Add fdclose(3) function.

This function is equivalent to fclose(3) function except that it
does not close the underlying file descriptor.
fdclose(3) is step forward to make FILE structure private.

Reviewed by:	wblock, jilles, jhb, pjd
Approved by:	pjd (mentor)
Differential Revision:	https://reviews.freebsd.org/D2697

include/stdio.h

@@ -396,6 +396,7 @@ int	 (dprintf)(int, const char * __restrict, ...);
 int	 asprintf(char **, const char *, ...) __printflike(2, 3);
 char	*ctermid_r(char *);
 void	 fcloseall(void);
+int	 fdclose(FILE *, int *);
 char	*fgetln(FILE *, size_t *);
 const char *fmtcheck(const char *, const char *) __format_arg(2);
 int	 fpurge(FILE *);

lib/libc/stdio/Symbol.map

@@ -162,6 +162,10 @@ FBSD_1.3 {
 	mkostemps;
 };
 
+FBSD_1.4 {
+	fdclose;
+};
+
 FBSDprivate_1.0 {
 	_flockfile;
 	_flockfile_debug_stub;

lib/libc/stdio/fclose.3

@@ -1,5 +1,6 @@
-.\" Copyright (c) 1990, 1991, 1993
-.\"	The Regents of the University of California.  All rights reserved.
+.\" Copyright (c) 1990, 1991, 1993 The Regents of the University of California.
+.\" Copyright (c) 2015 Mariusz Zaborski <oshogbo@FreeBSD.org>
+.\" All rights reserved.
 .\"
 .\" This code is derived from software contributed to Berkeley by
 .\" Chris Torek and the American National Standards Committee X3,
@@ -32,11 +33,12 @@
 .\"     @(#)fclose.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd April 22, 2006
+.Dd July 4, 2015
 .Dt FCLOSE 3
 .Os
 .Sh NAME
 .Nm fclose ,
+.Nm fdclose ,
 .Nm fcloseall
 .Nd close a stream
 .Sh LIBRARY
@@ -45,6 +47,8 @@
 .In stdio.h
 .Ft int
 .Fn fclose "FILE *stream"
+.Ft int
+.Fn fdclose "FILE *stream" "int *fdp"
 .Ft void
 .Fn fcloseall void
 .Sh DESCRIPTION
@@ -59,36 +63,77 @@ first, using
 .Xr fflush 3 .
 .Pp
 The
+.Fn fdclose
+function is equivalent to
+.Fn fclose
+except that it does not close the underlying file descriptor.
+If
+.Fa fdp
+is not
+.Dv NULL ,
+the file descriptor will be written to it.
+If the
+.Fa fdp
+argument will be different then NULL the file descriptor will be returned in it,
+If the stream does not have an associated file descriptor,
+.Fa fdp
+will be set to -1.
+This type of stream is created with functions such as
+.Xr fmemopen 3 ,
+.Xr funopen 3 ,
+or
+.Xr open_memstream 3 .
+.Pp
+The
 .Fn fcloseall
 function calls
 .Fn fclose
 on all open streams.
 .Sh RETURN VALUES
-Upon successful completion 0 is returned.
+.Fn fcloseall
+does not return a value.
+.Pp
+Upon successful completion the
+.Fn fclose
+and
+.Fn fdclose
+functions return 0.
 Otherwise,
 .Dv EOF
 is returned and the global variable
 .Va errno
 is set to indicate the error.
-In either case no further access to the stream is possible.
 .Sh ERRORS
+.Fn fdclose
+fails if:
+.Bl -tag -width Er
+.It Bq Er EOPNOTSUPP
+The stream does not have an associated file descriptor.
+.El
+.Pp
 The
 .Fn fclose
-function
-may also fail and set
+and
+.Fn fdclose
+functions may also fail and set
 .Va errno
-for any of the errors specified for the routines
-.Xr close 2
-or
+for any of the errors specified for
 .Xr fflush 3 .
+.Pp
+The
+.Fn fclose
+function may also fail and set errno for any of the errors specified for
+.Xr close 2 .
 .Sh NOTES
 The
 .Fn fclose
-function
-does not handle NULL arguments; they will result in a segmentation
-violation.
-This is intentional - it makes it easier to make sure programs written
-under
+and
+.Fn fdclose
+functions do not handle NULL arguments in the
+.Fa stream
+variable; this will result in a segmentation violation.
+This is intentional.
+It makes it easier to make sure programs written under
 .Fx
 are bug free.
 This behaviour is an implementation detail, and programs should not
@@ -104,8 +149,13 @@ The
 function
 conforms to
 .St -isoC .
-.Pp
+.Sh HISTORY
 The
 .Fn fcloseall
 function first appeared in
 .Fx 7.0 .
+.Pp
+The
+.Fn fdclose
+function first appeared in
+.Fx 11.0 .

