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std/io/read_delim.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { concat } from "../bytes/concat.ts";import type { Reader } from "./types.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. * * @deprecated (will be removed after 1.0.0) Use the {@link https://developer.mozilla.org/en-US/docs/Web/API/Streams_API | Web Streams API} instead. */export async function* readDelim( reader: Reader, delim: Uint8Array,): AsyncIterableIterator<Uint8Array> { // Avoid unicode problems const delimLen = delim.length; const delimLPS = createLPS(delim); let chunks = new Uint8Array(); 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; return; } else if (result < 0) { // Discard all remaining and silently fail. return; } chunks = concat([chunks, inspectArr.slice(0, result)]); let localIndex = 0; while (inspectIndex < chunks.length) { 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 = chunks.slice(inspectIndex); inspectIndex = 0; matchIndex = 0; } } else { if (matchIndex === 0) { inspectIndex++; localIndex++; } else { matchIndex = delimLPS[matchIndex - 1]!; } } } }}