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// Copyright 2018-2020 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.
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;  }}
/** * 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;  }}