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/**
* @file llpredicate.h
* @brief abstraction for filtering objects by predicates, with arbitrary boolean expressions
*
* $LicenseInfo:firstyear=2008&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#ifndef LL_LLPREDICATE_H
#define LL_LLPREDICATE_H
#include "llerror.h"
namespace LLPredicate
{
template<typename ENUM> class Rule;
int predicateFlagsFromValue(int value);
template<typename ENUM>
struct Value
{
friend Rule<ENUM>;
public:
Value(ENUM e)
: mPredicateCombinationFlags(0x1)
{
add(e);
}
Value()
: mPredicateCombinationFlags(0x1)
{}
void add(ENUM predicate)
{
llassert(predicate < 5);
if (!has(predicate))
{
int predicate_shift = 0x1 << (int)predicate;
mPredicateCombinationFlags <<= predicate_shift;
}
}
void remove(ENUM predicate)
{
llassert(predicate < 5);
int predicate_shift = 0x1 << (int)predicate;
int flag_mask = predicateFlagsFromValue(predicate);
int flags_to_modify = mPredicateCombinationFlags & flag_mask;
// clear flags containing predicate to be removed
mPredicateCombinationFlags &= ~flag_mask;
// shift flags, in effect removing predicate
flags_to_modify >>= predicate_shift;
// put modified flags back
mPredicateCombinationFlags |= flags_to_modify;
}
void unknown(ENUM predicate)
{
add(predicate);
int flags_with_predicate = mPredicateCombinationFlags;
remove(predicate);
// unknown is result of adding and removing predicate at the same time!
mPredicateCombinationFlags |= flags_with_predicate;
}
bool has(ENUM predicate)
{
int flag_mask = predicateFlagsFromValue(predicate);
return (mPredicateCombinationFlags & flag_mask) != 0;
}
private:
int mPredicateCombinationFlags;
};
struct EmptyRule {};
template<typename ENUM>
class Rule
{
public:
Rule(ENUM value)
: mPredicateRequirements(predicateFlagsFromValue(value))
{}
Rule()
: mPredicateRequirements(0x1)
{}
Rule operator~()
{
Rule new_rule;
new_rule.mPredicateRequirements = ~mPredicateRequirements;
return new_rule;
}
Rule operator &&(const Rule& other)
{
Rule new_rule;
new_rule.mPredicateRequirements = mPredicateRequirements & other.mPredicateRequirements;
return new_rule;
}
Rule operator ||(const Rule& other)
{
Rule new_rule;
new_rule.mPredicateRequirements = mPredicateRequirements | other.mPredicateRequirements;
return new_rule;
}
bool check(const Value<ENUM>& value) const
{
return ((value.mPredicateCombinationFlags | 0x1) & mPredicateRequirements) != 0;
}
bool isTriviallyTrue() const
{
return mPredicateRequirements & 0x1;
}
bool isTriviallyFalse() const
{
return mPredicateRequirements == 0;
}
private:
int mPredicateRequirements;
};
template<typename ENUM>
Rule<ENUM> make_rule(ENUM e) { return Rule<ENUM>(e);}
// return generic empty rule class to avoid requiring template argument to create an empty rule
EmptyRule make_rule();
}
#endif // LL_LLPREDICATE_H
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