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+// Copyright (c) 2017-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).
+
+/**
+ * The encoding of Cassandra Row Value.
+ *
+ * A Cassandra Row Value could either be a row tombstone,
+ * or contains multiple columns, it has following fields:
+ *
+ * struct row_value {
+ *   int32_t local_deletion_time;  // Time in second when the row is deleted,
+ *                                 // only used for Cassandra tombstone gc.
+ *   int64_t marked_for_delete_at; // Ms that marked this row is deleted.
+ *   struct column_base columns[]; // For non tombstone row, all columns
+ *                                 // are stored here.
+ * }
+ *
+ * If the local_deletion_time and marked_for_delete_at is set, then this is
+ * a tombstone, otherwise it contains multiple columns.
+ *
+ * There are three type of Columns: Normal Column, Expiring Column and Column
+ * Tombstone, which have following fields:
+ *
+ * // Identify the type of the column.
+ * enum mask {
+ *   DELETION_MASK = 0x01,
+ *   EXPIRATION_MASK = 0x02,
+ * };
+ *
+ * struct column  {
+ *   int8_t mask = 0;
+ *   int8_t index;
+ *   int64_t timestamp;
+ *   int32_t value_length;
+ *   char value[value_length];
+ * }
+ *
+ * struct expiring_column  {
+ *   int8_t mask = mask.EXPIRATION_MASK;
+ *   int8_t index;
+ *   int64_t timestamp;
+ *   int32_t value_length;
+ *   char value[value_length];
+ *   int32_t ttl;
+ * }
+ *
+ * struct tombstone_column  {
+ *   int8_t mask = mask.DELETION_MASK;
+ *   int8_t index;
+ *   int32_t local_deletion_time; // Similar to row_value's field.
+ *   int64_t marked_for_delete_at;
+ *  }
+ */
+
+#pragma once
+#include <chrono>
+#include <memory>
+#include <vector>
+
+#include "rocksdb/merge_operator.h"
+#include "rocksdb/slice.h"
+
+namespace ROCKSDB_NAMESPACE {
+namespace cassandra {
+
+// Identify the type of the column.
+enum ColumnTypeMask {
+  DELETION_MASK = 0x01,
+  EXPIRATION_MASK = 0x02,
+};
+
+class ColumnBase {
+ public:
+  ColumnBase(int8_t mask, int8_t index);
+  virtual ~ColumnBase() = default;
+
+  virtual int64_t Timestamp() const = 0;
+  virtual int8_t Mask() const;
+  virtual int8_t Index() const;
+  virtual std::size_t Size() const;
+  virtual void Serialize(std::string* dest) const;
+  static std::shared_ptr<ColumnBase> Deserialize(const char* src,
+                                                 std::size_t offset);
+
+ private:
+  int8_t mask_;
+  int8_t index_;
+};
+
+class Column : public ColumnBase {
+ public:
+  Column(int8_t mask, int8_t index, int64_t timestamp, int32_t value_size,
+         const char* value);
+
+  virtual int64_t Timestamp() const override;
+  virtual std::size_t Size() const override;
+  virtual void Serialize(std::string* dest) const override;
+  static std::shared_ptr<Column> Deserialize(const char* src,
+                                             std::size_t offset);
+
+ private:
+  int64_t timestamp_;
+  int32_t value_size_;
+  const char* value_;
+};
+
+class Tombstone : public ColumnBase {
+ public:
+  Tombstone(int8_t mask, int8_t index, int32_t local_deletion_time,
+            int64_t marked_for_delete_at);
+
+  virtual int64_t Timestamp() const override;
+  virtual std::size_t Size() const override;
+  virtual void Serialize(std::string* dest) const override;
+  bool Collectable(int32_t gc_grace_period) const;
+  static std::shared_ptr<Tombstone> Deserialize(const char* src,
+                                                std::size_t offset);
+
+ private:
+  int32_t local_deletion_time_;
+  int64_t marked_for_delete_at_;
+};
+
+class ExpiringColumn : public Column {
+ public:
+  ExpiringColumn(int8_t mask, int8_t index, int64_t timestamp,
+                 int32_t value_size, const char* value, int32_t ttl);
+
+  virtual std::size_t Size() const override;
+  virtual void Serialize(std::string* dest) const override;
+  bool Expired() const;
+  std::shared_ptr<Tombstone> ToTombstone() const;
+
+  static std::shared_ptr<ExpiringColumn> Deserialize(const char* src,
+                                                     std::size_t offset);
+
+ private:
+  int32_t ttl_;
+  std::chrono::time_point<std::chrono::system_clock> TimePoint() const;
+  std::chrono::seconds Ttl() const;
+};
+
+using Columns = std::vector<std::shared_ptr<ColumnBase>>;
+
+class RowValue {
+ public:
+  // Create a Row Tombstone.
+  RowValue(int32_t local_deletion_time, int64_t marked_for_delete_at);
+  // Create a Row containing columns.
+  RowValue(Columns columns, int64_t last_modified_time);
+  RowValue(const RowValue& /*that*/) = delete;
+  RowValue(RowValue&& /*that*/) noexcept = default;
+  RowValue& operator=(const RowValue& /*that*/) = delete;
+  RowValue& operator=(RowValue&& /*that*/) = default;
+
+  std::size_t Size() const;
+  bool IsTombstone() const;
+  // For Tombstone this returns the marked_for_delete_at_,
+  // otherwise it returns the max timestamp of containing columns.
+  int64_t LastModifiedTime() const;
+  void Serialize(std::string* dest) const;
+  RowValue RemoveExpiredColumns(bool* changed) const;
+  RowValue ConvertExpiredColumnsToTombstones(bool* changed) const;
+  RowValue RemoveTombstones(int32_t gc_grace_period) const;
+  bool Empty() const;
+
+  static RowValue Deserialize(const char* src, std::size_t size);
+  // Merge multiple rows according to their timestamp.
+  static RowValue Merge(std::vector<RowValue>&& values);
+
+  const Columns& get_columns() { return columns_; }
+
+ private:
+  int32_t local_deletion_time_;
+  int64_t marked_for_delete_at_;
+  Columns columns_;
+  int64_t last_modified_time_;
+};
+
+}  // namespace cassandra
+}  // namespace ROCKSDB_NAMESPACE