openmw/components/compiler/exprparser.cpp

#include "exprparser.hpp"

#include <stdexcept>
#include <cassert>
#include <algorithm>

#include "generator.hpp"
#include "scanner.hpp"
#include "errorhandler.hpp"
#include "locals.hpp"

namespace Compiler
{
    int ExprParser::getPriority (char op) const
    {
        switch (op)
        {
            case '(':
            
                return 0;
            
            case 'e': // ==
            case 'n': // !=
            case 'l': // <
            case 'L': // <=
            case 'g': // <
            case 'G': // >=
            
                return 1;
            
            case '+':
            case '-':
            
                return 2;
        
            case '*':
            case '/':
            
                return 3;
                
            case 'm':
            
                return 4;
        }
    
        return 0;
    }

    char ExprParser::getOperandType (int Index) const
    {
        assert (!mOperands.empty());
        assert (Index>=0);
        assert (Index<static_cast<int> (mOperands.size()));
        return mOperands[mOperands.size()-1-Index];
    }
    
    char ExprParser::getOperator() const
    {
        assert (!mOperators.empty());
        return mOperators[mOperators.size()-1];
    }

    bool ExprParser::isOpen() const
    {
        return std::find (mOperators.begin(), mOperators.end(), '(')!=mOperators.end();
    }
            
    void ExprParser::popOperator()
    {
        assert (!mOperators.empty());
        mOperators.resize (mOperators.size()-1);        
    }
    
    void ExprParser::popOperand()
    {
        assert (!mOperands.empty());
        mOperands.resize (mOperands.size()-1);    
    }

    void ExprParser::replaceBinaryOperands()
    {
        char t1 = getOperandType (1);
        char t2 = getOperandType();
        
        popOperand();
        popOperand();
        
        if (t1==t2)
            mOperands.push_back (t1);
        else if (t1=='f' || t2=='f')
            mOperands.push_back ('f');
        else
            std::logic_error ("failed to determine result operand type");
    }

    void ExprParser::pop()
    {
        char op = getOperator();
        
        switch (op)
        {
            case 'm':
            
                Generator::negate (mCode, getOperandType());
                popOperator();
                break;

            case '+':
                
                Generator::add (mCode, getOperandType (1), getOperandType());
                popOperator();
                replaceBinaryOperands();
                break;

            case '-':
                
                Generator::sub (mCode, getOperandType (1), getOperandType());
                popOperator();
                replaceBinaryOperands();
                break;
                
            case '*':
                
                Generator::mul (mCode, getOperandType (1), getOperandType());
                popOperator();
                replaceBinaryOperands();
                break;                
                
            case '/':
                
                Generator::div (mCode, getOperandType (1), getOperandType());
                popOperator();
                replaceBinaryOperands();
                break;
                            
            case 'e':
            case 'n':
            case 'l':
            case 'L':
            case 'g':
            case 'G':
            
                Generator::compare (mCode, op, getOperandType (1), getOperandType());
                popOperator();
                popOperand();
                popOperand();
                mOperands.push_back ('l');
                break;
                            
            default:
            
                throw std::logic_error ("unknown operator");
        }
    }

    void ExprParser::pushIntegerLiteral (int value)
    {
        mNextOperand = false;
        mOperands.push_back ('l');
        Generator::pushInt (mCode, mLiterals, value);
    }
    
    void ExprParser::pushFloatLiteral (float value)
    {
        mNextOperand = false;
        mOperands.push_back ('f');
        Generator::pushFloat (mCode, mLiterals, value);    
    }
            
    void ExprParser::pushBinaryOperator (char c)
    {
        while (!mOperators.empty() && getPriority (getOperator())>=getPriority (c))
            pop();
    
        mOperators.push_back (c);
        mNextOperand = true;
    }
            
    void ExprParser::close()
    {
        while (getOperator()!='(')
            pop();
            
        popOperator();
    }
            
    void ExprParser::parseArguments (const std::string& arguments, Scanner& scanner)
    {
        ExprParser parser (getErrorHandler(), getContext(), mLocals, mLiterals, true);
        
        for (std::string::const_iterator iter (arguments.begin()); iter!=arguments.end();
            ++iter)
        {
            parser.reset();    
            scanner.scan (parser);

            char type = parser.append (mCode);

            if (type!=*iter)
                Generator::convert (mCode, type, *iter);
                
            mOperands.push_back (*iter);
        }
    }
            
    ExprParser::ExprParser (ErrorHandler& errorHandler, Context& context, Locals& locals,
        Literals& literals, bool argument)
    : Parser (errorHandler, context), mLocals (locals), mLiterals (literals),
      mNextOperand (true), mFirst (true), mArgument (argument)
    {}

    bool ExprParser::parseInt (int value, const TokenLoc& loc, Scanner& scanner)
    {
        mFirst = false;
        
        if (mNextOperand)
        {       
            pushIntegerLiteral (value);
            mTokenLoc = loc;
            return true;
        }
        else
        {
            // no comma was used between arguments
            scanner.putbackInt (value, loc);
            return false;
        }
    }

