#! /usr/bin/perl -w

use strict;
use Fcntl 'SEEK_SET';

# Read Pintos.pm from the same directory as this program.
BEGIN { my $self = $0; $self =~ s%/+[^/]*$%%; require "$self/Pintos.pm"; }

# Get command-line arguments.
usage (0) if @ARGV == 1 && $ARGV[0] eq '--help';
usage (1) if @ARGV < 2 || $ARGV[1] ne '--';
my ($disk, undef, @kernel_args) = @ARGV;

# Open disk.
my ($handle);
open ($handle, '+<', $disk) or die "$disk: open: $!\n";

# Check that it's a partitioned disk with a PintOS loader.
my ($buffer) = read_fully ($handle, $disk, 512);
unpack ("x510 v", $buffer) == 0xaa55 or die "$disk: not a partitioned disk\n";
$buffer =~ /PintOS/ or die "$disk: does not contain PintOS loader\n";

# Write the command line.
our ($LOADER_SIZE);
sysseek ($handle, $LOADER_SIZE, SEEK_SET) == $LOADER_SIZE
  or die "$disk: seek: $!\n";
write_fully ($handle, $disk, make_kernel_command_line (@kernel_args));

# Close disk.
close ($handle) or die "$disk: close: $!\n";

exit 0;

sub usage {
    print <<'EOF';
pintos-set-cmdline, a utility for changing the command line in PintOS disks
Usage: pintos-set-cmdline DISK -- [ARGUMENT...]
where DISK is a bootable disk containing a PintOS loader
  and each ARGUMENT is inserted into the command line written to DISK.
EOF
    exit ($_[0]);
}
