C64 PRG to XBIN converter

c64xbin.py

#!/usr/bin/env python
#
# (c) 2015 Wijnand Modderman-Lenstra, https://maze.io/
#
# Convert a C64 memory dump (VICE) to eXtended Binary (XBIN)
#
# To capture a dump in VICE, attach to the monitor, and run the following::
#     > $01 $35
#     save "dump.ram" 0 $0000 $FFFF
#
# Now, using dump.ram, you can invoke this script and get an XBIN. Jay.
#
# Thanks to the folks over at NURDspace https://nurdspace.nl/ for explaining
# the C64 and VIC-II memory layout.

import argparse
import os
import struct
import sys

# VICE chargen ROM
# FIXME should actually read the chargen ROM from the C64 memory map, but for
#       now this will do as none of my PRGs have custom fonts
chargen = os.path.expanduser('~/.vice/C64/chargen')

# http://www.pepto.de/projects/colorvic/
colors = [
    0x000000, 0xffffff, 0x68372b, 0x70a4b2, 0x6f3d86, 0x588d43, 0x352879, 0xb8c76f,
    0x6f4f25, 0x433900, 0x9a6759, 0x444444, 0x6c6c6c, 0x9ad284, 0x6c5eb5, 0x959595
]


def load_dump(filename):
    with open(filename, 'rb') as fp:
        data = bytearray(fp.read())
        # VICE dumps include the loader address
        if len(data) == 0x10002 and data[0] == 0x00 and data[1] == 0x00:
            data = data[2:]
        assert len(data) == 0x10000, 'not a 64k dump'
        return data


def run():
    parser = argparse.ArgumentParser()
    parser.add_argument('ram', nargs=1)
    args = parser.parse_args()
    dump = load_dump(args.ram[0])
    base = os.path.splitext(os.path.basename(args.ram[0]))[0]

    # http://codebase64.org/doku.php?id=base:vicii_memory_organizing
    print '$d018 = {:08b}'.format(dump[0xd018])
    bitmap    = ((dump[0xd018] >> 3) & 0b1)    * 0x2000
    charmemp  = ((dump[0xd018] >> 1) & 0b111)  * 0x0800
    charmem   = 0xd800
    screenmem = ((dump[0xd018] >> 4) & 0b1111) * 0x0400
    if charmemp == 0x1000:
        case = 'upper'
    elif charmemp == 0x1800:
        case = 'mixed'
    else:
        case = 'unknown'
    print '        bitmap    ${:04x}'.format(bitmap)
    print '        charmem   ${:04x}'.format(charmem)
    print '        charmem   ${:04x} ({} case)'.format(charmemp, case)
    print '        screenmem ${:04x}'.format(screenmem)
    print '$dd00 = {:08b}'.format(dump[0xdd00]),
    bank = [3, 2, 1, 0][dump[0xdd00] & 3]
    print '-> bank{}'.format(bank)

    # Dump text map, 40x25 characters in screenmem
    textmap = []
    for offset in xrange(0x0000, 0x03e8, 40):
        p = screenmem + offset
        t = dump[p:p + 40]
        textmap.append(t)

    # Dump color map, 40x25 characters, 3 bits per color
    background = dump[0xd021] & 0xf
    colormap = []
    for offset in xrange(0x0000, 0x03e8, 40):
        p = charmem + offset
        c = dump[p:p + 40]
        colormap.append(map(lambda x: x & 0xf, c))

    # Let's make an XBin
    xbin = bytearray('XBIN\x1a')            # ID + EOF char
    xbin.extend(struct.pack('<HH', 40, 25)) # Width and Height
    xbin.extend(struct.pack('<B', 8))       # FontSize 8x256
    xbin.extend(struct.pack('<B',
        0b00001011,                         # Nonblink, Palette & Font
    )) # Flags
    for color in colors:
        r = (color >> 16) & 0xff
        g = (color >> 8) & 0xff
        b = (color >> 0) & 0xff
        xbin.extend(struct.pack('<BBB', r >> 2, g >> 2, b >> 2))
    with open(chargen, 'rb') as fp:
        if case == 'mixed':  # skip first 256 glyphs
            fp.read(2048)
        xbin.extend(fp.read(2048))
    for h in range(25):
        for w in range(40):
            xbin.append(textmap[h][w])
            xbin.append(colormap[h][w] | (background << 4))

    # SAUCE stuff
    size = len(xbin)
    xbin.extend('\x1aSAUCE00')
    xbin.extend('\x00' * 35) # Title
    xbin.extend('\x00' * 20) # Author
    xbin.extend('\x00' * 20) # Group
    xbin.extend('19700101')  # Date
    xbin.extend(struct.pack('<I', size))
    xbin.extend(struct.pack('<B', 6))               # DataType XBin
    xbin.extend(struct.pack('<B', 0))               # FileType None
    xbin.extend(struct.pack('<HHHH', 8, 25, 0, 0))  # Char Width, Lines, N/A, N/A
    xbin.extend(struct.pack('<B', 0))               # Comments
    xbin.extend(struct.pack('<B', 0b00001001))      # Legacy Ratio, iCE Colors
    xbin.extend('\x00' * 22) # TInfoS

    print 'saving to {}.xb'.format(base)
    with open(base + '.xb', 'wb') as fp:
        fp.write(xbin)


if __name__ == '__main__':
    sys.exit(run())