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readers.ts
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readers.ts
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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
type Reader = Deno.Reader;
import { encode } from "../encoding/utf8.ts";
/** Reader utility for strings */
export class StringReader implements Reader {
private offs = 0;
private buf = new Uint8Array(encode(this.s));
constructor(private readonly s: string) {}
read(p: Uint8Array): Promise<number | null> {
const n = Math.min(p.byteLength, this.buf.byteLength - this.offs);
p.set(this.buf.slice(this.offs, this.offs + n));
this.offs += n;
if (n === 0) {
return Promise.resolve(null);
}
return Promise.resolve(n);
}
}
/** Reader utility for combining multiple readers */
export class MultiReader implements Reader {
private readonly readers: Reader[];
private currentIndex = 0;
constructor(...readers: Reader[]) {
this.readers = readers;
}
async read(p: Uint8Array): Promise<number | null> {
const r = this.readers[this.currentIndex];
if (!r) return null;
const result = await r.read(p);
if (result === null) {
this.currentIndex++;
return 0;
}
return result;
}
}