Compact encoding

A series of binary encoders/decoders for building small and fast parsers and serializers.

GitHub (Compact-Encoding)

• Compact-Encoding

  • Methods

    • state()

      • enc.preencode(state, val)

      • enc.encode(state, val)

      • enc.decode(state)

  • Helpers

  • Bundled Encodings

Installation

Install with npm:

npm install compact-encoding

Encoder API

state()

An object with the keys{ start, end, buffer, cache }.

Keys	Description
start	Byte offset to start encoding/decoding at.
end	Byte offset indicating the end of the buffer.
buffer	Either a Node.js Buffer or Uint8Array.
cache	Used internally by codecs, starts as null.

Users can also get a blank state object usingcenc.state().

const cenc = require('compact-encoding')
const state = cenc.state()

enc.preencode(state, val)

Performs a fast preencode dry-run that only sets state.end. Use this to figure out how big the buffer needs to be.

const cenc = require('compact-encoding')

const state = cenc.state()

// use preencode to figure out how big a buffer is needed
cenc.uint.preencode(state, 42)
cenc.string.preencode(state, 'hi')

console.log(state) // { start: 0, end: 4, buffer: null, cache: null }

enc.encode(state, val)

Encodes val into state.buffer at position state.start and updates state.start to point after the encoded value when done.

state.buffer = Buffer.allocUnsafe(state.end)

// then use encode to actually encode it to the buffer
cenc.uint.encode(state, 42)
cenc.string.encode(state, 'hi')

val = enc.decode(state)

Decodes a value from state.buffer as position state.startand updates state.start to point after the decoded value when done in the buffer.

// to decode it simply use decode instead

state.start = 0
cenc.uint.decode(state) // 42
cenc.string.decode(state) // 'hi'

Helpers

To encode to a buffer or decode from one, use the encode and decode helpers to reduce boilerplate.

const buf = cenc.encode(cenc.bool, true)
const bool = cenc.decode(cenc.bool, buf)

Bundled encodings

The following encodings are bundled as they are primitives that can be used to build others on top.

Feel free to make a PR to add more encodings that are missing.

Encodings	Description
cenc.raw	Pass through encodes a buffer, i.e., a basic copy.
cenc.uint	Encodes a uint using compact-uint.
cenc.uint8	Encodes a fixed size uint8.
cenc.uint16	Encodes a fixed size uint16. Useful for things like ports.
cenc.uint24	Encodes a fixed size uint24. Useful for message framing.
cenc.uint32	Encodes a fixed size uint32. Useful for very large message framing.
cenc.uint40	Encodes a fixed size uint40.
cenc.uint48	Encodes a fixed size uint48.
cenc.uint56	Encodes a fixed size uint56.
cenc.uint64	Encodes a fixed size uint64.
cenc.int	Encodes an int using cenc.uint with ZigZag encoding.
cenc.int8	Encodes a fixed size int8 using cenc.uint8 with ZigZag encoding.
cenc.int16	Encodes a fixed size int16 using cenc.uint16 with ZigZag encoding.
cenc.int24	Encodes a fixed size int24 using cenc.uint24 with ZigZag encoding.
cenc.int32	Encodes a fixed size int32 using cenc.uint32 with ZigZag encoding.
cenc.int40	Encodes a fixed size int40 using cenc.uint40 with ZigZag encoding.
cenc.int48	Encodes a fixed size int48 using cenc.uint48 with ZigZag encoding.
cenc.int56	Encodes a fixed size int56 using cenc.uint56 with ZigZag encoding
cenc.int64	Encodes a fixed size int64 using cenc.uint64 with ZigZag encoding.
cenc.lexint	Encodes an int using lexicographic-integer encoding so that encoded values are lexicographically sorted in ascending numerical order.
cenc.float32	Encodes a fixed size float32.
cenc.float64	Encodes a fixed size float64.
cenc.buffer	Encodes a buffer with its length uint prefixed. When decoding an empty buffer, null is returned.
cenc.raw.buffer	Encodes a buffer without a length prefixed.
cenc.uint8array	Encodes a uint8array with its element length uint prefixed.
cenc.raw.uint8array	Encodes a uint8array without a length prefixed.
cenc.uint16array	Encodes a uint16array with its element length uint prefixed.
cenc.raw.uint16array	Encodes a uint16array without a length prefixed.
cenc.uint32array	Encodes a uint32array with its element length uint prefixed.
cenc.raw.uint32array	Encodes a uint32array without a length prefixed.
cenc.int8array	Encodes a int8array with its element length uint prefixed.
cenc.raw.int8array	Encodes a int8array without a length prefixed.
cenc.int16array	Encodes a int16array with its element length uint prefixed.
cenc.raw.int16array	Encodes a int16array without a length prefixed.
cenc.int32array	Encodes a int32array with its element length uint prefixed.
cenc.raw.int32array	Encodes a int32array without a length prefixed.
cenc.float32array	Encodes a float32array with its element length uint prefixed.
cenc.raw.float32array	Encodes a float32array without a length prefixed.
cenc.float64array	Encodes a float64array with its element length uint prefixed.
cenc.raw.float64array	Encodes a float64array without a length prefixed.
cenc.bool	Encodes a boolean as 1 or 0.
cenc.string, cenc.utf8	Encodes a utf-8 string, similar to buffer.
cenc.raw.string, cenc.raw.utf8	Encodes a utf-8 string without a length prefixed.
cenc.string.fixed(n), cenc.utf8.fixed(n)	Encodes a fixed sized utf-8 string.
cenc.ascii	Encodes an ascii string.
cenc.raw.ascii	Encodes an ascii string without a length prefixed.
cenc.ascii.fixed(n)	Encodes a fixed size ascii string.
cenc.hex	Encodes a hex string.
cenc.raw.hex	Encodes a hex string without a length prefixed.
cenc.hex.fixed(n)	Encodes a fixed size hex string.
cenc.base64	Encodes a base64 string.
cenc.raw.base64	Encodes a base64 string without a length prefixed.
cenc.base64.fixed(n)	Encodes a fixed size base64 string.
cenc.utf16le, cenc.ucs2	Encodes a utf16le string.
cenc.raw.utf16le, cenc.raw.ucs2	Encodes a utf16le string without a length prefixed.
cenc.utf16le.fixed(n), cenc.ucs2.fixed(n)	Encodes a fixed size utf16le string.
cenc.fixed32	Encodes a fixed 32 byte buffer.
cenc.fixed64	Encodes a fixed 64 byte buffer.
cenc.fixed(n)	Makes a fixed sized encoder.
cenc.array(enc)	Makes an array encoder from another encoder. Arrays are uint prefixed with their length.
cenc.raw.array(enc)	Makes an array encoder from another encoder, without a length prefixed.
cenc.json	Encodes a JSON value as utf-8.
cenc.raw.json	Encodes a JSON value as utf-8 without a length prefixed.
cenc.ndjson	Encodes a JSON value as newline delimited utf-8.
cenc.raw.ndjson	Encodes a JSON value as newline delimited utf-8 without a length prefixed.
cenc.from(enc)	Makes a compact encoder from a codec or abstract-encoding.