chunk-store-read-stream

Read an abstract-chunk-store as a stream

chunk-store-read-stream allows for a chunk-store to be read as a nodejs Readable stream. Only a portion of the chunk-store can be ready by supplying the start and end options, and the chunk-store can be read while it's not fully populated by supplying the onmiss option.

Usage

var Stream = require('chunk-store-read-stream')
var chunkStore // = some chunk store
 
stream.on('data', console.log)

Start or end at specified byte indexes of the chunk store

var stream = new Stream(chunkStore, {
  start: 1, // Start reading at byte index 1 of the chunk store
  end: 10   // End after reading the byte at index 10
})

Read a chunk-store that is missing some chunks

var stream = new Stream(chunkStore, { onmiss: onmiss })
 
function onmiss(err, index, retry) {
  // An error occured while retreiving a chunk at `index`
  // When a chunk is missing, an error is produced.
  
  // ... some time passes and we know the chunk exists now ...
  
  retry()
}

API

var stream = new Stream(chunkStore, [opts])

Instantiates a new nodejs Readable stream for the given chunkStore. The opts argument will be passed into the Readable Stream's options argument. It can also have the following properties:

• opts.start - The inclusive byte index to start reading at
• opts.end - The inclusive byte index to stop reading at
• opts.onmiss - The function to call to handle chunk misses

If opts.end is not given then chunkStore.length - 1 is used instead. One of these properties must be defined.

opts.onmiss = function (err, index, retry) {}

err is the error that was generated from retreiving the chunk at index. The chunk-store interface does not distinguish between errors that occured because the chunk is simply missing or because something worse happend.

Once you know that the chunk does exist, you can call retry(). If an error does occure, this can be passed into retry like retry(err).

License

MIT. Copyright (c) Austin Middleton.