Pasti STX disk image track merge utility (Atari ST)

stx_merge.py

#!/usr/bin/env python3

#
# Pasti .STX Atari ST disk image merger
# Allows combining of tracks from separate STX files,
# for cases where we can only dump part of a disk at a time.
#
# Usage:
#   stx_main("a.stx")
#   stx_add("b.stx")
#   stx_add("c.stx")
#   stx_out("merged.stx")
#
# Based on Pasti reverse engineering:
# http://info-coach.fr/atari/documents/_mydoc/Pasti-documentation.pdf
#
# See also: stx_dump.py
# https://gist.github.com/bbbradsmith/a0fb690f366c902e96f25a8351a5c46c
#
# Brad Smith, 2021
# http://rainwarrior.ca
#

import struct

header = None
tracks = [{},{}]

def stx_print_header(d):
    h = struct.unpack("<BBBBHHHBBL",d[0:16])
    print("id: $%02X $%02X $%02X $%02X \"%c%c%c\"+$%02X" % (h[0:4]+h[0:4]))
    print("version: %d" % h[4])
    print("tool: $%04X" % h[5])
    print("reserved: $%04X" % h[6])
    print("tracks: %d" % h[7])
    print("revision: %d" % h[8])
    print("reserved: $%08X" % h[9])

def stx_print_track_header(d):
    t = struct.unpack("<LLHHHBB",d[0:16])
    tside = t[5]>>7
    tnum = t[5]&0x7F
    print("Track: %d:%02d  %2d sectors, %d bytes" % (tside,tnum,t[2],t[0]))

def stx_main(filename):
    global header, tracks
    print("Main Pasti: " + filename)
    d = open(filename,"rb").read()
    stx_print_header(d)
    header = struct.unpack("<BBBBHHHBBL",d[0:16])
    p = 16
    for t in range(0,header[7]):
        thead = struct.unpack("<LLHHHBB",d[p:p+16])
        stx_print_track_header(d[p:p+16])
        tlen = thead[0]
        tside = thead[5]>>7
        tnum = thead[5]&0x7F
        if tnum in tracks[tside]:
            print("Warning: duplicate track %d:%02d" % (tside,tnum))
        tracks[tside][tnum] = d[p:p+tlen]
        p += tlen
    print(".")

def stx_add(filename):
    global tracks
    print("Add Pasti: " + filename)
    d = open(filename,"rb").read()
    h = struct.unpack("<BBBBHHHBBL",d[0:16])
    stx_print_header(d)
    p = 16
    for t in range(0,h[7]):
        thead = struct.unpack("<LLHHHBB",d[p:p+16])
        stx_print_track_header(d[p:p+16])
        tlen = thead[0]
        tside = thead[5]>>7
        tnum = thead[5]&0x7F
        if tnum in tracks[tside]:
            print("Warning: duplicate track %d:%02d" % (tside,tnum))
        tracks[tside][tnum] = d[p:p+tlen]
        p += tlen
    print(".")

def stx_out(filename):
    global header, tracks
    assert header,"No main loaded? Use stx_main first."
    print("Out Pasti: " + filename)
    f = open(filename,"wb")
    tcount = len(tracks[0]) + len(tracks[1])
    header = list(header)
    header[7] = tcount
    header = tuple(header)
    dh = struct.pack("<BBBBHHHBBL",*header)
    stx_print_header(dh)
    f.write(dh)
    for i in range(256):
        if i in tracks[0]:
            stx_print_track_header(tracks[0][i])
            f.write(tracks[0][i])
        if i in tracks[1]:
            stx_print_track_header(tracks[1][i])
            f.write(tracks[1][i])
    print(".")