Add fmemopen(3), an interface to get a FILE * from a buffer in memory…

…, along

with the respective regression test.
See http://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html

Reviewed by:	cognet
Approved by:	cognet

include/stdio.h

@@ -343,6 +343,7 @@ char	*tempnam(const char *, const char *);
 #endif
 
 #if __BSD_VISIBLE || __POSIX_VISIBLE >= 200809
+FILE	*fmemopen(void * __restrict, size_t, const char * __restrict);
 ssize_t	 getdelim(char ** __restrict, size_t * __restrict, int,
 	    FILE * __restrict);
 int	 renameat(int, const char *, int, const char *);

lib/libc/stdio/Makefile.inc

@@ -8,7 +8,8 @@ SRCS+=	_flock_stub.c asprintf.c clrerr.c dprintf.c \
 	fclose.c fcloseall.c fdopen.c \
 	feof.c ferror.c fflush.c fgetc.c fgetln.c fgetpos.c fgets.c fgetwc.c \
 	fgetwln.c fgetws.c \
-	fileno.c findfp.c flags.c fopen.c fprintf.c fpurge.c fputc.c fputs.c \
+	fileno.c findfp.c flags.c fmemopen.c fopen.c fprintf.c fpurge.c \
+	fputc.c fputs.c \
 	fputwc.c fputws.c fread.c freopen.c fscanf.c fseek.c fsetpos.c \
 	ftell.c funopen.c fvwrite.c fwalk.c fwide.c fwprintf.c fwscanf.c \
 	fwrite.c getc.c getchar.c getdelim.c getline.c \
@@ -48,7 +49,7 @@ MLINKS+=ferror.3 ferror_unlocked.3 \
 MLINKS+=fflush.3 fpurge.3
 MLINKS+=fgets.3 gets.3
 MLINKS+=flockfile.3 ftrylockfile.3 flockfile.3 funlockfile.3
-MLINKS+=fopen.3 fdopen.3 fopen.3 freopen.3
+MLINKS+=fopen.3 fdopen.3 fopen.3 freopen.3 fopen.3 fmemopen.3
 MLINKS+=fputs.3 puts.3
 MLINKS+=fread.3 fwrite.3
 MLINKS+=fseek.3 fgetpos.3 fseek.3 fseeko.3 fseek.3 fsetpos.3 fseek.3 ftell.3 \

lib/libc/stdio/Symbol.map

@@ -155,6 +155,7 @@ FBSD_1.3 {
 	getwchar_l;
 	putwc_l;
 	putwchar_l;
+	fmemopen;
 };
 
