AggregationBuilders.hpp

/*
(c) Copyright, Real-Time Innovations, 2018.
All rights reserved.

No duplications, whole or partial, manual or electronic, may be made
without express written permission.  Any such copies, or
revisions thereof, must display this notice unaltered.
This code contains trade secrets of Real-Time Innovations, Inc.
*/

#ifndef RTI_DDS_FLAT_AGGREGATIONBUILDERS_HPP_
#define RTI_DDS_FLAT_AGGREGATIONBUILDERS_HPP_

#include "rti/flat/BuilderHelper.hpp"
#include "rti/flat/Builder.hpp"

namespace rti { namespace flat {

/*
 * Provides the common functionality for builders of aggregated types
 * 
 * Extends and specializes AbstractBuilder to add or override the functionality
 * required to build an aggregated type:
 * 
 * - Add or build members, prepending the member header
 * - Add dheader at the beginning
 * - Add parameter-list-end header at the end
 */
class AggregationBuilder : public AbstractBuilder {
protected:
    AggregationBuilder() :
            dheader_position_(NULL),
            emheader_position_(NULL)
    {
    }

    // Create a new top-level builder
    AggregationBuilder(
            unsigned char *initial_buffer, 
            offset_t size,
            bool initialize_members) : 
        AbstractBuilder(initial_buffer, size, initialize_members),
        dheader_position_(NULL),
        emheader_position_(NULL)
    {
        dheader_position_ = stream().serialize_dheader();
        if (dheader_position_ == NULL) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(invalidate());
        }
    }

public:
    // For internal use and testing
    //
    // Modifies the encapsulation set in the constructor with a custom value.
    // This function can only be called after the construction of a non-nested
    // Builder, before any member is built or added.
    //
    void set_encapsulation_impl(RTIXCdrEncapsulationId encapsulation_id)
    {
        // Only a top-level Builder can change the encapsulation
        RTI_FLAT_CHECK_PRECONDITION(!is_nested(), return);

        char *current_position = (char *) owned_stream_.current_position();
        // This operation is only valid right after construction, when no
        // member has been added yet
        RTI_FLAT_CHECK_PRECONDITION(
                current_position == dheader_position_ + RTI_XCDR_DHEADER_SIZE, 
                return);

        owned_stream_.skip_back(
                RTI_XCDR_DHEADER_SIZE + RTI_XCDR_ENCAPSULATION_HEADER_SIZE);

        if (!RTIXCdrFlatSample_initializeEncapsulationAndStream(
                (char *) owned_stream_.buffer(), 
                &owned_stream_.c_stream(),
                encapsulation_id, 
                owned_stream_.total_size())) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(return);
        }

        stream().serialize_dheader();
    }
    
protected:

#if defined(RTI_FLAT_DATA_CXX11_RVALUE_REFERENCES)
    AggregationBuilder(AggregationBuilder&& other) = default;

    AggregationBuilder& operator=(AggregationBuilder&& other)
    {
        if (this == &other) {
            return *this;
        }

        finish_untyped_impl();

        AbstractBuilder::operator=(static_cast<AbstractBuilder&&>(other));

        dheader_position_ = other.dheader_position_;
        emheader_position_ = other.emheader_position_;

        return *this;
    }
#else
public:
    // Enable the safe-move-constructor idiom without C++11 move constructors
    struct UntypedAggregationBuilderMoveProxy : AbstractBuilderMoveProxy {
        char * dheader_position_;
        char * emheader_position_;
    };

    operator UntypedAggregationBuilderMoveProxy () throw() // move-constructor idiom
    {
        UntypedAggregationBuilderMoveProxy other;
        move_to(other);
        return other;
    }
    
protected:
    void move_from(UntypedAggregationBuilderMoveProxy& other)
    {
        AbstractBuilder::move_from(other);
        dheader_position_ = other.dheader_position_;
        emheader_position_ = other.emheader_position_;
    }

    void move_to(UntypedAggregationBuilderMoveProxy& other)
    {
        AbstractBuilder::move_to(other);
        other.dheader_position_ = dheader_position_;
        other.emheader_position_ = emheader_position_;
    }
#endif

protected:
    virtual ~AggregationBuilder()
    {
        // AggregationBuilder::finish_untyped_impl() is specialized
        // with respect to AbstractBuilder::finish_untyped_impl()
        finish_untyped_impl();
    }

    template <typename T>
    bool add_primitive_member(member_id_t id, T value)
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return false);

        rti::xcdr::Stream::Memento stream_memento(stream());

        if (!begin_emheader(id, detail::primitive_lc_code<T>::value)) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(return false);
        }
        // no need to call finish_emheader()

        if (!stream().serialize_no_align(value)) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(return false);
        }

        stream_memento.discard(); // success: do not restore the current position
        return true;
    }

    template <typename OffsetType>
    OffsetType add_member(member_id_t id)
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return OffsetType());

        // save state in case of error
        rti::xcdr::Stream::Memento stream_memento(stream());
        return add_member<OffsetType>(id, stream_memento);
    }

    template <typename OffsetType>
    OffsetType add_member(
            member_id_t id,
            rti::xcdr::Stream::Memento& stream_memento)
    {
        // EMHeader with LC = 4; any fixed-size non-primitive member will have
        // LC = 4 since they don't encode a length
        if (!begin_emheader(id, 4)) {
            return OffsetType();
        }

        OffsetType result = AbstractBuilder::add_element<OffsetType>();
        finish_emheader();

        stream_memento.discard(); // success - do not restore the previous state
        return result;
    }

    template <typename NestedBuilder>
    NestedBuilder build_member(member_id_t id)
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return NestedBuilder());

