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64 lines
1.7 KiB
TypeScript
64 lines
1.7 KiB
TypeScript
// Loaded from https://deno.land/std@0.88.0/io/readers.ts
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// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
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// Based on https://github.com/golang/go/blob/0452f9460f50f0f0aba18df43dc2b31906fb66cc/src/io/io.go
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/** Reader utility for strings */
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export class StringReader extends Deno.Buffer {
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constructor(s: string) {
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super(new TextEncoder().encode(s).buffer);
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}
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}
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/** Reader utility for combining multiple readers */
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export class MultiReader implements Deno.Reader {
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private readonly readers: Deno.Reader[];
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private currentIndex = 0;
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constructor(...readers: Deno.Reader[]) {
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this.readers = readers;
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}
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async read(p: Uint8Array): Promise<number | null> {
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const r = this.readers[this.currentIndex];
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if (!r) return null;
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const result = await r.read(p);
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if (result === null) {
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this.currentIndex++;
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return 0;
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}
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return result;
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}
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}
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/**
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* A `LimitedReader` reads from `reader` but limits the amount of data returned to just `limit` bytes.
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* Each call to `read` updates `limit` to reflect the new amount remaining.
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* `read` returns `null` when `limit` <= `0` or
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* when the underlying `reader` returns `null`.
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*/
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export class LimitedReader implements Deno.Reader {
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constructor(public reader: Deno.Reader, public limit: number) {}
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async read(p: Uint8Array): Promise<number | null> {
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if (this.limit <= 0) {
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return null;
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}
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if (p.length > this.limit) {
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p = p.subarray(0, this.limit);
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}
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const n = await this.reader.read(p);
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if (n == null) {
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return null;
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}
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this.limit -= n;
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return n;
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}
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}
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