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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { createLPS } from "./_common.ts";
import type { DelimiterDisposition, DelimiterStreamOptions,} from "./delimiter_stream.ts";
/** Transform a stream into a stream where each chunk is divided by a given delimiter. * * ```ts * import { TextDelimiterStream } from "https://deno.land/std@$STD_VERSION/streams/text_delimiter_stream.ts"; * const res = await fetch("https://example.com"); * const parts = res.body! * .pipeThrough(new TextDecoderStream()) * .pipeThrough(new TextDelimiterStream("foo")); * ``` */export class TextDelimiterStream extends TransformStream<string, string> { #buf = ""; #delimiter: string; #inspectIndex = 0; #matchIndex = 0; #delimLPS: Uint8Array; #disp: DelimiterDisposition;
constructor(delimiter: string, options?: DelimiterStreamOptions) { super({ transform: (chunk, controller) => { this.#handle(chunk, controller); }, flush: (controller) => { controller.enqueue(this.#buf); }, });
this.#delimiter = delimiter; this.#delimLPS = createLPS(new TextEncoder().encode(delimiter)); this.#disp = options?.disposition ?? "discard"; }
#handle( chunk: string, controller: TransformStreamDefaultController<string>, ) { this.#buf += chunk; let localIndex = 0; while (this.#inspectIndex < this.#buf.length) { if (chunk[localIndex] === this.#delimiter[this.#matchIndex]) { this.#inspectIndex++; localIndex++; this.#matchIndex++; if (this.#matchIndex === this.#delimiter.length) { // Full match const start = this.#inspectIndex - this.#delimiter.length; const end = this.#disp === "suffix" ? this.#inspectIndex : start; const copy = this.#buf.slice(0, end); controller.enqueue(copy); const shift = this.#disp == "prefix" ? start : this.#inspectIndex; this.#buf = this.#buf.slice(shift); this.#inspectIndex = this.#disp == "prefix" ? this.#delimiter.length : 0; this.#matchIndex = 0; } } else { if (this.#matchIndex === 0) { this.#inspectIndex++; localIndex++; } else { this.#matchIndex = this.#delimLPS[this.#matchIndex - 1]; } } } }}