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


==Syntax==
==Syntax==
<PRE>
DosSetFilePtrL (hFile, ib, method, ibActual)
#define INCL_DOSFILEMGR
#include <os2.h>
 
APIRET DosSetFilePtrL (HFILE hFile, LONGLONG ib, ULONG method, PLONGLONG ibActual)
</PRE>


==Parameters==
==Parameters==
;hFile HFILE) input : The handle returned by a previous DosOpenL function.  
;hFile ([[HFILE]]) input : The handle returned by a previous [[DosOpenL]] function.
;ib LONGLONG) input : The signed distance (offset) to move, in bytes.  
;ib ([[LONGLONG]]) input : The signed distance (offset) to move, in bytes.
;method ULONG) input : The method of moving.
;method ([[ULONG]]) input : The method of moving.
:Specifies a location in the file from where the ib to move the read/write pointer starts. The values and their meanings are described in the following list:
:Specifies a location in the file from where the ib to move the read/write pointer starts. The values and their meanings are described in the following list:
:*FILE_BEGIN - Move the pointer from the beginning of the file.
:*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_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.  
:*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.
; ibActual (PLONGLONG) output : Address of the new pointer location.


==Return Code==
==Return Code==
  ulrc APIRET) returns
  ulrc ([[APIRET]]) returns


DosSetFilePtrL returns one of the following values:
DosSetFilePtrL returns one of the following values:
Line 32: Line 26:


==Remarks==
==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. DosSetFilePtrL cannot be used to move to a negative position in the file.
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. ''DosSetFilePtrL'' cannot be used to move to a negative position in the file.
 
DosSetFilePtrL cannot be used for a character device or pipe.
 
==Example Code==
This example opens or creates and opens a file named DOSTEST.DAT, writes to it, positions the file pointer back to the beginning of the file, reads from the file, and finally closes it.
<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;    /* Handle for file being manipulated */
ULONG  ulAction      = 0;      /* Action taken by DosOpenL */
ULONG  ulBytesRead    = 0;      /* Number of bytes read by DosRead */
ULONG  ulWrote        = 0;      /* Number of bytes written by DosWrite */
LONGLONG  ullLocal    = 0;      /* File pointer position after DosSetFilePtr */
UCHAR  uchFileName 20  = "dostest.dat",    /* Name of file */
uchFileData 100  = " ";              /* Data to write to file */
APIRET rc            = NO_ERROR;            /* Return code */
 
/* Open the file test.dat.  Use an existing file or create a new */
/* one if it doesn't exist.                                      */
rc = DosOpenL(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 */if (rc != NO_ERROR)
 
printf("DosOpenL error  return code = %u\n", rc);
return 1;
  else 
printf ("DosOpenL  Action taken = %ld\n", ulAction);
  /* endif */
 
/* Write a string to the file */
strcpy (uchFileData, "testing...\n1...\n2...\n3\n");
 
rc = DosWrite (hfFileHandle,                /* File handle */
(PVOID) uchFileData,        /* String to be written */
sizeof (uchFileData),        /* Size of string to be written */
ulWrote);                  /* Bytes actually written */
 
if (rc != NO_ERROR) 
printf("DosWrite error  return code = %u\n", rc);
return 1;
  else 
printf ("DosWrite  Bytes written = %u\n", ulWrote);
  /* endif */
 
/* Move the file pointer back to the beginning of the file */
rc = DosSetFilePtrL (hfFileHandle,          /* File Handle */
(LONGLONG)0,            /* Offset */
FILE_BEGIN,            /* Move from BOF */
ullLocal);            /* New location address */
if (rc != NO_ERROR) 
printf("DosSetFilePtrL error  return code = %u\n", rc);
return 1;
 
/* Read the first 100 bytes of the file */
rc = DosRead (hfFileHandle,                /* File Handle */
uchFileData,                /* String to be read */
100L,                        /* Length of string to be read */
ulBytesRead);              /* Bytes actually read */
 
if (rc != NO_ERROR)
printf("DosRead error  return code = %u\n", rc);
return 1;
  else 
printf ("DosRead  Bytes read = %u\n%s\n", ulBytesRead, uchFileData);
  /* endif */
 
rc = DosClose(hfFileHandle);                /* Close the file */
 
if (rc != NO_ERROR) 
printf("DosClose error  return code = %u\n", rc);
return 1;


return NO_ERROR;
''DosSetFilePtrL'' cannot be used for a character device or pipe.
</PRE>


==Related Functions==
==Related Functions==

Revision as of 14:05, 14 June 2017

DosSetFilePtrL moves the read write pointer according to the type of move specified.

Syntax

DosSetFilePtrL (hFile, ib, method, ibActual)

Parameters

hFile (HFILE) input
The handle returned by a previous DosOpenL function.
ib (LONGLONG) input
The signed distance (offset) to move, in bytes.
method (ULONG) input
The method of moving.
Specifies a location in the file from where the ib to move the read/write pointer starts. The values and their meanings are described 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.

Return Code

ulrc (APIRET) returns

DosSetFilePtrL returns one of the following values:

  • 0 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. DosSetFilePtrL cannot be used to move to a negative position in the file.

DosSetFilePtrL cannot be used for a character device or pipe.

Related Functions

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