mirror of
https://github.com/pezkuwichain/pezkuwi-common.git
synced 2026-04-22 09:08:03 +00:00
49 lines
1.7 KiB
JavaScript
49 lines
1.7 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.compactToU8a = compactToU8a;
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const index_js_1 = require("../bn/index.js");
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const index_js_2 = require("../u8a/index.js");
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const MAX_U8 = index_js_1.BN_TWO.pow(new index_js_1.BN(8 - 2)).isub(index_js_1.BN_ONE);
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const MAX_U16 = index_js_1.BN_TWO.pow(new index_js_1.BN(16 - 2)).isub(index_js_1.BN_ONE);
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const MAX_U32 = index_js_1.BN_TWO.pow(new index_js_1.BN(32 - 2)).isub(index_js_1.BN_ONE);
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const BL_16 = { bitLength: 16 };
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const BL_32 = { bitLength: 32 };
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/**
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* @name compactToU8a
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* @description Encodes a number into a compact representation
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* @example
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* <BR>
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*
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* ```javascript
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* import { compactToU8a } from '@pezkuwi/util';
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*
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* console.log(compactToU8a(511, 32)); // Uint8Array([0b11111101, 0b00000111])
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* ```
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*/
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function compactToU8a(value) {
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const bn = (0, index_js_1.bnToBn)(value);
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if (bn.lte(MAX_U8)) {
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return new Uint8Array([bn.toNumber() << 2]);
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}
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else if (bn.lte(MAX_U16)) {
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return (0, index_js_1.bnToU8a)(bn.shln(2).iadd(index_js_1.BN_ONE), BL_16);
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}
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else if (bn.lte(MAX_U32)) {
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return (0, index_js_1.bnToU8a)(bn.shln(2).iadd(index_js_1.BN_TWO), BL_32);
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}
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const u8a = (0, index_js_1.bnToU8a)(bn);
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let length = u8a.length;
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// adjust to the minimum number of bytes
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while (u8a[length - 1] === 0) {
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length--;
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}
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if (length < 4) {
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throw new Error('Invalid length, previous checks match anything less than 2^30');
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}
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return (0, index_js_2.u8aConcatStrict)([
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// subtract 4 as minimum (also catered for in decoding)
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new Uint8Array([((length - 4) << 2) + 0b11]),
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u8a.subarray(0, length)
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]);
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}
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