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>

4 files changed, 124 insertions, 3 deletions

diff --git a/libglusterfs/src/Makefile.am b/libglusterfs/src/Makefile.am
index b1a8536877d..8934b35f2d8 100644
--- a/libglusterfs/src/Makefile.am
+++ b/libglusterfs/src/Makefile.am
@@ -26,7 +26,7 @@ libglusterfs_la_SOURCES = dict.c xlator.c logging.c \
 	graph-print.c trie.c run.c options.c fd-lk.c circ-buff.c \
 	event-history.c gidcache.c ctx.c client_t.c event-poll.c event-epoll.c \
 	$(CONTRIBDIR)/libgen/basename_r.c $(CONTRIBDIR)/libgen/dirname_r.c \
-	$(CONTRIBDIR)/stdlib/gf_mkostemp.c
+	$(CONTRIBDIR)/stdlib/gf_mkostemp.c strfd.c
 
 
 nodist_libglusterfs_la_SOURCES = y.tab.c graph.lex.c gf-error-codes.h
@@ -43,7 +43,7 @@ noinst_HEADERS = common-utils.h defaults.h dict.h glusterfs.h hashfn.h timespec.
 	$(CONTRIB_BUILDDIR)/uuid/uuid_types.h syncop.h graph-utils.h trie.h \
 	run.h options.h lkowner.h fd-lk.h circ-buff.h event-history.h \
 	gidcache.h client_t.h glusterfs-acl.h glfs-message-id.h \
-	template-component-messages.h
+	template-component-messages.h strfd.h
 
 EXTRA_DIST = graph.l graph.y
 
diff --git a/libglusterfs/src/mem-types.h b/libglusterfs/src/mem-types.h
index c01dfa75e90..c07d1387be3 100644
--- a/libglusterfs/src/mem-types.h
+++ b/libglusterfs/src/mem-types.h
@@ -122,6 +122,8 @@ enum gf_common_mem_types_ {
         gf_common_mt_uuid_t               = 106,
         gf_common_mt_mgmt_v3_lock_obj_t   = 107,
         gf_common_mt_txn_opinfo_obj_t     = 108,
-        gf_common_mt_end                  = 109
+	gf_common_mt_strfd_t              = 109,
+	gf_common_mt_strfd_data_t         = 110,
+        gf_common_mt_end
 };
 #endif
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;
+}
+
diff --git a/libglusterfs/src/strfd.h b/libglusterfs/src/strfd.h
new file mode 100644
index 00000000000..e386c8432e4
--- /dev/null
+++ b/libglusterfs/src/strfd.h
@@ -0,0 +1,28 @@
+/*
+   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 _STRFD_H
+#define _STRFD_H
+
+typedef struct {
+	void *data;
+	size_t alloc_size;
+	size_t size;
+	off_t pos;
+} strfd_t;
+
+strfd_t *strfd_open();
+
+int strprintf(strfd_t *strfd, const char *fmt, ...)
+	__attribute__ ((__format__ (__printf__, 2, 3)));
+
+int strfd_close(strfd_t *strfd);
+
+#endif