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Convert::BinHex(3) User Contributed Perl Documentation Convert::BinHex(3)

NAME

Convert::BinHex - extract data from Macintosh BinHex files

ALPHA WARNING: this code is currently in its Alpha release. Things may change drastically until the interface is hammered out: if you have suggestions or objections, please speak up now!

SYNOPSIS

SSiimmppllee ffuunnccttiioonnss::

use Convert::BinHex qw(binhexcrc macbinarycrc);

# Compute HQX7-style CRC for data, pumping in old CRC if desired:

$crc = binhexcrc($data, $crc);

# Compute the MacBinary-II-style CRC for the data:

$crc = macbinarycrc($data, $crc);

HHeexx ttoo bbiinn,, llooww-lleevveell iinntteerrffaaccee.. Conversion is actually done via an

object ("Convert::BinHex::Hex2Bin") which keeps internal conversion

state:

# Create and use a "translator" object:

my $H2B = Convert::BinHex->hex2bin; # get a converter object

while () {

print $STDOUT $H2B->next($); # convert some more input

}

print $STDOUT $H2B->done; # no more input: finish up

HHeexx ttoo bbiinn,, OOOO iinntteerrffaaccee.. The following operations must be done in the order shown!

# Read data in piecemeal:

$HQX = Convert::BinHex->open(FH=>\*STDIN) || die "open: $!";

$HQX->readheader; # read header info

@data = $HQX->readdata; # read in all the data

@rsrc = $HQX->readresource; # read in all the resource

BBiinn ttoo hheexx,, llooww-lleevveell iinntteerrffaaccee.. Conversion is actually done via an

object ("Convert::BinHex::Bin2Hex") which keeps internal conversion

state:

# Create and use a "translator" object:

my $B2H = Convert::BinHex->bin2hex; # get a converter object

while () {

print $STDOUT $B2H->next($); # convert some more input

}

print $STDOUT $B2H->done; # no more input: finish up

BBiinn ttoo hheexx,, ffiillee iinntteerrffaaccee.. Yes, you can convert to BinHex as well as from it!

# Create new, empty object:

my $HQX = Convert::BinHex->new;

# Set header attributes:

$HQX->filename("logo.gif");

$HQX->type("GIFA");

$HQX->creator("CNVS");

# Give it the data and resource forks (either can be absent):

$HQX->data(Path => "/path/to/data"); # here, data is on disk

$HQX->resource(Data => $resourcefork); # here, resource is in core

# Output as a BinHex stream, complete with leading comment:

$HQX->encode(\*STDOUT);

PPLLAANNNNEEDD!!!!!!!! BBiinn ttoo hheexx,, ""CCAAPP"" iinntteerrffaaccee.. Thanks to Ken Lunde for suggesting this.

# Create new, empty object from CAP tree:

my $HQX = Convert::BinHex->fromcap("/path/to/root/file");

$HQX->encode(\*STDOUT);

DESCRIPTION

BBiinnHHeexx is a format used by Macintosh for transporting Mac files safely

through electronic mail, as short-lined, 7-bit, semi-compressed data

streams. Ths module provides a means of converting those data streams back into into binary data. FFOORRMMAATT

(Some text taken from RFC-1741.) Files on the Macintosh consist of two

parts, called forks: Data fork The actual data included in the file. The Data fork is typically

the only meaningful part of a Macintosh file on a non-Macintosh

computer system. For example, if a Macintosh user wants to send a

file of data to a user on an IBM-PC, she would only send the Data

fork. Resource fork Contains a collection of arbitrary attribute/value pairs, including program segments, icon bitmaps, and parametric values. Additional information regarding Macintosh files is stored by the Finder in a hidden file, called the "Desktop Database". Because of the complications in storing different parts of a Macintosh

file in a non-Macintosh filesystem that only handles consecutive data

in one part, it is common to convert the Macintosh file into some other format before transferring it over the network. The BinHex format squashes that data into transmittable ASCII as follows: 1. The file is output as a bbyyttee ssttrreeaamm consisting of some basic header information (filename, type, creator), then the data fork, then the resource fork. 2. The byte stream is ccoommpprreesssseedd by looking for series of duplicated bytes and representing them using a special binary escape sequence (of course, any occurences of the escape character must also be escaped). 3. The compressed stream is eennccooddeedd via the "6/8 hemiola" common to

base64 and uuencode: each group of three 8-bit bytes (24 bits) is

chopped into four 6-bit numbers, which are used as indexes into an

ASCII "alphabet". (I assume that leftover bytes are zero-padded;

documentation is thin). FFUUNNCCTTIIOONNSS CCRRCC ccoommppuuttaattiioonn macbinarycrc DATA, SEED

