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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
import { copyBytes } from "../io/util.ts";
/** Find first index of binary pattern from a. If not found, then return -1 **/
export function findIndex(a: Uint8Array, pat: Uint8Array): number {
const s = pat[0];
for (let i = 0; i < a.length; i++) {
if (a[i] !== s) continue;
const pin = i;
let matched = 1,
j = i;
while (matched < pat.length) {
j++;
if (a[j] !== pat[j - pin]) {
break;
}
matched++;
}
if (matched === pat.length) {
return pin;
}
}
return -1;
}
/** Find last index of binary pattern from a. If not found, then return -1 **/
export function findLastIndex(a: Uint8Array, pat: Uint8Array): number {
const e = pat[pat.length - 1];
for (let i = a.length - 1; i >= 0; i--) {
if (a[i] !== e) continue;
const pin = i;
let matched = 1,
j = i;
while (matched < pat.length) {
j--;
if (a[j] !== pat[pat.length - 1 - (pin - j)]) {
break;
}
matched++;
}
if (matched === pat.length) {
return pin - pat.length + 1;
}
}
return -1;
}
/** Check whether binary arrays are equal to each other **/
export function equal(a: Uint8Array, match: Uint8Array): boolean {
if (a.length !== match.length) return false;
for (let i = 0; i < match.length; i++) {
if (a[i] !== match[i]) return false;
}
return true;
}
/** Check whether binary array has binary prefix **/
export function hasPrefix(a: Uint8Array, prefix: Uint8Array): boolean {
for (let i = 0, max = prefix.length; i < max; i++) {
if (a[i] !== prefix[i]) return false;
}
return true;
}
/**
* Repeat bytes. returns a new byte slice consisting of `count` copies of `b`.
* @param b The origin bytes
* @param count The count you want to repeat.
*/
export function repeat(b: Uint8Array, count: number): Uint8Array {
if (count === 0) {
return new Uint8Array();
}
if (count < 0) {
throw new Error("bytes: negative repeat count");
} else if ((b.length * count) / count !== b.length) {
throw new Error("bytes: repeat count causes overflow");
}
const int = Math.floor(count);
if (int !== count) {
throw new Error("bytes: repeat count must be an integer");
}
const nb = new Uint8Array(b.length * count);
let bp = copyBytes(nb, b);
for (; bp < nb.length; bp *= 2) {
copyBytes(nb, nb.slice(0, bp), bp);
}
return nb;
}
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