Hi Janne,
I have tried to answer your points in the attached patch.
> The unformatted sequential format part looks Ok, but the special files
> section is lacking. E.g. what about
>
> - The REWIND statement?
Not supported.
> - The ENDFILE statement?
Not supported.
> - ACCESS='stream' and the POS= specifier?
Only for inpquire.
> - ACCESS='direct'? (I suspect this should work for
> pipes/FIFO's/terminals in case REC= numbers are sequential, but is
> that a guarantee we want to make?)
I have not listed this as supported in the patch.
> - Special files which are special in other ways. E.g. block special
> files tend to allow seeking, but IO must be block aligned.
Also listed as not supported; I suspect buffering could cause grief
there.
I have updated an attached patch. OK?
Thomas
2013-08-30 Thomas Koenig <tkoe...@gcc.gnu.org>
PR fortran/30162
* gfortran.texi: Document unformatted sequential file format
and I/O with special files.
ig25@linux-fd1f:~/Krempel/Unformatt
Index: gfortran.texi
===================================================================
--- gfortran.texi (Revision 201996)
+++ gfortran.texi (Arbeitskopie)
@@ -1121,6 +1121,8 @@
* Internal representation of LOGICAL variables::
* Thread-safety of the runtime library::
* Data consistency and durability::
+* Unformatted sequential file format::
+* I/O with special files::
@end menu
@@ -1291,7 +1293,85 @@
releasing @code{fcntl} file locks, if the server supports them, will
also force cache validation and flushing dirty data and metadata.
+@node Unformatted sequential file format
+@section Unformatted sequential file format
+@cindex unformatted sequential files
+@cindex record marker
+@cindex subrecord
+Unformatted sequential files are stored using record markers. Each
+full record consists of a leading record marker, the data written
+by the user program, and a trailing record marker. The record markers
+are four-byte integers by default, and eight-byte integers if the
+@option{-fmax-subrecord-length=8} option is in effect. Each record
+marker contains the number of bytes of data in the record.
+
+The maximum number of bytes of user data in a record is 2147483639 for
+a four-byte record marker. If this is exceeded, a record is split into
+subrecords. Each subrecord also has a leading and a trailing record
+marker. If the leading record marker contains a negative number, the
+number of user data bytes in the subrecord equals the absolute value
+of this number, and another subrecord follows the current one. If the
+trailing record marker contains a negative number, then the number of
+bytes of user data equals the absolute value of that number, and there
+is a preceding subrecord.
+
+The format for unformatted sequential data can be duplicated using
+unformatted stream, as shown in this example program:
+
+@smallexample
+program main
+ implicit none
+ integer :: i
+ real, dimension(10) :: a, b
+ call random_number(a)
+ open (10,file='test.dat',form='unformatted',access='stream')
+ inquire (iolength=i) a
+ write (10) i, a, i
+ close (10)
+ open (10,file='test.dat',form='unformatted')
+ read (10) b
+ if (all (a == b)) print *,'success!'
+end program main
+@end smallexample
+
+@node I/O with special files
+@section I/O with special files
+@cindex special files
+@cindex pipes
+@cindex FIFO
+@cindex terminal devices
+@cindex block devices
+@cindex sockets
+@cindex BACKSPACE
+@cindex REWIND
+@cindex ENDFILE
+
+Special character-oriented files such as pipes, FIFOs or terminal
+devices are supported only for the following types of file access:
+
+@itemize
+
+@item Formatted sequential
+
+@item Formatted stream
+
+@item Unformatted stream
+
+@end itemize
+
+For special files, the @code{POS=} specifier for stream I/O can only
+be used in @code{INQUIRE} statements.
+
+Unformatted sequential file access is @emph{not} supported for special
+files. If necessary, it can be simulated using unformatted stream,
+see @ref{Unformatted sequential file format}.
+
+I/O to and from block devices are also not supported.
+
+@code{BACKSPACE}, @code{REWIND} and @code{ENDFILE} are not supported
+for special files.
+
@c ---------------------------------------------------------------------
@c Extensions
@c ---------------------------------------------------------------------
