strfd: memory backed file descriptor

A file descriptor like interface, backed by a string, on which
fprintf() like IO can be performed. Internally the backing string
is grown on demand.

Useful in generating virtual file content on the fly (used in meta)

Change-Id: I60d8751c4c750f3f06aa454a4ccd9909b3ac8ac7
BUG: 1089216
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-on: http://review.gluster.org/7508
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>

1 files changed, 91 insertions, 0 deletions

diff --git a/libglusterfs/src/strfd.c b/libglusterfs/src/strfd.c
new file mode 100644
index 00000000000..8c97670d4dd
--- /dev/null
+++ b/libglusterfs/src/strfd.c
@@ -0,0 +1,91 @@
+/*
+   Copyright (c) 2014 Red Hat, Inc. <http://www.redhat.com>
+   This file is part of GlusterFS.
+
+   This file is licensed to you under your choice of the GNU Lesser
+   General Public License, version 3 or any later version (LGPLv3 or
+   later), or the GNU General Public License, version 2 (GPLv2), in all
+   cases as published by the Free Software Foundation.
+*/
+
+#ifndef _CONFIG_H
+#define _CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdarg.h>
+
+#include "mem-types.h"
+#include "mem-pool.h"
+#include "strfd.h"
+#include "common-utils.h"
+
+
+strfd_t *
+strfd_open ()
+{
+	strfd_t *strfd = NULL;
+
+	strfd = GF_CALLOC(1, sizeof(*strfd), gf_common_mt_strfd_t);
+
+	return strfd;
+}
+
+
+int
+strprintf (strfd_t *strfd, const char *fmt, ...)
+{
+	va_list ap;
+	char *str = NULL;
+	int size = 0;
+
+	va_start (ap, fmt);
+
+	size = vasprintf (&str, fmt, ap);
+
+	if (size < 0)
+		return size;
+
+	if (!strfd->alloc_size) {
+		strfd->data = GF_CALLOC (max(size + 1, 4096), 1,
+					 gf_common_mt_strfd_data_t);
+		if (!strfd->data) {
+			free (str); /* NOT GF_FREE */
+			return -1;
+		}
+		strfd->alloc_size = max(size + 1, 4096);
+	}
+
+	if (strfd->alloc_size <= (strfd->size + size)) {
+		char *tmp_ptr = NULL;
+		int new_size = max ((strfd->alloc_size * 2),
+				    gf_roundup_next_power_of_two (strfd->size + size + 1));
+		tmp_ptr = GF_REALLOC (strfd->data, new_size);
+		if (!tmp_ptr) {
+			free (str); /* NOT GF_FREE */
+			return -1;
+		}
+		strfd->alloc_size = new_size;
+		strfd->data = tmp_ptr;
+	}
+
+	// Copy the trailing '\0', but do not account for it in ->size.
+	// This allows safe use of strfd->data as a string.
+	memcpy (strfd->data + strfd->size, str, size + 1);
+	strfd->size += size;
+
+	free (str); /* NOT GF_FREE */
+
+	return size;
+}
+
+
+int
+strfd_close (strfd_t *strfd)
+{
+	GF_FREE (strfd->data);
+	GF_FREE (strfd);
+
+	return 0;
+}
+