Source code for mrcrowbar.lib.os.dos

#!/usr/bin/python3

from __future__ import annotations

from mrcrowbar import ansi
from mrcrowbar import models as mrc
from mrcrowbar import utils
from mrcrowbar.lib.hardware import ibm_pc

# map of DOS code page 437 to Unicode
CP437 = """ ☺☻♥♦♣♠•◘○◙♂♀♪♫☼►◄↕‼¶§▬↨↑↓→←∟↔▲▼ !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~⌂ÇüéâäàåçêëèïîìÄÅÉæÆôöòûùÿÖÜ¢£¥₧ƒáíóúñѪº¿⌐¬½¼¡«»░▒▓│┤╡╢╖╕╣║╗╝╜╛┐└┴┬├─┼╞╟╚╔╩╦╠═╬╧╨╤╥╙╘╒╓╫╪┘┌█▄▌▐▀αßΓπΣσµτΦΘΩδ∞φε∩≡±≥≤⌠⌡÷≈°∙·√ⁿ²■ """


def decode_nfo( buffer ):
    """Decodes a byte string in NFO format (beloved by PC scener groups) from DOS Code Page 437
    to Unicode."""
    assert utils.is_bytes( buffer )
    return "\n".join(
        ["".join( [CP437[y] for y in x] ) for x in buffer.split( b"\r\n" )]
    )


class B800Char( mrc.Block ):
    _palette = ibm_pc.EGA_DEFAULT_PALETTE

    code_point = mrc.UInt8( 0x00 )
    fg_blink = mrc.Bits( 0x01, 0b10000000 )
    bg_colour = mrc.Bits( 0x01, 0b01110000 )
    fg_colour = mrc.Bits( 0x01, 0b00001111 )

    @property
    def char( self ):
        return CP437[self.code_point]

    def ansi_format( self ):
        return ansi.format_string(
            self.char,
            self._palette[self.fg_colour],
            self._palette[self.bg_colour],
            blink=self.fg_blink,
        )

    def __str__( self ):
        return self.ansi_format()

    def __repr__( self ):
        return "<{}: char {}, bg {}, fg {}>".format(
            self.__class__.__name__, self.char, self.bg_colour, self.fg_colour
        )


class B800Screen( mrc.Block ):
    B800_SCREEN_WIDTH = 80

    chars = mrc.BlockField( B800Char, 0x00, count=2000 )

    @property
    def text( self ):
        return "\n".join(
            [
                "".join(
                    [
                        c.char
                        for c in self.chars[i * self.B800_SCREEN_WIDTH :][
                            : self.B800_SCREEN_WIDTH
                        ]
                    ]
                )
                for i in range( (len( self.chars ) + 1) // self.B800_SCREEN_WIDTH )
            ]
        )

    def ansi_format( self ):
        result = []
        for i in range( (len( self.chars ) + 1) // self.B800_SCREEN_WIDTH ):
            for c in self.chars[i * self.B800_SCREEN_WIDTH :][: self.B800_SCREEN_WIDTH]:
                result.append( c.ansi_format() )
            result.append( "\n" )
        return "".join( result )

    def print( self ):
        print( self.ansi_format() )

    def __str__( self ):
        return self.ansi_format()

    def __repr__( self ):
        return "<{}: {} chars, {}x{}>".format(
            self.__class__.__name__,
            len( self.chars ),
            self.B800_SCREEN_WIDTH,
            1 + (len( self.chars ) - 1) // self.B800_SCREEN_WIDTH,
        )


# source: https://www.fileformat.info/format/exe/corion-mz.htm


class Relocation( mrc.Block ):
    offset = mrc.UInt16_LE( 0x00 )
    segment = mrc.UInt16_LE( 0x02 )


class MZHeader( mrc.Block ):
    magic = mrc.Const( mrc.Bytes( 0x00, length=2 ), b"MZ" )
    last_page_size = mrc.UInt16_LE( 0x02 )
    page_count = mrc.UInt16_LE( 0x04 )
    reltable_count = mrc.UInt16_LE( 0x06 )
    header_size_raw = mrc.UInt16_LE( 0x08 )
    min_alloc_raw = mrc.UInt16_LE( 0x0a )
    max_alloc_raw = mrc.UInt16_LE( 0x0c )
    initial_ss = mrc.UInt16_LE( 0x0e )
    initial_sp = mrc.UInt16_LE( 0x10 )
    checksum = mrc.UInt16_LE( 0x12 )
    initial_ip = mrc.UInt16_LE( 0x14 )
    initial_cs = mrc.UInt16_LE( 0x16 )
    reltable_offset = mrc.UInt16_LE( 0x18 )
    overlay = mrc.UInt16_LE( 0x1a )

    @property
    def header_size( self ):
        return self.header_size_raw * 16

    @header_size.setter
    def header_size( self, value ):
        self.header_size_raw = (value // 16) + (1 if value % 16 else 0)

    @property
    def extra_offset( self ):
        return self.page_count * 512


class EXE( mrc.Block ):
    mz_header = mrc.BlockField( MZHeader, 0x00 )