apple2js/test/js/formats/util.ts

83 lines
2.2 KiB
TypeScript
Raw Normal View History

import { memory } from 'js/types';
export function skipGap(track: memory, start: number = 0): number {
const end = start + 0x100; // no gap is this big
let i = start;
2022-05-18 15:19:45 +00:00
while (i < end && track[i] === 0xFF) {
i++;
}
2022-05-18 15:19:45 +00:00
if (i === end) {
throw new Error(`found more than 0x100 0xFF bytes after ${start}`);
}
return i;
}
export function compareSequences(track: memory, bytes: number[], pos: number): boolean {
for (let i = 0; i < bytes.length; i++) {
2022-05-18 15:19:45 +00:00
if (track[i + pos] !== bytes[i]) {
return false;
}
}
return true;
}
export function expectSequence(track: memory, pos: number, bytes: number[]): number {
if (!compareSequences(track, bytes, pos)) {
const track_slice = track.slice(pos, Math.min(track.length, pos + bytes.length));
throw new Error(`expected ${bytes.toString()} got ${track_slice.toString()}`);
}
return pos + bytes.length;
}
export function findBytes(track: memory, bytes: number[], start: number = 0): number {
if (start + bytes.length > track.length) {
return -1;
}
for (let i = start; i < track.length; i++) {
if (compareSequences(track, bytes, i)) {
return i + bytes.length;
}
}
return -1;
}
/**
* Convert an ASCII character string into an array of bytes, with optional
* padding.
*
* @param val ASCII character string
* @param pad ASCII character to fill reach padded length
* @param padLength padded length
* @returns an array of bytes
*/
export const stringToBytes = (val: string, pad: string = '\0', padLength: number = 0) => {
const result = [];
let idx = 0;
while (idx < val.length) {
result.push(val.charCodeAt(idx) & 0x7f);
idx++;
}
while (idx++ < padLength) {
result.push(pad.charCodeAt(0) & 0x7f);
}
return result;
};
/**
* Convert a number into a little endian array of bytes.
*
* @param val a number
* @param count number of bytes in result
* @returns an array of bytes
*/
export const numberToBytes = (val: number, count: number) => {
const result = [];
let idx = 0;
while (idx < count) {
result.push(val & 0xff);
val >>= 8;
idx++;
}
return result;
};