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

$3

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.

$3

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

$3

Takes an encoded value (such as the output from encode), a typeName
and formatName and returns the decoded counterparts as JavaScript
primitives. This is much faster than decode if you know the type.

$3

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
`

$3

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

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

$3

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

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

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

$3

Given any input, these functions tell you whether the input is of the specified
type (and format, if applicable). Example:

`js
const bfe = require('ssb-bfe')

const x = bfe.encode('@6CAxOI3f+LUOVrbAl0IemqiS7ATpQvr9Mdw9LC4+Uv0=.ed25519')

bfe.isEncodedFeedClassic(x) // true
`

List of functions:

- isEncodedFeed(input) => boolean
- isEncodedFeedClassic(input) => boolean
- isEncodedFeedGabbygroveV1(input) => boolean
- isEncodedFeedBamboo(input) => boolean
- isEncodedFeedBendybuttV1(input) => boolean
- isEncodedFeedButtwooV1(input) => boolean
- isEncodedMessage(input) => boolean
- isEncodedMessageClassic(input) => boolean
- isEncodedMessageGabbygroveV1(input) => boolean
- isEncodedMessageCloaked(input) => boolean
- isEncodedMessageBamboo(input) => boolean
- isEncodedMessageBendybuttV1(input) => boolean
- isEncodedMessageButtwooV1(input) => boolean
- isEncodedBlob(input) => boolean
- isEncodedBlobClassic(input) => boolean
- isEncodedEncryptionKey(input) => boolean
- isEncodedEncryptionKeyBox2DmDh(input) => boolean
- isEncodedEncryptionKeyBox2PoboxDh(input) => boolean
- isEncodedSignature(input) => boolean
- isEncodedSignatureMsgEd25519(input) => boolean
- isEncodedEncrypted(input) => boolean
- isEncodedEncryptedBox1(input) => boolean
- isEncodedEncryptedBox2(input) => boolean
- isEncodedGeneric(input) => boolean
- isEncodedGenericStringUTF8(input) => boolean
- isEncodedGenericBoolean(input) => boolean
- isEncodedGenericNil(input) => boolean
- isEncodedGenericAnyBytes(input) => boolean
- isEncodedIdentity(input) => boolean
- isEncodedIdentityPoBox(input) => boolean`

[ssb binary field encodings]: https://github.com/ssb-ngi-pointer/ssb-binary-field-encodings-spec
[TFD]: https://github.com/ssbc/envelope-spec/blob/master/encoding/tfk.md