script.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/>.
 *
 */

#ifndef KYRA_SCRIPT_H
#define KYRA_SCRIPT_H

#include "common/stream.h"
#include "common/array.h"
#include "common/func.h"
#include "common/formats/iff_container.h"

namespace Kyra {

struct EMCState;
typedef Common::Functor1<EMCState *, int> Opcode;

struct EMCData {
    char filename[13];

    byte *text;
    uint16 *data;
    uint32 ordrSize;
    uint16 *ordr;
    uint32 dataSize;

    const Common::Array<const Opcode *> *sysFuncs;
};

struct EMCState {
    enum {
        kStackSize = 100,
        kStackLastEntry = kStackSize - 1
    };

    const uint16 *ip;
    const EMCData *dataPtr;
    int16 retValue;
    uint16 bp;
    uint16 sp;
    int16 regs[30];           // VM registers
    int16 stack[kStackSize];  // VM stack
};

#ifdef RELEASE_BUILD
#define stackPos(x) (script->stack[script->sp+x])
#else
#define stackPos(x) emcSafeReadStack(script, x, __LINE__, __FILE__)
#endif
#define safeStackPos(x) (script->sp+x < EMCState::kStackSize ? stackPos(x) : 0)
#define stackPosString(x) ((const char *)&script->dataPtr->text[READ_BE_UINT16(&script->dataPtr->text[stackPos(x)<<1])])

class Resource;
class KyraEngine_v1;

class IFFParser : public Common::IFFParser {
public:
    IFFParser(Common::ReadStream &input) : Common::IFFParser(&input) {
        // It seems Westwood missunderstood the 'size' field of the FORM chunk.
        //
        // For EMC scripts (type EMC2) it's filesize instead of filesize - 8,
        // means accidentally including the 8 bytes used by the chunk header for the FORM
        // chunk.
        //
        // For TIM scripts (type AVFS) it's filesize - 12 instead of filesize - 8,
        // means it will not include the size of the 'type' field in the FORM chunk,
        // instead of only not including the chunk header size.
        //
        // Both lead to some problems in our IFF parser, either reading after the end
        // of file or producing a "Chunk overread" error message. To work around this
        // we need to adjust the size field properly.

        // Fix for certain Russian fan translations:
        // Westwood's original code completely ignores the FORM chunk and its size
        // setting. After opening a TIM or EMC file they just check whether the FORM
        // chunk exists (as a kind of file type verification) and then immediately seek
        // behind the FORM chunk.
        // This means that their parser is immune to weird fan translation scripts
        // where the file size doesn't match the form chunk size. In our implemetation
        // this would produce "Chunk overread" errors.
        // Westwood also always pads all chunk sizes to 2 byte alignment after reading
        // them from the file (not with FORM though, since they completely ignore it).
        // This seems to do the trick for our FORM chunk size issue with the Russian
        // fan translations. Another method which I have tried and which seems to work
        // well would be simply setting _formChunk.size to the file size (-12 for TIM).

        _formChunk.size = (_formChunk.size + 1) & ~1;

        if (_formType == MKTAG('E','M','C','2'))
            _formChunk.size -= 8;
        else if (_formType == MKTAG('A','V','F','S'))
            _formChunk.size += 4;
    }
};

class EMCInterpreter {
public:
    EMCInterpreter(KyraEngine_v1 *vm);

    bool load(const char *filename, EMCData *data, const Common::Array<const Opcode *> *opcodes);
    void unload(EMCData *data);

    void init(EMCState *scriptState, const EMCData *data);
    bool start(EMCState *script, int function);

    bool isValid(EMCState *script);

    bool run(EMCState *script);
protected:
    KyraEngine_v1 *_vm;
    int16 _parameter;

    const char *_filename;
    EMCData *_scriptData;

    bool callback(Common::IFFChunk &chunk);

    typedef void (EMCInterpreter::*OpcodeProc)(EMCState *);
    struct OpcodeEntry {
        OpcodeProc proc;
        const char *desc;
    };

    const OpcodeEntry *_opcodes;
private:
    void op_jmp(EMCState *);
    void op_setRetValue(EMCState *);
    void op_pushRetOrPos(EMCState *);
    void op_push(EMCState *);
    void op_pushReg(EMCState *);
    void op_pushBPNeg(EMCState *);
    void op_pushBPAdd(EMCState *);
    void op_popRetOrPos(EMCState *);
    void op_popReg(EMCState *);
    void op_popBPNeg(EMCState *);
    void op_popBPAdd(EMCState *);
    void op_addSP(EMCState *);
    void op_subSP(EMCState *);
    void op_sysCall(EMCState *);
    void op_ifNotJmp(EMCState *);
    void op_negate(EMCState *);
    void op_eval(EMCState *);
    void op_setRetAndJmp(EMCState *);
};
} // End of namespace Kyra

#endif