/usr/share/perl5/Device/Modem/Protocol/Xmodem.pm is in libdevice-modem-perl 1.47-2.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# Initial revision: 1 Oct 2003
#
# Copyright (C) 2003-2005 Cosimo Streppone, cosimo@cpan.org
#
# This program is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
# Additionally, this is ALPHA software, still needs extensive
# testing and support for generic AT commads, so use it at your own risk,
# and without ANY warranty! Have fun.
#
# This Xmodem protocol version is indeed very alpha code,
# probably does not work at all, so stay tuned...
#
# $Id: Xmodem.pm,v 1.7 2005/11/15 22:28:42 cosimo Exp $
package Xmodem::Constants;
# Define constants used in xmodem blocks
sub nul () { 0x00 } # ^@
sub soh () { 0x01 } # ^A
sub stx () { 0x02 } # ^B
sub eot () { 0x04 } # ^D
sub ack () { 0x06 } # ^E
sub nak () { 0x15 } # ^U
sub can () { 0x18 } # ^X
sub C () { 0x43 }
sub ctrl_z () { 0x1A } # ^Z
sub CHECKSUM () { 1 }
sub CRC16 () { 2 }
sub CRC32 () { 3 }
sub XMODEM () { 0x01 }
sub XMODEM_1K () { 0x02 }
sub XMODEM_CRC () { 0x03 }
#sub YMODEM () { 0x04 }
#sub ZMODEM () { 0x05 }
package Xmodem::Block;
use overload q[""] => \&to_string;
# Create a new block object
sub new {
my($proto, $num, $data, $length) = @_;
my $class = ref $proto || $proto;
# Define block type (128 or 1k chars) if not specified
$length ||= ( length $data > 128 ? 1024 : 128 );
# Define structure of a Xmodem transfer block object
my $self = {
number => defined $num ? $num : 0,
'length'=> $length,
data => defined $data ? substr($data, 0, $length) : "", # Blocks are limited to 128 or 1024 chars
};
bless $self, $class;
}
# Calculate checksum of current block data
sub checksum {
my $self = $_[0];
my $sum = 0;
foreach my $c ( $self->data() ) {
$sum += ord $c;
$sum %= 256;
}
return $sum % 256;
}
# Calculate CRC 16 bit on block data
sub crc16 {
my $self = $_[0];
return unpack('%C16*' => $self->data()) % 65536;
}
# Calculate CRC 32 bit on block data
sub crc32 {
my $self = $_[0];
return unpack('%C32' => $self->data());
}
# Return data one char at a time
sub data {
my $self = $_[0];
return wantarray
? split(//, $self->{data})
: substr($self->{data}, 0, $self->{'length'})
}
sub number {
my $self = $_[0];
return $self->{number};
}
# Calculate checksum/crc for the current block and stringify block for transfer
sub to_string {
my $self = $_[0];
my $block_num = $self->number();
# Assemble block to be transferred
my $xfer = pack(
'cccA'.$self->{'length'}.'c',
$self->{'length'} == 128
? Xmodem::Constants::soh # Start Of Header (block size = 128)
: Xmodem::Constants::stx, # Start Of Text (block size = 1024)
$block_num, # Block number
$block_num ^ 0xFF, # 2's complement of block number
scalar $self->data, # Data chars
$self->checksum() # Final checksum (or crc16 or crc32)
# TODO crc16, crc32 ?
);
return $xfer;
}
#
# verify( type, value )
# ex.: verify( 'checksum', 0x7F )
# ex.: verify( 'crc16', 0x8328 )
#
sub verify {
my($self, $type, $value) = @_;
# Detect type of value to be checked
# TODO use new constants
$type = 'checksum' unless defined $type;
if( $type eq 'checksum' ) {
$good_value = $self->checksum();
} elsif( $type eq 'crc16' ) {
$good_value = $self->crc16();
} elsif( $type eq 'crc32' ) {
$good_value = $self->crc32();
} else {
$good_value = $self->checksum();
}
print 'value:', $value, 'goodvalue:', $good_value;
return $good_value == $value;
}
# ----------------------------------------------------------------
package Xmodem::Buffer;
sub new {
my($proto, $num, $data) = @_;
my $class = ref $proto || $proto;
# Define structure of a Xmodem transfer buffer
my $self = [];
bless($self);
return $self;
}
# Push, pop, operations on buffer
sub push {
my $self = $_[0];
my $block = $_[1];
push @$self, $block;
}
sub pop {
my $self = $_[0];
pop @$self
}
# Get last block on buffer (to retransmit / re-receive)
sub last {
my $self = $_[0];
return $self->[ $#$self ];
}
sub blocks {
return @{$_[0]};
}
#
# Replace n-block with given block object
#
sub replace {
my $self = $_[0];
my $num = $_[1];
my $block = $_[2];
$self->[$num] = $block;
}
sub dump {
my $self = $_[0];
my $output;
# Join all blocks into string
for (my $pos = 0; $pos < scalar($self->blocks()); $pos++) {
$output .= $self->[$pos]->data();
}
# Clean out any end of file markers (^Z) in data
$output =~ s/\x1A*$//;
return $output;
}
# ----------------------------------------------------------------
package Xmodem::Receiver;
# Define default timeouts for CRC handshaking stage and checksum normal procedure
sub TIMEOUT_CRC () { 3 };
