View source for DosProtectSetFilePtrL

==Description==
DosProtectSetFilePtrL moves the read or write pointer according to the type of move specified. 

==Syntax==
<PRE>
#define INCL DOSFILEMGR
#include  os2.h 

    APIRET DosProtectSetFilePtrL
        (HFILE hFile, LONGLONG ib, ULONG method, PLONGLONG ibActual, FHLOCK fhFileHandleLockID)
</PRE>
==Parameters==
;  hFile HFILE) input : The handle returned by a previous DosOpenL function. 

; ib LONGLONG) input : The signed distance (offset) to move, in bytes. 

; method LONG) input : The method of moving.

This field specifies the location in the file at which the read/write pointer starts before adding the ib offset. The values and their meanings are as shown in the following list

    FILE_BEGIN
    Move the pointer from the beginning of the file.
 
    FILE_CURRENT
    Move the pointer from the current location of the read/write pointer.
 
    FILE_END
    Move the pointer from the end of the file. Use this method to determine a file s size. 

; ibActual PLONGLONG) output :  Address of the new pointer location. 

; fhFileHandleLockID FHLOCK) input : The filehandle lockid returned by a previous DosProtectOpenL.
==Return Code==
 ulrc APIRET) returns

DosProtectSetFilePtrL returns one of the following values

*            NO_ERROR
*            ERROR_INVALID_FUNCTION
*            ERROR_INVALID_HANDLE
* 132        ERROR_SEEK_ON_DEVICE 
* 131        ERROR_NEGATIVE_SEEK 
* 130        ERROR_DIRECT_ACCESS_HANDLE

==Remarks==
The read/write pointer in a file is a signed 64-bit number. A negative value for ib moves the pointer backward in the file; a positive value moves it forward. DosProtectSetFilePtrL cannot be used to move to a negative position in the file.

DosProtectSetFilePtrL cannot be used for a character device or pipe. 

==Example Code==
This example opens or creates and opens a file named DOSPROT.DAT , writes a string to it, returns the file pointer to the beginning of the file, reads it, and finally closes it using DosProtect functions.

<PRE>
#define INCL_DOSFILEMGR          /* File Manager values */#define INCL_DOSERRORS           /* DOS Error values    */
#include  os2.h 
#include  stdio.h 
#include  string.h 

int main(VOID)  
HFILE  hfFileHandle   = 0L;
ULONG  ulAction       = 0;
ULONG  ulBytesRead    = 0;
ULONG  ulWrote        = 0;
LONGLONG  ullLocal    = 0;
UCHAR  uchFileName 20   = "dosprot.dat",
uchFileData 100  = " ";
FHLOCK FileHandleLock = 0;        /* File handle lock   */
APIRET rc             = NO_ERROR; /* Return code */

/* Open the file test.dat.  Make it read/write, open it */
/* if it already exists and create it if it is new.     */
rc = DosProtectOpenL(uchFileName,             /* File path name          */
 hfFileHandle,                  /* File handle             */
 ulAction,                      /* Action taken            */
(LONGLONG)100,                           /* File primary allocation */
FILE_ARCHIVED | FILE_NORMAL,    /* File attribute          */
OPEN_ACTION_CREATE_IF_NEW |
OPEN_ACTION_OPEN_IF_EXISTS,     /* Open function type      */
OPEN_FLAGS_NOINHERIT |
OPEN_SHARE_DENYNONE  |
OPEN_ACCESS_READWRITE,          /* Open mode of the file   */
0L,                             /* No extended attribute   */
 FileHandleLock);               /* File handle lock id     */
if (rc != NO_ERROR)  
printf("DosProtectOpenL error  return code = %u\n", rc);
return 1;
  else  
printf ("DosProtectOpenL  Action taken = %u\n", ulAction);
  /* endif */

/* Write a string to the file */
strcpy (uchFileData, "testing...\n3...\n2...\n1\n");

rc = DosProtectWrite (hfFileHandle,       /* File handle                  */
(PVOID) uchFileData,       /* String to be written         */
sizeof (uchFileData),      /* Size of string to be written */
 ulWrote,                  /* Bytes actually written       */
FileHandleLock);           /* File handle lock id          */if (rc != NO_ERROR) 

printf("DosProtectWrite error  return code = %u\n", rc);
return 1;
  else  
printf ("DosProtectWrite  Bytes written = %u\n", ulWrote);
  /* endif */

/* Move the file pointer back to the beginning of the file */
rc = DosProtectSetFilePtrL (hfFileHandle,   /* File Handle          */
(LONGLONG)0,            /* Offset               */
FILE_BEGIN,             /* Move from BOF        */
 ullLocal,              /* New location address */
FileHandleLock);        /* File handle lock id  */
if (rc != NO_ERROR)  
printf("DosSetFilePtr error  return code = %u\n", rc);
return 1;
 

/* Read the first 100 bytes of the file */
rc = DosProtectRead (hfFileHandle,         /* File Handle                 */
uchFileData,                 /* String to be read           */
100L,                        /* Length of string to be read */
 ulBytesRead,                /* Bytes actually read         */
FileHandleLock);             /* File handle lock id         */
if (rc != NO_ERROR)  
printf("DosProtectRead error  return code = %u\n", rc);
return 1;
  else  
printf("DosProtectRead  Bytes read = %u\n%s\n", ulBytesRead, uchFileData);
  /* endif */

rc = DosProtectClose(hfFileHandle, FileHandleLock);   /* Close the file */
if (rc != NO_ERROR)  
printf("DosProtectClose error  return code = %u\n", rc);
return 1;
 
return NO_ERROR;
 

</PRE>
==Related Functions==
* [[OS2 API:CPI:DosProtectOpenL|CPI:DosProtectOpenL]]
* [[OS2 API:CPI:DosProtectRead|CPI:DosProtectRead]]
* [[OS2 API:CPI:DosProtectSetFileSizeL|CPI:DosProtectSetFileSizeL]]
* [[OS2 API:CPI:DosProtectWrite|CPI:DosProtectWrite]]

[[Category:The OS/2 API Project]]