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

1 files changed, 182 insertions, 0 deletions

diff --git a/lib/libc/stdio/fmemopen.c b/lib/libc/stdio/fmemopen.c
new file mode 100644
index 0000000..2cdf324
--- /dev/null
+++ b/lib/libc/stdio/fmemopen.c
@@ -0,0 +1,182 @@
+/*-
+Copyright (C) 2013 Pietro Cerutti <gahr@FreeBSD.org>
+
+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);
+}