//========= Copyright Valve Corporation, All rights reserved. ============//

//

// Purpose: common helpers for reuse among various Utl containers

//

// $NoKeywords: $

//

//=============================================================================//

#ifndef UTLCOMMON_H

#define UTLCOMMON_H

#pragma once

//-----------------------------------------------------------------------------

// Henry Goffin (henryg) was here. Questions? Bugs? Go slap him around a bit.

//-----------------------------------------------------------------------------

// empty_t is the canonical "no-value" type which is fully defined but empty.

struct empty_t {};

// undefined_t is the canonical "undefined" type, used mostly for typedefs;

// parameters of type undefined_t will not compile, which is actually useful

// behavior when it comes to template programming. Google "SFINAE" for info.

struct undefined_t;

// CTypeSelect<sel,A,B>::type is a typedef of A if sel is nonzero, else B

template <int sel, typename A, typename B>

struct CTypeSelect { typedef A type; };

template <typename A, typename B>

struct CTypeSelect<0, A, B> { typedef B type; };

// CTypeEquals<A, B>::value is nonzero if A and B are the same type

template <typename A, typename B, bool bIgnoreConstVolatile = false, bool bIgnoreReference = false>

struct CTypeEquals { enum { value = 0 }; };

template <typename Same>

struct CTypeEquals<Same, Same, false, false> { enum { value = 1 }; };

template <typename A, typename B>

struct CTypeEquals<A, B, true, true> : CTypeEquals< const volatile A&, const volatile B& > {};

template <typename A, typename B>

struct CTypeEquals<A, B, true, false> : CTypeEquals< const volatile A, const volatile B > {};

template <typename A, typename B>

struct CTypeEquals<A, B, false, true> : CTypeEquals< A&, B& > {};

// CUtlKeyValuePair is intended for use with key-lookup containers.

// Because it is specialized for "empty_t" values, one container can

// function as either a set of keys OR a key-value dictionary while

// avoiding storage waste or padding for the empty_t value objects.

template <typename K, typename V>

class CUtlKeyValuePair

};

template <typename K>

class CUtlKeyValuePair<K, empty_t>

{

public:

typedef const K ValueReturn_t;

K m_key;

CUtlKeyValuePair() {}

template < typename KInit >

explicit CUtlKeyValuePair( const KInit &k ) : m_key( k ) {}

template < typename KInit >

CUtlKeyValuePair( const KInit &k, empty_t ) : m_key( k ) {}

CUtlKeyValuePair( const K &k, const empty_t& ) : m_key( k ) {}

const K &GetValue() const { return m_key; }

};

// Default functors. You can specialize these if your type does

// not implement operator== or operator< in an efficient way for

// some odd reason.

template <typename T> struct DefaultLessFunctor;

template <typename T> struct DefaultEqualFunctor;

// Hashing functor used by hash tables. You can either specialize

// for types which are widely used, or plug a custom functor directly

// into the hash table. If you do roll your own, please read up on

// bit-mixing and the avalanche property; be sure that your values

// are reasonably well-distributed across the entire 32-bit range.

// http://en.wikipedia.org/wiki/Avalanche_effect

// http://home.comcast.net/~bretm/hash/5.html

//

template <typename T> struct DefaultHashFunctor;

// Argument type information. Struct currently contains one or two typedefs:

// typename Arg_t = primary argument type. Usually const T&, sometimes T.

// typename Alt_t = optional alternate type. Usually *undefined*.

//

// Any specializations should be implemented via simple inheritance

// from ArgumentTypeInfoImpl< BestArgType, [optional] AlternateArgType >

//

template <typename T> struct ArgumentTypeInfo;

// Some fundamental building-block functors...

struct StringLessFunctor { bool operator()( const char *a, const char *b ) const { return Q_strcmp( a, b ) < 0; } };

struct StringEqualFunctor { bool operator()( const char *a, const char *b ) const { return Q_strcmp( a, b ) == 0; } };

struct CaselessStringLessFunctor { bool operator()( const char *a, const char *b ) const { return Q_strcasecmp( a, b ) < 0; } };

struct CaselessStringEqualFunctor { bool operator()( const char *a, const char *b ) const { return Q_strcasecmp( a, b ) == 0; } };

struct Mix32HashFunctor { unsigned int operator()( uint32 s ) const; };

struct StringHashFunctor { unsigned int operator()( const char* s ) const; };

struct CaselessStringHashFunctor { unsigned int operator()( const char* s ) const; };

struct PointerLessFunctor { bool operator()( const void *a, const void *b ) const { return a < b; } };

struct PointerEqualFunctor { bool operator()( const void *a, const void *b ) const { return a == b; } };

struct PointerHashFunctor { unsigned int operator()( const void* s ) const { return Mix32HashFunctor()((uint32)POINTER_TO_INT(s)); } };

