gistfile1.txt

use nqp;
class ByteReader {
    has blob8 $.buf;
    has uint64 $.offset is rw;
    method read(\t) {
        if t =:= uint32 {
            my $res = $!buf.read-uint32($!offset);
            $!offset += 4;
            $res
        }
        elsif t =:= uint16 {
            my $res = $!buf.read-uint16($!offset);
            $!offset += 2;
            $res
        }
        else {
            die "unsupported type: {t.^name}";
        }
    }
    method read-struct(\t) {
        my $obj = t.new;
        for t.^attributes -> $attr {
            $attr.set_value($obj, self.read($attr.type));
        }
        $obj
    }
    method dump-struct($obj) {
        my $pos = 0;
        for $obj.^attributes -> $attr {
            say "$pos.base(16) $attr.name(): $attr.get_value($obj)";
            my $size = $attr.type =:= uint32 ?? 4 !! $attr.type =:= uint16 ?? 2 !! die "unsupported type";
            $pos += $size;
        }
        $obj
    }
}

class MoarVM::Bytecode {
    has $!mbc;
    has $.string-heap;
    has $!callsites;
    has $!annotations;
    has $!compunit;
    has @!frames;
    has $!bytecode;
    has @!sc_handle_idxs;
    has @!extop_name_idxs;

    my class Header {
        has uint32 $.version;
        has uint32 $.sc-deps-offset;
        has uint32 $.sc-deps-elems;
        has uint32 $.extops-offset;
        has uint32 $.extops-elems;
        has uint32 $.frames-offset;
        has uint32 $.frames-elems;
        has uint32 $.callsites-offset;
        has uint32 $.callsites-elems;
        has uint32 $.strings-offset;
        has uint32 $.strings-elems;
        has uint32 $.sc-offset;
        has uint32 $.sc-bytes;
        has uint32 $.bytecode-offset;
        has uint32 $.bytecode-bytes;
        has uint32 $.annotations-offset;
        has uint32 $.annotations-size;
        has uint32 $.hll-idx;
        has uint32 $.main-frame-idx;
        has uint32 $.load-frame-idx;
        has uint32 $.deserialize-frame-idx;
    }

    my class Frame {
        has uint32 $.bytecode-offset;
        has uint32 $.bytecode-length;
        has uint32 $.local-types;
        has uint32 $.lexicals;
        has uint32 $.cuuid-idx;
        has uint32 $.name-idx;
        has uint16 $.outer-idx;
        has uint32 $.annotations-offset;
        has uint32 $.num-annotations;
        has uint32 $.num-handlers;
        has uint16 $.flags;
        has uint16 $.num-static-lex-values;
        has uint32 $.code-obj-sc-dep-idx;
        has uint32 $.code-obj-sc-idx;
        has uint32 $.debug-map;
    }

    my class Handler {
        has uint32 $.start-offset;
        has uint32 $.end-offset;
        has uint32 $.category-mask;
        has uint16 $.action;
        has uint16 $.local;
        has uint32 $.label;
    }

    sub align_section($size) {
        my uint32 $aligned = nqp::ceil_n($size / 8) * 8;
        $aligned
    }

    method BUILD(:$!mbc) { }

    method from-file($file-name) {
        self.new(:mbc($file-name.IO.slurp(:bin)));
    }

    method read-string-heap($reader, $offset, $elems) {
        my @strings;
        $reader.offset = $offset;
        for ^$elems {
            my $bytes = $reader.read(uint32);
            my $utf8 = $bytes +& 1;
            $bytes +>= 1;
            @strings.push: $!mbc.subbuf($reader.offset, $bytes).decode($utf8 ?? 'utf8' !! 'latin-1');
            my int $pad = 4 - $bytes % 4;
            $pad = 0 if $pad == 4;
            $reader.offset += $bytes + $pad;
        }
        @strings;
    }

    method read-header() {
        # 92 bytes
        my $offset = 0;
        my $magic = $!mbc.subbuf($offset, 8).decode;
        die "Could not recognize header marker $magic" if $magic ne "MOARVM\r\n";
        $offset += 8;

        my $reader = ByteReader.new(:buf($!mbc), :$offset);
        my $header = $reader.read-struct(Header);

        my $version = $header.version;
        die "Unknown version $version" if $version != 6;

        say 'sc-deps: ' ~ $header.sc-deps-offset.base(16);
        say 'extops: ' ~ $header.extops-offset.base(16);
        say 'frames: ' ~ $header.frames-offset.base(16);
        say 'callsites: ' ~ $header.callsites-offset.base(16);
        say 'strings: ' ~ $header.strings-offset.base(16);
        say 'sc: ' ~ $header.sc-offset.base(16);
        say 'bytecode: ' ~ $header.bytecode-offset.base(16);
        say 'annotations: ' ~ $header.annotations-offset.base(16);

        $!string-heap = my @strings = self.read-string-heap($reader, $header.strings-offset, $header.strings-elems);

        $reader.offset = $header.frames-offset;

        for ^$header.frames-elems {
            my $start = $reader.offset;
            my $frame = $reader.read-struct(Frame);
            note "$start.base(16): @strings[$frame.name-idx] (cuid: @strings[$frame.cuuid-idx]), bytecode at {($frame.bytecode-offset() + $header.bytecode-offset).base(16)}";
            $reader.offset += $frame.local-types * 2;
            #for $frame.local-types {
            #    my $type = $reader.read(uint16);
            #    my $name = $reader.read(uint32);
            #    say @strings[$name];
            #}
            $reader.offset += $frame.lexicals * 6;
            for ^$frame.num-handlers {
                my $handler = $reader.read-struct(Handler);
                if $handler.category-mask +& 4096 {
                    $reader.read(uint16);
                }
            }
            $reader.offset += $frame.num-static-lex-values * 12;
            note("    debug map at $reader.offset().base(16)");
            $reader.offset += $frame.debug-map * 6;
        }

        $header;
    }
}

my $bytecode = MoarVM::Bytecode.from-file(@*ARGS[0]);
ByteReader.dump-struct($bytecode.read-header);
for $bytecode.string-heap {
    say $_
};