sub TIMEOUT_CHECKSUM () { 10 };
our $TIMEOUT = TIMEOUT_CRC;
our $DEBUG = 1;
sub abort_transfer {
my $self = $_[0];
# Send a cancel char to abort transfer
_log('aborting transfer');
$self->modem->atsend( chr(Xmodem::Constants::can) );
$self->modem->port->write_drain() unless $self->modem->ostype() eq 'windoze';
$self->{aborted} = 1;
return 1;
}
#
# TODO protocol management
#
sub new {
my $proto = shift;
my %opt = @_;
my $class = ref $proto || $proto;
# Create `modem' object if does not exist
_log('opt{modem} = ', $opt{modem});
if( ! exists $opt{modem} ) {
require Device::Modem;
$opt{modem} = Device::Modem->new();
}
my $self = {
_modem => $opt{modem},
_filename => $opt{filename} || 'received.dat',
current_block => 0,
timeouts => 0,
};
bless $self, $class;
}
# Get `modem' Device::SerialPort member
sub modem {
$_[0]->{_modem};
}
#
# Try to receive a block. If receive is correct, push a new block on buffer
#
sub receive_message {
my $self = $_[0];
my $message_type;
my $message_number = 0;
my $message_complement = 0;
my $message_data;
my $message_checksum;
# Receive answer
#my $received = $self->modem->answer( undef, 1000 );
#my $received = $self->modem->answer( "/.{132}/", 1000 );
# Had problems dropping bytes from block messages that caused the checksum
# to be missing on rare occasions.
($count_in, $received) = $self->modem->port->read(132);
_log('[receive_message][', $count_in, '] received [', unpack('H*',$received), '] data');
# Get Message Type
$message_type = ord(substr($received, 0, 1));
# If this is a block extract data from message
if( $message_type eq Xmodem::Constants::soh ) {
# Check block number and its 2's complement
($message_number, $message_complement) = ( ord(substr($received,1,1)), ord(substr($received,2,1)) );
# Extract data string from message
$message_data = substr($received,3,128);
# Extract checksum from message
$message_checksum = ord(substr($received, 131, 1));
}
my %message = (
type => $message_type, # Message Type
number => $message_number, # Message Sequence Number
complement => $message_complement, # Message Number's Complement
data => $message_data, # Message Data String
checksum => $message_checksum, # Message Data Checksum
);
return %message;
}
sub run {
my $self = $_[0];
my $modem = $self->{_modem};
my $file = $_[1] || $self->{_filename};
my $protocol = $_[2] || Xmodem::Constants::XMODEM;
_log('[run] checking modem[', $modem, '] or file[', $file, '] members');
return 0 unless $modem and $file;
# Initialize transfer
$self->{current_block} = 0;
$self->{timeouts} = 0;
# Initialize a receiving buffer
_log('[run] creating new receive buffer');
my $buffer = Xmodem::Buffer->new();
# Stage 1: handshaking for xmodem standard version
_log('[run] sending first timeout');
$self->send_timeout();
my $file_complete = 0;
$self->{current_block} = Xmodem::Block->new(0);
# Open output file
return undef unless open OUTFILE, '>'.$file;
# Main receive cycle (subsequent timeout cycles)
do {
# Try to receive a message
my %message = $self->receive_message();
if ( $message{type} eq Xmodem::Constants::nul ) {
# Nothing received yet, do nothing
_log('[run] <NUL>', $message{type});
} elsif ( $message{type} eq Xmodem::Constants::eot ) {
# If last block transmitted mark complete and close file
_log('[run] <EOT>', $message{type});
# Acknoledge we received <EOT>
$self->send_ack();
$file_complete = 1;
# Write buffer data to file
print(OUTFILE $buffer->dump());
close OUTFILE;
} elsif ( $message{type} eq Xmodem::Constants::soh ) {
# If message header, check integrity and build block
_log('[run] <SOH>', $message{type});
my $message_status = 1;
# Check block number
if ( (255 - $message{complement}) != $message{number} ) {
_log('[run] bad block number: ', $message{number}, ' != (255 - ', $message{complement}, ')' );
$message_status = 0;
}
# Check block numbers for out of sequence blocks
if ( $message{number} < $self->{current_block}->number() || $message{number} > ($self->{current_block}->number() + 1) ) {
_log('[run] bad block sequence');
$self->abort_transfer();
}
# Instance a new "block" object from message data received
my $new_block = Xmodem::Block->new( $message{number}, $message{data} );
# Check block against checksum
if (!( defined $new_block && $new_block->verify( 'checksum', $message{checksum}) )) {
_log('[run] bad block checksum');
$message_status = 0;
}
# This message block was good, update current_block and push onto buffer
if ($message_status) {
_log('[run] received block ', $new_block->number());
