add leveldb

lib/leveldb/table/iterator.cc

@@ -0,0 +1,76 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+Iterator::Iterator() {
+  cleanup_head_.function = nullptr;
+  cleanup_head_.next = nullptr;
+}
+
+Iterator::~Iterator() {
+  if (!cleanup_head_.IsEmpty()) {
+    cleanup_head_.Run();
+    for (CleanupNode* node = cleanup_head_.next; node != nullptr;) {
+      node->Run();
+      CleanupNode* next_node = node->next;
+      delete node;
+      node = next_node;
+    }
+  }
+}
+
+void Iterator::RegisterCleanup(CleanupFunction func, void* arg1, void* arg2) {
+  assert(func != nullptr);
+  CleanupNode* node;
+  if (cleanup_head_.IsEmpty()) {
+    node = &cleanup_head_;
+  } else {
+    node = new CleanupNode();
+    node->next = cleanup_head_.next;
+    cleanup_head_.next = node;
+  }
+  node->function = func;
+  node->arg1 = arg1;
+  node->arg2 = arg2;
+}
+
+namespace {
+
+class EmptyIterator : public Iterator {
+ public:
+  EmptyIterator(const Status& s) : status_(s) {}
+  ~EmptyIterator() override = default;
+
+  bool Valid() const override { return false; }
+  void Seek(const Slice& target) override {}
+  void SeekToFirst() override {}
+  void SeekToLast() override {}
+  void Next() override { assert(false); }
+  void Prev() override { assert(false); }
+  Slice key() const override {
+    assert(false);
+    return Slice();
+  }
+  Slice value() const override {
+    assert(false);
+    return Slice();
+  }
+  Status status() const override { return status_; }
+
+ private:
+  Status status_;
+};
+
+}  // anonymous namespace
+
+Iterator* NewEmptyIterator() { return new EmptyIterator(Status::OK()); }
+
+Iterator* NewErrorIterator(const Status& status) {
+  return new EmptyIterator(status);
+}
+
+}  // namespace leveldb