cc_script_object.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/>.
 *
 */

//=============================================================================
//
// IScriptObject: script managed object interface.
// Provides interaction with a object which allocation and lifetime is
// managed by the engine and/or the managed pool rather than the script VM.
// These may be both static objects existing throughout the game, and
// dynamic objects allocated by the script command.
//
//=============================================================================

#ifndef AGS_ENGINE_AC_DYNOBJ_CC_SCRIPT_OBJECT_H
#define AGS_ENGINE_AC_DYNOBJ_CC_SCRIPT_OBJECT_H

#include "common/std/utility.h"
#include "ags/shared/core/types.h"

namespace AGS3 {

// Forward declaration
namespace AGS {
namespace Shared {
class Stream;
} // namespace Shared
} // namespace AGS

struct IScriptObject;

// A convenience struct for grouping handle and dynamic object
struct DynObjectRef {
    const int Handle = 0;
    void *const Obj = nullptr;
    IScriptObject *const Mgr = nullptr;

    DynObjectRef() = default;
    DynObjectRef(int handle, void *obj, IScriptObject *mgr)
        : Handle(handle), Obj(obj), Mgr(mgr) {}
};

struct IScriptObject {
    // WARNING: The first section of this interface is also a part of the AGS plugin API!

    // when a ref count reaches 0, this is called with the address
    // of the object. Return 1 to remove the object from memory, 0 to
    // leave it
    // The "force" flag tells system to detach the object, breaking any links and references
    // to other managed objects or game resources (instead of disposing these too).
    // TODO: it might be better to rewrite the managed pool and remove this flag at all,
    // because it makes the use of this interface prone to mistakes.
    virtual int Dispose(void *address, bool force = false) = 0;
    // return the type name of the object
    virtual const char *GetType() = 0;
    // serialize the object into BUFFER (which is BUFSIZE bytes)
    // return number of bytes used
    // TODO: pass savegame format version
    virtual int Serialize(void *address, uint8_t *buffer, int bufsize) = 0;

    // WARNING: following section is not a part of plugin API, therefore these methods
    // should **never** be called for kScValPluginObject script objects!

    // Legacy support for reading and writing object values by their relative offset.
    // These methods allow to "remap" script struct field access, by taking the
    // legacy offset, and using it rather as a field ID than an address, for example.
    // Consequently these also let trigger side-effects, such as updating an object
    // after a field value is written to.
    // RE: GetFieldPtr() -
    // According to AGS script specification, when the old-string pointer or char array is passed
    // as an argument, the byte-code does not include any specific command for the member variable
    // retrieval and instructs to pass an address of the object itself with certain offset.
    // This results in functions like StrCopy writing directly over object address.
    // There may be other implementations, but the big question is: how to detect when this is
    // necessary, because byte-code does not contain any distinct operation for this case.
    // The worst thing here is that with the current byte-code structure we can never tell whether
    // offset 0 means getting pointer to whole object or a pointer to its first field.
    virtual void    *GetFieldPtr(void *address, intptr_t offset) = 0;
    virtual void    Read(void *address, intptr_t offset, uint8_t *dest, size_t size) = 0;
    virtual uint8_t ReadInt8(void *address, intptr_t offset) = 0;
    virtual int16_t ReadInt16(void *address, intptr_t offset) = 0;
    virtual int32_t ReadInt32(void *address, intptr_t offset) = 0;
    virtual float   ReadFloat(void *address, intptr_t offset) = 0;
    virtual void    Write(void *address, intptr_t offset, const uint8_t *src, size_t size) = 0;
    virtual void    WriteInt8(void *address, intptr_t offset, uint8_t val) = 0;
    virtual void    WriteInt16(void *address, intptr_t offset, int16_t val) = 0;
    virtual void    WriteInt32(void *address, intptr_t offset, int32_t val) = 0;
    virtual void    WriteFloat(void *address, intptr_t offset, float val) = 0;

protected:
    IScriptObject() {}
    virtual ~IScriptObject() {}
};

// The interface of a script objects deserializer that handles multiple types.
struct ICCObjectCollectionReader {
    virtual ~ICCObjectCollectionReader() {}
    // TODO: pass savegame format version
    virtual void Unserialize(int32_t handle, const char *objectType, const char *serializedData, int dataSize) = 0;
};

// The interface of a script objects deserializer that handles a single type.
// WARNING: a part of the plugin API.
struct ICCObjectReader {
    virtual ~ICCObjectReader() {}
    virtual void Unserialize(int32_t handle, const char *serializedData, int dataSize) = 0;
};

} // namespace AGS3

#endif