mirror of
https://github.com/whscullin/apple2js.git
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302 lines
11 KiB
TypeScript
302 lines
11 KiB
TypeScript
import DOS from './do';
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import Nibble from './nib';
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import ProDOS from './po';
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import { BlockDisk, DiskOptions } from './types';
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import { byte, ReadonlyUint8Array } from 'js/types';
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/**
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* Offsets in bytes to the various header fields. All number fields are
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* in little-endian order (least significant byte first). These values
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* come from the spec at:
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*
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* https://apple2.org.za/gswv/a2zine/Docs/DiskImage_2MG_Info.txt
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*/
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const OFFSETS = {
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/** File signature ('2IMG', 4 bytes) */
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SIGNATURE: 0x00,
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/** Creator ID (4 bytes) */
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CREATOR: 0x04,
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/** Header length (2 bytes) */
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HEADER_LENGTH: 0x08,
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/** Version number (2 bytes). (Version of what? Format? Image?). */
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VERSION: 0x0A,
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/** Image format ID (4 bytes) */
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FORMAT: 0x0C,
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/** Flags and DOS 3.3 volume number */
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FLAGS: 0x10,
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/**
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* Number of ProDOS blocks (4 bytes). ProDOS blocks are 512 bytes each.
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* This field must be zero if the image format is not 0x01 (ProDOS).
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* (ASIMOV2 always fills in this field.)
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*/
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BLOCKS: 0x14,
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/**
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* Disk data start in bytes from the beginning of the image file
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* (4 bytes).
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*/
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DATA_OFFSET: 0x18,
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/**
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* Length of disk data in bytes (4 bytes). (143,360 bytes for 5.25"
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* floppies; 512 × blocks for ProDOS volumes.)
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*/
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DATA_LENGTH: 0x1C,
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/**
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* Comment start in bytes from the beginning of the image file (4 bytes).
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* Must be zero if there is no comment. The comment must come after the
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* disk data and before the creator data. The comment should be "raw text"
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* with no terminating null. By "raw text", we assume UTF-8.
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*/
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COMMENT: 0x20,
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/**
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* Comment length in bytes (4 bytes). Must be zero if there is no comment.
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*/
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COMMENT_LENGTH: 0x24,
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/**
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* Optional creator data start in bytes from the beginning of the image
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* file (4 bytes). Must be zero if there is no creator data.
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*/
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CREATOR_DATA: 0x28,
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/**
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* Creator data length in bytes (4 bytes). Must be zero if there is no
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* creator data.
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*/
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CREATOR_DATA_LENGTH: 0x2C,
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/** Padding (16 bytes). Must be zero. */
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PADDING: 0x30,
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} as const;
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const FLAGS = {
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READ_ONLY: 0x80000000,
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VOLUME_VALID: 0x00000100,
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VOLUME_MASK: 0x000000FF
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} as const;
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export enum FORMAT {
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DOS = 0,
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ProDOS = 1,
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NIB = 2,
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}
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export interface HeaderData {
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bytes: number;
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creator: string;
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format: FORMAT;
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offset: number;
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readOnly: boolean;
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volume: byte;
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comment?: string;
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creatorData?: ReadonlyUint8Array;
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}
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export function read2MGHeader(rawData: ArrayBuffer): HeaderData {
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const prefix = new DataView(rawData);
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const decoder = new TextDecoder('ascii');
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const signature = decoder.decode(rawData.slice(OFFSETS.SIGNATURE, OFFSETS.SIGNATURE + 4));
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if (signature !== '2IMG') {
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throw new Error(`Unrecognized 2mg signature: ${signature}`);
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}
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const creator = decoder.decode(rawData.slice(OFFSETS.CREATOR, OFFSETS.CREATOR + 4));
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const headerLength = prefix.getInt16(OFFSETS.HEADER_LENGTH, true);
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if (headerLength !== 64) {
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throw new Error(`2mg header length is incorrect ${headerLength} !== 64`);
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}
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const format = prefix.getInt32(OFFSETS.FORMAT, true);
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const flags = prefix.getInt32(OFFSETS.FLAGS, true);
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const blocks = prefix.getInt32(OFFSETS.BLOCKS, true);
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const offset = prefix.getInt32(OFFSETS.DATA_OFFSET, true);
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const bytes = prefix.getInt32(OFFSETS.DATA_LENGTH, true);
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const commentOffset = prefix.getInt32(OFFSETS.COMMENT, true);
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const commentLength = prefix.getInt32(OFFSETS.COMMENT_LENGTH, true);
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const creatorDataOffset = prefix.getInt32(OFFSETS.CREATOR_DATA, true);
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const creatorDataLength = prefix.getInt32(OFFSETS.CREATOR_DATA_LENGTH, true);
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// Though the spec says that it should be zero if the format is not
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// ProDOS, we don't check that since we know that it is violated.