Compute the MacBinary-II-style CRC for the given DATA, with the CRC

seeded to SEED. Normally, you start with a SEED of 0, and you pump in the previous CRC as the SEED if you're handling a lot of data one chunk at a time. That is:

$crc = 0;

while () {

$crc = macbinarycrc($, $crc);

} Note: Extracted from the mcvert utility (Doug Moore, April '87), using a "magic array" algorithm by Jim Van Verth for efficiency. Converted to Perl5 by Eryq. UUnntteesstteedd.. binhexcrc DATA, SEED

Compute the HQX-style CRC for the given DATA, with the CRC seeded

to SEED. Normally, you start with a SEED of 0, and you pump in the previous CRC as the SEED if you're handling a lot of data one chunk at a time. That is:

$crc = 0;

while () {

$crc = binhexcrc($, $crc);

} Note: Extracted from the mcvert utility (Doug Moore, April '87), using a "magic array" algorithm by Jim Van Verth for efficiency. Converted to Perl5 by Eryq. OOOO IINNTTEERRFFAACCEE CCoonnvveerrssiioonn bin2hex Class method, constructor. Return a converter object. Just

creates a new instance of "Convert::BinHex::Bin2Hex"; see that

class for details. hex2bin Class method, constructor. Return a converter object. Just

creates a new instance of "Convert::BinHex::Hex2Bin"; see that

class for details. CCoonnssttrruuccttiioonn new PARAMHASH Class method, constructor. Return a handle on a BinHex'able entity. In general, the data and resource forks for such an entity are stored in native format (binary) format.

Parameters in the PARAMHASH are the same as header-oriented method

names, and may be used to set attributes:

$HQX = new Convert::BinHex filename => "icon.gif",

type => "GIFB", creator => "CNVS"; open PARAMHASH Class method, constructor. Return a handle on a new BinHex'ed stream, for parsing. Params are: Data Input a HEX stream from the given data. This can be a scalar, or a reference to an array of scalars. Expr Input a HEX stream from any open()able expression. It will be opened and binmode'd, and the filehandle will be closed either on a "close()" or when the object is destructed. FH Input a HEX stream from the given filehandle. NoComment If true, the parser should not attempt to skip a leading "(This file...)" comment. That means that the first nonwhite characters encountered must be the binhex'ed data. GGeett//sseett hheeaaddeerr iinnffoorrmmaattiioonn creator [VALUE]

Instance method. Get/set the creator of the file. This is a four-

character string (though I don't know if it's guaranteed to be printable ASCII!) that serves as part of the Macintosh's version

of a MIME "content-type".

For example, a document created by "Canvas" might have creator "CNVS". data [PARAMHASH] Instance method. Get/set the data fork. Any arguments are passed

into the new() method of "Convert::BinHex::Fork".

filename [VALUE] Instance method. Get/set the name of the file. flags [VALUE] Instance method. Return the flags, as an integer. Use bitmasking to get as the values you need. headerasstring Return a stringified version of the header that you might use for logging/debugging purposes. It looks like this:

X-HQX-Software: BinHex 4.0 (Convert::BinHex 1.102)

X-HQX-Filename: Somethingnew.eps

X-HQX-Version: 0

X-HQX-Type: EPSF

X-HQX-Creator: ART5

X-HQX-Data-Length: 49731

X-HQX-Rsrc-Length: 23096

As some of you might have guessed, this is RFC-822-style, and may

be easily plunked down into the middle of a mail header, or split into lines, etc. requires [VALUE] Instance method. Get/set the software version required to convert this file, as extracted from the comment that preceded the actual binhex'ed data; e.g.: (This file must be converted with BinHex 4.0) In this case, after parsing in the comment, the code:

$HQX->requires;

would get back "4.0". resource [PARAMHASH] Instance method. Get/set the resource fork. Any arguments are

passed into the new() method of "Convert::BinHex::Fork".

type [VALUE]

Instance method. Get/set the type of the file. This is a four-

character string (though I don't know if it's guaranteed to be printable ASCII!) that serves as part of the Macintosh's version

of a MIME "content-type".

For example, a GIF89a file might have type "GF89". version [VALUE] Instance method. Get/set the version, as an integer.

