[M3devel] unix - unknown qualification

[Rodney M. Bates]

Sounds like a good idea to me.  IT moves the M3/C boundary back just
enough to pick up all the #ifdef stuff, etc.
but not the application-specific code.

On 07/13/2012 04:33 AM, Jay K wrote:
> Hey, how about I just provide copying wrappers here, like we do for stat?
> Where we define an idealized portable struct flock and copy it back and forth in C to the real struct flock?
>
> It is a little strange -- the wrapper is fnctl.
> It must check the first parameter, and know/assume its meaning.
>
>
>   - Jay
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 --
> From: jay.krell at cornell.edu
> To: pgoltzsch at gmail.com; m3devel at elegosoft.com
> Date: Thu, 12 Jul 2012 22:12:49 +0000
> Subject: Re: [M3devel] unix - unknown qualification
>
> Unix.i3 has always been a maintenance and portability problem.
> As such, it has been dramatically reduced.
> This stuff was probably removed, esp. struct_flock.
> The constants can exposed easily enough, portably, but aren't useful without the struct, prpbably.
>
>
> You REALLY REALLY REALLY want to write this in C.
> Writing it in Modula-3 has many downsides. You lose safety. You losestatic checking. You loseportability.
> You gain infinitely small efficiency.
> Something like:
>
>
> jbook2:libm3 jay$ pwd
> /dev2/cm3/m3-libs/libm3
> jbook2:libm3 jay$ find . | xargs grep flock
> ./src/os/POSIX/FilePosixC.c:saves us from having to declare struct flock, which is gnarled up in #ifdefs.
> ./src/os/POSIX/FilePosixC.c:    struct flock lock;
> ./src/os/POSIX/FilePosixC.c:    struct flock lock;
> ./tests/os/src/locktest.c:  struct flock param;
>
>
> ./src/os/POSIX/FilePosixC.c:
>
> /* Copyright (C) 1993, Digital Equipment Corporation           */
> /* All rights reserved.                                        */
> /* See the file COPYRIGHT for a full description.              */
>
> /*
> Writing part of libm3/os/POSIX/FilePosix.m3/RegularFileLock, RegularFileUnlock in C
> saves us from having to declare struct flock, which is gnarled up in #ifdefs.
>
> see http://www.opengroup.org/onlinepubs/009695399/functions/fcntl.html
> */
>
> #include "m3core.h"
> #include <string.h>
>
> #ifdef __cplusplus
> extern "C" {
> #endif
>
> #define FALSE 0
> #define TRUE 1
>
> INTEGER FilePosixC__RegularFileLock(int fd)
> {
>      struct flock lock;
>      int err;
>
>      ZeroMemory(&lock, sizeof(lock));
>      lock.l_type = F_WRLCK;
>      lock.l_whence = SEEK_SET;
>
>      if (fcntl(fd, F_SETLK, &lock) < 0)
>      {
>          err = errno;
>          if (err == EACCES || err == EAGAIN)
>              return FALSE;
>          return -1;
>      }
>      return TRUE;
> }
>
> INTEGER FilePosixC__RegularFileUnlock(int fd)
> {
>      struct flock lock;
>
>      ZeroMemory(&lock, sizeof(lock));
>      lock.l_type = F_UNLCK;
>      lock.l_whence = SEEK_SET;
>
>      return fcntl(fd, F_SETLK, &lock);
> }
>
> #ifdef __cplusplus
> } /* extern "C" */
> #endif
>
>
>
> We can add this to libm3 probably.
>
>
>   - Jay
>
>
>  > Date: Thu, 12 Jul 2012 14:58:11 +0200
>  > From: pgoltzsch at gmail.com
>  > To: m3devel at elegosoft.com
>  > Subject: Re: [M3devel] unix - unknown qualification
>  >
>  > >>>>> Rodney M. Bates wrote:
>  >
>  > > I think we need to see some source code for ClsShare.m3.
>  > > particularly to see what is before the dot on these lines. I
>  > > don't see any of the failing qualifications in Unix.i3 in my
>  > > cm3 directory.
>  >
>  > The first errors are caused by the following procedure,
>  > which seems to copied from old DEC example code as I found
>  > out while looking for a solution:
>  >
>  > PROCEDURE FilePartLock( h : INTEGER; start, len : INTEGER ) : BOOLEAN RAISES {OSError.E} =
>  > VAR flock := Unix.struct_flock {
>  > l_type := Unix.F_WRLCK,
>  > l_whence := Unix.L_SET,
>  > l_start := 0,
>  > l_len := 0, (* i.e., whole file *)
>  > l_pid := 0 }; (* don't care *)
>  > BEGIN
>  > flock.l_start := start;
>  > flock.l_len := len;
>  > IF Unix.fcntl( h, Unix.F_SETLK, LOOPHOLE( ADR( flock ), Ctypes.long ) ) < 0
>  > THEN
>  > IF Uerror.errno = Uerror.EACCES OR
>  > Uerror.errno = Uerror.EAGAIN THEN
>  > RETURN FALSE
>  > END;
>  > OSErrorPosix.Raise()
>  > END;
>  > RETURN TRUE
>  > END FilePartLock;
>  >
>  >
>  >
>  > Regards,
>  >
>  > Patrick