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# Assembler.pm
#
# Copyright (c) 1996 Malcolm Beattie
#
# You may distribute under the terms of either the GNU General Public
# License or the Artistic License, as specified in the README file.
package B::Assembler;
use Exporter;
use B qw(ppname);
use B::Asmdata qw(%insn_data @insn_name);
@ISA = qw(Exporter);
@EXPORT_OK = qw(assemble_fh assemble_insn strip_comments
parse_statement uncstring);
use strict;
my %opnumber;
my ($i, $opname);
for ($i = 0; defined($opname = ppname($i)); $i++) {
$opnumber{$opname} = $i;
}
my ($linenum, $errors);
sub error {
my $str = shift;
warn "$linenum: $str\n";
$errors++;
}
my $debug = 0;
sub debug { $debug = shift }
#
# First define all the data conversion subs to which Asmdata will refer
#
sub B::Asmdata::PUT_U8 {
my $arg = shift;
my $c = uncstring($arg);
if (defined($c)) {
if (length($c) != 1) {
error "argument for U8 is too long: $c";
$c = substr($c, 0, 1);
}
} else {
$c = chr($arg);
}
return $c;
}
sub B::Asmdata::PUT_U16 { pack("n", $_[0]) }
sub B::Asmdata::PUT_U32 { pack("N", $_[0]) }
sub B::Asmdata::PUT_I32 { pack("N", $_[0]) }
sub B::Asmdata::PUT_objindex { pack("N", $_[0]) } # could allow names here
sub B::Asmdata::PUT_strconst {
my $arg = shift;
$arg = uncstring($arg);
if (!defined($arg)) {
error "bad string constant: $arg";
return "";
}
if ($arg =~ s/\0//g) {
error "string constant argument contains NUL: $arg";
}
return $arg . "\0";
}
sub B::Asmdata::PUT_pvcontents {
my $arg = shift;
error "extraneous argument: $arg" if defined $arg;
return "";
}
sub B::Asmdata::PUT_PV {
my $arg = shift;
$arg = uncstring($arg);
error "bad string argument: $arg" unless defined($arg);
return pack("N", length($arg)) . $arg;
}
sub B::Asmdata::PUT_comment {
my $arg = shift;
$arg = uncstring($arg);
error "bad string argument: $arg" unless defined($arg);
if ($arg =~ s/\n//g) {
error "comment argument contains linefeed: $arg";
}
return $arg . "\n";
}
sub B::Asmdata::PUT_double { sprintf("%s\0", $_[0]) }
sub B::Asmdata::PUT_none {
my $arg = shift;
error "extraneous argument: $arg" if defined $arg;
return "";
}
sub B::Asmdata::PUT_op_tr_array {
my $arg = shift;
my @ary = split(/\s*,\s*/, $arg);
if (@ary != 256) {
error "wrong number of arguments to op_tr_array";
@ary = (0) x 256;
}
return pack("n256", @ary);
}
# XXX Check this works
sub B::Asmdata::PUT_IV64 {
my $arg = shift;
return pack("NN", $arg >> 32, $arg & 0xffffffff);
}
my %unesc = (n => "\n", r => "\r", t => "\t", a => "\a",
b => "\b", f => "\f", v => "\013");
sub uncstring {
my $s = shift;
$s =~ s/^"// and $s =~ s/"$// or return undef;
$s =~ s/\\(\d\d\d|.)/length($1) == 3 ? chr(oct($1)) : ($unesc{$1}||$1)/eg;
return $s;
}
sub strip_comments {
my $stmt = shift;
# Comments only allowed in instructions which don't take string arguments
$stmt =~ s{
(?sx) # Snazzy extended regexp coming up. Also, treat
# string as a single line so .* eats \n characters.
^\s* # Ignore leading whitespace
(
[^"]* # A double quote '"' indicates a string argument. If we
# find a double quote, the match fails and we strip nothing.
)
\s*\# # Any amount of whitespace plus the comment marker...
.*$ # ...which carries on to end-of-string.
}{$1}; # Keep only the instruction and optional argument.
return $stmt;
}
sub parse_statement {
my $stmt = shift;
my ($insn, $arg) = $stmt =~ m{
(?sx)
^\s* # allow (but ignore) leading whitespace
(.*?) # Instruction continues up until...
(?: # ...an optional whitespace+argument group
\s+ # first whitespace.
(.*) # The argument is all the rest (newlines included).
)?$ # anchor at end-of-line
};
if (defined($arg)) {
if ($arg =~ s/^0x(?=[0-9a-fA-F]+$)//) {
$arg = hex($arg);
} elsif ($arg =~ s/^0(?=[0-7]+$)//) {
$arg = oct($arg);
} elsif ($arg =~ /^pp_/) {
$arg =~ s/\s*$//; # strip trailing whitespace
my $opnum = $opnumber{$arg};
if (defined($opnum)) {
$arg = $opnum;
} else {
error qq(No such op type "$arg");
$arg = 0;
}
}
}
return ($insn, $arg);
}
sub assemble_insn {
my ($insn, $arg) = @_;
my $data = $insn_data{$insn};
if (defined($data)) {
my ($bytecode, $putsub) = @{$data}[0, 1];
my $argcode = &$putsub($arg);
return chr($bytecode).$argcode;
} else {
error qq(no such instruction "$insn");
return "";
}
}
sub assemble_fh {
my ($fh, $out) = @_;
my ($line, $insn, $arg);
$linenum = 0;
$errors = 0;
while ($line = <$fh>) {
$linenum++;
chomp $line;
if ($debug) {
my $quotedline = $line;
$quotedline =~ s/\\/\\\\/g;
$quotedline =~ s/"/\\"/g;
&$out(assemble_insn("comment", qq("$quotedline")));
}
$line = strip_comments($line) or next;
($insn, $arg) = parse_statement($line);
&$out(assemble_insn($insn, $arg));
if ($debug) {
&$out(assemble_insn("nop", undef));
}
}
if ($errors) {
die "Assembly failed with $errors error(s)\n";
}
}
1;
__END__
=head1 NAME
B::Assembler - Assemble Perl bytecode
=head1 SYNOPSIS
use Assembler;
=head1 DESCRIPTION
See F<ext/B/B/Assembler.pm>.
=head1 AUTHOR
Malcolm Beattie, C<mbeattie@sable.ox.ac.uk>
=cut
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