use strict;
use POSIX ();

# Example Perl plugin.
#
# This example can be freely used for any purpose.

# Run it from the build directory like this:
#
#   ./nbdkit -f -v perl ./plugins/perl/example.pl test1=foo test2=bar
#
# Or run it after installing nbdkit like this:
#
#   nbdkit -f -v perl ./plugins/perl/example.pl test1=foo test2=bar
#
# The -f -v arguments are optional.  They cause the server to stay in
# the foreground and print debugging, which is useful when testing.
#
# You can connect to the server using guestfish or qemu, eg:
#
#   guestfish --format=raw -a nbd://localhost
#   ><fs> run
#   ><fs> part-disk /dev/sda mbr
#   ><fs> mkfs ext2 /dev/sda1
#   ><fs> list-filesystems
#   ><fs> mount /dev/sda1 /
#   ><fs> [etc]

# This is the string used to store the emulated disk (initially all
# zero bytes).  There is one disk per nbdkit instance, so if you
# reconnect to the same server you should see the same disk.  You
# could also put this into the handle, so there would be a fresh disk
# per handle.
my $disk = "\0" x (1024*1024);

# This just prints the extra command line parameters, but real plugins
# should parse them and reject any unknown parameters.
sub config
{
    my $key = shift;
    my $value = shift;

    print "$0: ignored parameter $key=$value\n";
}

sub open
{
    my $readonly = shift;

    printf ("$0: open: readonly=%d\n", $readonly);

    # You can return any Perl value from open, and the same Perl value
    # will be passed as the first arg to the other callbacks [in the
    # client connected phase].  In most cases it's convenient to use a
    # hashref.
    my $h = { readonly => $readonly };

    return $h;
}

sub get_size
{
    my $h = shift;

    return length ($disk);
}

sub pread
{
    my $h = shift;
    my $count = shift;
    my $offset = shift;

    return substr ($disk, $offset, $count);
}

sub pwrite
{
    my $h = shift;
    my $buf = shift;
    my $count = length ($buf);
    my $offset = shift;

    substr ($disk, $offset, $count) = $buf;
}

sub zero
{
    my $h = shift;
    my $count = shift;
    my $offset = shift;
    my $may_trim = shift;

    if ($may_trim) {
	substr ($disk, $offset, $count) = "\0" x $count;
    } else {
	Nbdkit::set_error(POSIX::EOPNOTSUPP);
	die "fall back to pwrite";
    }
}
