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Re: stdio patch


Great. Patch checked in.

-- Jeff J.

Eric Blake wrote:
Jeff, this patch is based on what you sent me privately, plus a typo fix for SEEK_SET instead of SEEK_CUR, and the additional fix to keep fp->offset up-to-
date when __SOFF. With it, I now get the POSIX-mandated behavior on cygwin for:


$ echo 1 2 3 | tr ' ' '\n' > file
$ (sed -n 1q; cat) < file
2
3


2006-12-14 Jeff Johnston <jjohnstn@redhat.com> and Eric Blake <ebb9@byu.net>

        * libc/stdio/fflush.c (fflush): On seekable streams, always flush
        read but unused data.
        * libc/stdio/fclose.c (_fclose_r): Always flush streams, since
        even read streams may have side effects that must happen.

Index: libc/stdio/fclose.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/stdio/fclose.c,v
retrieving revision 1.11
diff -u -p -r1.11 fclose.c
--- libc/stdio/fclose.c 26 Sep 2006 21:22:19 -0000 1.11
+++ libc/stdio/fclose.c 14 Dec 2006 21:22:44 -0000
@@ -86,7 +86,10 @@ _DEFUN(_fclose_r, (rptr, fp),
__sfp_lock_release ();
return (0);
}
- r = fp->_flags & __SWR ? fflush (fp) : 0;
+ /* Unconditionally flush to allow special handling for seekable read
+ files to reposition file to last byte processed as opposed to
+ last byte read ahead into the buffer. */
+ r = fflush (fp);
if (fp->_close != NULL && (*fp->_close) (fp->_cookie) < 0)
r = EOF;
if (fp->_flags & __SMBF)
Index: libc/stdio/fflush.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/stdio/fflush.c,v
retrieving revision 1.7
diff -u -p -r1.7 fflush.c
--- libc/stdio/fflush.c 26 Sep 2006 21:22:19 -0000 1.7
+++ libc/stdio/fflush.c 14 Dec 2006 21:22:44 -0000
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1990 The Regents of the University of California.
+ * Copyright (c) 1990, 2006 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
@@ -74,10 +74,56 @@ _DEFUN(fflush, (fp),
t = fp->_flags;
if ((t & __SWR) == 0)
{
+ _fpos_t _EXFUN((*seekfn), (_PTR, _fpos_t, int));
+
/* For a read stream, an fflush causes the next seek to be
unoptimized (i.e. forces a system-level seek). This conforms
to the POSIX and SUSv3 standards. */
fp->_flags |= __SNPT;
+
+ /* For a seekable stream with buffered read characters, we will attempt
+ a seek to the current position now. A subsequent read will then get
+ the next byte from the file rather than the buffer. This conforms
+ to the POSIX and SUSv3 standards. Note that the standards allow
+ this seek to be deferred until necessary, but we choose to do it here
+ to make the change simpler, more contained, and less likely
+ to miss a code scenario. */
+ if ((fp->_r > 0 || fp->_ur > 0) && (seekfn = fp->_seek) != NULL)
+ {
+ _fpos_t curoff;
+
+ /* Get the physical position we are at in the file. */
+ if (fp->_flags & __SOFF)
+ curoff = fp->_offset;
+ else
+ {
+ /* We don't know current physical offset, so ask for it. */
+ curoff = (*seekfn) (fp->_cookie, (_fpos_t) 0, SEEK_CUR);
+ if (curoff == -1L)
+ {
+ _funlockfile (fp);
+ return 0;
+ }
+ }
+ if (fp->_flags & __SRD)
+ {
+ /* Current offset is at end of buffer. Compensate for
+ characters not yet read. */
+ curoff -= fp->_r;
+ if (HASUB (fp))
+ curoff -= fp->_ur;
+ }
+ /* Now physically seek to after byte last read. */
+ if ((*seekfn)(fp->_cookie, curoff, SEEK_SET) != -1)
+ {
+ /* Seek successful. We can clear read buffer now. */
+ fp->_flags &= ~__SNPT;
+ fp->_r = 0;
+ fp->_p = fp->_bf._base;
+ if (fp->_flags & __SOFF)
+ fp->_offset = curoff;
+ }
+ } _funlockfile (fp);
return 0;
}





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