If the file is actually a directory, the caller can also specify the following generic access rights. Use InitializeObjectAttributes to initialize this structure. In particular, the Information member receives one of the following values:. If no file is created or overwritten, AllocationSize is ignored. If no file is created or overwritten, FileAttributes is ignored.
Device and intermediate drivers usually set ShareAccess to zero, which gives the caller exclusive access to the open file. Specifies the action to perform if the file does or does not exist. CreateDisposition can be one of the values in the following table.
Specifies the options to apply when the driver creates or opens the file. Use one or more of the flags in the following table. In the latter case, the caller can determine the cause of the failure by checking the IoStatusBlock parameter. ZwCreateFile supplies a handle that the caller can use to manipulate a file's data, or the file object's state and attributes.
For more information, see Using Files in a Driver. Once the handle pointed to by FileHandle is no longer in use, the driver must call ZwClose to close it. If the caller is not running in a system thread context, it must ensure that any handles it creates are private handles. Otherwise, the handle can be accessed by the process in whose context the driver is running.
For more information, see Object Handles. There are two alternate ways to specify the name of the file to be created or opened with ZwCreateFile :. To successfully open a shared file, the DesiredAccess flags must be compatible with the DesiredAccess and ShareAccess flags of all the previous open operations that have not yet been released through. That is, the DesiredAccess specified to ZwCreateFile for a given file must not conflict with the accesses that other openers of the file have disallowed.
To avoid the sharing violation in this scenario, open the remote file or directory with the DELETE access right only, or call DeleteFile without first opening the file or directory for deletion. Some file systems, such as the NTFS file system, support compression or encryption for individual files and directories.
On volumes that have a mounted file system with this support, a new file inherits the compression and encryption attributes of its directory. You cannot use CreateFile to control compression, decompression, or decryption on a file or directory.
Windows Server and Windows XP: For backward compatibility purposes, CreateFile does not apply inheritance rules when you specify a security descriptor in lpSecurityAttributes. To support inheritance, functions that later query the security descriptor of this file may heuristically determine and report that inheritance is in effect.
As stated previously, if the lpSecurityAttributes parameter is NULL , the handle returned by CreateFile cannot be inherited by any child processes your application may create. The following information regarding this parameter also applies:. Note that CreateFile with supersede disposition will fail if performed on a file where there is already an open alternate data stream. Some of these flags should not be combined. Performance gains can be even more noticeable for applications that read large files mostly sequentially, but occasionally skip forward over small ranges of bytes.
If an application moves the file pointer for random access, optimum caching performance most likely will not occur. However, correct operation is still guaranteed. The operating system also requests a write-through of the hard disk's local hardware cache to persistent media. Using these flags together avoids those penalties. For general information about the caching of files and metadata, see File Caching. Also, the file metadata may still be cached for example, when creating an empty file.
To ensure that the metadata is flushed to disk, use the FlushFileBuffers function. In that case, the system can entirely avoid writing the data. If you call CreateFile on a file that is pending deletion as a result of a previous call to DeleteFile , the function fails. The operating system delays file deletion until all handles to the file are closed. The dwDesiredAccess parameter can be zero, allowing the application to query file attributes without accessing the file if the application is running with adequate security settings.
To avoid the error, specify the same attributes as the existing file. The resulting code is faster, because the redirector can use the cache manager and send fewer SMBs with more data. For more information, see Creating and Opening Files. Access to the directory is denied if this is done. We specialize in file system filter driver development. We architect, implement and test file system filter drivers for a wide range of functionalities.
We can offer several levels of assistance to meet your specific needs. Note The sharing options for each open handle remain in effect until that handle is closed, regardless of process context. Value Meaning 0 0x Prevents other processes from opening a file or device if they request delete, read, or write access. Otherwise, other processes cannot open the file or device if they request delete access. Note Delete access allows both delete and rename operations.
Public BaudRate As Int32 Txt Public wReserved As Int16 Public XonLim As Int16 Public XoffLim As Int16 Public ByteSize As Byte Public Parity As Byte Public StopBits As Byte Public XonChar As Byte Public XoffChar As Byte Public ErrorChar As Byte Public EofChar As Byte Public EvtChar As Byte End Structure Sebelum Anda dapat mengakses serial port atau port paralel, Anda harus mendapatkan handle ke port yang sesuai dan kemudian mengkonfigurasi port komunikasi.
Untuk melakukannya, tambahkan kode inisialisasi berikut untuk Module1. Untuk melakukannya, gunakan alat layanan di Alat administratif. Dim Success As Boolean Dim Buffer As Byte Dim oEncoder As New System.
Dim oEnc As System. Search related threads. Remove From My Forums. Asked by:. Archived Forums. Visual C. Sign in to vote. I was adviced to create a new thread for this query and hoping to get it fixed. Thanks for any help in advance.
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