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fix: fix the issue when loading new version created files.

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- Fix the CRC check issue when loading new Virtools created files (> 4.0)
	* This is caused by a bug written by stupid Virtools programmer. For more detail, see code annotation.
	* After this patch, LibCmo have ability that load new Virtools created files including max2nmo exported NMO, Virtools 5.0 created CMO and etc.
This commit is contained in:
yyc12345 2024-12-28 16:29:35 +08:00
parent 86b27557c9
commit aeb2e86b14
1 changed files with 33 additions and 7 deletions
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40
LibCmo/CK2/CKFileReader.cpp
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@ -89,20 +89,46 @@ namespace LibCmo::CK2 {
// reset crc field of header
rawHeader.Crc = 0u;
// compute crc
// Compute and check CRC in theory (< Virtools 4.0)
CKDWORD gotten_crc = CKComputeDataCRC(&rawHeader, CKSizeof(CKRawFileInfo), 0u);
parser->SetCursor(sizeof(CKRawFileInfo));
parser->SetCursor(CKSizeof(CKRawFileInfo));
gotten_crc = CKComputeDataCRC(parser->GetPtr(), this->m_FileInfo.Hdr1PackSize, gotten_crc);
parser->MoveCursor(this->m_FileInfo.Hdr1PackSize);
gotten_crc = CKComputeDataCRC(parser->GetPtr(), this->m_FileInfo.DataPackSize, gotten_crc);
if (gotten_crc != this->m_FileInfo.Crc) {
this->m_Ctx->OutputToConsole(u8"Virtools file CRC error.");
return CKERROR::CKERR_FILECRCERROR;
// MARK:
// If the CRC check failed, there is another way to compute CRC. (>= Virtools 4.0)
// This is a patch for Dassault stupid programmer.
//
// After Virtools 4.0, Dassault use a new way to compute the CRC of file.
// Dassault introduce a new class called CKMemoryBufferWriter which use file and memory map to handle big file properly.
// However, there is a bug in virtual function CKMemoryBufferWriter::ComputeCRC.
// It takes `PreviousCRC` as argument but never use it in function. In this function, the start value of CRC compution is hardcoded 0.
// So, although Dassault programmer try to compute CRC for file header, header part and daat part in code, it actually only compute CRC for data part!
// I 100% sure this is the mistake of Dassault stupid programmer and this bug cause horrible result.
//
// In Virtools 2.1, engine will check CRC of file first. If no matched CRC, engine will reject loading file.
// So the obvious result is that we can not load file saved by Virtools 4.0 in Virtools 2.1.
// But this is not the point which makes me indignant.
// The real weird point is that we can use Virtools 3.5 to open file saved by Virtools 4.0 but why?
// After some research, I found that the programmer of Dassault totally removed CRC check when loading file since some version which I don't know!
// This is totally cheat and commercial-oriented behavior!
// I guess Dassault programmer also find that they can not load new created file in old Virtools.
// But they entirely don't know how to resolve it. So they just directly remove the whole of CRC checker!
// That's the point which makes me indignant.
gotten_crc = CKComputeDataCRC(parser->GetPtr(), this->m_FileInfo.DataPackSize, 0u);
// Both CRC compute methods are failed, this file may be really broken.
// Report exception directly.
if (gotten_crc != this->m_FileInfo.Crc) {
this->m_Ctx->OutputToConsole(u8"Virtools file CRC error.");
return CKERROR::CKERR_FILECRCERROR;
}
}
// reset cursor
parser->SetCursor(sizeof(CKRawFileInfo));
parser->SetCursor(CKSizeof(CKRawFileInfo));
// compare size to decide wheher use compress feature
if (this->m_FileInfo.Hdr1PackSize != this->m_FileInfo.Hdr1UnPackSize) {
@ -189,7 +215,7 @@ namespace LibCmo::CK2 {
if (this->m_FileInfo.FileVersion >= 8) {
// file ver >= 8, use header offset
// because it have compress feature
ParserPtr->SetCursor(this->m_FileInfo.Hdr1PackSize + sizeof(CKRawFileInfo));
ParserPtr->SetCursor(this->m_FileInfo.Hdr1PackSize + CKSizeof(CKRawFileInfo));
} else {
// otherwise, sync with current parser.
ParserPtr->SetCursor(parser->GetCursor());
@ -397,7 +423,7 @@ namespace LibCmo::CK2 {
}
// ========== finalize work ==========
// set done flag and return
this->m_Done = true;