// Generic implementation of Less and Equal functors

template < typename T >

struct DefaultLessFunctor

};

template < typename T >

struct DefaultEqualFunctor

};

// Hashes for basic types

template <> struct DefaultHashFunctor<char> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<signed char> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<unsigned char> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<signed short> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<unsigned short> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<signed int> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<unsigned int> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<signed long> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<unsigned long> : Mix32HashFunctor { };

template <> struct DefaultHashFunctor<void*> : PointerHashFunctor { };

template <> struct DefaultHashFunctor<const void*> : PointerHashFunctor { };

#if !defined(_MSC_VER) || defined(_NATIVE_WCHAR_T_DEFINED)

template <> struct DefaultHashFunctor<wchar_t> : Mix32HashFunctor { };

#endif

// String specializations. If you want to operate on raw values, use

// PointerLessFunctor and friends from the "building-block" section above

template <> struct DefaultLessFunctor<char*> : StringLessFunctor { };

template <> struct DefaultLessFunctor<const char*> : StringLessFunctor { };

template <> struct DefaultEqualFunctor<char*> : StringEqualFunctor { };

template <> struct DefaultEqualFunctor<const char*> : StringEqualFunctor { };

template <> struct DefaultHashFunctor<char*> : StringHashFunctor { };

template <> struct DefaultHashFunctor<const char*> : StringHashFunctor { };

// CUtlString/CUtlConstString are specialized here and not in utlstring.h

// because I consider string datatypes to be fundamental, and don't feel

// comfortable making that header file dependent on this one. (henryg)

class CUtlString;

template < typename T > class CUtlConstStringBase;

template <> struct DefaultLessFunctor<CUtlString> : StringLessFunctor { };

template <> struct DefaultHashFunctor<CUtlString> : StringHashFunctor { };

template < typename T > struct DefaultLessFunctor< CUtlConstStringBase<T> > : StringLessFunctor { };

template < typename T > struct DefaultHashFunctor< CUtlConstStringBase<T> > : StringHashFunctor { };

// Helpers to deduce if a type defines a public AltArgumentType_t typedef:

template < typename T >

struct HasClassAltArgumentType

};

template < typename T, bool = HasClassAltArgumentType< T >::value >

struct GetClassAltArgumentType { typedef typename T::AltArgumentType_t Result_t; };

template < typename T >

struct GetClassAltArgumentType< T, false > { typedef undefined_t Result_t; };

// Unwrap references; reference types don't have member typedefs.

template < typename T >

struct GetClassAltArgumentType< T&, false > : GetClassAltArgumentType< T > { };

// ArgumentTypeInfoImpl is the base for all ArgumentTypeInfo specializations.

template < typename ArgT, typename AltT = typename GetClassAltArgumentType<ArgT>::Result_t >

struct ArgumentTypeInfoImpl

};

// Handle cases where AltArgumentType_t is typedef'd to undefined_t

template < typename ArgT >

struct ArgumentTypeInfoImpl< ArgT, undefined_t >

{

enum { has_alt = 0 };

typedef ArgT Arg_t;

typedef undefined_t Alt_t;

};

// Handle cases where AltArgumentType_t is typedef'd to the primary type

template < typename ArgT >

struct ArgumentTypeInfoImpl< ArgT, ArgT >

{

enum { has_alt = 0 };

typedef ArgT Arg_t;

typedef undefined_t Alt_t;

};

// By default, everything is passed via const ref and doesn't define an alternate type.

template <typename T> struct ArgumentTypeInfo : ArgumentTypeInfoImpl< const T& > { };

// Small native types are most efficiently passed by value.

template <> struct ArgumentTypeInfo< bool > : ArgumentTypeInfoImpl< bool > { };

template <> struct ArgumentTypeInfo< char > : ArgumentTypeInfoImpl< char > { };

template <> struct ArgumentTypeInfo< signed char > : ArgumentTypeInfoImpl< signed char > { };

template <> struct ArgumentTypeInfo< unsigned char > : ArgumentTypeInfoImpl< unsigned char > { };

template <> struct ArgumentTypeInfo< signed short > : ArgumentTypeInfoImpl< signed short > { };

template <> struct ArgumentTypeInfo< unsigned short > : ArgumentTypeInfoImpl< unsigned short > { };

template <> struct ArgumentTypeInfo< signed int > : ArgumentTypeInfoImpl< signed int > { };

template <> struct ArgumentTypeInfo< unsigned int > : ArgumentTypeInfoImpl< unsigned int > { };

template <> struct ArgumentTypeInfo< signed long > : ArgumentTypeInfoImpl< signed long > { };

template <> struct ArgumentTypeInfo< unsigned long > : ArgumentTypeInfoImpl< unsigned long > { };

template <> struct ArgumentTypeInfo< signed long long > : ArgumentTypeInfoImpl< signed long long > { };

template <> struct ArgumentTypeInfo< unsigned long long > : ArgumentTypeInfoImpl< unsigned long long > { };

template <> struct ArgumentTypeInfo< float > : ArgumentTypeInfoImpl< float > { };

template <> struct ArgumentTypeInfo< double > : ArgumentTypeInfoImpl< double > { };

template <> struct ArgumentTypeInfo< long double > : ArgumentTypeInfoImpl< long double > { };

