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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
import { BytesList } from "../bytes/bytes_list.ts";import { createLPS } from "./_common.ts";
/** Transform a stream into a stream where each chunk is divided by a given delimiter. * * ```ts * import { DelimiterStream } from "https://deno.land/std@$STD_VERSION/streams/delimiter_stream.ts"; * const res = await fetch("https://example.com"); * const parts = res.body! *   .pipeThrough(new DelimiterStream(new TextEncoder().encode("foo"))) *   .pipeThrough(new TextDecoderStream()); * ``` */export class DelimiterStream extends TransformStream<Uint8Array, Uint8Array> {  #bufs = new BytesList();  #delimiter: Uint8Array;  #inspectIndex = 0;  #matchIndex = 0;  #delimLen: number;  #delimLPS: Uint8Array;
  constructor(delimiter: Uint8Array) {    super({      transform: (chunk, controller) => {        this.#handle(chunk, controller);      },      flush: (controller) => {        controller.enqueue(this.#bufs.concat());      },    });
    this.#delimiter = delimiter;    this.#delimLen = delimiter.length;    this.#delimLPS = createLPS(delimiter);  }
  #handle(    chunk: Uint8Array,    controller: TransformStreamDefaultController<Uint8Array>,  ) {    this.#bufs.add(chunk);    let localIndex = 0;    while (this.#inspectIndex < this.#bufs.size()) {      if (chunk[localIndex] === this.#delimiter[this.#matchIndex]) {        this.#inspectIndex++;        localIndex++;        this.#matchIndex++;        if (this.#matchIndex === this.#delimLen) {          // Full match          const matchEnd = this.#inspectIndex - this.#delimLen;          const readyBytes = this.#bufs.slice(0, matchEnd);          controller.enqueue(readyBytes);          // Reset match, different from KMP.          this.#bufs.shift(this.#inspectIndex);          this.#inspectIndex = 0;          this.#matchIndex = 0;        }      } else {        if (this.#matchIndex === 0) {          this.#inspectIndex++;          localIndex++;        } else {          this.#matchIndex = this.#delimLPS[this.#matchIndex - 1];        }      }    }  }}