Method Open

src/engine/shared/datafile.cpp:454–671

}

bool CDataFileReader::Open(const char *pFullName, IStorage *pStorage, const char *pPath, int StorageType)
{
	dbg_assert(m_pDataFile == nullptr, "File already open");

	log_trace("datafile", "loading '%s' from '%s'", pFullName, pPath);

	IOHANDLE File = pStorage->OpenFile(pPath, IOFLAG_READ, StorageType);
	if(!File)
	{
		log_error("datafile", "failed to open file '%s' for reading", pPath);
		return false;
	}

	// determine size and hashes of the file and store them
	int64_t FileSize = 0;
	unsigned Crc = 0;
	SHA256_DIGEST Sha256;
	{
		SHA256_CTX Sha256Ctxt;
		sha256_init(&Sha256Ctxt);
		unsigned char aBuffer[64 * 1024];
		while(true)
		{
			const unsigned Bytes = io_read(File, aBuffer, sizeof(aBuffer));
			if(Bytes == 0)
				break;
			FileSize += Bytes;
			Crc = crc32(Crc, aBuffer, Bytes);
			sha256_update(&Sha256Ctxt, aBuffer, Bytes);
		}
		Sha256 = sha256_finish(&Sha256Ctxt);
		if(io_seek(File, 0, IOSEEK_START) != 0)
		{
			io_close(File);
			log_error("datafile", "could not seek to start after calculating hashes");
			return false;
		}
	}

	// read header
	CDatafileHeader Header;
	if(io_read(File, &Header, sizeof(Header)) != sizeof(Header))
	{
		io_close(File);
		log_error("datafile", "could not read file header. file truncated or not a datafile.");
		return false;
	}

	// check header magic
	if((Header.m_aId[0] != 'A' || Header.m_aId[1] != 'T' || Header.m_aId[2] != 'A' || Header.m_aId[3] != 'D') &&
		(Header.m_aId[0] != 'D' || Header.m_aId[1] != 'A' || Header.m_aId[2] != 'T' || Header.m_aId[3] != 'A'))
	{
		io_close(File);
		log_error("datafile", "wrong header magic. magic=%x%x%x%x", Header.m_aId[0], Header.m_aId[1], Header.m_aId[2], Header.m_aId[3]);
		return false;
	}

	SwapEndianInPlace(&Header);