#if !defined(_MSC_VER) || defined(_NATIVE_WCHAR_T_DEFINED)

template <> struct ArgumentTypeInfo< wchar_t > : ArgumentTypeInfoImpl< wchar_t > { };

#endif

// Pointers are also most efficiently passed by value.

template < typename T > struct ArgumentTypeInfo< T* > : ArgumentTypeInfoImpl< T* > { };

// Specializations to unwrap const-decorated types and references

template <typename T> struct ArgumentTypeInfo<const T> : ArgumentTypeInfo<T> { };

template <typename T> struct ArgumentTypeInfo<volatile T> : ArgumentTypeInfo<T> { };

template <typename T> struct ArgumentTypeInfo<const volatile T> : ArgumentTypeInfo<T> { };

template <typename T> struct ArgumentTypeInfo<T&> : ArgumentTypeInfo<T> { };

template <typename T> struct DefaultLessFunctor<const T> : DefaultLessFunctor<T> { };

template <typename T> struct DefaultLessFunctor<volatile T> : DefaultLessFunctor<T> { };

template <typename T> struct DefaultLessFunctor<const volatile T> : DefaultLessFunctor<T> { };

template <typename T> struct DefaultLessFunctor<T&> : DefaultLessFunctor<T> { };

template <typename T> struct DefaultEqualFunctor<const T> : DefaultEqualFunctor<T> { };

template <typename T> struct DefaultEqualFunctor<volatile T> : DefaultEqualFunctor<T> { };

template <typename T> struct DefaultEqualFunctor<const volatile T> : DefaultEqualFunctor<T> { };

template <typename T> struct DefaultEqualFunctor<T&> : DefaultEqualFunctor<T> { };

template <typename T> struct DefaultHashFunctor<const T> : DefaultHashFunctor<T> { };

template <typename T> struct DefaultHashFunctor<volatile T> : DefaultHashFunctor<T> { };

template <typename T> struct DefaultHashFunctor<const volatile T> : DefaultHashFunctor<T> { };

template <typename T> struct DefaultHashFunctor<T&> : DefaultHashFunctor<T> { };

// Hash all pointer types as raw pointers by default

template <typename T> struct DefaultHashFunctor< T * > : PointerHashFunctor { };

// Here follow the useful implementations.

// Bob Jenkins's 32-bit mix function.

inline unsigned int Mix32HashFunctor::operator()( uint32 n ) const

{

// Perform a mixture of the bits in n, where each bit

// of the input value has an equal chance to affect each

// bit of the output. This turns tightly clustered input

// values into a smooth distribution.

//

// This takes 16-20 cycles on modern x86 architectures;

// that's roughly the same cost as a mispredicted branch.

// It's also reasonably efficient on PPC-based consoles.

//

// If you're still thinking, "too many instructions!",

// do keep in mind that reading one byte of uncached RAM

// is about 30x slower than executing this code. It pays

// to have a good hash function which minimizes collisions

// (and therefore long lookup chains).

n = ( n + 0x7ed55d16 ) + ( n << 12 );

n = ( n ^ 0xc761c23c ) ^ ( n >> 19 );

n = ( n + 0x165667b1 ) + ( n << 5 );

n = ( n + 0xd3a2646c ) ^ ( n << 9 );

n = ( n + 0xfd7046c5 ) + ( n << 3 );

n = ( n ^ 0xb55a4f09 ) ^ ( n >> 16 );

return n;

}

// Based on the widely-used FNV-1A string hash with a final

// mixing step to improve dispersion for very small and very

// large hash table sizes.

inline unsigned int StringHashFunctor::operator()( const char* s ) const

{

uint32 h = 2166136261u;

for ( ; *s; ++s )

{

uint32 c = (unsigned char) *s;

h = (h ^ c) * 16777619;

}

return (h ^ (h << 17)) + (h >> 21);

}

// Equivalent to StringHashFunctor on lower-case strings.

inline unsigned int CaselessStringHashFunctor::operator()( const char* s ) const

{

uint32 h = 2166136261u;

for ( ; *s; ++s )

{

uint32 c = (unsigned char) *s;

// Brutally fast branchless ASCII tolower():

// if ((c >= 'A') && (c <= 'Z')) c += ('a' - 'A');

c += (((('A'-1) - c) & (c - ('Z'+1))) >> 26) & 32;

h = (h ^ c) * 16777619;

}

return (h ^ (h << 17)) + (h >> 21);

}

#endif // UTLCOMMON_H