DosProtectOpen
Description
Opens a new file, an existing file, or a replacement for an existing file and returns a protected file handle. An open file can have extended attributes.
Syntax
#define INCL_DOSFILEMGR
#include <os2.h>
PSZ pszFileName; /* Address of the ASCIIZ path name of the file or device to be opened. */
PHFILE phf; /* Address of the handle for the file. */
PULONG pulAction; /* A pointer to the ULONG in which the value that specifies the action taken by DosProtectOpen is returned. */
ULONG cbFile; /* New logical size of the file (end of data, EOD), in bytes. */
ULONG ulAttribute; /* File attributes. */
ULONG fsOpenFlags; /* The action to be taken depending on whether the file exists or does not exist. */
ULONG fsOpenMode; /* The mode of the open function. */
PEAOP2 peaop2; /* A pointer to an extended attribute buffer. */
PFHLOCK pfhFileHandleLockID;
APIRET ulrc; /* Return Code. */
ulrc = DosProtectOpen(pszFileName, phf, pulAction,
cbFile, ulAttribute, fsOpenFlags,
fsOpenMode, peaop2, pfhFileHandleLockID);
Parameters
- pszFileName (PSZ) - input
- Address of the ASCIIZ path name of the file or device to be opened.
- phf (PHFILE) - output
- Address of the handle for the file.
- pulAction (PULONG) - output
- A pointer to the ULONG in which the value that specifies the action taken by DosProtectOpen is returned.
If DosProtectOpen fails, this value has no meaning. Otherwise, it is one of the following values:
1 FILE_EXISTED File already existed. 2 FILE_CREATED File was created. 3 FILE_TRUNCATED File existed and was changed to a given size (file was replaced).
- cbFile (ULONG) - input
- New logical size of the file (end of data, EOD), in bytes.
This parameter is significant only when creating a new file or replacing an existing one. Otherwise, it is ignored. It is an error to create or replace a file with a nonzero length if the fsOpenMode Access-Mode flag is set to read-only.
- ulAttribute (ULONG) - input
- File attributes.
This parameter contains the following bit fields:
Bit Description
31-6 Reserved, must be 0.
5 FILE_ARCHIVED (0x00000020) File has been archived.
4 FILE_DIRECTORY (0x00000010)
File is a subdirectory.
3 Reserved, must be 0.
2 FILE_SYSTEM (0x00000004)
File is a system file.
1 FILE_HIDDEN (0x00000002)
File is hidden and does not appear in a directory listing.
0 FILE_READONLY (0x00000001)
File can be read from, but not written to.
0 FILE_NORMAL (0x00000000)
File can be read from or written to. File attributes apply only if the file is created.
These bits may be set individually or in combination. For example, an attribute value of 0x00000021 (bits 5 and 0 set to 1) indicates a read-only file that has been archived.
- fsOpenFlags (ULONG) - input
- The action to be taken depending on whether the file exists or does not exist.
This parameter contains the following bit fields.:
Bits Description 31-8 Reserved, must be 0. 7-4 The following flags apply if the file does not exist:
0000 OPEN_ACTION_FAIL_IF_NEW Open an existing file; fail if the file does not exist.
0001 OPEN_ACTION_CREATE_IF_NEW Create the file if the file does not exist.
3-0 The following flags apply if the file does not exist:
0000 OPEN_ACTION_FAIL_IF_EXISTS
Open the file; fail if the file already exists.
0001 OPEN_ACTION_OPEN_IF_EXISTS
Open the file if it already exists.
0010 OPEN_ACTION_REPLACE_IF_EXISTS
Replace the file if it already exists.
- fsOpenMode (ULONG) - input
- The mode of the open function.
This parameter contains the following bit fields:
Bit Description
29-16 Reserved, must be zero.
30 OPEN_FLAGS_PROTECTED_HANDLE (0x40000000)
Protected file handle flag.
0 Unprotected Handle
1 Protected Handle
Protected handle requires the pfhFileHandleLockID to be specified on subsequent DosProtectxxxx calls.
Unprotected handle requires the pfhFileHandleLockID value to be specified as zero on subsequent
DosProtectxxxx calls. An unprotected handle may be used with the unprotected calls such as DosRead
and DosWrite.
31 Reserved, must be zero.
15 OPEN_FLAGS_DASD (x00008000)
Direct Open flag:
0 pszFileName represents a file to be opened normally.
1 pszFileName is "drive:" (such as C: or A:), and represents a mounted disk
or diskette volume to be opened for direct access.
