⚠️ This repo was moved to https://github.com/ssbc/ssb-bfe. This archival will remain in this GitHub org ssb-ngi-pointer to demonstrate the outcome of the work done by the SSB NGI Pointer team during 2020 and 2021. The SSB NGI Pointer team is no longer active because we completed our grant project.

SSB BFE

Javascript implementation of the SSB binary field encodings spec.

The spec only has one type of nil, but JavaScript has two: null and undefined. ssb-bfe will treat these two values in a way that mirrors what JSON.stringify does:

• BFE Encoding an object with a null field becomes an object with the nil marker
  • Similar to JSON.stringify({a: null}) === '{"a": null}'
• BFE Encoding an array with a null element becomes an array with the nil marker
  • Similar to JSON.stringify([null]) === '[null]'
• BFE Encoding an object with a undefined field will omit that field
  • Similar to JSON.stringify({a: undefined}) === '{}'
• BFE Encoding an array with an undefined element becomes an array with the nil marker
  • Similar to JSON.stringify([undefined]) === '[null]'

API

encode(input)

Takes any JavaScript primitive and returns its encoded counterpart. Is applied recursively in case the input is an object or an array. All inputs are converted to TFD Buffers, except for objects, arrays, and numbers, which remain the same.

decode(input)

Takes an encoded value (such as the output from encode) and returns the decoded counterparts as JavaScript primitives.

bfeTypes

Returns the bfe.json object that can be used to look up information based on Type and Field. Example:

const { bfeTypes } = require('ssb-bfe')
const classic_key_size = bfeTypes[0][0].data_length

bfeNamedTypes

Returns the bfe.json object converted to a map where the keys are the type and format names. Example:

const { bfeNamedTypes } = require('ssb-bfe')
const FEED = bfeNamedTypes['feed']
const CLASSIC_FEED_TF = Buffer.from([FEED.code, FEED.formats['classic'].code])

toTF(typeName, formatName)

Sometimes when you're wanting to check what sort of buffer you're handling, you want to pivot on the type and format bytes.

const CLASSIC_MSG_TF = Buffer.from([1, 0])  // << Did I get the right codes?

if (buf.slice(0, 2).equals(CLASSIC_MSG_TF)) {
  // ...
}

because remembering those codes is tricky, it's safer to use this convenience method:

const CLASSIC_MSG_TF = bfe.toTF('msg', 'classic')

If you remembered the type or format name wrong, you'll instantly get an error!