/home/cube/sources/osgearth/src/osgEarthSymbology/Expression.cpp

Go to the documentation of this file.

/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
* Copyright 2008-2010 Pelican Mapping
* http://osgearth.org
*
* osgEarth 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; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 program.  If not, see <http://www.gnu.org/licenses/>
*/
#include <osgEarthSymbology/Expression>
#include <osgEarth/StringUtils>
#include <algorithm>

using namespace osgEarth;
using namespace osgEarth::Symbology;

NumericExpression::NumericExpression( const std::string& expr ) : 
_src  ( expr ),
_value( 0.0 ),
_dirty( true )
{
    init();
}

NumericExpression::NumericExpression( const NumericExpression& rhs ) :
_src  ( rhs._src ),
_rpn  ( rhs._rpn ),
_vars ( rhs._vars ),
_value( rhs._value ),
_dirty( rhs._dirty )
{
    //nop
}

NumericExpression::NumericExpression( double staticValue ) :
_value( staticValue ),
_dirty( false )
{
    _src = Stringify() << staticValue;
    init();
}

NumericExpression::NumericExpression( const Config& conf )
{
    mergeConfig( conf );
    init();
}

void
NumericExpression::mergeConfig( const Config& conf )
{
    _src = conf.value();
    init();
    _dirty = true;
}

Config
NumericExpression::getConfig() const
{
    return Config( "numeric_expression", _src );
}

#define IS_OPERATOR(a) ( a .first == ADD || a .first == SUB || a .first == MULT || a .first == DIV || a .first == MOD )

void
NumericExpression::init()
{
    _vars.clear();
    _rpn.clear();

    StringTokenizer tokenizer( "", "'\"" );
    tokenizer.addDelims( "[],()%*/+-", true );
    tokenizer.keepEmpties() = false;

    StringVector t;
    tokenizer.tokenize( _src, t );
    //tokenize(_src, t, "[],()%*/+-", "'\"", false, true);

    // identify tokens:
    AtomVector infix;
    bool invar = false;
    for( unsigned i=0; i<t.size(); ++i ) {
        if ( t[i] == "[" && !invar ) {
            invar = true;
        }
        else if ( t[i] == "]" && invar ) {
            invar = false;
            infix.push_back( Atom(VARIABLE,0.0) );
            _vars.push_back( Variable(t[i-1],0) );
        }
        else if ( t[i] == "(" ) infix.push_back( Atom(LPAREN,0.0) );
        else if ( t[i] == ")" ) infix.push_back( Atom(RPAREN,0.0) );
        else if ( t[i] == "," ) infix.push_back( Atom(COMMA,0.0) );
        else if ( t[i] == "%" ) infix.push_back( Atom(MOD,0.0) );
        else if ( t[i] == "*" ) infix.push_back( Atom(MULT,0.0) );
        else if ( t[i] == "/" ) infix.push_back( Atom(DIV,0.0) );
        else if ( t[i] == "+" ) infix.push_back( Atom(ADD,0.0) );
        else if ( t[i] == "-" ) infix.push_back( Atom(SUB,0.0) );
        else if ( t[i] == "min" ) infix.push_back( Atom(MIN,0.0) );
        else if ( t[i] == "max" ) infix.push_back( Atom(MAX,0.0) );
        else if ( (t[i][0] >= '0' && t[i][0] <= '9') || t[i][0] == '.' )
            infix.push_back( Atom(OPERAND,as<double>(t[i],0.0)) );

        // note: do nothing for a comma
    }

    // convert to RPN:
    // http://en.wikipedia.org/wiki/Shunting-yard_algorithm
    AtomStack s;
    unsigned var_i = 0;

    for( unsigned i=0; i<infix.size(); ++i )
    {
        Atom& a = infix[i];