14 OPEN_FLAGS_WRITE_THROUGH (0x00004000)
Write-Through flag:
0 Writes to the file may go through the file-system driver's cache.
The file-system driver writes the sectors when the cache is full or the file is closed.
1 Writes to the file may go through the file-system driver's cache, but the sectors are
written (the actual file I/Ooperationiscompleted )before asynchronous write call returns.
This state of the file defines it as asynchronous file .For synchronous files ,
this bit must be set ,because the data must be written to the medium for synchronous write operations .
This bit flag is not inherited by child processes.
13 OPEN_FLAGS_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 always get
reported directly to the caller by way of return code. The Fail-Errors function applies only to
non-IOCtl handle-based file I/O calls.
This flag bit is not inherited by child processes.
12 OPEN_FLAGS_NO_CACHE (0x00001000)
No-Cache/Cache flag:
0 The file-system driver should place data from I/O operations into its cache.
1 I/O operations to the file need not be done through the file-system driver's cache.
The setting of this bit determines whether file-system drivers should place data into the cache.
Like the write-through bit, this is a per-handle bit, and is not inherited by child processes.
11 Reserved; must be 0.
10-8 The locality of reference flags contain information about how the application is to get access
to the file. The values are as follows:
000 OPEN_FLAGS_NO_LOCALITY (0x00000000)
No locality known.
001 OPEN_FLAGS_SEQUENTIAL (0x00000100)
Mainly sequential access.
010 OPEN_FLAGS_RANDOM (0x00000200)
Mainly random access.
011 OPEN_FLAGS_RANDOMSEQUENTIAL (0x00000300)
Random with some locality.
7 OPEN_FLAGS_NOINHERIT (0x00000080)
Inheritance flag:
0 File handle is inherited by a process created from a call to DosExecPgm.
1 File handle is private to the current process.
This bit is not inherited by child processes.
6-4 Sharing Mode flags. This field defines any restrictions to file access placed by the
caller on other processes. The values are as follows:
001 OPEN_SHARE_DENYREADWRITE (0x00000010)
Deny read/write access.
010 OPEN_SHARE_DENYWRITE (0x00000020)
Deny write access.
011 OPEN_SHARE_DENYREAD (0x00000030)
Deny read access.
100 OPEN_SHARE_DENYNONE (0x00000040)
Deny neither read nor write access (deny none). Any other value is invalid.
3 Reserved; must be 0.
2-0 Access-Mode flags. This field defines the file access required by the caller.
The values are as follows:
000 OPEN_ACCESS_READONLY (0x00000000)
Read-only access
001 OPEN_ACCESS_WRITEONLY (0x00000001)
Write-only access
010 OPEN_ACCESS_READWRITE (0x00000002)
Read/write access.
Any other value is invalid, as are any other combinations.
File sharing requires the cooperation of sharing processes. This cooperation is communicated through sharing and access modes. Any sharing restrictions placed on a file opened by a process are removed when the process closes the file with a DosClose request.
Sharing Mode: Specifies the type of file access that other processes may have. For example, if other processes can continue to read the file while your process is operating on it, specify Deny Write. The sharing mode prevents other processes from writing to the file but still allows them to read it.
Access Mode: Specifies the type of file access (access mode) needed by your process. For example, if your process requires read/write access, and another process has already opened the file with a sharing mode of Deny None, your DosProtectOpen request succeeds. However, if the file is open with a sharing mode of Deny Write, the process is denied access.
If the file is inherited by a child process, all sharing and access restrictions also are inherited.
If an open file handle is duplicated by a call to DosDupHandle, all sharing and access restrictions also are duplicated.
- peaop2 (PEAOP2) - in/out
- A pointer to an extended attribute buffer.
Input : The address of the extended-attribute buffer, which contains an EAOP2 structure. The fpFEA2List field in the EAOP2 structure. points to a data area where the relevant FEA2 list is to be found. The fpGEA2List and oError fields are ignored.
Output: fpGEA2List and fpFEA2List are unchanged. The area that fpFEA2List points to is unchanged. If an error occurred during the set, oError is the offset of the FEA2 entry where the error occurred. The return code from DosProtectOpen is the error code for that error condition. If no error occurred, oError is undefined. If peaop2 is zero, then no extended attributes are defined for the file. If extended attributes are not to be defined or modified, the pointer peaop2 must be set to zero.
- pfhFileHandleLockID (PFHLOCK) - output
- The address of the 32-bit lockid for the file handle.
Return Code
Remarks
Example Code
Related Functions
- [[OS2 API:CPI: