DosSetFHState

Sets the state of the specified file handle.

Syntax
DosSetFHState(hFile, mode)

Parameters

 * hFile (HFILE) - input : File handle to be set.
 * mode (ULONG) - input : Contents of the fsOpenMode field defined in a previous DosOpen function.
 * This parameter contains the following bit fields:
 * 15 - OPEN_FLAGS_DASD (0x00008000) This bit must be set to 0.
 * 14 - OPEN_FLAGS_WRITE_THROUGH (0x00004000) Write-Through flag:
 * 0 Writes to the file may go through the system-buffer cache.
 * 1 Writes to the file may go through the system-buffer cache, but the data is written (the actual file I/O operation is completed) before a synchronous-write call returns. This state of the file defines it as a synchronous file. For synchronous files, this bit must be set, because the data must be written to the medium for synchronous-write operations.
 * This flag bit is not inherited by child processes.
 * 13 - OPEN_FAIL_ON_ERROR (0x00002000) Fail-Errors flag. Media I/O errors are handled as follows:
 * 0 Reported through the system critical-error handler.
 * 1 Reported directly to the caller by way of a return code.
 * Media I/O errors generated through Category 08h Logical Disk Control IOCtl Commands are always reported directly to the caller by way of a return code. The Fail-Errors function applies only to non-IOCtl handle-based file I/O functions.
 * This flag bit is not inherited by child processes.
 * 12 - OPEN_FLAGS_NO_CACHE (x00002000) Cache or No-Cache flag. The file is opened as follows:
 * The disk driver should place data from I/O operations into cache.
 * I/O operations to the file need not be done through the disk-driver cache.
 * This bit is an advisory bit, and is used to advise file-system drivers and device drivers about whether the data should be cached. This bit, like the write-through bit, is a per-handle bit.
 * This bit is not inherited by child processes.
 * 11-8 - These bits must be set to 0.
 * 7 - OPEN_FLAGS_NOINHERIT (0x00000080) Inheritance flag:
 * 0 File handle is inherited by a process created by DosExecPgm.
 * 1 File handle is private to the current process.
 * 6-4 - These bits must be set to 0. Any other values are invalid.
 * 3 - This bit must be set to 0.
 * 2-0 - These bits must be set to 0. Any other values are invalid.

Return Code

 * ulrc (APIRET) - returns:DosSetFHState returns one of the following values:
 * 0 NO_ERROR
 * 6 ERROR_INVALID_HANDLE
 * 87 ERROR_INVALID_PARAMETER

Remarks
The operating system does not guarantee the write order for multiple-sector write operations. If an application requires several sectors to be written in a specific order, the operator should issue the sectors as separate synchronous-write operations. Setting the Write-Through flag does not affect any previous write operation. That data can remain in the buffers.

When the application cannot handle a critical error that occurs, critical-error handling can be reset to the system. This is done by having DosSetFHState turn off the fail/errors bit, and then reissuing the I/O operation. The expected critical error recurs, and control is passed to the system critical-error handler. The precise time that the effect of this function is visible at the application level is unpredictable when asynchronous I/O operations are pending.

The file-handle-state bits set by this function can be queried by DosQueryFHState.

Named-Pipe Considerations
With DosSetFHState, the inheritance (I) bit and Write-Through (W) bit can be set or reset. Setting W to 1 prevents write-behind operations on remote pipes.

Example Code
This example queries the file handle state of the file "DOSQFH.DAT". 
 * 1) define INCL_DOSFILEMGR  /* File Manager values */
 * 2) define INCL_DOSERRORS   /* DOS error values    */
 * 3) include 
 * 4) include 

int main(VOID) {

UCHAR      uchFileName[]   = "DOSQFH.DAT";    /* File to manipulate        */ HFILE      fhQryFile       = 0;               /* File handle from DosOpen  */ FILESTATUS3 fsts3FileInfo  = ;  /* Information associated with file   */ ULONG      ulOpenAction    = 0;                 /* Action taken by DosOpen */ ULONG      FHState         = 0;                 /* File Handle State       */ APIRET     rc              = NO_ERROR;          /* Return code             */

/* Create a file */

rc = DosOpen(uchFileName, &fhQryFile,              &ulOpenAction, 10L, FILE_NORMAL,               OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS,               OPEN_ACCESS_READWRITE | OPEN_SHARE_DENYNONE, 0L); if (rc != NO_ERROR) { printf("DosOpen error: return code = %u\n", rc); return 1; }

rc = DosQueryFHState(fhQryFile, &FHState); if (rc != NO_ERROR) { printf("DosQueryFHState error: return code = %u\n", rc); return 1; } else printf("FHState is: %x\n", FHState);

/*  Change state to indicate that data should not be cached */

FHState &= 0x7F88;                 /* Turn off non-participating bits */ rc = DosSetFHState(fhQryFile, FHState | OPEN_FLAGS_NO_CACHE); if (rc != NO_ERROR) { printf("DosSetFHState error: return code = %u\n", rc); return 1; }

rc = DosClose(fhQryFile); /* Should check if (rc != NO_ERROR) here... */

rc = DosDelete(uchFileName);     /* Delete the file */ if (rc != NO_ERROR) { printf("DosDelete error: return code = %u\n", rc); return 1; } else { printf("File %s has been deleted.\n",uchFileName); }

return NO_ERROR; } 

Related Functions

 * DosClose
 * DosDevIOCtl
 * DosDupHandle
 * DosExecPgm
 * DosOpen
 * DosQueryFHState