expression.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * This file is dual-licensed.
 * In addition to the GPLv3 license mentioned above, this code is also
 * licensed under LGPL 2.1. See LICENSES/COPYING.LGPL file for the
 * full text of the license.
 *
 */

#ifndef GOB_EXPRESSION_H
#define GOB_EXPRESSION_H

#include "common/scummsys.h"

namespace Gob {

class GobEngine;

enum {
    OP_NEG        =  1,
    OP_ADD        =  2,
    OP_SUB        =  3,
    OP_BITOR      =  4,
    OP_MUL        =  5,
    OP_DIV        =  6,
    OP_MOD        =  7,
    OP_BITAND     =  8,
    OP_BEGIN_EXPR =  9,
    OP_END_EXPR   = 10,
    OP_NOT        = 11,

    OP_END_MARKER = 12, // Marks end of an array or string


    OP_ARRAY_INT8              = 16,
    OP_LOAD_VAR_INT16          = 17,
    OP_LOAD_VAR_INT8           = 18,
    OP_LOAD_IMM_INT32          = 19,
    OP_LOAD_IMM_INT16          = 20,
    OP_LOAD_IMM_INT8           = 21,
    OP_LOAD_IMM_STR            = 22,
    OP_LOAD_VAR_INT32          = 23,
    OP_LOAD_VAR_INT32_AS_INT16 = 24,
    OP_LOAD_VAR_STR            = 25,
    OP_ARRAY_INT32             = 26,
    OP_ARRAY_INT16             = 27,
    OP_ARRAY_STR               = 28,

    OP_FUNC = 29,

    OP_OR      = 30, // Logical OR
    OP_AND     = 31, // Logical AND
    OP_LESS    = 32,
    OP_LEQ     = 33,
    OP_GREATER = 34,
    OP_GEQ     = 35,
    OP_EQ      = 36,
    OP_NEQ     = 37
};

enum {
    FUNC_SQRT1 =  0,
    FUNC_SQRT2 =  1,
    FUNC_SQRT3 =  6,

    FUNC_SQR   =  5,
    FUNC_ABS   =  7,
    FUNC_RAND  = 10
};

enum {
    TYPE_IMM_INT8           = OP_LOAD_IMM_INT8,          // 21
    TYPE_IMM_INT32          = OP_LOAD_IMM_INT32,         // 19
    TYPE_IMM_INT16          = OP_LOAD_IMM_INT16,         // 20
    TYPE_IMM_STR            = OP_LOAD_IMM_STR,           // 22
    TYPE_VAR_INT8           = OP_LOAD_VAR_INT8,          // 18
    TYPE_VAR_INT16          = OP_LOAD_VAR_INT16,         // 17
    TYPE_VAR_INT32          = OP_LOAD_VAR_INT32,         // 23
    TYPE_VAR_STR            = OP_LOAD_VAR_STR,           // 25
    TYPE_ARRAY_INT8         = OP_ARRAY_INT8,             // 16
    TYPE_ARRAY_INT16        = OP_ARRAY_INT16,            // 27
    TYPE_ARRAY_INT32        = OP_ARRAY_INT32,            // 26
    TYPE_ARRAY_STR          = OP_ARRAY_STR,              // 28
    TYPE_VAR_INT32_AS_INT16 = OP_LOAD_VAR_INT32_AS_INT16 // 24
};

enum {
    // FIXME: The following two 'truth values' are stored inside the list
    // of "operators". So they somehow coincide with OP_LOAD_VAR_INT32
    // and OP_LOAD_VAR_INT32_AS_INT16. I haven't yet quite understood
    // how, resp. what that means. You have been warned.
    GOB_TRUE  = 24,
    GOB_FALSE = 23
};

class Expression {
public:
    Expression(GobEngine *vm);
    virtual ~Expression() {}

    void skipExpr(char stopToken);
    void printExpr(char stopToken);
    void printVarIndex();

    uint16 parseVarIndex(uint16 *size = 0, uint16 *type = 0);
    int16 parseValExpr(byte stopToken = 99);
    int16 parseExpr(byte stopToken, byte *type);

    int32 getResultInt();
    char *getResultStr();

private:
    class Stack {
    public:
        byte *opers;
        int32 *values;

        Stack(size_t size = 20);
        ~Stack();
    };
    class StackFrame {
    public:
        byte *opers;
        int32 *values;
        int16 pos;

        StackFrame(const Stack &stack);

        void push(int count = 1);
        void pop(int count = 1);
    };

    enum PointerType {
        kExecPtr  = 0,
        kInterVar = 1,
        kResStr   = 2
    };

    GobEngine *_vm;

    int32 _resultInt;
    char _resultStr[200];

    int32 encodePtr(byte *ptr, int type);
    byte *decodePtr(int32 n);

    void printExpr_internal(char stopToken);

    bool getVarBase(uint32 &varBase, bool mindStop = false,
            uint16 *size = 0, uint16 *type = 0);
    int cmpHelper(const StackFrame &stackFrame);
    void loadValue(byte operation, uint32 varBase, const StackFrame &stackFrame);

    void simpleArithmetic1(StackFrame &stackFrame);
    void simpleArithmetic2(StackFrame &stackFrame);
    bool complexArithmetic(Stack &stack, StackFrame &stackFrame, int16 brackStart);
    void getResult(byte operation, int32 value, byte *type);
};

} // End of namespace Gob

#endif // GOB_EXPRESSION_H