97 lines
4.0 KiB
C++
97 lines
4.0 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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//=============================================================================
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//
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// CCStaticArray manages access to an array of script objects,
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// where an element's size counted by script's bytecode may differ from the
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// real element size in the engine's memory.
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// The purpose of this is to remove size restriction from the engine's structs
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// exposed to scripts.
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//
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// FIXME: [ivan-mogilko] the above was meant to work, but in reality it doesn't
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// and won't, at least not without some extra workarounds.
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// The problem that I missed here is following:
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// when the script compiler is told to get an Nth element of a global struct
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// array, such as character[n], it calculates the memory address as
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// array address + sizeof(Character) * n.
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// If this address is used for the read/write operations, these ops can be
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// intercepted by interpreter and remapped into the real fields
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// (see IScriptObject::ReadN, WriteN interface)
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// But if this address is used IN POINTER COMPARISON, then we cannot do
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// anything. And if our real struct in the engine is stored on a different
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// relative memory offset than one expected by compiler, then this pointer
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// comparison will fail, e.g. script expression like
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// if (player == character[n])
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//
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// NOTE: on the other hand, similar effect could be achieved by separating
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// object data into two or more structs, where "base" structs are stored in
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// the exposed arrays (part of API), while extending structs are stored
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// separately. This is more an issue of engine data design.
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//
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//=============================================================================
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#ifndef AGS_ENGINE_AC_DYNOBJ_STATIC_ARRAY_H
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#define AGS_ENGINE_AC_DYNOBJ_STATIC_ARRAY_H
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#include "ags/engine/ac/dynobj/cc_ags_dynamic_object.h"
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namespace AGS3 {
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struct CCStaticArray : public AGSCCStaticObject {
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public:
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~CCStaticArray() override {}
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void Create(IScriptObject *mgr, size_t elem_script_size, size_t elem_mem_size, size_t elem_count = SIZE_MAX /*unknown*/);
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inline IScriptObject *GetObjectManager() const {
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return _mgr;
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}
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// Legacy support for reading and writing object values by their relative offset
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inline void *GetElementPtr(void *address, intptr_t legacy_offset) {
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return static_cast<uint8_t *>(address) + (legacy_offset / _elemScriptSize) * _elemMemSize;
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}
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void *GetFieldPtr(void *address, intptr_t offset) override;
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void Read(void *address, intptr_t offset, uint8_t *dest, size_t size) override;
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uint8_t ReadInt8(void *address, intptr_t offset) override;
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int16_t ReadInt16(void *address, intptr_t offset) override;
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int32_t ReadInt32(void *address, intptr_t offset) override;
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float ReadFloat(void *address, intptr_t offset) override;
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void Write(void *address, intptr_t offset, const uint8_t *src, size_t size) override;
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void WriteInt8(void *address, intptr_t offset, uint8_t val) override;
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void WriteInt16(void *address, intptr_t offset, int16_t val) override;
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void WriteInt32(void *address, intptr_t offset, int32_t val) override;
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void WriteFloat(void *address, intptr_t offset, float val) override;
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private:
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IScriptObject *_mgr = nullptr;
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size_t _elemScriptSize = 0u;
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size_t _elemMemSize = 0u;
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size_t _elemCount = 0u;
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};
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} // namespace AGS3
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#endif
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