How do I replicate this specific pack example in crystal?

Question

Ruby code sample:

"\u0000\u0000\u0000\u0002".unpack('N')[0]  #=> 2

How can I do this with crystal language?

See [this issue](https://github.com/crystal-lang/crystal/issues/276) on the Crystal GitHub. — Joe Clay, Nov 30 '17 at 16:38
Possible duplicated of https://stackoverflow.com/questions/32725506/pack-the-contents-of-arr-into-a-binary-sequence-in-crystal — Vitalii Elenhaupt, Nov 30 '17 at 17:46
I think the question is not "how do I use unpack in crystal", it's "how do I replicate this *specific* pack example in crystal", which is not a duplicate. perhaps the question could be phrased more generically though. — Stephie, Nov 30 '17 at 19:32

score 6 · Accepted Answer · edited Dec 01 '17 at 08:33

6

You can use the IO#read_bytes method to read integers from many places. For example

io = IO::Memory.new("\u0000\u0000\u0000\u0002")
io.read_bytes(UInt32, format: IO::ByteFormat::NetworkEndian) # => 2

I would advise against using strings to store binary data though, reading directly from IO, or storing using the Bytes type is much more idiomatic Crystal.

edited Dec 01 '17 at 08:33

Vitalii Elenhaupt

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answered Nov 30 '17 at 19:38

Stephie

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How do I replicate this specific pack example in crystal?

1 Answers1