picofeed

code style | standard

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|_)|(_(_)|(/_(/_(_| v5
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Space Efficient Chain of Blocks

• Flat memory layout / zero copy access
• Single dependency EdDSA
• Fast & compact Curve25519 + Ed25519 signatures
• Pure ES6 (+JSDoc Type annotations)
• ~450LOC / +41.3kB bundle size
• Test Coverage 💯
• Uint8Arrays (no node:buffer or bn.js)

Intro

Imagine git as a jar, then using pliers pull out a branch. That single detached branch is synonymous with one picofeed - a memorybuffer containing cryptographically signed blocks:

|------|-----|------------------|----------------------|
| PiC0 | Key | Block 0: "hello" | Block 1: "picoverse" |
| 4B   | 33B |    71 Bytes      |     138 Bytes        |
|------|-----|------------------|----------------------|

This library provides a high level API to append, slice and merge such feeds - block contents is upto application.

Picofeeds have so far been observed within:

• QR-Codes (out-of-band-signaling)
• URLs (cross-messenger / platform-as-a-public-database)
• DNS-Records (webhosting)

We target user devices, this module is the basic building block for the frontend-blockchain-toolkit picostack

discord

Install

yarn add picofeed
# or
npm install picofeed

Usage

import { Feed, toHex } from 'picofeed'

const { pk: publicKey, sk: secret } = Feed.signPair()

const feed = new Feed()

feed.append('Hello', secret) // => height 1
feed.blocks[0].body // => 'Hello'
feed.blocks[0].blockSize // => 72 bytes

const verifiableData = feed.buffer

// -- Share buffer anyhow --

const remoteFeed = Feed.from(verifiableData) // Verifies signatures

remoteFeed.blocks[0].body // => 'Hello'

toHex(remoteFeed.blocks[0].key) === alice.pk // true

Changelog

5.0.1

• phat-bit replaced with varint
• changed secp256k1 in favour of Ed25519
• fixed merge() bug
• removed u8n util

4.x

• signPair() returns hexstring keys
• sk.slice(32) no longer works, use getPublicKey(sk)
• block.parentSig renamed to block.psig
• block.isGenesis renamed to block.genesis
• feed.get(n) renamed to feed.block(n)
• feed.blocks() removed in favour of feed.blocks
• feed.pickle() removed until further notice.
• feed.fromBlocksArray() incorporated into feedFrom() / Feed.from()
• Not backwards compatible with 3.x feeds

3.4.0

• updated README.md
• added Feed.fromBlocksArray(Block[]) to perform bulk-merge, 24x perf increase compared to Feed.merge(block)
• removed Feed subclassing/metaprogramming support, it was fun but footgun (don't solve problems by subclassing Feed).

3.3.0

• added Feed.first
• added Feed.get(-3) as equivalent of f.get(f.length - 3)
• added Block.isGenesis getter
• added static Feed.KEY_SIZE constant
• replaced hardcoded key-size lenghts with KEY_SIZE constant

3.2.2

• optimization feed._steal() also steals cache

3.2.1

• fixed bug feed._steal(other) causing cache corruption
• changed return value of feed.inspect() is now conditional
• fixed bug where A < B; A.merge(B, withCallback) did not merge
• fixed bug where keychain cache contained boatloads of duplicate keys

3.1.0

• added feed.merge(block) support

3.0.0

• removed automatic encodings
• changed feed.get(n) returns instance of BlockMapper.
• changed feed.slice(start, end)
• added block cache to avoid redundant signature-verifications
• added BlockMapper now also contains public-key
• sodium-universal upgraded to 3.0.0

2.2.0

• Added feed.merge(other, opts, indexingCallback) that allows validation + abort merge interactively
• Added feed.last which returns the block-contents using provided encoding.

2.0.0

• Added feed slices and merge

License

AGPL-3.0-or-later

2020-2023 🄯 Tony Ivanov