# `base32/base32`

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_(no submodules)_
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## Purpose

RFC 4648 §6 base32 encode + decode. The OTP profile defaults to **unpadded**
output to match the Google Authenticator Key URI Format (`secret=...` is
unpadded in the wild); spec-strict consumers can opt in via `padding: true`.
Decode is case-insensitive and tolerates whitespace between groups so QR-code
URLs that wrap long secrets round-trip cleanly.

## Features

- `base32Encode(bytes, opts?)` — bit-packed five-at-a-time encode.
- `base32Decode(input)` — single-pass reverse-table decode.
- 32-character alphabet `A–Z2–7` per RFC 4648 §6.
- Lower-case alias only for letters (digits 2–7 are case-invariant).
- `OTP.BASE32_INVALID` raised on non-alphabet character.

## Usage: Basic Example

```ts
import { base32Decode, base32Encode } from "@suaveplan/otp/base32";

const bytes = base32Decode("JBSWY3DPEHPK3PXP");
const back = base32Encode(bytes);
```

## Usage: Advanced Example

```ts
import { base32Encode } from "@suaveplan/otp/base32";

// Spec-strict consumer that needs `=` padding.
const padded = base32Encode(new Uint8Array([0x66, 0x6f, 0x6f]), {
  padding: true,
});
// padded === "MZXW6==="
```

## API Reference

- `base32Encode(bytes: Uint8Array, opts?: { padding?: boolean }): string`
  — returns the base32 form. `padding` defaults to `false`.
- `base32Decode(input: string): Uint8Array` — decodes padded or unpadded
  input; whitespace is stripped; case-insensitive; non-alphabet characters
  raise `OtpError(OTP.BASE32_INVALID)` with the offending position.

## Implementation Notes

The decode table is a 128-entry `Int8Array` indexed by char-code. Letters are
aliased to their lower-case slots; digits are not aliased because '2'+32 ='R'
which would otherwise overwrite the letter slot for `R`. The encoder emits
unpadded output by default to match the prevailing Google Authenticator wire
format; `padding: true` makes the output multiple-of-eight characters and
RFC-4648-compliant for spec-strict consumers.