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/* 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/>.
*
*/
//=============================================================================
//
// CCStaticArray manages access to an array of script objects,
// where an element's size counted by script's bytecode may differ from the
// real element size in the engine's memory.
// The purpose of this is to remove size restriction from the engine's structs
// exposed to scripts.
//
// FIXME: [ivan-mogilko] the above was meant to work, but in reality it doesn't
// and won't, at least not without some extra workarounds.
// The problem that I missed here is following:
// when the script compiler is told to get an Nth element of a global struct
// array, such as character[n], it calculates the memory address as
// array address + sizeof(Character) * n.
// If this address is used for the read/write operations, these ops can be
// intercepted by interpreter and remapped into the real fields
// (see IScriptObject::ReadN, WriteN interface)
// But if this address is used IN POINTER COMPARISON, then we cannot do
// anything. And if our real struct in the engine is stored on a different
// relative memory offset than one expected by compiler, then this pointer
// comparison will fail, e.g. script expression like
// if (player == character[n])
//
// NOTE: on the other hand, similar effect could be achieved by separating
// object data into two or more structs, where "base" structs are stored in
// the exposed arrays (part of API), while extending structs are stored
// separately. This is more an issue of engine data design.
//
//=============================================================================
#ifndef AGS_ENGINE_AC_DYNOBJ_STATIC_ARRAY_H
#define AGS_ENGINE_AC_DYNOBJ_STATIC_ARRAY_H
#include "ags/engine/ac/dynobj/cc_ags_dynamic_object.h"
namespace AGS3 {
struct CCStaticArray : public AGSCCStaticObject {
public:
~CCStaticArray() override {}
void Create(IScriptObject *mgr, size_t elem_script_size, size_t elem_mem_size, size_t elem_count = SIZE_MAX /*unknown*/);
inline IScriptObject *GetObjectManager() const {
return _mgr;
}
// Legacy support for reading and writing object values by their relative offset
inline void *GetElementPtr(void *address, intptr_t legacy_offset) {
return static_cast<uint8_t *>(address) + (legacy_offset / _elemScriptSize) * _elemMemSize;
}
void *GetFieldPtr(void *address, intptr_t offset) override;
void Read(void *address, intptr_t offset, uint8_t *dest, size_t size) override;
uint8_t ReadInt8(void *address, intptr_t offset) override;
int16_t ReadInt16(void *address, intptr_t offset) override;
int32_t ReadInt32(void *address, intptr_t offset) override;
float ReadFloat(void *address, intptr_t offset) override;
void Write(void *address, intptr_t offset, const uint8_t *src, size_t size) override;
void WriteInt8(void *address, intptr_t offset, uint8_t val) override;
void WriteInt16(void *address, intptr_t offset, int16_t val) override;
void WriteInt32(void *address, intptr_t offset, int32_t val) override;
void WriteFloat(void *address, intptr_t offset, float val) override;
private:
IScriptObject *_mgr = nullptr;
size_t _elemScriptSize = 0u;
size_t _elemMemSize = 0u;
size_t _elemCount = 0u;
};
} // namespace AGS3
#endif
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