Add an implementation based on tedu@'s design of fmemopen(3) and

open_memstream(3) so they can be polished in-tree.

One of the manpages comes from NetBSD with some tweaks.

Prodded by espie@, krw@, guenther@

1 files changed, 166 insertions, 0 deletions

diff --git a/lib/libc/stdio/open_memstream.c b/lib/libc/stdio/open_memstream.c
new file mode 100644
index 00000000000..48ae2900f6d
--- /dev/null
+++ b/lib/libc/stdio/open_memstream.c
@@ -0,0 +1,166 @@
+/*	$OpenBSD: open_memstream.c,v 1.1 2013/01/01 17:41:13 mpi Exp $	*/
+/*
+ * Copyright (c) 2011 Martin Pieuchot <mpi@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "local.h"
+
+struct state {
+	char		 *string;	/* actual stream */
+	char		**pbuf;		/* point to the stream */
+	size_t		 *psize;	/* point to min(pos, len) */
+	size_t		  pos;		/* current position */
+	size_t		  size;		/* allocated size */
+	size_t		  len;		/* length of the data */
+};
+
+static int
+memstream_write(void *v, const char *b, int l)
+{
+	struct state	*st = v;
+	int		 i;
+	char		*p;
+
+	if (st->pos + l >= st->size) {
+		/* 1.6 is (very) close to the golden ratio. */
+		size_t	sz = st->size * 8 / 5;
+
+		if (sz < st->pos + l + 1)
+			sz = st->pos + l + 1;
+		p = realloc(st->string, sz);
+		if (!p)
+			return (-1);
+		bzero(p + st->size, sz - st->size);
+		*st->pbuf = st->string = p;
+		st->size = sz;
+	}
+
+	for (i = 0; i < l; i++)
+		st->string[st->pos + i] = b[i];
+	st->pos += i;
+
+	if (st->pos > st->len) {
+		st->len = st->pos;
+		st->string[st->len] = '\0';
+	}
+
+	*st->psize = st->pos;
+
+	return (i);
+}
+
+static fpos_t
+memstream_seek(void *v, fpos_t pos, int w)
+{
+	struct state	*st = v;
+	char		*p;
+
+	switch (w) {
+	case SEEK_SET:
+		break;
+	case SEEK_CUR:
+		pos += st->pos;
+		break;
+	case SEEK_END:
+		pos += st->len;
+		break;
+	default:
+		errno = EINVAL;
+		return (-1);
+	}
+
+	if (pos < 0)
+		return (-1);
+
+	st->pos = pos;
+
+	if (st->pos < st->len)
+		*st->psize = st->pos;
+	else
+		*st->psize = st->len;
+
+	return (pos);
+}
+
+static int
+memstream_close(void *v)
+{
+	struct state	*st = v;
+	char		*p;
+#define MIN(x, y) (((x) < (y)) ? (x) : (y))
+
+	*st->psize = MIN(st->pos, st->len);
+	*st->pbuf = st->string;
+
+	free(st);
+
+	return (0);
+#undef MIN
+}
+
+FILE *
+open_memstream(char **pbuf, size_t *psize)
+{
+	struct state	*st;
+	FILE		*fp;
+
+	if (pbuf == NULL || psize == NULL) {
+		errno = EINVAL;
+		return (NULL);
+	}
+
+	if ((st = malloc(sizeof(*st))) == NULL)
+		return (NULL);
+
+	if ((fp = __sfp()) == NULL) {
+		free(st);
+		return (NULL);
+	}
+
+	if (*psize < 128)
+		st->size = 128;
+	else
+		st->size = *psize;
+
+	if ((st->string = calloc(1, st->size)) == NULL) {
+		free(st);
+		fp->_flags = 0;
+		return (NULL);
+	}
+
+	*st->string = '\0';
+	st->pos = 0;
+	st->len = 0;
+	st->pbuf = pbuf;
+	st->psize = psize;
+
+	*pbuf = st->string;
+	*psize = st->len;
+
+	fp->_flags = __SWR;
+	fp->_file = -1;
+	fp->_cookie = st;
+	fp->_read = NULL;
+	fp->_write = memstream_write;
+	fp->_seek = memstream_seek;
+	fp->_close = memstream_close;
+
+	return (fp);
+}