# Update current block to the one received
$self->{current_block} = $new_block;
# Push block onto buffer
$buffer->push($self->{current_block});
# Acknoledge we successfully received block
$self->send_ack();
} else {
# Send nak since did not receive block successfully
_log('[run] message_status = 0, sending <NAK>');
$self->send_nak();
}
} else {
_log('[run] neither types found, sending timingout');
$self->send_timeout();
}
} until $file_complete or $self->timeouts() >= 10;
}
sub send_ack {
my $self = $_[0];
_log('sending ack');
$self->modem->atsend( chr(Xmodem::Constants::ack) );
$self->modem->port->write_drain();
$self->{timeouts} = 0;
return 1;
}
sub send_nak {
my $self = $_[0];
_log('sending timeout (', $self->{timeouts}, ')');
$self->modem->atsend( chr(Xmodem::Constants::nak) );
my $received = $self->modem->answer( undef, TIMEOUT_CHECKSUM );
_log('[nak_dump] received [', unpack('H*',$received), '] data');
$self->modem->port->write_drain();
$self->{timeouts}++;
return 1;
}
sub send_timeout {
my $self = $_[0];
_log('sending timeout (', $self->{timeouts}, ')');
$self->modem->atsend( chr(Xmodem::Constants::nak) );
$self->modem->port->write_drain();
$self->{timeouts}++;
return 1;
}
sub timeouts {
my $self = $_[0];
$self->{timeouts};
}
sub _log {
print STDERR @_, "\n" if $DEBUG
}
1;
=head1 NAME
Device::Modem::Protocol::Xmodem
=head1 Xmodem::Block
Class that represents a single Xmodem data block.
=head2 Synopsis
my $b = Xmodem::Block->new( 1, 'My Data...<until-128-chars>...' );
if( defined $b ) {
# Ok, block instanced, verify its checksum
if( $b->verify( 'checksum', <my_chksum> ) ) {
...
} else {
...
}
} else {
# No block
}
# Calculate checksum, crc16, 32, ...
$crc16 = $b->crc16();
$crc32 = $b->crc32();
$chksm = $b->checksum();
=head1 Xmodem::Buffer
Class that implements an Xmodem receive buffer of data blocks. Every block of data
is represented by a C<Xmodem::Block> object.
Blocks can be B<push>ed and B<pop>ped from the buffer. You can retrieve the B<last>
block, or the list of B<blocks> from buffer.
=head2 Synopsis
my $buf = Xmodem::Buffer->new();
my $b1 = Xmodem::Block->new(1, 'Data...');
$buf->push($b1);
my $b2 = Xmodem::Block->new(2, 'More data...');
$buf->push($b2);
my $last_block = $buf->last();
print 'now I have ', scalar($buf->blocks()), ' in the buffer';
# TODO document replace() function ???
=head1 Xmodem::Constants
Package that contains all useful Xmodem protocol constants used in handshaking and
data blocks encoding procedures
=head2 Synopsis
Xmodem::Constants::soh ........... 'start of header'
Xmodem::Constants::eot ........... 'end of trasmission'
Xmodem::Constants::ack ........... 'acknowlegded'
Xmodem::Constants::nak ........... 'not acknowledged'
Xmodem::Constants::can ........... 'cancel'
Xmodem::Constants::C ........... `C' ASCII char
Xmodem::Constants::XMODEM ........ basic xmodem protocol
Xmodem::Constants::XMODEM_1K ..... xmodem protocol with 1k blocks
Xmodem::Constants::XMODEM_CRC .... xmodem protocol with CRC checks
Xmodem::Constants::CHECKSUM ...... type of block checksum
Xmodem::Constants::CRC16 ......... type of block crc16
Xmodem::Constants::CRC32 ......... type of block crc32
=head1 Xmodem::Receiver
Control class to initiate and complete a C<X-modem> file transfer in receive mode
=head2 Synopsis
my $recv = Xmodem::Receiver->new(
modem => {Device::Modem object},
filename => 'name of file',
XXX protocol => 'xmodem' | 'xmodem-crc', | 'xmodem-1k'
);
$recv->run();
=head2 Object methods
=over 4
=item abort_transfer()
Sends a B<cancel> char (C<can>), that signals to sender that transfer is aborted. This is
issued if we receive a bad block number, which usually means we got a bad line.
=item modem()
Returns the underlying L<Device::Modem> object.
=item receive_message()
Retreives message from modem and if a block is detected it breaks it into appropriate
parts.
=item run()
Starts a new transfer until file receive is complete. The only parameter accepted
is the (optional) local filename to be written.
=item send_ack()
Sends an acknowledge (C<ack>) char, to signal that we received and stored a correct block
Resets count of timeouts and returns the C<Xmodem::Block> object of the data block
received.
=item send_timeout()
Sends a B<timeout> (C<nak>) char, to signal that we received a bad block header (either
a bad start char or a bad block number), or a bad data checksum. Increments count
of timeouts and at ten timeouts, aborts transfer.
=back
=head2 See also
=over 4
=item - L<Device::Modem>
=back
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