LNP — Length-Notation Protocol

LNP is a compact, deterministic, length-prefixed data serialization format. It encodes structured data (objects, arrays, primitives, and binary) using a minimal grammar and unambiguous parsing rules. The design goal is to provide a simple, stream-friendly, and implementation-agnostic protocol suitable for storage, messaging, and structured binary or textual data exchange.

Core Idea

Every value is encoded as:

<type-char><byte-length>:<payload-bytes>

Where:

• <type-char> — a single ASCII character indicating the value type
• <byte-length> — decimal ASCII length of the payload in bytes
• : — required separator
• <payload-bytes> — exactly <byte-length> bytes of content

This eliminates the need for delimiters, escaping, or structural markers. All nested values remain valid LNP values.

Type Table

| Type | Char | Payload Description | | ------- | ---- | ----------------------------------------------------------- | | Object | o | Sequence of entries <klen>:<kbytes><value> | | Array | a | Sequence of complete LNP values | | String | s | Raw UTF-8 string bytes | | Number | n | ASCII numeric representation (-12, 3.14, etc.) | | Boolean | b | Single byte: t or f | | Null | N | Must have zero-length payload | | Bytes | B | Base64-encoded bytes (or raw bytes, implementation defined) |

Objects

Object payloads consist of repeated entries:

<key-length>:<key-bytes><value>

Where <value> is a complete LNP value including its type and length prefix.

Example:

o27:name4:Johnage2:n24

Represents:

{
  "name": "John",
  "age": 24
}

Arrays

Arrays concatenate multiple full LNP values inside the payload:

a14s3:foos3:bar

Equivalent to:

["foo", "bar"]

Primitives

String

s5:hello

Number

n4:-2.5

Boolean

b1:t     // true
b1:f     // false

Null

N0:

Bytes

B12:SGVsbG8gV29ybGQ=

EBNF Specification

value       = typeChar length ":" payload ;
typeChar    = "o" | "a" | "s" | "n" | "b" | "N" | "B" ;
length      = digits ;
digits      = digit { digit } ;
payload     = bytes(length) ;

object      = "o" length ":" { entry } ;
entry       = digits ":" bytes(keylen) value ;

array       = "a" length ":" { value } ;

bytes(n) means exactly n raw bytes, without interpretation.

Design Properties

• Deterministic: identical input always produces identical output.
• Non-ambiguous: no quoting, escaping, or delimiter rules.
• Streaming-friendly: parser can process values incrementally.
• Compact: minimal overhead, fixed structural cost.
• Easy to implement: simple state machine and length-bounded reads.
• Suitable for hashing: stable representation ideal for merkle-tree or content-addressed storage.

Roadmap

• [x] Official Node.js encoder/decoder
• [ ] Reference test suite
• [ ] Implementations in Rust, Go, Python
• [ ] Optional binary variant (BLNP)