add feed.audit

README.md

@@ -322,6 +322,22 @@ Fully close this feed.
 
 Calls the callback with `(err)` when all storage has been closed.
 
+#### `feed.audit([callback])`
+
+Audit all data in the feed. Will check that all current data stored
+matches the hashes in the merkle tree and clear the bitfield if not.
+
+When done a report is passed to the callback that looks like this:
+
+```js
+{
+  valid: 10, // how many data blocks matches the hashes
+  invalid: 0, // how many did not
+}
+```
+
+If a block does not match the hash it is cleared from the data bitfield.
+
 #### `feed.on('ready')`
 
 Emitted when the feed is ready and all properties have been populated.

index.js

@@ -1283,6 +1283,52 @@ Feed.prototype._roots = function (index, cb) {
   }
 }
 
+Feed.prototype.audit = function (cb) {
+  if (!cb) cb = noop
+
+  var self = this
+  var report = {
+    valid: 0,
+    invalid: 0
+  }
+
+  this.ready(function (err) {
+    if (err) return cb(err)
+
+    var block = 0
+    var max = self.length
+
+    next()
+
+    function onnode (err, node) {
+      if (err) return ondata(null, null)
+      self._storage.getData(block, ondata)
+
+      function ondata (_, data) {
+        var verified = data && crypto.data(data).equals(node.hash)
+        if (verified) report.valid++
+        else report.invalid++
+        self.bitfield.set(block, verified)
+        block++
+        next()
+      }
+    }
+
+    function next () {
+      while (block < max && !self.bitfield.get(block)) block++
+      if (block >= max) return done()
+      self._storage.getNode(2 * block, onnode)
+    }
+
+    function done () {
+      self._sync(null, function (err) {
+        if (err) return cb(err)
+        cb(null, report)
+      })
+    }
+  })
+}
+
 function noop () {}
 
 function verifyNode (trusted, node) {

test/audit.js

@@ -0,0 +1,36 @@
+var tape = require('tape')
+var create = require('./helpers/create')
+
+tape('basic audit', function (t) {
+  var feed = create()
+
+  feed.append('hello')
+  feed.append('world', function () {
+    feed.audit(function (err, report) {
+      t.error(err, 'no error')
+      t.same(report, { valid: 2, invalid: 0 })
+      t.end()
+    })
+  })
+})
+
+tape('basic audit with bad data', function (t) {
+  var feed = create()
+
+  feed.append('hello')
+  feed.append('world', function () {
+    feed._storage.data.write(0, Buffer.from('H'), function () {
+      t.ok(feed.has(0))
+      feed.audit(function (err, report) {
+        t.error(err, 'no error')
+        t.same(report, { valid: 1, invalid: 1 })
+        t.notOk(feed.has(0))
+        feed.audit(function (err, report) {
+          t.error(err, 'no error')
+          t.same(report, { valid: 1, invalid: 0 })
+          t.end()
+        })
+      })
+    })
+  })
+})