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dc13b6a59a
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.
61 lines
2.0 KiB
JavaScript
61 lines
2.0 KiB
JavaScript
/* Copyright 2010-2019 Will Scullin <scullin@scullinsteel.com>
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*
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* Permission to use, copy, modify, distribute, and sell this software and its
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* documentation for any purpose is hereby granted without fee, provided that
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* the above copyright notice appear in all copies and that both that
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* copyright notice and this permission notice appear in supporting
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* documentation. No representations are made about the suitability of this
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* software for any purpose. It is provided "as is" without express or
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* implied warranty.
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*/
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import { explodeSector13, D13O } from './format_utils';
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/**
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* Returns a `Disk` object from DOS 3.2-ordered image data.
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* @param {*} options the disk image and options
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* @returns {import('./format_utils').Disk}
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*/
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export default function DOS13(options) {
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var { data, name, rawData, volume, readOnly } = options;
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var disk = {
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format: 'd13',
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name,
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volume,
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readOnly,
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tracks: [],
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trackMap: null,
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rawTracks: null
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};
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/*
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* DOS 13-sector disks have the physical sectors skewed on the track. The skew
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* between physical sectors is 10 (A), resulting in the following physical order:
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*
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* 0 A 7 4 1 B 8 5 2 C 9 6 3
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*
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* Note that because physical sector == logical sector, this works slightly
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* differently from the DOS and ProDOS nibblizers.
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*/
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for (var t = 0; t < 35; t++) {
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var track = [];
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for (var disk_sector = 0; disk_sector < 13; disk_sector++) {
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var physical_sector = D13O[disk_sector];
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var sector;
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if (rawData) {
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var off = (13 * t + physical_sector) * 256;
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sector = new Uint8Array(rawData.slice(off, off + 256));
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} else {
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sector = data[t][physical_sector];
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}
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track = track.concat(
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explodeSector13(volume, t, physical_sector, sector)
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);
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}
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disk.tracks.push(track);
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}
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return disk;
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}
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