apple2js/js/formats/d13.js
Ian Flanigan dc13b6a59a
DOS 13-sector tests and fixes (#53)
Like the DOS 3.3 and ProDOS sector order issues, this change fixes the
physical order of the sectors on 13-sector disks when nibblized.

This change also adds tests for the 13-sector format to verify the
sector order.

One of the crazy things is that _Beneath Apple DOS_ failed me in this
instance because it doesn't discuss what happens to the last byte in
"5 and 3" encoding anywhere (AFAICT). I went back to the DOS 3.1
source released by the Computer History Museum here:

    https://computerhistory.org/blog/apple-ii-dos-source-code/

The code is in `appdos31.lst` in the `POSTNIB` routine on line 4777.
2021-01-03 15:01:30 -08:00

61 lines
2.0 KiB
JavaScript

/* Copyright 2010-2019 Will Scullin <scullin@scullinsteel.com>
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation. No representations are made about the suitability of this
* software for any purpose. It is provided "as is" without express or
* implied warranty.
*/
import { explodeSector13, D13O } from './format_utils';
/**
* Returns a `Disk` object from DOS 3.2-ordered image data.
* @param {*} options the disk image and options
* @returns {import('./format_utils').Disk}
*/
export default function DOS13(options) {
var { data, name, rawData, volume, readOnly } = options;
var disk = {
format: 'd13',
name,
volume,
readOnly,
tracks: [],
trackMap: null,
rawTracks: null
};
/*
* DOS 13-sector disks have the physical sectors skewed on the track. The skew
* between physical sectors is 10 (A), resulting in the following physical order:
*
* 0 A 7 4 1 B 8 5 2 C 9 6 3
*
* Note that because physical sector == logical sector, this works slightly
* differently from the DOS and ProDOS nibblizers.
*/
for (var t = 0; t < 35; t++) {
var track = [];
for (var disk_sector = 0; disk_sector < 13; disk_sector++) {
var physical_sector = D13O[disk_sector];
var sector;
if (rawData) {
var off = (13 * t + physical_sector) * 256;
sector = new Uint8Array(rawData.slice(off, off + 256));
} else {
sector = data[t][physical_sector];
}
track = track.concat(
explodeSector13(volume, t, physical_sector, sector)
);
}
disk.tracks.push(track);
}
return disk;
}