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.\" ========================================================================
.\"
.IX Title "Parse::Binary::FixedFormat 3pm"
.TH Parse::Binary::FixedFormat 3pm "2018-12-20" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Parse::Binary::FixedFormat \- Convert between fixed\-length fields and hashes
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&   use Parse::Binary::FixedFormat;
\&
\&   my $tarhdr =
\&      new Parse::Binary::FixedFormat [ qw(name:a100 mode:a8 uid:a8 gid:a8 size:a12
\&                                 mtime:a12 chksum:a8 typeflag:a1 linkname:a100
\&                                 magic:a6 version:a2 uname:a32 gname:a32
\&                                 devmajor:a8 devminor:a8 prefix:a155) ];
\&   my $buf;
\&   read TARFILE, $buf, 512;
\&
\&   # create a hash from the buffer read from the file
\&   my $hdr = $tarhdr\->unformat($buf);   # $hdr gets a hash ref
\&
\&   # create a flat record from a hash reference
\&   my $buf = $tarhdr\->format($hdr);     # $hdr is a hash ref
\&
\&   # create a hash for a new record
\&   my $newrec = $tarhdr\->blank();
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBParse::Binary::FixedFormat\fR can be used to convert between a buffer with
fixed-length field definitions and a hash with named entries for each
field.  The perl \f(CW\*(C`pack\*(C'\fR and \f(CW\*(C`unpack\*(C'\fR functions are used to perform
the conversions.  \fBParse::Binary::FixedFormat\fR builds the format string by
concatenating the field descriptions and converts between the lists
used by \f(CW\*(C`pack\*(C'\fR and \f(CW\*(C`unpack\*(C'\fR and a hash that can be reference by
field name.
.SH "METHODS"
.IX Header "METHODS"
\&\fBParse::Binary::FixedFormat\fR provides the following methods.
.SS "new"
.IX Subsection "new"
To create a converter, invoke the \fBnew\fR method with a reference to a
list of field specifications.
.PP
.Vb 2
\&    my $cvt =
\&        new Parse::Binary::FixedFormat [ \*(Aqfield\-name:descriptor:count\*(Aq, ... ];
.Ve
.PP
Field specifications contain the following information.
.IP "field-name" 4
.IX Item "field-name"
This is the name of the field and will be used as the hash index.
.IP "descriptor" 4
.IX Item "descriptor"
This describes the content and size of the field.  All of the
descriptors get strung together and passed to \fBpack\fR and \fBunpack\fR as
part of the template argument.  See \fBperldoc \-f pack\fR for information
on what can be specified here.
.Sp
Don't use repeat counts in the descriptor except for string types
(\*(L"a\*(R", \*(L"A\*(R", \*(L"h, \*(R"H\*(L", and \*(R"Z").  If you want to get an array out of the
buffer, use the \f(CW\*(C`count\*(C'\fR argument.
.IP "count" 4
.IX Item "count"
This specifies a repeat count for the field.  If specified as a
non-zero value, this field's entry in the resultant hash will be an
array reference instead of a scalar.
.SS "unformat"
.IX Subsection "unformat"
To convert a buffer of data into a hash, pass the buffer to the
\&\fBunformat\fR method.
.PP
.Vb 1
\&    $hashref = $cvt\->unformat($buf);
.Ve
.PP
Parse::Binary::FixedFormat applies the constructed format to the buffer with
\&\f(CW\*(C`unpack\*(C'\fR and maps the returned list of elements to hash entries.
Fields can now be accessed by name though the hash:
.PP
.Vb 2
\&    print $hashref\->{field\-name};
\&    print $hashref\->{array\-field}[3];
.Ve
.SS "format"
.IX Subsection "format"
To convert the hash back into a fixed-format buffer, pass the hash
reference to the \fBformat\fR method.
.PP
.Vb 1
\&    $buf = $cvt\->format($hashref);
.Ve
.SS "blank"
.IX Subsection "blank"
To get a hash that can be used to create a new record, call the
\&\fBblank\fR method.
.PP
.Vb 1
\&    $newrec = $cvt\->blank();
.Ve
.SH "ATTRIBUTES"
.IX Header "ATTRIBUTES"
Each Parse::Binary::FixedFormat instance contains the following attributes.
.IP "Names" 4
.IX Item "Names"
Names contains a list of the field names for this variant.
.IP "Count" 4
.IX Item "Count"
Count contains a list of occurrence counts.  This is used to indicate
which fields contain arrays.
.IP "Format" 4
.IX Item "Format"
Format contains the template string for the Perl \fBpack\fR and \fBunpack\fR
functions.
.SH "AUTHORS"
.IX Header "AUTHORS"
Audrey Tang <cpan@audreyt.org>
.PP
Based on Data::FixedFormat, written by Thomas Pfau <pfau@nbpfaus.net>
http://nbpfaus.net/~pfau/.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2004\-2009 by Audrey Tang <cpan@audreyt.org>.
.PP
Copyright (C) 2000,2002 Thomas Pfau.  All rights reserved.
.PP
This module is free software; you can redistribute it and/or modify it
under the terms of the \s-1GNU\s0 General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
.PP
This library is distributed in the hope that it will be useful, but
\&\s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of
\&\s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0  See the \s-1GNU\s0
Library General Public License for more details.
.PP
You should have received a copy of the \s-1GNU\s0 General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 59 Temple Place \- Suite 330, Boston, \s-1MA 02111\-1307, USA.\s0