lib/libc/stdio/fclose.c

@@ -1,6 +1,7 @@
 /*-
- * Copyright (c) 1990, 1993
- *	The Regents of the University of California.  All rights reserved.
+ * Copyright (c) 1990, 1993 The Regents of the University of California.
+ * Copyright (c) 2013 Mariusz Zaborski <oshogbo@FreeBSD.org>
+ * All rights reserved.
  *
  * This code is derived from software contributed to Berkeley by
  * Chris Torek.
@@ -38,6 +39,7 @@ __FBSDID("$FreeBSD$");
 
 #include "namespace.h"
 #include <errno.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include "un-namespace.h"
@@ -45,19 +47,17 @@ __FBSDID("$FreeBSD$");
 #include "libc_private.h"
 #include "local.h"
 
-int
-fclose(FILE *fp)
+static int
+cleanfile(FILE *fp, bool c)
 {
 	int r;
 
-	if (fp->_flags == 0) {	/* not open! */
-		errno = EBADF;
-		return (EOF);
-	}
-	FLOCKFILE(fp);
 	r = fp->_flags & __SWR ? __sflush(fp) : 0;
-	if (fp->_close != NULL && (*fp->_close)(fp->_cookie) < 0)
-		r = EOF;
+	if (c) {
+		if (fp->_close != NULL && (*fp->_close)(fp->_cookie) < 0)
+			r = EOF;
+	}
+
 	if (fp->_flags & __SMBF)
 		free((char *)fp->_bf._base);
 	if (HASUB(fp))
@@ -80,6 +80,59 @@ fclose(FILE *fp)
 	STDIO_THREAD_LOCK();
 	fp->_flags = 0;		/* Release this FILE for reuse. */
 	STDIO_THREAD_UNLOCK();
-	FUNLOCKFILE(fp);
+
+	return (r);
+}
+
+int
+fdclose(FILE *fp, int *fdp)
+{
+	int r, err;
+
+	if (fdp != NULL)
+		*fdp = -1;
+
+	if (fp->_flags == 0) {	/* not open! */
+		errno = EBADF;
+		return (EOF);
+	}
+
+	FLOCKFILE(fp);
+	r = 0;
+	if (fp->_close != __sclose) {
+		r = EOF;
+		errno = EOPNOTSUPP;
+	} else if (fp->_file < 0) {
+		r = EOF;
+		errno = EBADF;
+	}
+	if (r == EOF) {
+		err = errno;
+		(void)cleanfile(fp, true);
+		errno = err;
+	} else {
+		if (fdp != NULL)
+			*fdp = fp->_file;
+		r = cleanfile(fp, false);
+	}
+	FUNLOCKFILE(fp);
+
+	return (r);
+}
+
+int
+fclose(FILE *fp)
+{
+	int r;
+
+	if (fp->_flags == 0) {	/* not open! */
+		errno = EBADF;
+		return (EOF);
+	}
+
+	FLOCKFILE(fp);
+	r = cleanfile(fp, true);
+	FUNLOCKFILE(fp);
+
 	return (r);
 }