@thi.ng/bencode/encode.js

Bencode binary encoder / decoder with optional UTF8 encoding & floating point support

import { isArrayLike } from "@thi.ng/checks/is-arraylike";
import { isBoolean } from "@thi.ng/checks/is-boolean";
import { isNumber } from "@thi.ng/checks/is-number";
import { isPlainObject } from "@thi.ng/checks/is-plain-object";
import { isString } from "@thi.ng/checks/is-string";
import { assert } from "@thi.ng/errors/assert";
import { unsupported } from "@thi.ng/errors/unsupported";
import { utf8Length } from "@thi.ng/strings/utf8";
import { bytes, str, u8, u8array } from "@thi.ng/transducers-binary/bytes";
import { mapcat } from "@thi.ng/transducers/mapcat";
const FLOAT_RE = /^[0-9.-]+$/;
const ENCODERS = {
  i: (x) => {
    __ensureValidNumber(x);
    return [str(`i${Math.floor(x)}e`)];
  },
  f: (x) => {
    __ensureValidNumber(x);
    assert(
      FLOAT_RE.test(x.toString()),
      `values requiring exponential notation not allowed (${x})`
    );
    return [str(`f${x}e`)];
  },
  b: (buf) => [str(buf.length + ":"), u8array(buf)],
  s: (x) => [str(utf8Length(x) + ":" + x)],
  l: (x) => [u8(108), ...mapcat(__encodeBin, x), u8(101)],
  d: (x) => [
    u8(100),
    ...mapcat(
      (k) => __encodeBin(k).concat(__encodeBin(x[k])),
      Object.keys(x).sort()
    ),
    u8(101)
  ]
};
const encode = (x, cap = 1024) => bytes(cap, __encodeBin(x));
const __encodeBin = (x) => ENCODERS[isNumber(x) ? Math.floor(x) !== x ? "f" : "i" : isBoolean(x) ? "i" : isString(x) ? "s" : x instanceof Uint8Array ? "b" : isPlainObject(x) ? "d" : isArrayLike(x) ? "l" : unsupported(`unsupported data type: ${x}`)](x);
const __ensureValidNumber = (x) => {
  assert(isFinite(x), `can't encode infinite value`);
  assert(!isNaN(x), `can't encode NaN`);
};
export {
  encode
};