Whenever I do much with pack/unpack, I'm reminded that these really need to support stream operations.

unpack needs to be able to read from a stream or, more likely, to start reading at pos($input) and to set pos($input) to note where it left off (in other words, treat the input string as a stream).

You can already do print STREAM pack ... so pack doesn't really need to be able to write to a stream. But it'd be cool if pack supported starting at pos($string) and overwriting as many bytes after that as needed and setting pos($string) to where it left off at.

I even started writing a module to implement such. But I didn't finish and now pack/unpack have gotten quite a bit fancier such that this either needs to be patched directly into pack/unpack or (at least) they need some introspection features added to make implementing these in a module reasonable/possible.

For example "." could be the format for "current seek offset" which you could use like: 

my( $z, $zEnd, $i, $iEnd )= unpack "z.I.", $buf;
# $zEnd == length($z)
# $iEnd == 4 + $zEnd

my( $z, $i )= getData();
my $buf= pack "z.I.", $z, my $zEnd, $i, my $iEnd;
# $zEnd == length($z)
# $iEnd == 4 + $zEnd

[download]

- tye        

In reply to Re: How much was unpack()ed? (stream) by tye
in thread How much was unpack()ed? by Stevie-O

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.