StringRef.h

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/*
* Copyright Onix Solutions Limited [OnixS]. All rights reserved.
*
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* and international copyright treaties.
*
* Access to and use of the software is governed by the terms of the applicable OnixS Software
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*
* Except as otherwise granted within the terms of the Agreement, copying or reproduction of any part
* of this source code or associated reference material to any other location for further reproduction
* or redistribution, and any amendments to this copyright notice, are expressly prohibited.
*
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* the terms of the Agreement is a violation of copyright law.
*/

#pragma once

#include <string>
#include <cstring>
#include <functional>
#include <stdexcept>

#include <OnixS/Eurex/MarketData/ABI.h>
#include <OnixS/Eurex/MarketData/Numeric.h>
#include <OnixS/Eurex/MarketData/Compiler.h>

namespace OnixS
{
    namespace Eurex
    {
        namespace MarketData
        {
            /// Provides efficient way of accessing text-based FIX field values.
            ///
            /// By default, OnixS::FIX::Message and OnixS::FIX::GroupInstance classes
            /// convert all values assigned to the fields into their text presentations
            /// and store textual data. This approach optimizes message reuse when same
            /// instance of message is used to update a few fields and is sent over FIX
            /// session multiple times. Also, when message comes from the network and is
            /// deserialized from its raw (tag=value) presentation, all field values in
            /// fact represent segments of text. To have access to textual values, StringRef
            /// class was added together with new access members (FieldSet::getStringRef()).
            /// If value is accessed using FieldSet::getStringRef() member, instance of
            /// StringRef class is returned. That instance holds reference to a read-only
            /// segment of text. An important aspect is that no memory is allocated and
            /// copied while accessing field values that way.
            class
                ONIXS_EUREX_EMDI_API
                StringRef
            {
                public:
                    /// Immutable iterator over chars.
                    typedef const char* ConstIterator;

                    /// Initializes blank instance.
                    StringRef() :
                        chars_ (ONIXS_EUREX_EMDI_NULLPTR),
                        size_ (0)
                    {
                    }

                    /// Full initialization.
                    StringRef (const char* chars, size_t size) :
                        chars_ (chars),
                        size_ (size)

                    {
                    }

                    /// Initializes as clone of other instance.
                    /// Data referenced by clone is not copied.
                    /// Instead both instances will refer to same
                    /// text segment.
                    StringRef (const StringRef& other) :
                        chars_ (other.chars_),
                        size_ (other.size_)

                    {
                    }

                    /// Initializes instance from string content.
                    explicit StringRef (const std::string& stdStr) :
                        chars_ (stdStr.c_str() ),
                        size_ (stdStr.size() )
                    {
                    }

                    /// Initializes instance from zero-terminated string.
                    StringRef (const char* cStr) :
                        chars_ (cStr),
                        size_ (cStr ? strlen (cStr) : 0)
                    {
                    }

                    /// Indicates whether array of zero length.
                    bool empty() const
                    {
                        return (0 == size_);
                    }

                    /// Read-only content.
                    const char* data() const
                    {
                        return chars_;
                    }

                    /// STL-like begin().
                    ConstIterator begin() const
                    {
                        return chars_;
                    }

                    /// STL-like end().
                    ConstIterator end() const
                    {
                        return chars_ + size_;
                    }

                    /// Number of chars.
                    size_t size() const
                    {
                        return size_;
                    }

                    /// Resets reference to nothing.
                    void reset()
                    {
                        reset (ONIXS_EUREX_EMDI_NULLPTR, 0);
                    }

                    /// Updates data being referenced.
                    void
                    reset (
                        const char* chars,
                        size_t size)
                    {
                        chars_ = chars;
                        size_ = size;
                    }

                    const char&
                    operator [] (size_t index) const
                    {
                        return chars_[index];
                    }

                    const char&
                    at (size_t index) const
                    {
                        if (index < size_)
                            return chars_[index];

                        throw std::invalid_argument ("index");
                    }

                    /// Returns number if text is string
                    /// representation of an integer.
                    template
                    <
                    typename NumericType
                    >
                    bool
                    toNumber (NumericType& number) const
                    {
                        return OnixS::Eurex::MarketData::Number::
                               tryParse (chars_, size_, number);
                    }

                    // Appends copy of text to the std::string.
                    void
                    toString (std::string& str) const
                    {
                        str.append (chars_, size_);
                    }

                    // Return copy of text as std::string.
                    std::string
                    toString() const
                    {
                        return std::string (chars_, size_);
                    }

                    /// Compares with another instance.
                    bool
                    operator == (
                        const StringRef& other) const
                    {
                        return (
                                   size_ == other.size_
                                   &&
                                   0 == memcmp (
                                       chars_, other.chars_, size_) );
                    }

                    /// Compares with another instance.
                    bool
                    operator != (
                        const StringRef& other) const
                    {
                        return (
                                   size_ != other.size_
                                   ||
                                   0 != memcmp (
                                       chars_, other.chars_, size_) );
                    }

                    /// Reinitializes from another instance.
                    StringRef&
                    operator = (
                        const StringRef& other)
                    {
                        chars_ = other.chars_;
                        size_ = other.size_;

                        return *this;
                    }

                    /// Swaps content with other instance.
                    void
                    swap (StringRef& other)
                    {
                        std::swap (chars_, other.chars_);
                        std::swap (size_, other.size_);
                    }

                private:
                    /// Items being referenced.
                    const char* chars_;

                    /// Number of chars being referenced.
                    size_t size_;
            };

            inline
            bool
            operator == (
                const StringRef& ref,
                const std::string& str)
            {
                return ref == StringRef (str);
            }

            inline
            bool
            operator != (
                const StringRef& ref,
                const std::string& str)
            {
                return ref != StringRef (str);
            }

            inline
            bool
            operator == (
                const std::string& str,
                const StringRef& ref)
            {
                return ref == StringRef (str);
            }

            inline
            bool
            operator != (
                const std::string& str,
                const StringRef& ref)
            {
                return ref != StringRef (str);
            }

            //

            inline
            bool
            operator == (
                const StringRef& ref,
                const char* str)
            {
                return ref == StringRef (str);
            }

            inline
            bool
            operator != (
                const StringRef& ref,
                const char* str)
            {
                return ref != StringRef (str);
            }

            inline
            bool
            operator == (
                const char* str,
                const StringRef& ref)
            {
                return ref == StringRef (str);
            }

            inline
            bool
            operator != (
                const char* str,
                const StringRef& ref)
            {
                return ref != StringRef (str);
            }
        }
    }
}

namespace std
{
    /// Allows using of StringRef in collections like std::map.
    template<>
    struct
            ONIXS_EUREX_EMDI_API
            less<OnixS::Eurex::MarketData::StringRef>
    {
        bool
        operator () (
            const OnixS::Eurex::MarketData::StringRef& left,
            const OnixS::Eurex::MarketData::StringRef& right) const
        {
            ptrdiff_t
            compareResult = memcmp (
                                left.data(), right.data(),
                                left.size() < right.size()
                                ? left.size() : right.size() );

            if (0 == compareResult)
            {
                compareResult =
                    static_cast<ptrdiff_t> (
                        left.size() - right.size() );
            }

            return (0 > compareResult);
        }
    };
}