apple2js/js/formats/d13.ts

import { explodeSector13, D13O } from './format_utils';
import { NibbleDisk, DiskOptions, ENCODING_NIBBLE } from './types';

/**
 * Returns a `Disk` object from DOS 3.2-ordered image data.
 * @param options the disk image and options
 * @returns A nibblized disk
 */
export default function createDiskFromDOS13(options: DiskOptions) {
    const { data, name, side, rawData, volume, readOnly } = options;
    const disk: NibbleDisk = {
        format: 'd13',
        encoding: ENCODING_NIBBLE,
        name,
        side,
        volume,
        readOnly,
        tracks: []
    };

    if (!data && !rawData) {
        throw new Error('data or rawData required');
    }

    /*
     * 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 (let t = 0; t < 35; t++) {
        let track: number[] = [];
        for (let disk_sector = 0; disk_sector < 13; disk_sector++) {
            const physical_sector = D13O[disk_sector];
            let sector: Uint8Array;
            if (rawData) {
                const off = (13 * t + physical_sector) * 256;
                sector = new Uint8Array(rawData.slice(off, off + 256));
            } else if (data) {
                sector = data[t][physical_sector];
            } else {
                throw new Error('Requires data or rawData');
            }
            track = track.concat(
                explodeSector13(volume, t, physical_sector, sector)
            );
        }
        disk.tracks.push(new Uint8Array(track));
    }

    return disk;
}