StringRef.h

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#pragma once
/*
* Copyright Onix Solutions Limited [OnixS]. All rights reserved.
*
* This software owned by Onix Solutions Limited [OnixS] and is protected by copyright law
* and international copyright treaties.
*
* Access to and use of the software is governed by the terms of the applicable OnixS Software
* Services Agreement (the Agreement) and Customer end user license agreements granting
* a non-assignable, non-transferable and non-exclusive license to use the software
* for it's own data processing purposes under the terms defined in the Agreement.
*
* 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.
*
* Any reproduction or redistribution for sale or hiring of the Software not in accordance with
* the terms of the Agreement is a violation of copyright law.
*/

#include <cstring>
#include <functional>
#include <ostream>
#include <string>

#include <OnixS/FIXEngine/Compiler.h>
#include <OnixS/FIXEngine/FIX/Numeric.h>

#ifdef ONIXS_FIXENGINE_CXX17

#include <string_view>

#endif

namespace OnixS {
namespace FIX {

#ifdef ONIXS_FIXENGINE_CXX17

using StringRef = std::basic_string_view<Char>;

#else

/// Provides an 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 the same
/// message instance is used to update a few fields and is sent over the FIX
/// session multiple times. Also, when a message comes from the network and is
/// deserialized from its raw (tag=value) presentation, all field values
/// represent text segments. To access textual values, the 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 a 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_FIXENGINE_API
    StringRef
{
public:
    /// An immutable iterator over chars.
    typedef const char * ConstIterator;

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

    /// The full initialization.
    ONIXS_FIXENGINE_CONSTEXPR
    StringRef(
        const char * chars,
        size_t size)
        : chars_(chars),
          size_(size) {
    }

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

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

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

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

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

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

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

    /// The number of chars.
    size_t length() const {
        return size_;
    }

    /// Resets the reference to nothing.
    void reset() {
        reset(ONIXS_FIXENGINE_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 the number if the text is a string
    /// representation of an integer.
    template
    <
        typename NumericType
        >
    bool
    toNumber(NumericType & number) const {
        return OnixS::FIX::Number::
               tryParse(chars_, size_, number);
    }

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

    // Returns a copy of the text as the 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 == std::memcmp(
                       chars_, other.chars_, size_));
    }

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

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

    friend std::ostream & operator<< (std::ostream & out, const StringRef & ref);

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

    /// The 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);
}

inline std::ostream & operator<< (std::ostream & out, const StringRef & ref)
{
    if(! ref.empty())
        out.write(ref.chars_, ref.size_);

    return out;
}

#endif

template <size_t Size>
ONIXS_FIXENGINE_NODISCARD
inline
ONIXS_FIXENGINE_CONSTEXPR
StringRef constructStrRef(const char (&value)[Size]) ONIXS_FIXENGINE_NOTHROW
{
    return StringRef(value, Size - 1);
}

}
}

namespace std {
/// Allows the use of the StringRef in collections like std::map.
template<>
struct
    ONIXS_FIXENGINE_API
    less<OnixS::FIX::StringRef> {
    bool
    operator()(
        const OnixS::FIX::StringRef & left,
        const OnixS::FIX::StringRef & right) const {
        ptrdiff_t
        compareResult = std::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);
    }
};
}