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https://github.com/telamon/picofeed

Microscopic Secure Feed occupying a single buffer
https://github.com/telamon/picofeed

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Microscopic Secure Feed occupying a single buffer

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README 

        
[`code style | standard`](https://standardjs.com/)

```

          _

 _ . _  _|__  _  _|

|_)|(_(_)|(/_(/_(_| v8

|

```



> Space Efficient Chain of Blocks



- Flat memory layout / zero copy access

- Single dependency [EdDSA](https://github.com/paulmillr/noble-curves)

- 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



( For those who are new to linked blocks )



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:_



This package provides 2 primitves  



**Feed**

```

|------|------------------|----------------------|

| PiC0 | Block 0: "hello" | Block 1: "picoverse" |

|------|------------------|----------------------|

```

and



**Block**

```

| SIG: 64B     |

| SIZE: varint |

| DATA: buffer[SIZE] |

```

minimal overhead, quite simple.



This library provides a high level API to `append`, `slice` and `merge`

such feeds - block contents is upto application.



We target user devices, picofeed is the basic building block for the frontend-block-engine [picostack](https://github.com/telamon/picostack)



[discord](https://discord.gg/8RMRUPZ9RS)



##  Install



```

yarn add picofeed

# or

npm install picofeed

```



##  Usage



```js

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 // => 71 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



#### `8.0.0`



Reworked binary format, less overhead



- removed `fmt` byte

- added Headers instead



#### `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](./LICENSE)



2020-2023 🄯 Tony Ivanov