#!/usr/bin/perl

# echo __ ___ ._. ... .  _._. ___ _.. . | morse2midi.pl > out.mid

$input = join /\|/, <>;
binmode (STDOUT);

# Variable length values are split to 7-bit parts. If byte is greater or
# equal to 0x80 (128 decimal) then the next byte is also part of the VLV,
# else byte is the last byte in a VLV.
# Conversion examples:
# perl -e 'my $num=360; printf("0x%02X 0x%02X\n",(0x80|($num>>7)),(0x7F&$num));'
# perl -e 'printf("%u\n",(((0x81 & 0x7F) << 7) | (0x68 & 0x7F)));'
$dottime = pack ('C1', 0x78);	# 120
$dashtime = pack ('C2', 0x82, 0x68);	# 360
$interword = pack ('C2', 0x86, 0x48);	# 840
$interletter = $dashtime;
$intersymbol = $dottime;

$sound = pack ('C3', 0x90, 0x4E, 0x7F);
$nosound = pack ('C3', 0x80, 0x4E, 0x7F);

# start making raw track: text, tempo meta events
# first, time signature:
$track = pack('C8', 0xFF, 0x58, 0x04, 0x01, 0x02, 0x18, 0x08, 0x00);
# set tempo 0x0249f0 == 150000
$track .= pack('C7', 0xFF, 0x51, 0x03, 0x02, 0x49, 0xF0, 0x00);
# set instrument name to "Sqrwave"
$track .= (pack('C3', 0xFF, 0x04, 0x07) . "Sqrwave" . pack('C1', 0x00));
# change instrument to 0x50
$track .= pack('C2', 0xC0, 0x50);	# no 0x00 delimiter!

$etime = $interletter;
foreach (split(//, $input))
{
 /\./ && (($track .= ($etime . $sound . $dottime . $nosound)), $etime = $intersymbol);
 /[_\-]/ && (($track .= ($etime . $sound . $dashtime . $nosound)), $etime = $intersymbol);
 / / && ($etime = $interletter);
 /\|/ && ($etime = $interword);
}

$track .= ($interword . $nosound);
$track .= pack('C4', 0, 0xFF, 0x2F, 0);

# write header
print "MThd", # signature
 pack('Nn3',
 6, # len 0x00000006
 0, # format 0x0000 - single multi-channel track
 1, # 0x0001 track(s)
 0xF0); # number of delay ticks in a quarter-note

# track header, raw track
print	"MTrk", # signature
	pack('NC1', length($track), 0), # track length and delimiter
	$track;