@thi.ng/base-n/encode.js

Arbitrary base-n conversions w/ presets for base8/16/32/36/58/62/64/83/85, support for bigints and encoding/decoding of byte arrays

import { B16_LC_CHARS } from "./chars/16.js";
const MAX_SAFE_INT = BigInt(2 ** 53 - 1);
class BaseNEncoder {
  constructor(base) {
    this.base = base;
    this.N = base.length;
  }
  N;
  __pc = [];
  clear() {
    this.__pc.length = 0;
  }
  encode(x, size = 0) {
    const { base, N } = this;
    if (x === 0) return this.__pad(base[0], size);
    let res = "";
    while (x > 0) {
      res = base[x % N] + res;
      x = Math.floor(x / N);
    }
    return this.__pad(res, size);
  }
  encodeBigInt(x, size = 0) {
    if (x <= MAX_SAFE_INT) return this.encode(Number(x), size);
    const { base, N } = this;
    if (x === 0n) return this.__pad(base[0], size);
    const NN = BigInt(N);
    let res = "";
    while (x > 0n) {
      res = base[Number(x % NN)] + res;
      x /= NN;
    }
    return this.__pad(res, size);
  }
  encodeBytes(buf, size = 0) {
    let hex = "0x";
    for (let i = 0, n = buf.length; i < n; i++) hex += __u8(buf[i]);
    return this.encodeBigInt(BigInt(hex), size);
  }
  size(x) {
    return Math.ceil(Math.log(x) / Math.log(this.N));
  }
  __pad(x, size) {
    const d = size - x.length;
    return d > 0 ? (this.__pc[d] || (this.__pc[d] = this.base[0].repeat(d))) + x : x;
  }
}
const __u8 = (x) => B16_LC_CHARS[x >>> 4 & 15] + B16_LC_CHARS[x & 15];
export {
  BaseNEncoder
};