tmeta.h

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/***************************************************************************
 * include/stxxl/bits/common/tmeta.h
 *
 * Template Metaprogramming Tools
 * (from the Generative Programming book Krysztof Czarnecki, Ulrich Eisenecker)
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2003 Roman Dementiev <[email protected]>
 * Copyright (C) 2008 Andreas Beckmann <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#ifndef STXXL_COMMON_TMETA_HEADER
#define STXXL_COMMON_TMETA_HEADER

#include <stxxl/bits/namespace.h>
#include <stxxl/bits/common/types.h>

STXXL_BEGIN_NAMESPACE

//! IF template metaprogramming statement.
//!
//! If \c Flag is \c true then \c IF<>::result is of type Type1
//! otherwise of \c IF<>::result is of type Type2
template <bool Flag, class Type1, class Type2>
struct IF
{
 typedef Type1 result;
};

template <class Type1, class Type2>
struct IF<false, Type1, Type2>
{
 typedef Type2 result;
};

//! If \c Flag is \c true then \c IF<>::result is Num1
//! otherwise of \c IF<>::result is Num2
template <bool Flag, unsigned Num1, unsigned Num2>
struct IF_N
{
 enum
 {
 result = Num1
 };
};

template <unsigned Num1, unsigned Num2>
struct IF_N<false, Num1, Num2>
{
 enum
 {
 result = Num2
 };
};

const int DEFAULT = ~(~0u >> 1); // initialize with the smallest int

struct NilCase { };

template <int tag_, class Type_, class Next_ = NilCase>
struct CASE
{
 enum { tag = tag_ };
 typedef Type_ Type;
 typedef Next_ Next;
};

template <int tag, class Case>
class SWITCH
{
 typedef typename Case::Next NextCase;
 enum
 {
 caseTag = Case::tag,
 found = (caseTag == tag || caseTag == DEFAULT)
 };

public:
 typedef typename IF<found,
 typename Case::Type,
 typename SWITCH<tag, NextCase>::result
 >::result result;
};

template <int tag>
class SWITCH<tag, NilCase>
{
public:
 typedef NilCase result;
};

//! \internal, use LOG2 instead
template <unsigned_type Input>
class LOG2_floor
{
public:
 enum
 {
 value = LOG2_floor<Input / 2>::value + 1
 };
};

template <>
class LOG2_floor<1>
{
public:
 enum
 {
 value = 0
 };
};

template <>
class LOG2_floor<0>
{
public:
 enum
 {
 value = 0
 };
};

template <unsigned_type Input>
class LOG2
{
public:
 enum
 {
 floor = LOG2_floor<Input>::value,
 ceil = LOG2_floor<Input - 1>::value + 1
 };
};

template <>
class LOG2<1>
{
public:
 enum
 {
 floor = 0,
 ceil = 0
 };
};

template <>
class LOG2<0>
{
public:
 enum
 {
 floor = 0,
 ceil = 0
 };
};

STXXL_END_NAMESPACE

#endif // !STXXL_COMMON_TMETA_HEADER