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Module

std/io/string_writer.ts

Deno standard library
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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import type { Writer, WriterSync } from "../types.d.ts";
const decoder = new TextDecoder();
/** * Writer utility for buffering string chunks. * * @example * ```ts * import { * copyN, * StringReader, * StringWriter, * } from "https://deno.land/std@$STD_VERSION/io/mod.ts"; * import { copy } from "https://deno.land/std@$STD_VERSION/streams/copy.ts"; * * const w = new StringWriter("base"); * const r = new StringReader("0123456789"); * await copyN(r, w, 4); // copy 4 bytes * * // Number of bytes read * console.log(w.toString()); //base0123 * * await copy(r, w); // copy all * console.log(w.toString()); // base0123456789 * ``` * * **Output:** * * ```text * base0123 * base0123456789 * ``` * * @deprecated (will be removed after 1.0.0) Use Web Streams instead. */export class StringWriter implements Writer, WriterSync { #chunks: Uint8Array[] = []; #byteLength = 0; #cache: string | undefined;
constructor(private base: string = "") { const c = new TextEncoder().encode(base); this.#chunks.push(c); this.#byteLength += c.byteLength; }
write(p: Uint8Array): Promise<number> { return Promise.resolve(this.writeSync(p)); }
writeSync(p: Uint8Array): number { this.#chunks.push(new Uint8Array(p)); this.#byteLength += p.byteLength; this.#cache = undefined; return p.byteLength; }
toString(): string { if (this.#cache) { return this.#cache; } const buf = new Uint8Array(this.#byteLength); let offs = 0; for (const chunk of this.#chunks) { buf.set(chunk, offs); offs += chunk.byteLength; } this.#cache = decoder.decode(buf); return this.#cache; }}