Expose bitfields

README.md

@@ -200,6 +200,10 @@ See the [Hypercore docs](https://github.com/hypercore-protocol/hypercore) for mo
 
 Append a block or array of blocks to the hypercore
 
+#### `await feed.getBitfield([start], [length])
+
+Get a bitfield of downloaded blocks. Optionally restrict to the range from `start` for `length` blocks. Resolves to a [bitfield](https://github.com/fb55/bitfield) instance.
+
 #### `feed.peers`
 
 A list of peers this feed is connected to.

index.js

@@ -1,4 +1,6 @@
 const { EventEmitter } = require('events')
+const rle = require('bitfield-rle')
+const Bitfield = require('bitfield')
 const maybe = require('call-me-maybe')
 const codecs = require('codecs')
 const hypercoreCrypto = require('hypercore-crypto')
@@ -545,6 +547,17 @@ class RemoteHypercore extends Nanoresource {
     return rsp.has
   }
 
+  async _getBitfield (start, length) {
+    const rsp = await this._client.hypercore.has({
+      seq: start || 0,
+      bitfield: true,
+      length,
+      id: this._id
+    })
+    if (!rsp.bitfield) throw new Error('Did not receive a bitfield')
+    return new Bitfield(rle.decode(rsp.bitfield))
+  }
+
   async _download (range, resourceId) {
     if (!this.opened) await this.open()
     if (this.closed) throw new Error('Feed is closed')
@@ -611,6 +624,10 @@ class RemoteHypercore extends Nanoresource {
     return maybe(cb, this._has(seq))
   }
 
+  getBitfield (start, length, cb) {
+    return maybe(cb, this._getBitfield(start, length))
+  }
+
   cancel (get) {
     if (typeof get.resourceId !== 'number') throw new Error('Must pass a get return value')
     return this._cancel(get.resourceId)

package.json

@@ -23,6 +23,8 @@
   "homepage": "https://github.com/hyperspace-org/hyperspace#readme",
   "dependencies": {
     "@hyperspace/rpc": "^1.0.0",
+    "bitfield": "^3.0.0",
+    "bitfield-rle": "^2.2.1",
     "call-me-maybe": "^1.0.1",
     "codecs": "^2.1.0",
     "freemap": "^1.0.0",