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// However we do check that it's correct if the image _is_ ProDOS.
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if (format === FORMAT.ProDOS && blocks * 512 !== bytes) {
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throw new Error(`2mg blocks does not match disk data length: ${blocks} * 512 !== ${bytes}`);
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}
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if (offset < headerLength) {
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throw new Error(`2mg data offset is less than header length: ${offset} < ${headerLength}`);
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}
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if (offset + bytes > prefix.byteLength) {
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throw new Error(`2mg data extends beyond disk image: ${offset} + ${bytes} > ${prefix.byteLength}`);
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}
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const dataEnd = offset + bytes;
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if (commentOffset && commentOffset < dataEnd) {
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throw new Error(`2mg comment is before the end of the disk data: ${commentOffset} < ${offset} + ${bytes}`);
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}
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const commentEnd = commentOffset ? commentOffset + commentLength : dataEnd;
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if (commentEnd > prefix.byteLength) {
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throw new Error(`2mg comment extends beyond disk image: ${commentEnd} > ${prefix.byteLength}`);
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}
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if (creatorDataOffset && creatorDataOffset < commentEnd) {
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throw new Error(`2mg creator data is before the end of the comment: ${creatorDataOffset} < ${commentEnd}`);
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}
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const creatorDataEnd = creatorDataOffset ? creatorDataOffset + creatorDataLength : commentEnd;
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if (creatorDataEnd > prefix.byteLength) {
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throw new Error(`2mg creator data extends beyond disk image: ${creatorDataEnd} > ${prefix.byteLength}`);
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}
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const extras: { comment?: string; creatorData?: ReadonlyUint8Array } = {};
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if (commentOffset) {
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extras.comment = new TextDecoder('utf-8').decode(
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new Uint8Array(rawData, commentOffset, commentLength));
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}
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if (creatorDataOffset) {
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extras.creatorData = new Uint8Array(rawData, creatorDataOffset, creatorDataLength);
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}
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const readOnly = (flags & FLAGS.READ_ONLY) !== 0;
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let volume = format === FORMAT.DOS ? 254 : 0;
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if (flags & FLAGS.VOLUME_VALID) {
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volume = flags & FLAGS.VOLUME_MASK;
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}
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return {
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bytes,
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creator,
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format,
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offset,
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readOnly,
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volume,
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...extras
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};
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}
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/**
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* Creates the prefix and suffix parts of a 2mg file. Will use
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* default header values if headerData is null.
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*
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* Currently only supports blocks disks but should be adaptable
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* for nibble formats.