    bool ExprParser::parseFloat (float value, const TokenLoc& loc, Scanner& scanner)
    {
        mFirst = false;
        
        if (mNextOperand)
        {    
            pushFloatLiteral (value);
            mTokenLoc = loc;
            return true;
        }            
        else
        {
            // no comma was used between arguments
            scanner.putbackFloat (value, loc);
            return false;
        }
    }

    bool ExprParser::parseName (const std::string& name, const TokenLoc& loc,
        Scanner& scanner)
    {
        mFirst = false;

        if (mNextOperand)
        {    
            char type = mLocals.getType (name);
            
            if (type!=' ')
            {
                Generator::fetchLocal (mCode, type, mLocals.getIndex (name));
                mNextOperand = false;
                mOperands.push_back (type=='f' ? 'f' : 'l');    
                return true;    
            }
        }
        else
        {
            // no comma was used between arguments
            scanner.putbackName (name, loc);
            return false;
        }
        
        return Parser::parseName (name, loc, scanner);
    }

    bool ExprParser::parseKeyword (int keyword, const TokenLoc& loc, Scanner& scanner)
    {
        mFirst = false;

        if (mNextOperand)
        {        
            if (keyword==Scanner::K_getsquareroot)
            {
                mTokenLoc = loc;        
                parseArguments ("f", scanner);

                Generator::squareRoot (mCode);
                
                mNextOperand = false;
                return true;
            }
        }
        else
        {
            // no comma was used between arguments
            scanner.putbackKeyword (keyword, loc);
            return false;
        }
        
        return Parser::parseKeyword (keyword, loc, scanner);
    }

    bool ExprParser::parseSpecial (int code, const TokenLoc& loc, Scanner& scanner)
    {
        if (code==Scanner::S_comma)
        {
            mTokenLoc = loc;

            if (mFirst)
            {
                // leading comma
                mFirst = false;
                return true;
            }
            
            // end marker
            scanner.putbackSpecial (code, loc);
            return false;
        }

        mFirst = false;
                
        if (code==Scanner::S_newline)
        {
            // end marker
            mTokenLoc = loc;
            scanner.putbackSpecial (code, loc);
            return false;
        }
        
        if (code==Scanner::S_minus && mNextOperand)
        {
            // unary
            mOperators.push_back ('m');
            mTokenLoc = loc;
            return true;
        }
        
        if (code==Scanner::S_open)
        {
            if (mNextOperand)
            {
                mOperators.push_back ('(');
                mTokenLoc = loc;
                return true;
            }
            else
            {
                // no comma was used between arguments
                scanner.putbackKeyword (code, loc);
                return false;
            }
        }
        
        if (code==Scanner::S_close && !mNextOperand)
        {
            if (isOpen())
            {
                close();
                return true;
            }
            
            mTokenLoc = loc;
            scanner.putbackSpecial (code, loc);
            return false;
        }
        
        if (!mNextOperand)
        {
            mTokenLoc = loc;
            char c = 0; // comparison
   
            switch (code)
            {
                case Scanner::S_plus: pushBinaryOperator ('+'); return true;
                case Scanner::S_minus: pushBinaryOperator ('-'); return true;
                case Scanner::S_mult: pushBinaryOperator ('*'); return true;
                case Scanner::S_div: pushBinaryOperator ('/'); return true;
                case Scanner::S_cmpEQ: c = 'e'; break;
                case Scanner::S_cmpNE: c = 'n'; break;
                case Scanner::S_cmpLT: c = 'l'; break;
                case Scanner::S_cmpLE: c = 'L'; break;
                case Scanner::S_cmpGT: c = 'g'; break;
                case Scanner::S_cmpGE: c = 'G'; break;
            }
            
            if (c)
            {
                if (mArgument && !isOpen())
                {
                    // expression ends here
                    // Thank you Morrowind for this rotten syntax :(
                    scanner.putbackSpecial (code, loc);
                    return false;
                }
            
                pushBinaryOperator (c);
                return true;
            }
        }
        
        return Parser::parseSpecial (code, loc, scanner);
    }
    
    void ExprParser::reset()
    {
        mOperands.clear();
        mOperators.clear();
        mNextOperand = true;
        mCode.clear();
        mFirst = true;
    }
    
    char ExprParser::append (std::vector<Interpreter::Type_Code>& code)
    {
        if (mOperands.empty() && mOperators.empty())
        {
            getErrorHandler().error ("missing expression", mTokenLoc);
            return 'l';
        }
            
        if (mNextOperand || mOperands.empty())
        {
            getErrorHandler().error ("syntax error in expression", mTokenLoc);
            return 'l';
        }

        while (!mOperators.empty())
            pop();

        std::copy (mCode.begin(), mCode.end(), std::back_inserter (code));

        assert (mOperands.size()==1);
        return mOperands[0];
    }    
}