        // save state in case of error
        rti::xcdr::Stream::Memento stream_memento(stream());
        return build_member<NestedBuilder>(id, stream_memento);
    }

    template <typename NestedBuilder>
    NestedBuilder build_member(
            member_id_t id, 
            rti::xcdr::Stream::Memento& stream_memento)
    {
        if (!begin_emheader(id, detail::lc_code<NestedBuilder>::value)) {
            return NestedBuilder();
        }

        return AbstractBuilder::build_element_no_align<NestedBuilder>(
                stream_memento);
    }    

    unsigned char* finish_sample_impl()
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return NULL);
        RTI_FLAT_BUILDER_CHECK_NOT_BOUND(return NULL);
        RTI_FLAT_BUILDER_CHECK_CAN_FINISH_SAMPLE(return NULL);

        if (!stream().finish_dheader(dheader_position_)) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(return NULL);
        }

        unsigned char *return_sample = stream().buffer();
        invalidate();
        
        return return_sample;
    }    

    // Same as finish_impl() but it doesn't throw exceptions or return an Offset
    void finish_untyped_impl()
    {
        if (is_valid() && is_nested()) {
            stream().finish_dheader(dheader_position_);
            AbstractBuilder::finish_untyped_impl();
        }
    }

    template <typename OffsetType>
    OffsetType finish_impl()
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return OffsetType());
        RTI_FLAT_BUILDER_CHECK_CAN_FINISH(return OffsetType());

        stream().finish_dheader(dheader_position_);
        return AbstractBuilder::finish_impl<OffsetType>();
    }

public:
    // For internal use; need to use rti::flat::discard_sample(writer, builder)
    unsigned char * discard_sample_impl()
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return NULL);
        RTI_FLAT_BUILDER_CHECK_NOT_BOUND(return NULL);
        RTI_FLAT_BUILDER_CHECK_CAN_FINISH_SAMPLE(return NULL);
                
        unsigned char *buffer = this->buffer();
        invalidate();
        return buffer;
    }

private:
    void finish_member() // override noexcept
    {
        if (!is_valid()) {
            return;
        }

        finish_emheader();
        AbstractBuilder::finish_member();
    }

private:

    bool begin_emheader(member_id_t id, RTIXCdrUnsignedLong lc)
    {
        RTI_FLAT_BUILDER_CHECK_NOT_BOUND(return false);

        if (!stream().serialize_emheader(emheader_position_, id, lc)) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(return false);
        }

        return true;
    }

    void finish_emheader() // noexcept
    {
        if (emheader_position_ != NULL) {
            stream().finish_emheader(emheader_position_);
            emheader_position_ = NULL;
        }
    }

protected:
    // Create a nested builder
    AggregationBuilder(nested_tag_t, AbstractBuilder& parent, unsigned int alignment)
        : AbstractBuilder(nested_tag_t(), parent, alignment),
          dheader_position_(NULL),
          emheader_position_(NULL)
    {
        dheader_position_ = stream().serialize_dheader();
        if (dheader_position_ == NULL) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(invalidate());            
        }
    }

private:
    char * dheader_position_;
    char * emheader_position_;
};

// Specializes an AggregationBuilder to enforce that only one member can
// be set at a time
template <typename Discriminator>
class UnionBuilder : public AggregationBuilder {
protected:
    UnionBuilder()
    {
    }

    // Create a new top-level builder
    UnionBuilder(
            unsigned char *initial_buffer, 
            offset_t size, 
            bool initialize_members) : 
        AggregationBuilder(initial_buffer, size, initialize_members)
    {
    }

    template <typename T>
    bool add_primitive_member(member_id_t id, Discriminator disc, T value)
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return false);

        // Always start at the beginning and override any member or discriminator
        // that may have been set
        move_to_discriminator();
        rti::xcdr::Stream::Memento stream_memento(stream());

        if (!add_discriminator(disc)) {
            return false;
        }

        if (!AggregationBuilder::add_primitive_member(id, value)) {
            return false;
        }

        stream_memento.discard(); // success: do not restore the current position
        return true;
    }

    template <typename OffsetType>
    OffsetType add_member(member_id_t id, Discriminator disc)
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return OffsetType());

        move_to_discriminator();
        rti::xcdr::Stream::Memento stream_memento(stream());
        if (!add_discriminator(disc)) {
            RTI_FLAT_BUILDER_OUT_OF_RESOURCES_ERROR(return OffsetType());
        }

        return AggregationBuilder::add_member<OffsetType>(id, stream_memento);
    }

    template <typename NestedBuilder>
    NestedBuilder build_member(member_id_t id, Discriminator disc)
    {
        RTI_FLAT_BUILDER_CHECK_VALID(return NestedBuilder());

        move_to_discriminator();
        rti::xcdr::Stream::Memento stream_memento(stream());
        add_discriminator(disc);

        return AggregationBuilder::build_member<NestedBuilder>(id, stream_memento);
    }

    // Create a nested builder
    UnionBuilder(nested_tag_t, AbstractBuilder& parent, unsigned int alignment)
        : AggregationBuilder(nested_tag_t(), parent, alignment)
    {
    }

private:
    void move_to_discriminator()
    {
        stream().current_position(begin_position() + RTI_XCDR_DHEADER_SIZE);
    }

    bool add_discriminator(Discriminator disc)
    {
        return AggregationBuilder::add_primitive_member(0, disc);
    }
};


} }

#endif // RTI_DDS_FLAT_AGGREGATIONBUILDERS_HPP_