Convert::BinHex(3pm) User Contributed Perl Documentation Convert::BinHex(3pm)
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
Simple functions:
use Convert::BinHex qw(binhex_crc macbinary_crc);
# Compute HQX7-style CRC for data, pumping in old CRC if desired:
$crc = binhex_crc($data, $crc);
# Compute the MacBinary-II-style CRC for the data:
$crc = macbinary_crc($data, $crc);
Hex to bin, low-level interface. 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 (<STDIN>) {
print $STDOUT $H2B->next($_); # convert some more input
}
print $STDOUT $H2B->done; # no more input: finish up
Hex to bin, OO interface. The following operations must be done in the
order shown!
# Read data in piecemeal:
$HQX = Convert::BinHex->open(FH=>\*STDIN) || die "open: $!";
$HQX->read_header; # read header info
@data = $HQX->read_data; # read in all the data
@rsrc = $HQX->read_resource; # read in all the resource
Bin to hex, low-level interface. 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 (<STDIN>) {
print $STDOUT $B2H->next($_); # convert some more input
}
print $STDOUT $B2H->done; # no more input: finish up
Bin to hex, file interface. 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);
PLANNED!!!! Bin to hex, "CAP" interface. Thanks to Ken Lunde for
suggesting this.
# Create new, empty object from CAP tree:
my $HQX = Convert::BinHex->from_cap("/path/to/root/file");
$HQX->encode(\*STDOUT);
DESCRIPTION
BinHex 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.
FORMAT
(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 byte stream consisting of some basic header
information (filename, type, creator), then the data fork, then the
resource fork.
2. The byte stream is compressed 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 encoded 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).
FUNCTIONS
CRC computation
macbinary_crc 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 (<STDIN>) {
$crc = macbinary_crc($_, $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. Untested.
binhex_crc 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 (<STDIN>) {
$crc = binhex_crc($_, $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.
OO INTERFACE
Conversion
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.
Construction
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.
Get/set header information
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.
header_as_string
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: Something_new.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.
Decode, high-level
read_comment
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; "read_header()" will
do it for you. After the call, the version number in the comment
is accessible via the "requires()" method.
read_header
Instance method. Read in the BinHex file header. You must do this
first!
read_data [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 = $HQX->read_data;
Or use it in a scalar context to get the data piecemeal:
while (defined($data = $HQX->read_data)) {
# do stuff with $data
}
The NBYTES to read defaults to 2048.
read_resource [NBYTES]
Instance method. Read in all/some of the resource fork. See
"read_data()" for usage.
Encode, high-level
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.
SUBMODULES
Convert::BinHex::Bin2Hex
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 (<STDIN>) {
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 (<MOREIN>) { ...
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.
Convert::BinHex::Hex2Bin
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 (<STDIN>) {
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 (<MOREIN>) { ...
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 ":".
Convert::BinHex::Fork
A fork in a Macintosh file.
# How to get them...
$data_fork = $HQX->data; # get the data fork
$rsrc_fork = $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 => \@array_of_scalars);
# 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(\@array_of_scalars);
# Get/set the CRC:
$crc = $FORK->crc;
$FORK->crc($crc);
UNDER THE HOOD
Design issues
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 (<STDIN>) { # 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 seem 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...
How it works
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 accommodate 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.
WARNINGS
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->read_data) { s/\r/\n/g; print }
AUTHOR AND CREDITS
Maintained by Stephen Nelson <stephenenelson@mac.com>
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.
LICENSE
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 NO WARRANTY of any kind. See the COPYING file
in the distribution for details.
perl v5.34.0 2022-10-13 Convert::BinHex(3pm)
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