1 files changed, 75 insertions, 0 deletions
diff --git a/src/rocksdb/utilities/merge_operators/uint64add.cc b/src/rocksdb/utilities/merge_operators/uint64add.cc
new file mode 100644
index 000000000..5be2f5641
--- /dev/null
+++ b/src/rocksdb/utilities/merge_operators/uint64add.cc
@@ -0,0 +1,75 @@
+// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include <memory>
+
+#include "logging/logging.h"
+#include "rocksdb/env.h"
+#include "rocksdb/merge_operator.h"
+#include "rocksdb/slice.h"
+#include "util/coding.h"
+#include "utilities/merge_operators.h"
+
+namespace {  // anonymous namespace
+
+using ROCKSDB_NAMESPACE::AssociativeMergeOperator;
+using ROCKSDB_NAMESPACE::InfoLogLevel;
+using ROCKSDB_NAMESPACE::Logger;
+using ROCKSDB_NAMESPACE::Slice;
+
+// A 'model' merge operator with uint64 addition semantics
+// Implemented as an AssociativeMergeOperator for simplicity and example.
+class UInt64AddOperator : public AssociativeMergeOperator {
+ public:
+  bool Merge(const Slice& /*key*/, const Slice* existing_value,
+             const Slice& value, std::string* new_value,
+             Logger* logger) const override {
+    uint64_t orig_value = 0;
+    if (existing_value) {
+      orig_value = DecodeInteger(*existing_value, logger);
+    }
+    uint64_t operand = DecodeInteger(value, logger);
+
+    assert(new_value);
+    new_value->clear();
+    ROCKSDB_NAMESPACE::PutFixed64(new_value, orig_value + operand);
+
+    return true;  // Return true always since corruption will be treated as 0
+  }
+
+  static const char* kClassName() { return "UInt64AddOperator"; }
+  static const char* kNickName() { return "uint64add"; }
+  const char* Name() const override { return kClassName(); }
+  const char* NickName() const override { return kNickName(); }
+
+ private:
+  // Takes the string and decodes it into a uint64_t
+  // On error, prints a message and returns 0
+  uint64_t DecodeInteger(const Slice& value, Logger* logger) const {
+    uint64_t result = 0;
+
+    if (value.size() == sizeof(uint64_t)) {
+      result = ROCKSDB_NAMESPACE::DecodeFixed64(value.data());
+    } else if (logger != nullptr) {
+      // If value is corrupted, treat it as 0
+      ROCKS_LOG_ERROR(logger,
+                      "uint64 value corruption, size: %" ROCKSDB_PRIszt
+                      " > %" ROCKSDB_PRIszt,
+                      value.size(), sizeof(uint64_t));
+    }
+
+    return result;
+  }
+};
+
+}  // anonymous namespace
+
+namespace ROCKSDB_NAMESPACE {
+
+std::shared_ptr<MergeOperator> MergeOperators::CreateUInt64AddOperator() {
+  return std::make_shared<UInt64AddOperator>();
+}
+
+}  // namespace ROCKSDB_NAMESPACE