 FBSDprivate_1.0 {

lib/libc/stdio/fmemopen.c

@@ -0,0 +1,182 @@
+/*-
+Copyright (C) 2013 Pietro Cerutti <[email protected]>
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
+*/
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+struct __fmemopen_cookie
+{
+	char *buf;	/* pointer to the memory region */
+	char  own;	/* did we allocate the buffer ourselves? */
+	long  len;	/* buffer length in bytes */
+	long  off;	/* current offset into the buffer */
+};
+
+static int	fmemopen_read  (void *cookie, char *buf, int nbytes);
+static int	fmemopen_write (void *cookie, const char *buf, int nbytes);
+static fpos_t	fmemopen_seek  (void *cookie, fpos_t offset, int whence);
+static int	fmemopen_close (void *cookie);
+
+FILE *
+fmemopen (void * __restrict buf, size_t size, const char * __restrict mode)
+{
+	/* allocate cookie */
+	struct __fmemopen_cookie *ck = malloc (sizeof (struct __fmemopen_cookie));
+	if (ck == NULL) {
+		errno = ENOMEM;
+		return (NULL);
+	}
+
+	ck->off = 0;
+	ck->len = size;
+
+	/* do we have to allocate the buffer ourselves? */
+	ck->own = ((ck->buf = buf) == NULL);
+	if (ck->own) {
+		ck->buf = malloc (size);
+		if (ck->buf == NULL) {
+			free (ck);
+			errno = ENOMEM;
+			return (NULL);
+		}
+		ck->buf[0] = '\0';
+	}
+
+	if (mode[0] == 'a')
+		ck->off = strnlen(ck->buf, ck->len);
+
+	/* actuall wrapper */
+	FILE *f = funopen ((void *)ck, fmemopen_read, fmemopen_write,
+	    fmemopen_seek, fmemopen_close);
+
+	if (f == NULL) {
+		if (ck->own)
+			free (ck->buf);
+		free (ck);
+		return (NULL);
+	}
+
+	/* turn off buffering, so a write past the end of the buffer
+	 * correctly returns a short object count */
+	setvbuf (f, (char *) NULL, _IONBF, 0);
+
+	return (f);
+}
+
+static int
+fmemopen_read (void *cookie, char *buf, int nbytes)
+{
+	struct __fmemopen_cookie *ck = cookie;
+
+	if (nbytes > ck->len - ck->off)
+		nbytes = ck->len - ck->off;
+
+	if (nbytes == 0)
+		return (0);
+
+	memcpy (buf, ck->buf + ck->off, nbytes);
+
+	ck->off += nbytes;
+
+	return (nbytes);
+}
+
+static int
+fmemopen_write (void *cookie, const char *buf, int nbytes)
+{
+	struct __fmemopen_cookie *ck = cookie;
+
+	if (nbytes > ck->len - ck->off)
+		nbytes = ck->len - ck->off;
+
+	if (nbytes == 0)
+		return (0);
+
+	memcpy (ck->buf + ck->off, buf, nbytes);
+
+	ck->off += nbytes;
+
+	if (ck->off < ck->len && ck->buf[ck->off - 1] != '\0')
+		ck->buf[ck->off] = '\0';
+
+	return (nbytes);
+}
+
+static fpos_t
+fmemopen_seek (void *cookie, fpos_t offset, int whence)
+{
+	struct __fmemopen_cookie *ck = cookie;
+
+
+	switch (whence) {
+	case SEEK_SET:
+		if (offset > ck->len) {
+			errno = EINVAL;
+			return (-1);
+		}
+		ck->off = offset;
+		break;
+
+	case SEEK_CUR:
+		if (ck->off + offset > ck->len) {
+			errno = EINVAL;
+			return (-1);
+		}
+		ck->off += offset;
+		break;
+
+	case SEEK_END:
+		if (offset > 0 || -offset > ck->len) {
+			errno = EINVAL;
+			return (-1);
+		}
+		ck->off = ck->len + offset;
+		break;
+
+	default:
+		errno = EINVAL;
+		return (-1);
+	}
+
+	return (ck->off);
+}
+
+static int
+fmemopen_close (void *cookie)
+{
+	struct __fmemopen_cookie *ck = cookie;
+
+	if (ck->own)
+		free (ck->buf);
+
+	free (ck);
+
+	return (0);
+}

lib/libc/stdio/fopen.3

@@ -32,13 +32,14 @@
 .\"     @(#)fopen.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd November 30, 2012
+.Dd January 30, 2013
 .Dt FOPEN 3
 .Os
 .Sh NAME
 .Nm fopen ,
 .Nm fdopen ,
-.Nm freopen
+.Nm freopen ,
+.Nm fmemopen
 .Nd stream open functions
 .Sh LIBRARY
 .Lb libc
@@ -50,6 +51,8 @@
 .Fn fdopen "int fildes" "const char *mode"
 .Ft FILE *
 .Fn freopen "const char *path" "const char *mode" "FILE *stream"
+.Ft FILE *
+.Fn fmemopen "void *restrict *buf" "size_t size" "const char * restrict mode"
 .Sh DESCRIPTION
 The
 .Fn fopen
@@ -202,6 +205,29 @@ standard text stream
 .Dv ( stderr , stdin ,
 or
 .Dv stdout ) .
+.Pp
+The
+.Fn fmemopen
+function
+associates the buffer given by the
+.Fa buf
+and
+.Fa size
+arguments with a stream.
+The
+.Fa buf
+argument shall be either a null pointer or point to a buffer that
+is at least
+.Fa size
+bytes long.
+If a null pointer is specified as the
+.Fa buf
+argument,
+.Fn fmemopen
+shall allocate
+.Fa size
+bytes of memory. This buffer shall be automatically freed when the
+stream is closed.
 .Sh RETURN VALUES
 Upon successful completion
 .Fn fopen ,
@@ -225,16 +251,18 @@ argument
 to
 .Fn fopen ,
 .Fn fdopen ,
+.Fn freopen ,
 or
-.Fn freopen
+.Fn fmemopen
 was invalid.
 .El
 .Pp
 The
 .Fn fopen ,
-.Fn fdopen
-and
+.Fn fdopen ,
 .Fn freopen
+and
+.Fn fmemopen
 functions
 may also fail and set
 .Va errno
@@ -294,3 +322,8 @@ The
 .Dq Li e
 mode option does not conform to any standard
 but is also supported by glibc.
+The
+.Fn fmemopen
+function
+conforms to 
+.St -p1003.1-2008 .