hyperblobs/README.md

A blob store for Hypercore

# hyperblobs

A simple blob store for Hypercore.

Each blob is identified by its unique bounds within the Hypercore, e.g. `{ byteOffset: 0, blockOffset: 0, blockLength: 5, byteLength: 327680 }`, which makes them easy to save and retrieve:
```js
const blobs = new Hyperblobs(core)
// ID is { byteOffset: 0, blockOffset: 0, blockLength: 1, byteLength: 11 }
const id = await blobs.put(Buffer.from('hello world', 'utf-8')) 
await blobs.get(id) // Buffer.from('hello world', 'utf-8')
```

You can also get from start/end bounds within a single blob:
```js
const blobs = new Hyperblobs(core)
// ID is { byteOffset: 0, blockOffset: 0, blockLength: 1, byteLength: 11 }
const id = await blobs.put(Buffer.from('hello world', 'utf-8')) 
await blobs.get(id, { start: 1, length: 2 }) // Buffer.from('el', 'utf-8')
```

If the blob is large, there's a Streams interface (`createReadStream` and `createWriteStream`) too.

## Installation
```
npm i hyperblobs
```

## API
```js
const Hyperblobs = require('hyperblobs')
```

#### `const blobs = new Hyperblobs(core, opts)`
Create a new blob store wrapping a single Hypercore.

Options can include:
```js
{
  blockSize: 64KB // The block size that will be used when storing large blobs.
}
```

#### `const id = await blobs.put(blob, opts)`
Store a new blob. If the blob is large, it will be chunked according to `opts.blockSize` (default 64KB).

Options can include:
```js
{
  blockSize: 64KB, // The block size that will be used when storing large blobs.
  start: 0, // Relative offset to start within the blob
  end: blob.length - 1, // End offset within the blob (inclusive)
  length: blob.length, // Number of bytes to read.
  core // A custom core to write (overrides the default core)
}
```

#### `const content = await blobs.get(id, opts)`
Return a complete blob as a `Buffer`.

`id` is the value returned by `put`

Options can include:
```js
{
  core, // A custom core to read from (overrides the default core)
  wait: true, // Wait for block to be downloaded
  timeout: 0 // Wait at max some milliseconds (0 means no timeout)
}
```

#### `await blobs.clear(id, opts)`
Remove a blob from the core.

`opts` are the same as `Hypercore.clear` method.

#### `const stream = blobs.createReadStream(id, opts)`
Create a Readable stream that will yield the `id` blob.

Options match the `get` options.

#### `const stream = blobs.createWriteStream(opts)`
Create a Writable stream that will save a blob.

The corresponding ID will be set on the stream at `stream.id`.

## License
Apache-2.0