Zappy

Lightweight library for compressing and encoding web-related text (json, URLs, UUIDs, etc.) into a URL-safe format for efficient transport.

Read the spec here!

Goals

• Capable of encoding any valid utf-8 string.
• Transportable as URL-safe plain text.
• Produce smaller encoded string than vanilla base64 on ASCII payloads.
• Fast encoding and decoding.

Non-Goals

• Encryption. This ain't it. It's obfuscation at best.

Notes

To fully take advantage of Zappy, you as a dev should provide contraction tables specialized to your payloads.

Zappy strings should not be stored. They are designed for transport where one side encodes before transmitting and the other side decodes after receiving. If the contraction tables change between encoding and decoding, it's very possible the output will not be the same or even invalid. Keep this in mind when decoding and handle these cases accordingly. That is, always sanitize your (decoded) output and handle decoding error conditions.

API

// Constructor.
Zappy(source: Map<number, string[]> | null, throwOnDecodeErrors = false)

// Base64 string encode/decode.
base64StringEncode(str: string): string
base64StringDecode(str: string): string | null

// Zappy encode/decode.
encode(str: string): string
decode(str: string): string | null

How to use

Add to your project

npm install @glitchybyte/zappy

Define contraction tables

There are 17 contraction tables available for use.

Table 0 is called the fast lookup table, it gets the best compression gains, but only 16 entries are permitted. Entries in table 0 can have a minimum of 2 characters (or 2 bytes when converted to UTF-8) and still have a gain.

Tables 1-17 allow 256 entries each. Entries can have a minimum of 3 characters (or 3 bytes when converted to UTF-8).

Developer defined contraction tables are overlaid onto default tables. There is a default table 0 specialized in json, and a default table 16 with common strings.

Define your contraction tables like so:

const contractions = new Map<number, string[]>([
  [1, [
    "glitchybyte",
    "defenestration",
    "internationalization"
  ]]
])

Encode and decode

const zappy = new Zappy(contractions)
const json = '{' +
  '"codeUrl":"https://github.com/glitchybyte/zappy",' +
  '"msg":"When I deal with internationalization I think of defenestration."' +
  '}'
const encoded = zappy.encode(json)
console.log(`[${encoded.length}] ${encoded}`)
//  [90] 6mNvZGVVcmzm4GdpdGh1Yv8EL_ACL3phcHB5521zZ-ZXaGVuIEkgZGVhbCB3
//       aXRoIPAAIEkgdGhpbmsgb2Yg8AEu6w

// While vanilla base64 is:
const base64Encoded = zappy.base64StringEncode(json)
console.log(`[${base64Encoded.length}] ${base64Encoded}`)
// [164] eyJjb2RlVXJsIjoiaHR0cHM6Ly9naXRodWIuY29tL2dsaXRjaHlieXRlL3ph
//       cHB5IiwibXNnIjoiV2hlbiBJIGRlYWwgd2l0aCBpbnRlcm5hdGlvbmFsaXph
//       dGlvbiBJIHRoaW5rIG9mIGRlZmVuZXN0cmF0aW9uLiJ9

const decoded = zappy.decode(encoded)!
console.log(`[${decoded.length}] ${decoded}`)
// [123] {"codeUrl":"https://github.com/glitchybyte/zappy","msg":"Whe
//       n I deal with internationalization I think of defenestration
//       ."}