DDeeccooddee,, hhiigghh-lleevveell

readcomment Instance method. Skip past the opening comment in the file, which is of the form: (This file must be converted with BinHex 4.0)

As per RFC-1741, this comment must immediately precede the BinHex

data, and any text before it will be ignored. You don't need to invoke this method yourself; "readheader()" will do it for you. After the call, the version number in the comment is accessible via the "requires()" method. readheader Instance method. Read in the BinHex file header. You must do this first! readdata [NBYTES] Instance method. Read information from the data fork. Use it in an array context to slurp all the data into an array of scalars:

@data = $HQX->readdata;

Or use it in a scalar context to get the data piecemeal:

while (defined($data = $HQX->readdata)) {

# do stuff with $data

} The NBYTES to read defaults to 2048. readresource [NBYTES] Instance method. Read in all/some of the resource fork. See "readdata()" for usage.

EEnnccooddee,, hhiigghh-lleevveell

encode OUT Encode the object as a BinHex stream to the given output handle OUT. OUT can be a filehandle, or any blessed object that responds to a "print()" message. The leading comment is output, using the "requires()" attribute. SSUUBBMMOODDUULLEESS CCoonnvveerrtt::::BBiinnHHeexx::::BBiinn22HHeexx

A BINary-to-HEX converter. This kind of conversion requires a certain

amount of state information; it cannot be done by just calling a simple function repeatedly. Use it like this:

# Create and use a "translator" object:

my $B2H = Convert::BinHex->bin2hex; # get a converter object

while () {

print STDOUT $B2H->next($); # convert some more input

}

print STDOUT $B2H->done; # no more input: finish up

# Re-use the object:

$B2H->rewind; # ready for more action!

while () { ...

On each iteration, "next()" (and "done()") may return either a decent-

sized non-empty string (indicating that more converted data is ready

for you) or an empty string (indicating that the converter is waiting to amass more input in its private buffers before handing you more stuff to output. Note that "done()" always converts and hands you whatever is left. This may have been a good approach. It may not. Someday, the converter may also allow you give it an object that responds to read(),

or a FileHandle, and it will do all the nasty buffer-filling on its

own, serving you stuff line by line:

# Someday, maybe...

my $B2H = Convert::BinHex->bin2hex(\*STDIN);

while (defined($ = $B2H->getline)) {

print STDOUT $;

} Someday, maybe. Feel free to voice your opinions. CCoonnvveerrtt::::BBiinnHHeexx::::HHeexx22BBiinn

A HEX-to-BINary converter. This kind of conversion requires a certain

amount of state information; it cannot be done by just calling a simple function repeatedly. Use it like this:

# Create and use a "translator" object:

my $H2B = Convert::BinHex->hex2bin; # get a converter object

while () {

print STDOUT $H2B->next($); # convert some more input

}

print STDOUT $H2B->done; # no more input: finish up

# Re-use the object:

$H2B->rewind; # ready for more action!

while () { ...

On each iteration, "next()" (and "done()") may return either a decent-

sized non-empty string (indicating that more converted data is ready

for you) or an empty string (indicating that the converter is waiting to amass more input in its private buffers before handing you more stuff to output. Note that "done()" always converts and hands you whatever is left. Note that this converter does not find the initial "BinHex version" comment. You have to skip that yourself. It only handles data between the opening and closing ":". CCoonnvveerrtt::::BBiinnHHeexx::::FFoorrkk A fork in a Macintosh file.

# How to get them...

$datafork = $HQX->data; # get the data fork

$rsrcfork = $HQX->resource; # get the resource fork

# Make a new fork:

$FORK = Convert::BinHex::Fork->new(Path => "/tmp/file.data");

$FORK = Convert::BinHex::Fork->new(Data => $scalar);

$FORK = Convert::BinHex::Fork->new(Data => \@arrayofscalars);

# Get/set the length of the data fork:

$len = $FORK->length;

$FORK->length(170); # this overrides the REAL value: be careful!