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*
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* @param headerData 2mg header data
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* @param blocks The number of blocks in a block volume
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* @returns 2mg prefix and suffix for creating a 2mg disk image
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*/
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export const create2MGFragments = (headerData: HeaderData | null, { blocks } : { blocks: number }) => {
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if (!headerData) {
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headerData = {
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bytes: blocks * 512,
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creator: 'A2JS',
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format: FORMAT.ProDOS,
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offset: 64,
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readOnly: false,
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volume: 0,
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};
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}
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if (headerData.format !== FORMAT.ProDOS) {
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throw new Error('Nibble formats not supported yet');
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}
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if (headerData.bytes !== blocks * 512) {
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throw new Error('Byte count does not match block count');
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}
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const prefix = new Uint8Array(64);
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const prefixView = new DataView(prefix.buffer);
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const volumeFlags = headerData.volume ? headerData.volume | FLAGS.VOLUME_VALID : 0;
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const readOnlyFlag = headerData.readOnly ? FLAGS.READ_ONLY : 0;
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const flags = volumeFlags | readOnlyFlag;
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const prefixLength = prefix.length;
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const dataLength = blocks * 512;
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let commentOffset = 0;
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let commentLength = 0;
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let commentData = new Uint8Array(0);
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if (headerData.comment) {
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commentData = new TextEncoder().encode(headerData.comment);
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commentOffset = prefixLength + dataLength;
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commentLength = commentData.length;
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}
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let creatorDataOffset = 0;
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let creatorDataLength = 0;
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let creatorData = new Uint8Array(0);
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if (headerData.creatorData) {
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creatorData = new Uint8Array(headerData.creatorData);
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creatorDataOffset = prefixLength + dataLength + commentLength;
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creatorDataLength = headerData.creatorData.length;
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}
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const encoder = new TextEncoder();
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prefix.set(encoder.encode('2IMG'), OFFSETS.SIGNATURE);
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prefix.set(encoder.encode(headerData.creator.slice(0, 4)), OFFSETS.CREATOR);
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prefixView.setInt32(OFFSETS.HEADER_LENGTH, 64, true);
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prefixView.setInt16(OFFSETS.VERSION, 1, true);
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prefixView.setInt32(OFFSETS.FORMAT, headerData.format, true);
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prefixView.setInt32(OFFSETS.FLAGS, flags, true);
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prefixView.setInt32(OFFSETS.BLOCKS, blocks, true);
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prefixView.setInt32(OFFSETS.DATA_OFFSET, prefixLength, true);
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prefixView.setInt32(OFFSETS.DATA_LENGTH, dataLength, true);
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prefixView.setInt32(OFFSETS.COMMENT, commentOffset, true);
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prefixView.setInt32(OFFSETS.COMMENT_LENGTH, commentLength, true);
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prefixView.setInt32(OFFSETS.CREATOR_DATA, creatorDataOffset, true);
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prefixView.setInt32(OFFSETS.CREATOR_DATA_LENGTH, creatorDataLength, true);
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const suffix = new Uint8Array(commentLength + creatorDataLength);
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suffix.set(commentData);
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suffix.set(creatorData, commentLength);
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return { prefix, suffix };
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};
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/**
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* Creates a 2MG image from stored 2MG header data and a block disk. Will use
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* default header values if headerData is null.
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*
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* @param headerData 2MG style header data
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* @param blocks Prodos volume blocks
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* @returns 2MS
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*/
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export const create2MGFromBlockDisk = (headerData: HeaderData | null, { blocks }: BlockDisk): ArrayBuffer => {
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const { prefix, suffix } = create2MGFragments(headerData, { blocks: blocks.length });
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const imageLength = prefix.length + blocks.length * 512 + suffix.length;
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const byteArray = new Uint8Array(imageLength);
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byteArray.set(prefix);
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for (let idx = 0; idx < blocks.length; idx++) {
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byteArray.set(blocks[idx], prefix.length + idx * 512);
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}
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byteArray.set(suffix, prefix.length + blocks.length * 512);
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return byteArray.buffer;
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};
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/**
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* Returns a `Disk` object from a 2mg image.
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* @param options the disk image and options
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*/
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export default function createDiskFrom2MG(options: DiskOptions) {
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let { rawData } = options;
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let disk;
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if (!rawData) {
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throw new Error('Requires rawData');
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}
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const { bytes, format, offset, readOnly, volume } = read2MGHeader(rawData);
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rawData = rawData.slice(offset, offset + bytes);
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options = { ...options, rawData, readOnly, volume };
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// Check image format.
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// Sure, it's really 64 bits. But only 2 are actually used.
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switch (format) {
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case FORMAT.ProDOS: // PO
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disk = ProDOS(options);
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break;
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case FORMAT.NIB: // NIB
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disk = Nibble(options);
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break;
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case FORMAT.DOS: // dsk
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default: // Something hinky, assume 'dsk'
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disk = DOS(options);
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break;
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}
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return disk;
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}
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