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.

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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.

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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)

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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
}

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Arrays

Arrays concatenate multiple full LNP values inside the payload:

a14s3:foos3:bar

Equivalent to:

["foo", "bar"]

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Primitives

String

s5:hello

Number

n4:-2.5

Boolean

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

Null

N0:

Bytes

B12:SGVsbG8gV29ybGQ=

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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.

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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.

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Roadmap

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