Parsing a binary file in Ruby

Question

I need to be able to parse a binary file with Ruby. This file contains chunks of data that are found via a header that includes the file offset and length of each chunk.

How do I get the data out correctly? I've been unable so far to seek around in the file based on the offsets I read out since they come out in strings that I don't know how to convert to a format IO#seek understands.

Any help? A general way to convert the offset and length into something usable (like an integer or something) would be helpful.

hhaamu · Accepted Answer · 2009-07-23 19:11:32Z

6

You want String#unpack.

answered Jul 23, 2009 at 19:11

hhaamu

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2 Comments

Robert Rouse Over a year ago

That was it. unpack('L*') is what I needed.

hhaamu Over a year ago

You should be explicitly using the little-endian or big-endian unpacks instead of native-endian, to keep a bit of portability.

Pierre Riteau · Accepted Answer · 2009-07-24 11:15:45Z

2

You could also take a look at BitStruct which offers a nice high-level interface for parsing binary data.

answered Jul 24, 2009 at 11:15

Pierre Riteau

Comments

aaron · Accepted Answer · 2011-08-10 18:06:09Z

2

Check out the BinData gem, and the alternatives it lists:

http://bindata.rubyforge.org/#alternatives

answered Aug 10, 2011 at 18:06

aaron

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