        if ( a.first == LPAREN )
        {
            s.push( a );
        }
        else if ( a.first == RPAREN )
        {
            while( s.size() > 0 )
            {
                Atom top = s.top();
                s.pop();
                if ( top.first == LPAREN )
                    break;
                else
                    _rpn.push_back( top );
            }
        }
        else if ( a.first == COMMA )
        {
            while( s.size() > 0 && s.top().first != LPAREN )
            {
                _rpn.push_back( s.top() );
                s.pop();
            }
        }
        else if ( IS_OPERATOR(a) )
        {
            if ( s.empty() || a.first > s.top().first )
            {
                s.push( a );
            }
            else 
            {
                while( s.size() > 0 && a.first < s.top().first && IS_OPERATOR(s.top()) )
                {
                    _rpn.push_back( s.top() );
                    s.pop();
                }
                s.push( a );
            }
        }
        else if ( a.first == MIN || a.first == MAX )
        {
            s.push( a );
        }
        else if ( a.first == OPERAND )
        {
            _rpn.push_back( a );
        }
        else if ( a.first == VARIABLE )
        {
            _rpn.push_back( a );
            _vars[var_i++].second = _rpn.size()-1; // store the index
        }
    }

    while( s.size() > 0 )
    {
        _rpn.push_back( s.top() );
        s.pop();
    }
}

void 
NumericExpression::set( const Variable& var, double value )
{
    Atom& a = _rpn[var.second];
    if ( a.second != value )
    {
        a.second = value;
        _dirty = true;
    }
}

double
NumericExpression::eval() const
{
    if ( _dirty )
    {
        std::stack<double> s;

        for( unsigned i=0; i<_rpn.size(); ++i )
        {
            const Atom& a = _rpn[i];

            if ( a.first == ADD )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( op1 + op2 );
                }
            }
            else if ( a.first == SUB )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( op1 - op2 );
                }
            }
            else if ( a.first == MULT )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( op1 * op2 );
                }
            }
            else if ( a.first == DIV )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( op1 / op2 );
                }
            }
            else if ( a.first == MOD )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( fmod(op1, op2) );
                }
            }
            else if ( a.first == MIN )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( std::min(op1, op2) );
                }
            }
            else if ( a.first == MAX )
            {
                if ( s.size() >= 2 )
                {
                    double op2 = s.top(); s.pop();
                    double op1 = s.top(); s.pop();
                    s.push( std::max(op1, op2) );
                }
            }
            else // OPERAND or VARIABLE
            {
                s.push( a.second );
            }
        }

        const_cast<NumericExpression*>(this)->_value = s.size() > 0 ? s.top() : 0.0;
        const_cast<NumericExpression*>(this)->_dirty = false;
    }

    return !osg::isNaN( _value ) ? _value : 0.0;
}

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

StringExpression::StringExpression( const std::string& expr ) : 
_src( expr ),
_dirty( true )
{
    init();
}

StringExpression::StringExpression( const StringExpression& rhs ) :
_src( rhs._src ),
_vars( rhs._vars ),
_value( rhs._value ),
_infix( rhs._infix ),
_dirty( rhs._dirty ),
_uriContext( rhs._uriContext )
{
    //nop
}

StringExpression::StringExpression( const Config& conf )
{
    mergeConfig( conf );
    init();
}

void
StringExpression::mergeConfig( const Config& conf )
{
    _src = conf.value();
    _dirty = true;
}

Config
StringExpression::getConfig() const
{
    return Config( "string_expression", _src );
}

void
StringExpression::init()
{
    StringTokenizer izer("", "");
    izer.addDelims( "[]", true );
    izer.addQuotes( "'\"", false );
    izer.keepEmpties() = false;
    izer.trimTokens() = false;

    StringVector t;
    izer.tokenize( _src, t );
    //tokenize(_src, t, "[]", "'\"", false, true, false);

    // identify tokens:
    bool invar = false;
    for( unsigned i=0; i<t.size(); ++i )
    {
        if ( t[i] == "[" && !invar )
        {
            invar = true;
        }
        else if ( t[i] == "]" && invar )
        {
            invar = false;
            _infix.push_back( Atom(VARIABLE,"") );
            _vars.push_back( Variable(t[i-1],0) );
        }
        else
            _infix.push_back( Atom(OPERAND,t[i]) );
    }
}

void 
StringExpression::set( const Variable& var, const std::string& value )
{
    Atom& a = _infix[var.second];
    if ( a.second != value )
    {
        a.second = value;
        _dirty = true;
    }
}

const std::string&
StringExpression::eval() const
{
    if ( _dirty )
    {
        std::stringstream buf;
        for( AtomVector::const_iterator i = _infix.begin(); i != _infix.end(); ++i )
            buf << i->second;

        const_cast<StringExpression*>(this)->_value = buf.str();
        const_cast<StringExpression*>(this)->_dirty = false;
    }

    return _value;
}