fcntl(O_NONBLOCK) does not work on a named pipe

[komh]

Hi/2.

As a title, fcntl(O_NONBLOCK) does not work on a named pipe.

Here is the test code.

#define INCL_DOS
#include <os2.h>

#include <stdio.h>
#include <io.h>
#include <fcntl.h>

#define PIPE_NAME "\\PIPE\\FCNTL\\NAMED_PIPE"

static int named_pipe( int *ph )
{
    HPIPE hpipe;
    HFILE hpipeWrite;
    ULONG ulAction;

    DosCreateNPipe( PIPE_NAME,
                    &hpipe,
                    NP_ACCESS_DUPLEX,
                    NP_NOWAIT | NP_TYPE_BYTE | NP_READMODE_BYTE | 1,
                    32768, 32768, 0 );

    DosConnectNPipe( hpipe );

    DosOpen( PIPE_NAME, &hpipeWrite, &ulAction, 0, FILE_NORMAL,
             OPEN_ACTION_OPEN_IF_EXISTS,
             OPEN_SHARE_DENYREADWRITE | OPEN_ACCESS_WRITEONLY,
             NULL );

    ph[ 0 ] = hpipe;
    ph[ 1 ] = hpipeWrite;

    return 0;

}

int check( const char *msg, int fd )
{
    ULONG ulState;
    int fl;
    int failed;
    ULONG rc;

    rc = DosQueryNPHState( fd, &ulState );
    if(!rc)
    {
        fl = fcntl(fd, F_GETFL);

        rc = fl != -1 ? 0 : 1;
    }

    failed = rc ||
             ((( ulState & NP_NOWAIT ) == NP_NOWAIT ) !=
              (( fl & O_NONBLOCK ) == O_NONBLOCK ));

    printf("%s: %s, fcntl() = %s(%s)\n",
           failed ? "FAILED" : "PASSED", msg,
           ( fl & O_NONBLOCK ) ? "Non-block" : "Block",
           ( ulState & NP_NOWAIT ) ? "Non-block" : "Block");

    return failed;
}

int main( void )
{
    int ph[ 2 ];
    int fd;
    int fl;
    int errors = 0;

    printf("Testing fcntl(O_NONBLOCK) for a named pipe\n");

    named_pipe( ph );

    fd = ph[ 0 ];
    fl = fcntl( fd, F_GETFL );
    errors += check("S: Import", fd );

    fcntl( fd, F_SETFL, fl & ~O_NONBLOCK );
    errors += check("S: Set to BLOCK", fd );

    fcntl( fd, F_SETFL, fl | O_NONBLOCK );
    errors += check("S: Set to NON-BLOCK", fd );

    fd = ph[ 1 ];
    fl = fcntl( fd, F_GETFL );
    errors += check("C: Import", fd );

    fcntl( fd, F_SETFL, fl & ~O_NONBLOCK );
    errors += check("C: Set to BLOCK", fd );

    fcntl( fd, F_SETFL, fl | O_NONBLOCK );
    errors += check("C: Set to NON-BLOCK", fd );

    close( ph[ 0 ]);
    close( ph[ 1 ]);

    return !!errors;
}

And I attach the patch.

0001-filehandles-support-O_NONBLOCK-for-a-named-pipe.patch

From c39ae307a1cc08f93b24bc085e1363248a98f650 Mon Sep 17 00:00:00 2001
From: KO Myung-Hun <komh@chollian.net>
Date: Tue, 7 Oct 2014 17:13:05 +0900
Subject: [PATCH] filehandles: support O_NONBLOCK for a named pipe

---
 src/emx/src/lib/sys/filehandles.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/emx/src/lib/sys/filehandles.c b/src/emx/src/lib/sys/filehandles.c
index 2b8a9cc..9c6a154 100644
--- a/src/emx/src/lib/sys/filehandles.c
+++ b/src/emx/src/lib/sys/filehandles.c
@@ -1347,6 +1347,12 @@ static __LIBC_PFH fhGet(int fh)
             if (!_fmode_bin)
                 fLibc |= O_TEXT;
 
+            /*
+             * Blocking flag for a named pipe.
+             */
+            if (!DosQueryNPHState((HFILE)fh, &fulMode) && (fulMode & NP_NOWAIT))
+                fLibc |= O_NONBLOCK;
+
 
             /*
              * Allocate a new handle for this filehandle.
@@ -1461,6 +1467,23 @@ int __libc_FHSetFlags(__LIBC_PFH pFH, int fh, unsigned fFlags)
             rc = DosSetFHState(fh, fulNewState);
         }
     }
+    if (!rc && !DosQueryNPHState(fh, &fulState))
+    {
+        ULONG fulNewState;
+        LIBC_ASSERTM(     ((fulState & NP_NOWAIT) != 0 )
+                      ==  ((pFH->fFlags & O_NONBLOCK) != 0),
+                     "Nowait flags are out of sync for file hFile %d (%#x)! fulState=%08lx fFlags=%08x\n",
+                     fh, fh, fulState, pFH->fFlags);
+        if (fFlags & O_NONBLOCK)
+            fulNewState = fulState | NP_NOWAIT;
+        else
+            fulNewState = fulState & ~NP_NOWAIT;
+        if (fulNewState != fulState)
+        {
+            fulNewState &= NP_NOWAIT | NP_READMODE_MESSAGE; /* Turn off non-participating bits. */
+            rc = DosSetNPHState(fh, fulNewState);
+        }
+    }
     FS_RESTORE();
 
     if (!rc)
-- 
2.50.1

[dmik]

Named pipes were never implemented in kLIBC. These patches with some additions should make importing native named pipes supported to some degree but it makes sense to combine it with implementing mkfifo which is a stub at the moment (shouldn't be difficult either):

libc/src/emx/src/lib/misc/mkfifo.c

Lines 47 to 52 in cd7288c

	int _STD(mkfifo)(const char *path, mode_t mode)
	{
	LIBCLOG_ENTER("path=%p:{%s} mode=%x\n", (void *)path, path, mode);
	int rc = ENOSYS;
	LIBCLOG_ERROR_RETURN_INT(rc);
	}

Any case where it's practically needed?

[komh]

When porting libarchive, I used a named pipe. Libc imported a named pipe handle flawlessly, but did not support fcntl(O_NONBLOCK) on it.

[dmik]

Doesn't libarchive use mkfifo on Posix platforms?

[komh]

mkfifo() was optional for some functions.