From: Robert Klemme <shortcutter@...>
Date: 2009-07-01T00:26:12+09:00
Subject: Re: Question on networking with custom binary interface.

2009/6/30 Greg Chambers <gregory.w.chambers@gmail.com>:
> Joel VanderWerf wrote:
>> Greg Chambers wrote:
>>> Any advice for doing this type of binary IO?
>>
>> Array#pack, String#unpack are your friends.
>
> I am looking at the documentation of these methods and this covers a LOT
> of what I need to do, but I am worried in a couple areas.  For example,
> part of the binary string I will be getting will contain an eight byte
> unsigned long long.  How should I approach custom byte structures like
> this?

irb(main):004:0> s = (1..8).map {|x| x.chr}.join
=> "\x01\x02\x03\x04\x05\x06\a\b"
irb(main):005:0> x = s.unpack "Q"
=> [578437695752307201]
irb(main):006:0> x.first.class
=> Bignum

If you need more flexibility you can do something like this

irb(main):009:0> s.unpack("N2").inject(0) {|s,a| s << 32 | a}
=> 72623859790382856
irb(main):010:0> s.unpack("L2").inject(0) {|s,a| s << 32 | a}
=> 289077004534744581

Note, I did not bother to check byte orderings which you can easily
guess from the different results.  This is just an illustration to
give you an idea.

Kind regards

robert


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