From: Robert Klemme <shortcutter@...>
Date: 2007-03-11T20:10:07+09:00
Subject: Re: parse hex ascii

On 11.03.2007 10:44, Brian Candler wrote:
> On Sun, Mar 11, 2007 at 11:20:16AM +0900, Mark Zvilius wrote:
>> I want to parse a hex-ascii string into an array of numbers. For
>> example:
>>
>> "0164" => [1,100]
>>
>> Essentially I need to iterate through character pairs and use
>> String#hex:
>>
>> "01".hex => 1
>> "64".hex => 100
>>
>> I can do this easily enough in "C style" with an index into the string,
>> i.e. equivalent to a C "for" loop. But I'm interested in solutions that
>> are more in the "Ruby style," using an iterator.
>>
>> Suggestions?
> 
> ["01FF"].pack("H*").each_byte { |b| puts b }
> 
> or:
> 
> ["01FF"].pack("H*").unpack("C*").each { |b| puts b }
> 
> (the second form constructs an explicit array of Fixnums)

While Brian's solution is much more elegant, here's another one:

irb(main):002:0> i="0164".to_i(16)
=> 356
irb(main):003:0> a=[]
=> []
irb(main):004:0> begin; a << (i&0xFF); i/=0x100; end while i>0
=> nil
irb(main):005:0> a
=> [100, 1]

If you do not actually need the array then String#to_i might actually be 
faster / easier.  But that of course depends on what you want to do with 
the result.

Kind regards

	robert