hashedstring.h

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// © Copyright 2010 - 2016 BlackTopp Studios Inc.
/* This file is part of The Mezzanine Engine.

    The Mezzanine Engine is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with The Mezzanine Engine.  If not, see <http://www.gnu.org/licenses/>.
*/
/* The original authors have included a copy of the license specified above in the
   'Docs' folder. See 'gpl.txt'
*/
/* We welcome the use of the Mezzanine engine to anyone, including companies who wish to
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   However there are some practical restrictions, so if your project involves
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   These and other limitations could cause serious legal problems if you ignore
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   Joseph Toppi - toppij@gmail.com
   John Blackwood - makoenergy02@gmail.com
*/
#ifndef _hashedstring_h
#define _hashedstring_h

#include "datatypes.h"
#include "XML/xml.h"

/// @file
/// @brief This implemenation of

namespace Mezzanine
{

#ifndef HASHED_STRING_32_SEED
/// @def HASHED_STRING_32_SEED
/// @brief A value used to tweak the hash function for maximum randomness.
#define HASHED_STRING_32_SEED 1
#endif

    ///////////////////////////////////////////////////////////////////////////////
    /// @brief An identifier that compares as fast as an integer but has a string.
    /// @details This computes a MurmurA(x86 32bit) hash on creation. This is used
    /// in all comparisons, this means that in excedingly rare situations that
    /// hash collisions could cause silent failure. @n @n
    /// Internally programming la
    ///////////////////////////////////////
    class MEZZ_LIB HashedString32
    {
        public:
            ///////////////////////////////////////////////////////////////////////////////
            // Utility

            /// @brief Compute a MurmurA aka MurmurX86-32bit has of a string and return it.
            /// @param ToBeHashed The string to hash
            /// @return A 32 bit value approximating unique, which represents the passed string.
            static Int32 Murmur32bit(const String& ToBeHashed);

        protected:
            ///////////////////////////////////////////////////////////////////////////////
            // Data

            /// The Actual string to store.
            String TheString;
            /// @brief The computed hash.
            Int32 Hash;

        public:
            ///////////////////////////////////////////////////////////////////////////////
            // Creation

            /// @brief NonComputing Constructor
            /// @details Skip the hashing overhead and just do the work for h
            HashedString32();
            /// @brief String Constructor
            /// @param StartingString The String to work with
            /// @details Compute the hash of the String and hang onto both for future use.
            HashedString32(const String& StartingString);
            /// @brief Precomputed Constructor
            /// @param StartingString The String to work with
            /// @param PrecomputedHash The value
            /// @details Does not Compute the hash of the String, Just trusts whatever it is given.
            HashedString32(const String& StartingString, Int32 PrecomputedHash);
            /// @brief Copy constructor
            /// @param StartingString The other hashed string
            HashedString32(const HashedString32& StartingString);

            ///////////////////////////////////////////////////////////////////////////////
            // Comparisons

            /// @brief Compare The hash of this and another string for equality.
            /// @param Other The other string to compare this one too.
            /// @return True if the hashes are the same.
            /// @note It is imcredibly unlikely, but this could return true in the event of a hash collision.
            bool operator==(const HashedString32& Other) const;
            /// @brief Compare The hash of this and another string for inequality.
            /// @param Other The other string to compare this one too.
            /// @return True if the hashes are different.
            bool operator!=(const HashedString32& Other) const;
            /// @brief Provide a semantically useless, but quite fast sorting order for std containers based on only hashes.
            /// @param Other The other string to compare this one too.
            /// @return true If the Hash of this is smaller than the hash of the other
            bool operator<(const HashedString32& Other) const;
            /// @brief Provide a semantically useless, but quite fast sorting order for std containers based on only hashes.
            /// @param Other The other string to compare this one too.
            /// @return true If the Hash of this is larger than the hash of the other
            bool operator>(const HashedString32& Other) const;


            ///////////////////////////////////////////////////////////////////////////////
            // Data Modifiers/observers

            /// @brief Get the 32 bit as an Int32.
            /// @return an Int32 with the hash in it.
            Int32 GetHash() const;
            /// @brief Get the string that was used to calculate the hash.
            /// @return A Mezzanine::String
            String GetString() const;
            /// @brief Set a new string and recalculate its hash.
            /// @param NewString The data to hash and store for later use.
            void SetString(const String& NewString);

            ///////////////////////////////////////////////////////////////////////////////
            // Serialization

            /// @brief Convert this class to an XML::Node ready for serialization
            /// @param CurrentRoot The point in the XML hierarchy that all this HashedString32 should be appended to.
            void ProtoSerialize(XML::Node& CurrentRoot) const;
            /// @brief Take the data stored in an XML and overwrite this instance of this object with it
            /// @param OneNode and XML::Node containing the data.
            void ProtoDeSerialize(const XML::Node& OneNode);
            /// @brief Get the name of the the XML tag this class will leave behind as its instances are serialized.
            /// @return A string containing "HashedString32"
            static String GetSerializableName();
    }; // HashedString32

    ///////////////////////////////////////////////////////////////////////////////
    // Class External << Operators for streaming or assignment

    /// @brief Send a HashedString32 down a stream serialized.
    /// @param stream The std::ostream to send it down.
    /// @param x The HashedString32 to Send
    std::ostream& MEZZ_LIB operator << (std::ostream& stream, const Mezzanine::HashedString32& x);
}//Mezzanine


#endif