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Re: Missing byte using unpack, pack, read(in terms of bytes)

by BrowserUk (Patriarch)
on Jul 23, 2012 at 23:12 UTC ( #983252=note: print w/replies, xml ) Need Help??


in reply to Missing byte using unpack, pack, read(in terms of bytes)

On the basis of the code you have posted, you are making really hard work of parsing those files.

Commensurate with refining the templates for records 1 & 2 which you haven't fully described, something like this would read the entire thing:

#! perl -slw use strict; use constant { RECORD_1 => 'f512 l512', RECORD_2 => 'f3 l3', RECORD_3 => 'ff ll s2', ## index of field in rec2 that contains count of type 3 records that f +ollow it COUNT => 3, }; open I, '<:raw', $ARGV[0] or die "$ARGV[0] { $!"; my @rec1 = unpack RECORD_1, do{ local $/ = \4096; <I> }; until( eof( I ) ) { my @rec2 = unpack RECORD_2, do{ local $/ = \36; <I> }; for ( 1 .. $rec2[ COUNT ] ) { my @rec3 = unpack RECORD_3, do{ local $/ = \28; <I> }; } } close I;

Note also, that on recent versions of Perl (since 5.10), unpack can deal with little/big-endian issues for you.

Say your type 2 records contain 2 big-endian floats; followed by 2 little-endian int32s and then 2 big-endian int32s:

Use a template of:'f>2 l<2 l>2'


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