Defer pending ops (#12)

index.js

@@ -41,6 +41,8 @@ const RocksDB = module.exports = class RocksDB extends ReadyResource {
     this.tableFormatVersion = tableFormatVersion
 
     this._snapshots = new Set()
+    this._refs = 0
+    this._resolvePreclose = null
 
     this._handle = binding.init()
   }
@@ -87,6 +89,12 @@ const RocksDB = module.exports = class RocksDB extends ReadyResource {
   }
 
   async _close () {
+    if (this._refs > 0) {
+      await new Promise((resolve) => {
+        this._resolvePreclose = resolve
+      })
+    }
+
     for (const snapshot of this._snapshots) snapshot.destroy()
 
     const req = { resolve: null, reject: null, handle: null }
@@ -108,6 +116,18 @@ const RocksDB = module.exports = class RocksDB extends ReadyResource {
     }
   }
 
+  _incRef () {
+    this._refs++
+  }
+
+  _decRef () {
+    if (--this._refs === 0 && this._resolvePreclose !== null) {
+      const resolve = this._resolvePreclose
+      this._resolvePreclose = null
+      resolve()
+    }
+  }
+
   snapshot (opts) {
     return new Snapshot(this, opts)
   }

lib/batch.js

@@ -3,6 +3,7 @@ const b4a = require('b4a')
 const binding = require('../binding')
 
 const empty = b4a.alloc(0)
+const emptyPromise = Promise.resolve()
 
 class RocksDBBatch {
   constructor (db, opts = {}) {
@@ -13,6 +14,8 @@ class RocksDBBatch {
       valueEncoding = encoding
     } = opts
 
+    db._incRef()
+
     this._db = db
     this._capacity = capacity
     this._operations = []
@@ -39,6 +42,7 @@ class RocksDBBatch {
     this._promises = []
     this._request = null
     this._resolveRequest = null
+    this._db._decRef()
 
     if (resolve !== null) resolve()
   }
@@ -73,7 +77,7 @@ class RocksDBBatch {
   tryFlush () {
     if (this._request) throw new Error('Request already in progress')
 
-    this._request = true
+    this._request = emptyPromise
     this._flush()
   }
 

lib/iterator.js

@@ -23,6 +23,8 @@ module.exports = class RocksDBIterator extends Readable {
 
     super()
 
+    db._incRef()
+
     this._db = db
 
     this._keyEncoding = keyEncoding
@@ -75,6 +77,7 @@ module.exports = class RocksDBIterator extends Readable {
   _onclose (err) {
     const cb = this._pendingDestroy
     this._pendingDestroy = null
+    this._db._decRef()
     cb(err)
   }