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std/io/writers.ts

Deno standard library
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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.type Writer = Deno.Writer;type WriterSync = Deno.WriterSync;import { decode, encode } from "../encoding/utf8.ts";
/** Writer utility for buffering string chunks */export class StringWriter implements Writer, WriterSync { private chunks: Uint8Array[] = []; private byteLength = 0; private cache: string | undefined;
constructor(private base: string = "") { const c = 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(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 = decode(buf); return this.cache; }}