# Unpack block? **URL:** \ **Category:** Ruby\ **Created:** [October 14, 2006, 1:14am UTC](https://www.ruby-forum.com/t/unpack-block/72075 "2006-10-14T01:14:25Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![tbobker](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/73ab20/32.png) [@tbobker](https://www.ruby-forum.com/u/tbobker)\ **Post date:** [October 14, 2006, 1:14am UTC](https://www.ruby-forum.com/t/unpack-block/72075/1 "2006-10-14T01:14:25Z")
unpack doesn’t seem to take a block. This seems like an obvious thing to want if I’m going to work with a big input string and not burn memory. Am I missing something? -Tim ---
**Author:** ![tbobker](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/73ab20/32.png) [@tbobker](https://www.ruby-forum.com/u/tbobker)\ **Post date:** [October 14, 2006, 1:46am UTC](https://www.ruby-forum.com/t/unpack-block/72075/2 "2006-10-14T01:46:40Z")
On 10/13/06, Tim B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > unpack doesn’t seem to take a block. This seems like an obvious > thing to want if I’m going to work with a big input string and not > burn memory. Am I missing something? -Tim Possibly a good idea. Lets go ahead and try it out. class String def unpack\_each(format) index = 0 loop { break if index \>= self.size - 1 yield ary = self[index…-1].unpack(format) # We can’t pack nils nor can we compact and pack too little data. break if ary.include? nil index += ary.pack(format).size } end end So it’s not the greatest code ever but it seems to work [1]: input = ([42] \* 99).pack(‘c\*’) count = 0 last = nil input.unpack\_each(‘cc’) {|a| last = a; count += 1} p count #=\> 50 p last #=\> [42, nil] Ok. boundaries should work like normal pack. Of course, it might also be a good idea to consider reading conservative chunks from whatever you are unpacking and iterating over those while unpacking but having both ways available might be nice. Brian. [1] The usual disclaimers apply. I have not build a good test suite for this because I only plan on using it as a proof of concept in this email. I recommend doing so if any of the code is used. 😉 ---
**Author:** ![tbobker](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/73ab20/32.png) [@tbobker](https://www.ruby-forum.com/u/tbobker)\ **Post date:** [October 14, 2006, 1:52am UTC](https://www.ruby-forum.com/t/unpack-block/72075/3 "2006-10-14T01:52:44Z")
On 10/13/06, Brian M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On 10/13/06, Tim B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > unpack doesn’t seem to take a block. This seems like an obvious > > thing to want if I’m going to work with a big input string and not > > burn memory. Am I missing something? -Tim > > Possibly a good idea. Lets go ahead and try it out. > > class String > def unpack\_each(format) On second thought… each\_unapck is a much better name. Brian. ---
**Author:** ![tbobker](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/73ab20/32.png) [@tbobker](https://www.ruby-forum.com/u/tbobker)\ **Post date:** [October 14, 2006, 2:04am UTC](https://www.ruby-forum.com/t/unpack-block/72075/4 "2006-10-14T02:04:46Z")
On 10/13/06, Brian M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On second thought… each\_unapck is a much better name. Shouldn’t it just be ‘unpack’, and have some ‘if block\_given?’ juice squeezed on it? ---
**Author:** ![tbobker](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/73ab20/32.png) [@tbobker](https://www.ruby-forum.com/u/tbobker)\ **Post date:** [October 14, 2006, 5:55pm UTC](https://www.ruby-forum.com/t/unpack-block/72075/5 "2006-10-14T17:55:49Z")
Hi, In message “Re: unpack block?” on Sat, 14 Oct 2006 08:14:14 +0900, Tim B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes: |unpack doesn’t seem to take a block. This seems like an obvious |thing to want if I’m going to work with a big input string and not |burn memory. Am I missing something? -Tim No, it’s a quite interesting idea. I implemented it with a few minutes hack. I will check it in later and try to see how it works (in HEAD, of course). ``` matz. ``` ---
**Author:** ![tbobker](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/73ab20/32.png) [@tbobker](https://www.ruby-forum.com/u/tbobker)\ **Post date:** [October 14, 2006, 5:35pm UTC](https://www.ruby-forum.com/t/unpack-block/72075/6 "2006-10-14T17:35:45Z")
On 10/13/06, Wilson B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > def unpack\_each(format) > > > > On second thought… each\_unapck is a much better name. > > Shouldn’t it just be ‘unpack’, and have some ‘if block\_given?’ juice > squeezed on it? Not when I am monkey patching [1] like this. If I felt like writing a worthwhile implementation… then that might happen. I am an advocate of intelligent interfaces but I am also an advocate of avoiding too many invasive changes when they really aren’t needed. It is perfectly sensible to play around with this using a name each\_unpack. And it is a sort of iteration… like each\_line and each\_byte, we get repeated results from a sort of scan like transformation process. Each series of unpacked array… I think it fits. Anyway… I sound like a broken record. Just woke up from the aftermath of an 8 hour long party at my apartment here in NYC. 😉 Brian. [1] I have no problem reopening classes but when I override something I always take great care to minimize change. If this is so great, we could merge the idea into ruby’s code base and call it standard.