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