BinaryMessage.h

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// Copyright Onix Solutions Limited [OnixS]. All rights reserved.
//
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//
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// agreements granting a non-assignable, non-transferable and non-exclusive license 
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// in the Agreement.
//
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// amendments to this copyright notice, are expressly prohibited.
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#pragma once

#include <OnixS/CboeCFE/Trading/BOE/Memory.h>
#include <OnixS/CboeCFE/Trading/BOE/Defines.h>
#include <OnixS/CboeCFE/Trading/BOE/String.h>

#include <cassert>

namespace OnixS
{
    namespace CboeCFE
    {
        namespace Trading
        {
            namespace BOE
            {
                /// Value extractor helper
                template <class FieldValue>
                struct OrdinaryExtractor
                {
                    static FieldValue extract(const void* p)
                    {
                        return unalignedCopy<FieldValue>(p);
                    }
                };

                template<class MantissaType, class ExponentType>
                struct OrdinaryExtractor<FixedPointDecimal<MantissaType, ExponentType> >
                {
                    static FixedPointDecimal<MantissaType, ExponentType> extract(const void* p)
                    {
                        return FixedPointDecimal<MantissaType, ExponentType>(
                            unalignedCopy<typename FixedPointDecimal<MantissaType, ExponentType>::Mantissa>(p));
                    }
                };

                /// Exposes base services to access fields stored in 
                /// little Endian block of memory. Class represents an 
                /// abstraction, instance construction available through 
                /// descendants implementing actual access to encoded data. 
                template <class Block, class BlockSize> 
                class BinaryFields
                {
                    /// Instance of block providing 
                    /// actual access to encoded data.
                    const Block& block() const
                    {
                        return *static_cast<const Block*>(this);
                    }

                protected:
                    /// Returns sub message. 
                    template <class SubMessage>
                    const SubMessage submessage(BlockSize offset, BlockSize size) const
                    {
                        assert(block().binarySize() >= (offset + size));

                        const void* const data = advanceByBytes(block().binary(), offset);

                        return SubMessage(data, size);
                    }

                    /// Returns value of a field by its offset. 
                    template <class FieldValue>
                    const FieldValue& ordinaryRef(BlockSize offset) const
                    {
                        assert(block().binarySize() >= (offset + sizeof(FieldValue)));

                        const void* const fieldValue = advanceByBytes(block().binary(), offset);
                        return *static_cast <const FieldValue*>(fieldValue);
                    }

                    /// Returns value of a field by its offset.
                    template <class FieldValue>
                    FieldValue ordinary(BlockSize offset) const
                    {
                        assert(block().binarySize() >= (offset + sizeof(FieldValue)));

                        return OrdinaryExtractor<FieldValue>::extract(advanceByBytes(block().binary(), offset));
                    }

                    /// Returns value of a field by its offset. 
                    /// 
                    /// Given function serves as specialization of 
                    /// general case for fields of enumeration type. 
                    template <class Enumeration>
                    typename Enumeration::Enum enumeration(BlockSize offset) const
                    {
                        typedef typename Enumeration::Base Base;

                        typedef typename Enumeration::Enum Enum;

                        return static_cast<Enum>( ordinary<Base>(offset));
                    }

                    /// Provides access to string field by its offset. 
                    /// 
                    /// Given function serves as specialization 
                    /// of general case for fields of string type. 
                    template <BlockSize Size> 
                    StrRef fixedStr(BlockSize offset) const
                    {
                        typedef Char Str[Size];

                        const Str& str = ordinaryRef<Str>(offset);

                        return StrRef(str, strnlen(str, Size));
                    }
                };

                /// Aliases message length type. 
                typedef Binary2 MessageSize;

                /// Encapsulates services for manipulating little endian encoded messages.
                class ONIXS_CBOE_CFE_BOE_API BinaryMessage : public BinaryFields<BinaryMessage, MessageSize>
                {
                    const void* data_;
                    MessageSize size_;

                public:
                    /// Length of message binary data. 
                    typedef MessageSize BinarySize;

                    /// Initializes blank instance referencing to nothing. 
                    BinaryMessage()
                        : data_(ONIXS_BATS_BOE_NULLPTR)
                        , size_(0)
                    {
                    }

                    /// Initializes instance over given memory block.
                    BinaryMessage(
                        const void* data,
                        MessageSize size)
                        : data_(data)
                        , size_(size)
                    {
                        assert(ONIXS_BATS_BOE_NULLPTR != data);
                    }

                    /// Initializes instance as copy of the other one.
                    BinaryMessage(
                        const BinaryMessage& other)
                        : data_(other.data_)
                        , size_(other.size_)
                    {
                    }

                    /// Indicates whether instance refers to a valid message. 
                    operator bool() const
                    {
                        return (ONIXS_BATS_BOE_NULLPTR != data_);
                    }

                    /// Message content. 
                    const void* binary() const
                    {
                        return data_;
                    }

                    /// Size of message. 
                    MessageSize binarySize() const
                    {
                        return size_;
                    }

                    /// Re-initializes instance as a copy of the other one.
                    BinaryMessage&
                        operator =(
                            const BinaryMessage& other)
                    {
                        data_ = other.data_;
                        size_ = other.size_;

                        return *this;
                    }
                };
            }
        }
    }
}