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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;
extern const U32 cPredicateFlagsFromEnum[5];
template<typename ENUM>
class Value
{
public:
typedef U32 predicate_flag_t;
static const S32 cMaxEnum = 5;
Value(ENUM e, bool predicate_value = true)
: mPredicateFlags(predicate_value ? cPredicateFlagsFromEnum[e] : ~cPredicateFlagsFromEnum[e])
{
llassert(0 <= e && e < cMaxEnum);
}
Value()
: mPredicateFlags(0xFFFFffff)
{}
Value operator!() const
{
Value new_value;
new_value.mPredicateFlags = ~mPredicateFlags;
return new_value;
}
Value operator &&(const Value other) const
{
Value new_value;
new_value.mPredicateFlags = mPredicateFlags & other.mPredicateFlags;
return new_value;
}
Value operator ||(const Value other) const
{
Value new_value;
new_value.mPredicateFlags = mPredicateFlags | other.mPredicateFlags;
return new_value;
}
void set(ENUM e, bool value = true)
{
llassert(0 <= e && e < cMaxEnum);
predicate_flag_t flags_to_modify;
predicate_flag_t mask = cPredicateFlagsFromEnum[e];
if (value)
{ // add predicate "e" to flags that don't contain it already
flags_to_modify = (mPredicateFlags & ~mask);
// clear flags not containing e
mPredicateFlags &= mask;
// add back flags shifted to contain e
mPredicateFlags |= flags_to_modify << (0x1 << e);
}
else
{ // remove predicate "e" from flags that contain it
flags_to_modify = (mPredicateFlags & mask);
// clear flags containing e
mPredicateFlags &= ~mask;
// add back flags shifted to not contain e
mPredicateFlags |= flags_to_modify >> (0x1 << e);
}
}
void forget(ENUM e)
{
set(e, true);
U32 flags_with_predicate = mPredicateFlags;
set(e, false);
// ambiguous value is result of adding and removing predicate at the same time!
mPredicateFlags |= flags_with_predicate;
}
bool allSet() const
{
return mPredicateFlags == ~0;
}
bool noneSet() const
{
return mPredicateFlags == 0;
}
bool someSet() const
{
return mPredicateFlags != 0;
}
private:
predicate_flag_t mPredicateFlags;
};
template<typename ENUM>
class Rule
{
public:
Rule(ENUM value)
: mRule(value)
{}
Rule(const Value<ENUM> other)
: mRule(other)
{}
Rule()
{}
void require(ENUM e)
{
mRule.set(e, require);
}
void allow(ENUM e)
{
mRule.forget(e);
}
bool check(const Value<ENUM> value) const
{
return (mRule && value).someSet();
}
bool requires(const Value<ENUM> value) const
{
return (mRule && value).someSet() && (!mRule && value).noneSet();
}
bool isAmbivalent(const Value<ENUM> value) const
{
return (mRule && value).someSet() && (!mRule && value).someSet();
}
bool acceptsAll() const
{
return mRule.allSet();
}
bool acceptsNone() const
{
return mRule.noneSet();
}
Rule operator!() const
{
Rule new_rule;
new_rule.mRule = !mRule;
return new_rule;
}
Rule operator &&(const Rule other) const
{
Rule new_rule;
new_rule.mRule = mRule && other.mRule;
return new_rule;
}
Rule operator ||(const Rule other) const
{
Rule new_rule;
new_rule.mRule = mRule || other.mRule;
return new_rule;
}
private:
Value<ENUM> mRule;
};
}
template<typename ENUM>
LLPredicate::Value<ENUM> ll_make_predicate(ENUM e, bool predicate_value = true)
{
return LLPredicate::Value<ENUM>(e, predicate_value);
}
#endif // LL_LLPREDICATE_H
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