Initial

resources/app/node_modules/abstract-level/lib/deferred-iterator.js

@@ -0,0 +1,108 @@
+'use strict'
+
+const { AbstractIterator, AbstractKeyIterator, AbstractValueIterator } = require('../abstract-iterator')
+const ModuleError = require('module-error')
+
+const kNut = Symbol('nut')
+const kUndefer = Symbol('undefer')
+const kFactory = Symbol('factory')
+
+class DeferredIterator extends AbstractIterator {
+  constructor (db, options) {
+    super(db, options)
+
+    this[kNut] = null
+    this[kFactory] = () => db.iterator(options)
+
+    this.db.defer(() => this[kUndefer]())
+  }
+}
+
+class DeferredKeyIterator extends AbstractKeyIterator {
+  constructor (db, options) {
+    super(db, options)
+
+    this[kNut] = null
+    this[kFactory] = () => db.keys(options)
+
+    this.db.defer(() => this[kUndefer]())
+  }
+}
+
+class DeferredValueIterator extends AbstractValueIterator {
+  constructor (db, options) {
+    super(db, options)
+
+    this[kNut] = null
+    this[kFactory] = () => db.values(options)
+
+    this.db.defer(() => this[kUndefer]())
+  }
+}
+
+for (const Iterator of [DeferredIterator, DeferredKeyIterator, DeferredValueIterator]) {
+  Iterator.prototype[kUndefer] = function () {
+    if (this.db.status === 'open') {
+      this[kNut] = this[kFactory]()
+    }
+  }
+
+  Iterator.prototype._next = function (callback) {
+    if (this[kNut] !== null) {
+      this[kNut].next(callback)
+    } else if (this.db.status === 'opening') {
+      this.db.defer(() => this._next(callback))
+    } else {
+      this.nextTick(callback, new ModuleError('Iterator is not open: cannot call next() after close()', {
+        code: 'LEVEL_ITERATOR_NOT_OPEN'
+      }))
+    }
+  }
+
+  Iterator.prototype._nextv = function (size, options, callback) {
+    if (this[kNut] !== null) {
+      this[kNut].nextv(size, options, callback)
+    } else if (this.db.status === 'opening') {
+      this.db.defer(() => this._nextv(size, options, callback))
+    } else {
+      this.nextTick(callback, new ModuleError('Iterator is not open: cannot call nextv() after close()', {
+        code: 'LEVEL_ITERATOR_NOT_OPEN'
+      }))
+    }
+  }
+
+  Iterator.prototype._all = function (options, callback) {
+    if (this[kNut] !== null) {
+      this[kNut].all(callback)
+    } else if (this.db.status === 'opening') {
+      this.db.defer(() => this._all(options, callback))
+    } else {
+      this.nextTick(callback, new ModuleError('Iterator is not open: cannot call all() after close()', {
+        code: 'LEVEL_ITERATOR_NOT_OPEN'
+      }))
+    }
+  }
+
+  Iterator.prototype._seek = function (target, options) {
+    if (this[kNut] !== null) {
+      // TODO: explain why we need _seek() rather than seek() here
+      this[kNut]._seek(target, options)
+    } else if (this.db.status === 'opening') {
+      this.db.defer(() => this._seek(target, options))
+    }
+  }
+
+  Iterator.prototype._close = function (callback) {
+    if (this[kNut] !== null) {
+      this[kNut].close(callback)
+    } else if (this.db.status === 'opening') {
+      this.db.defer(() => this._close(callback))
+    } else {
+      this.nextTick(callback)
+    }
+  }
+}
+
+exports.DeferredIterator = DeferredIterator
+exports.DeferredKeyIterator = DeferredKeyIterator
+exports.DeferredValueIterator = DeferredValueIterator