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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
import { BytesList } from "../bytes/bytes_list.ts";import type { Reader } from "../types.d.ts";
/** Generate longest proper prefix which is also suffix array. */function createLPS(pat: Uint8Array): Uint8Array {  const lps = new Uint8Array(pat.length);  lps[0] = 0;  let prefixEnd = 0;  let i = 1;  while (i < lps.length) {    if (pat[i] == pat[prefixEnd]) {      prefixEnd++;      lps[i] = prefixEnd;      i++;    } else if (prefixEnd === 0) {      lps[i] = 0;      i++;    } else {      prefixEnd = lps[prefixEnd - 1];    }  }  return lps;}
/** Read delimited bytes from a Reader. */export async function* readDelim(  reader: Reader,  delim: Uint8Array,): AsyncIterableIterator<Uint8Array> {  // Avoid unicode problems  const delimLen = delim.length;  const delimLPS = createLPS(delim);  const chunks = new BytesList();  const bufSize = Math.max(1024, delimLen + 1);
  // Modified KMP  let inspectIndex = 0;  let matchIndex = 0;  while (true) {    const inspectArr = new Uint8Array(bufSize);    const result = await reader.read(inspectArr);    if (result === null) {      // Yield last chunk.      yield chunks.concat();      return;    } else if (result < 0) {      // Discard all remaining and silently fail.      return;    }    chunks.add(inspectArr, 0, result);    let localIndex = 0;    while (inspectIndex < chunks.size()) {      if (inspectArr[localIndex] === delim[matchIndex]) {        inspectIndex++;        localIndex++;        matchIndex++;        if (matchIndex === delimLen) {          // Full match          const matchEnd = inspectIndex - delimLen;          const readyBytes = chunks.slice(0, matchEnd);          yield readyBytes;          // Reset match, different from KMP.          chunks.shift(inspectIndex);          inspectIndex = 0;          matchIndex = 0;        }      } else {        if (matchIndex === 0) {          inspectIndex++;          localIndex++;        } else {          matchIndex = delimLPS[matchIndex - 1];        }      }    }  }}