruby it must consist of bytes. There no such thing as a partial byte. If the data is only 9 bits then it will be represented as 2 bytes and the rest will be padded with zeros.

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