@iota/bcs/src/uleb.ts

BCS - Canonical Binary Serialization implementation for JavaScript

// Copyright (c) Mysten Labs, Inc.
// Modifications Copyright (c) 2024 IOTA Stiftung
// SPDX-License-Identifier: Apache-2.0

// Helper utility: write number as an ULEB array.
// Original code is taken from: https://www.npmjs.com/package/uleb128 (no longer exists)
export function ulebEncode(num: number): number[] {
    const arr = [];
    let len = 0;

    if (num === 0) {
        return [0];
    }

    while (num > 0) {
        arr[len] = num & 0x7f;
        if ((num >>= 7)) {
            arr[len] |= 0x80;
        }
        len += 1;
    }

    return arr;
}

// Helper utility: decode ULEB as an array of numbers.
// Original code is taken from: https://www.npmjs.com/package/uleb128 (no longer exists)
export function ulebDecode(arr: number[] | Uint8Array): {
    value: number;
    length: number;
} {
    let total = 0;
    let shift = 0;
    let len = 0;

    // eslint-disable-next-line no-constant-condition
    while (true) {
        const byte = arr[len];
        len += 1;
        total |= (byte & 0x7f) << shift;
        if ((byte & 0x80) === 0) {
            break;
        }
        shift += 7;
    }

    return {
        value: total,
        length: len,
    };
}