apple1js/js/ram.ts

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/* Copyright 2010-2023 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.
*/
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import { base64_decode, base64_encode } from './base64';
import { allocMemPages } from './util';
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import type { byte, memory } from '@whscullin/cpu6502';
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export interface RAMState {
start: byte;
end: byte;
mem: string;
}
export default class RAM {
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mem: memory;
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constructor(
private start_page: byte,
private end_page: byte,
) {
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this.mem = allocMemPages(end_page - start_page + 1);
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for (let page = 0; page <= end_page; page++) {
for (let off = 0; off < 0x100; off++) {
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this.mem[page * 0x100 + off] = 0; // Math.floor(Math.random()*256);
}
}
}
start() {
return this.start_page;
}
end() {
return this.end_page;
}
read(page: byte, off: byte) {
return this.mem[(page - this.start_page) * 0x100 + off];
}
write(page: byte, off: byte, val: byte) {
this.mem[(page - this.start_page) * 0x100 + off] = val;
}
getState(): RAMState {
return {
start: this.start_page,
end: this.end_page,
mem: base64_encode(this.mem),
};
}
setState(state: RAMState) {
this.start_page = state.start;
this.end_page = state.end;
this.mem = base64_decode(state.mem);
}
}