Implemented main class for writing protobufs.

dbms/src/Common/ErrorCodes.cpp

@@ -409,6 +409,9 @@ namespace ErrorCodes
     extern const int UNKNOWN_CODEC = 432;
     extern const int ILLEGAL_CODEC_PARAMETER = 433;
     extern const int CANNOT_PARSE_PROTOBUF_SCHEMA = 434;
+    extern const int NO_DATA_FOR_REQUIRED_PROTOBUF_FIELD = 435;
+    extern const int CANNOT_CONVERT_TO_PROTOBUF_TYPE = 436;
+    extern const int PROTOBUF_FIELD_NOT_REPEATED = 437;
 
     extern const int KEEPER_EXCEPTION = 999;
     extern const int POCO_EXCEPTION = 1000;

dbms/src/Formats/ProtobufWriter.h

+#pragma once
+
+#include <Core/UUID.h>
+#include <Formats/ProtobufSimpleWriter.h>
+#include <boost/noncopyable.hpp>
+#include <Common/PODArray.h>
+#include <Common/UInt128.h>
+#include <common/DayNum.h>
+
+
+namespace google
+{
+namespace protobuf
+{
+    class Descriptor;
+    class FieldDescriptor;
+}
+}
+
+
+namespace DB
+{
+class IAggregateFunction;
+using AggregateFunctionPtr = std::shared_ptr<IAggregateFunction>;
+using ConstAggregateDataPtr = const char *;
+
+
+/** Serializes a protobuf, tries to cast types if necessarily.
+  */
+class ProtobufWriter : private boost::noncopyable
+{
+public:
+    ProtobufWriter(WriteBuffer & out, const google::protobuf::Descriptor * message_type);
+    ~ProtobufWriter();
+
+    /// Returns fields of the protobuf schema sorted by their numbers.
+    const std::vector<const google::protobuf::FieldDescriptor *> & fieldsInWriteOrder() const;
+
+    /// Should be called when we start writing a new message.
+    void newMessage();
+
+    /// Should be called when we start writing a new field.
+    /// Returns false if there is no more fields in the message type.
+    bool nextField();
+
+    /// Returns the current field of the message type.
+    /// The value returned by this function changes after calling nextField() or newMessage().
+    const google::protobuf::FieldDescriptor * currentField() const { return current_field; }
+
+    void writeNumber(Int8 value);
+    void writeNumber(UInt8 value);
+    void writeNumber(Int16 value);
+    void writeNumber(UInt16 value);
+    void writeNumber(Int32 value);
+    void writeNumber(UInt32 value);
+    void writeNumber(Int64 value);
+    void writeNumber(UInt64 value);
+    void writeNumber(UInt128 value);
+    void writeNumber(Float32 value);
+    void writeNumber(Float64 value);
+
+    void writeString(const StringRef & value);
+
+    void prepareEnumMapping(const std::vector<std::pair<std::string, Int8>> & name_value_pairs);
+    void prepareEnumMapping(const std::vector<std::pair<std::string, Int16>> & name_value_pairs);
+    void writeEnum(Int8 value);
+    void writeEnum(Int16 value);
+
+    void writeUUID(const UUID & value);
+    void writeDate(DayNum date);
+    void writeDateTime(time_t tm);
+
+    void writeDecimal(Decimal32 decimal, UInt32 scale);
+    void writeDecimal(Decimal64 decimal, UInt32 scale);
+    void writeDecimal(const Decimal128 & decimal, UInt32 scale);
+
+    void writeAggregateFunction(const AggregateFunctionPtr & function, ConstAggregateDataPtr place);
+
+private:
+    void enumerateFieldsInWriteOrder(const google::protobuf::Descriptor * message_type);
+    void createConverters();
+
+    void finishCurrentMessage();
+    void finishCurrentField();
+
+    ProtobufSimpleWriter simple_writer;
+    std::vector<const google::protobuf::FieldDescriptor *> fields_in_write_order;
+    size_t current_field_index = -1;
+    const google::protobuf::FieldDescriptor * current_field = nullptr;
+
+    class Converter;
+    class ToStringConverter;
+    template <typename T>
+    class ToNumberConverter;
+    class ToBoolConverter;
+    class ToEnumConverter;
+
+    std::vector<std::unique_ptr<Converter>> converters;
+    Converter * current_converter = nullptr;
+};
+
+}