hilbert-geohash/lib/conversion.js

Node.js implementation of Hilbert-curve based geohashing.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.decode_int = exports.encode_int = void 0;
const IntConversion = {
    // https://stackoverflow.com/questions/6213227/fastest-way-to-convert-a-number-to-radix-64-in-javascript
    Base64: "0123456789@ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz",
    Base16: "0123456789abcdef",
    Base4: "0123",
    fromNumber: function (number, base) {
        let residual = number;
        let result = "";
        while (true) {
            const digit = Number(BigInt(residual) % BigInt(base));
            result = this[("Base" + base)].charAt(digit) + result;
            residual = BigInt(residual) / BigInt(base);
            if (residual == 0n)
                break;
        }
        return result;
    },
    toNumber: function (string, base) {
        var result = 0n;
        let chars = string.split("");
        for (var e = 0; e < chars.length; e++) {
            result =
                result * BigInt(base) +
                    BigInt(this[("Base" + base)].indexOf(chars[e]));
        }
        return result;
    },
};
exports.encode_int = (n, bits_per_char = 6) => {
    if (bits_per_char === 6) {
        return IntConversion.fromNumber(n, 64);
    }
    if (bits_per_char === 4) {
        return IntConversion.fromNumber(n, 16);
    }
    if (bits_per_char === 2) {
        return IntConversion.fromNumber(n, 4);
    }
    return "";
};
exports.decode_int = (n, bits_per_char = 6) => {
    if (bits_per_char === 6) {
        return IntConversion.toNumber(n, 64);
    }
    if (bits_per_char === 4) {
        return IntConversion.toNumber(n, 16);
    }
    if (bits_per_char === 2) {
        return IntConversion.toNumber(n, 4);
    }
    return 0n;
};