# Get/set the path to the underlying data (if in a disk file):

$path = $FORK->path;

$FORK->path("/tmp/file.data");

# Get/set the in-core data itself, which may be a scalar or an arrayref:

$data = $FORK->data;

$FORK->data($scalar);

$FORK->data(\@arrayofscalars);

# Get/set the CRC:

$crc = $FORK->crc;

$FORK->crc($crc);

UUNNDDEERR TTHHEE HHOOOODD DDeessiiggnn iissssuueess BinHex needs a stateful parser Unlike its cousins base64 and uuencode, BinHex format is not

amenable to being parsed line-by-line. There appears to be no

guarantee that lines contain 4n encoded characters... and even if there is one, the BinHex compression algorithm interferes: even when you can decode one line at a time, you can't necessarily decompress a line at a time. For example: a decoded line ending with the byte "\x90" (the escape or "mark" character) is ambiguous: depending on the next decoded byte, it could mean a literal "\x90" (if the next byte is a

"\x00"), or it could mean n-1 more repetitions of the previous

character (if the next byte is some nonzero "n"). For this reason, a BinHex parser has to be somewhat stateful: you cannot have code like this:

#### NO! #### NO! #### NO! #### NO! #### NO! ####

while () { # read HEX

print hexbin($); # convert and write BIN

} unless something is happening "behind the scenes" to keep track of what was last done. The dangerous thing, however, is that this approach will sseeeemm to work, if you only test it on BinHex files which do not use compression and which have 4n HEX characters on each line. Since we have to be stateful anyway, we use the parser object to keep our state. We need to be handle large input files Solutions that demand reading everything into core don't cut it in my book. The first MPEG file that comes along can louse up your whole day. So, there are no size limitations in this module: the

data is read on-demand, and filehandles are always an option.

Boy, is this slow!

A lot of the byte-level manipulation that has to go on,

particularly the CRC computing (which involves intensive bit-

shifting and masking) slows this module down significantly. What is needed perhaps is an optional extension library where the slow

pieces can be done more quickly... a Convert::BinHex::CRC, if you

will. Volunteers, anyone? Even considering that, however, it's slower than I'd like. I'm

sure many improvements can be made in the HEX-to-BIN end of things.

No doubt I'll attempt some as time goes on... HHooww iitt wwoorrkkss Since BinHex is a layered format, consisting of... A Macintosh file [the "BIN"]...

Encoded as a structured 8-bit bytestream, then...

Compressed to reduce duplicate bytes, then...

Encoded as 7-bit ASCII [the "HEX"]

...there is a layered parsing algorithm to reverse the process. Basically, it works in a similar fashion to stdio's fread(): 0. There is an internal buffer of decompressed (BIN) data, initially empty. 1. Application asks to read() n bytes of data from object 2. If the buffer is not full enough to accomodate the request: 2a. The read() method grabs the next available chunk of input data (the HEX). 2b. HEX data is converted and decompressed into as many BIN bytes as possible. 2c. BIN bytes are added to the read() buffer. 2d. Go back to step 2a. until the buffer is full enough

or we hit end-of-input.

The conversion-and-decompression algorithms need their own internal

buffers and state (since the next input chunk may not contain all the data needed for a complete conversion/decompression operation). These are maintained in the object, so parsing two different input streams simultaneously is possible. WWAARRNNIINNGGSS

Only handles "Hqx7" files, as per RFC-1741.

Remember that Macintosh text files use "\r" as end-of-line: this means

that if you want a textual file to look normal on a non-Mac system, you

probably want to do this to the data:

# Get the data, and output it according to normal conventions:

foreach ($HQX->readdata) { s/\r/\n/g; print }

CCHHAANNGGEE LLOOGG

Current version: $Id: BinHex.pm,v 1.119 1997/06/28 05:12:42 eryq Exp $

Version 1.118 Ready to go public (with Paul's version, patched for native Mac support)! Warnings have been suppressed in a few places where undefined values appear. Version 1.115 Fixed another bug in comp2bin, related to the MARK falling on a boundary between inputs. Added testing code. Version 1.114

Added BIN-to-HEX conversion. Eh. It's a start. Also, a lot of

documentation additions and cleanups. Some methods were also renamed. Version 1.103 Fixed bug in decompression (wasn't saving last character). Fixed "NoComment" bug. Version 1.102 Initial release. AUTHOR AND CREDITS Written by Eryq, http://www.enteract.com/~eryq / eryq@enteract.com

Support for native-Mac conversion, plus invaluable contributions in

Alpha Testing, plus a few patches, plus the baseline binhex/debinhex programs, were provided by Paul J. Schinder (NASA/GSFC). Ken Lunde (Adobe) suggested incorporating the CAP file representation. TTEERRMMSS AANNDD CCOONNDDIITTIIOONNSS Copyright (c) 1997 by Eryq. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. This software comes with NNOO WWAARRRRAANNTTYY of any kind. See the COPYING file in the distribution for details.