I'm just looking for historical context on this method. It looks like
one of those old-school Unix-isms that must have been incredibly
useful in the past but never comes up in the course of run-of-the-mill
Web programming. I'm pretty sure I first saw it ten years ago in Perl
and never once used it myself. I think I did copy/paste it in some
encryption code or something related, but I'm not sure. Just
wondering, what's it for? Who uses it, and why?
···
--
Giles Bowkett
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/
Giles Bowkett wrote:
I'm just looking for historical context on this method. It looks like
one of those old-school Unix-isms that must have been incredibly
useful in the past but never comes up in the course of run-of-the-mill
Web programming. I'm pretty sure I first saw it ten years ago in Perl
and never once used it myself. I think I did copy/paste it in some
encryption code or something related, but I'm not sure. Just
wondering, what's it for? Who uses it, and why?
Array#pack and String#unpack are useful for handling _binary_ network protocols and file formats.
···
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
String#unpack, along with its partner Array#pack is used for dealing
with binary input and output streams respectively.
···
On 10/26/07, Giles Bowkett <gilesb@gmail.com> wrote:
I'm just looking for historical context on this method. It looks like
one of those old-school Unix-isms that must have been incredibly
useful in the past but never comes up in the course of run-of-the-mill
Web programming. I'm pretty sure I first saw it ten years ago in Perl
and never once used it myself. I think I did copy/paste it in some
encryption code or something related, but I'm not sure. Just
wondering, what's it for? Who uses it, and why?
--
Rick DeNatale
My blog on Ruby
http://talklikeaduck.denhaven2.com/
Giles Bowkett wrote:
I'm just looking for historical context on this method. It looks like
one of those old-school Unix-isms that must have been incredibly
useful in the past but never comes up in the course of run-of-the-mill
Web programming. I'm pretty sure I first saw it ten years ago in Perl
and never once used it myself. I think I did copy/paste it in some
encryption code or something related, but I'm not sure. Just
wondering, what's it for? Who uses it, and why?
--
Giles Bowkett
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/
Since it came up here and is somewhat related: I recently wrote out of
fun some wrapper methods to make it a bit nicer to read/write binary
datastructures. IMHO it's a bit cumbersome to do things like:
size = socket.read(4).unpack("I").first
meta = SomeStruct.new(*socket.read(x).unpack(format))
data = socket.read(size)
The wrappers are attached and here: http://pastie.caboo.se/111365
Use it at your own risk 
Regards
Stefan
Attachments:
http://www.ruby-forum.com/attachment/790/packed.rb
···
--
Posted via http://www.ruby-forum.com/\.
> encryption code or something related, but I'm not sure. Just
> wondering, what's it for? Who uses it, and why?
Array#pack and String#unpack are useful for handling _binary_ network
protocols and file formats.
So would this be accurate? Use cases would include implementing
graphics formats and extracting text from proprietary-format word
processor files?
···
--
Giles Bowkett
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/
Stefan Rusterholz wrote:
Since it came up here and is somewhat related: I recently wrote out of fun some wrapper methods to make it a bit nicer to read/write binary datastructures. IMHO it's a bit cumbersome to do things like:
size = socket.read(4).unpack("I").first
meta = SomeStruct.new(*socket.read(x).unpack(format))
data = socket.read(size)
See also:
binaryparse
bindata
bitstruct
The first two are gems, the last is tgz, available at BitStruct (that one's mine).
···
--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
Right. I wrote about that some in the summary to this quiz:
http://www.rubyquiz.com/quiz136.html
James Edward Gray II
···
On Oct 26, 2007, at 1:22 PM, Giles Bowkett wrote:
encryption code or something related, but I'm not sure. Just
wondering, what's it for? Who uses it, and why?
Array#pack and String#unpack are useful for handling _binary_ network
protocols and file formats.
So would this be accurate? Use cases would include implementing
graphics formats and extracting text from proprietary-format word
processor files?
Here's a real world example where I am trying to figure out how to use
string#unpack. I'm using the ruby-net-ldap library to pull info from Active
Directory. One of the fields, objectguid, comes back as a binary field. I
need to be able to compare it to (I think, I'm no expert here) what looks
like a hexidecimal representation of this field. So, I'm trying to figure
out how to convert this binary field I get back from Active Directory, into
a hexidecimal field. I think I need to use the unpack method, but I haven't
figured out what format string to pass the method yet.
Didn't mean to hijack the thread, just thought it kind of tied in with what
you were asking.
Jamey Cribbs
···
On 10/26/07, Giles Bowkett <gilesb@gmail.com> wrote:
> > encryption code or something related, but I'm not sure. Just
> > wondering, what's it for? Who uses it, and why?
>
> Array#pack and String#unpack are useful for handling _binary_ network
> protocols and file formats.
So would this be accurate? Use cases would include implementing
graphics formats and extracting text from proprietary-format word
processor files?
--
Giles Bowkett
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/
Anything that's encoded (URL-encoding, for instance), binary encoding.
Binary data sent down from pipes/sockets, etc.
Just look at the formatting options for it.
-- Thomas Adam
···
On 26/10/2007, Giles Bowkett <gilesb@gmail.com> wrote:
> > encryption code or something related, but I'm not sure. Just
> > wondering, what's it for? Who uses it, and why?
>
> Array#pack and String#unpack are useful for handling _binary_ network
> protocols and file formats.
So would this be accurate? Use cases would include implementing
graphics formats and extracting text from proprietary-format word
processor files?
Giles Bowkett wrote:
> encryption code or something related, but I'm not sure. Just
> wondering, what's it for? Who uses it, and why?
Array#pack and String#unpack are useful for handling _binary_ network
protocols and file formats.
So would this be accurate? Use cases would include implementing
graphics formats and extracting text from proprietary-format word
processor files?
I had occasion to use these methods in code dealing with IPTC (image)
metadata.
···
--
Posted via http://www.ruby-forum.com/\.
> So would this be accurate? Use cases would include implementing
> graphics formats and extracting text from proprietary-format word
> processor files?
Anything that's encoded (URL-encoding, for instance), binary encoding.
Binary data sent down from pipes/sockets, etc.
Just look at the formatting options for it.
I think that's one of the times I've used it. URL-decoding in Perl
before the days of CGI.pm. I think I've seen it or used it in
JavaScript that way as well, actually, for URLs.
···
--
Giles Bowkett
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/
Here's a real world example where I am trying to figure out how to use
string#unpack. I'm using the ruby-net-ldap library to pull info from Active
Directory. One of the fields, objectguid, comes back as a binary field. I
need to be able to compare it to (I think, I'm no expert here) what looks
like a hexidecimal representation of this field. So, I'm trying to figure
out how to convert this binary field I get back from Active Directory, into
a hexidecimal field. I think I need to use the unpack method, but I haven't
figured out what format string to pass the method yet.
Didn't mean to hijack the thread, just thought it kind of tied in with what
you were asking.
Here's a Perl snippet that seems to do it:
$binary = unpack("B32", pack("N", hex($hex)));
presumably the Ruby equivalent would be similar. although actually I
think this converts hex to binary instead of converting binary to hex.
There's a Perl tutorial on it
(http://perldoc.perl.org/perlpacktut.html\) but I don't know how much
the syntax for pack/unpack statements in Perl and Ruby conform or
differ. Seems like an old-school Unix DSL, like regexen.
···
--
Giles Bowkett
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com/