runelib/dist/leb128.js

runestones encode and decode

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.decodeLEB128 = exports.encodeLEB128 = void 0;
function encodeLEB128(value) {
    const bytes = [];
    let more = true;
    while (more) {
        let byte = Number(value & BigInt(0x7F)); // Get the lowest 7 bits
        value >>= BigInt(7);
        if (value === BigInt(0)) { // No more data to encode
            more = false;
        }
        else { // More bytes to come
            byte |= 0x80; // Set the continuation bit
        }
        bytes.push(byte);
    }
    // Convert array to Buffer
    return bytes;
}
exports.encodeLEB128 = encodeLEB128;
function decodeLEB128(buf) {
    let n = BigInt(0);
    for (let i = 0; i < buf.length; i++) {
        const byte = BigInt(buf[i]);
        if (i > 18) {
            throw new Error("Overlong");
        }
        let value = byte & BigInt(127);
        if ((i == 18) && ((value & BigInt(124)) != BigInt(0))) {
            throw new Error("Overflow");
        }
        n |= value << (BigInt(7) * BigInt(i));
        if ((byte & BigInt(128)) == BigInt(0)) {
            return {
                n,
                len: i + 1
            };
        }
    }
    throw new Error("Unterminated");
}
exports.decodeLEB128 = decodeLEB128;