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std/io/readers.ts

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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// Based on https://github.com/golang/go/blob/0452f9460f50f0f0aba18df43dc2b31906fb66cc/src/io/io.go// Copyright 2009 The Go Authors. All rights reserved.// Use of this source code is governed by a BSD-style// license that can be found in the LICENSE file.
import { Buffer } from "./buffer.ts";
/** Reader utility for strings */export class StringReader extends Buffer { constructor(s: string) { super(new TextEncoder().encode(s).buffer); }}
/** Reader utility for combining multiple readers */export class MultiReader implements Deno.Reader { readonly #readers: Deno.Reader[]; #currentIndex = 0;
constructor(readers: Deno.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; }}
/** * A `LimitedReader` reads from `reader` but limits the amount of data returned to just `limit` bytes. * Each call to `read` updates `limit` to reflect the new amount remaining. * `read` returns `null` when `limit` <= `0` or * when the underlying `reader` returns `null`. */export class LimitedReader implements Deno.Reader { constructor(public reader: Deno.Reader, public limit: number) {}
async read(p: Uint8Array): Promise<number | null> { if (this.limit <= 0) { return null; }
if (p.length > this.limit) { p = p.subarray(0, this.limit); } const n = await this.reader.read(p); if (n == null) { return null; }
this.limit -= n; return n; }}