util: add sprintf_alloc() function

Like sprintf() with automatic buffer allocation.

This should help to avoid fixed-size buffers in
non-performance-sensitive code that formats strings.

Change-Id: I35209ae84014ed5daf41baa5b03af8a5f6b02b8e
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>

examples/nvme/perf/perf.c

@@ -46,6 +46,7 @@
 
 #include "spdk/nvme.h"
 #include "spdk/pci.h"
+#include "spdk/string.h"
 
 struct ctrlr_entry {
 	struct nvme_controller	*ctrlr;
@@ -528,7 +529,7 @@ unregister_controllers(void)
 	}
 }
 
-static const char *ealargs[] = {
+static char *ealargs[] = {
 	"perf",
 	"-c 0x1", /* This must be the second parameter. It is overwritten by index in main(). */
 	"-n 4",
@@ -537,7 +538,6 @@ static const char *ealargs[] = {
 int main(int argc, char **argv)
 {
 	int rc;
-	char core_mask_arg[128];
 	struct worker_thread *worker;
 
 	rc = parse_args(argc, argv);
@@ -545,13 +545,12 @@ int main(int argc, char **argv)
 		return rc;
 	}
 
-	if (g_core_mask != NULL) {
+	ealargs[1] = sprintf_alloc("-c %s", g_core_mask ? g_core_mask : "0x1");
-		snprintf(core_mask_arg, sizeof(core_mask_arg), "-c %s", g_core_mask);
+
-		ealargs[1] = strdup(core_mask_arg);
+	rc = rte_eal_init(sizeof(ealargs) / sizeof(ealargs[0]), ealargs);
-	}
+
+	free(ealargs[1]);
 
-	rc = rte_eal_init(sizeof(ealargs) / sizeof(ealargs[0]),
-			  (char **)(void *)(uintptr_t)ealargs);
 	if (rc < 0) {
 		fprintf(stderr, "could not initialize dpdk\n");
 		return 1;

include/spdk/string.h

@@ -0,0 +1,46 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2015 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 THE COPYRIGHT
+ *   OWNER 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.
+ */
+
+#ifndef SPDK_STRING_H
+#define SPDK_STRING_H
+
+/**
+ * sprintf with automatic buffer allocation.
+ *
+ * The return value is the formatted string,
+ * which should be passed to free() when no longer needed,
+ * or NULL on failure.
+ */
+char *sprintf_alloc(const char *format, ...) __attribute__((format(printf, 1, 2)));
+
+#endif

lib/util/Makefile

@@ -35,7 +35,7 @@ include $(SPDK_ROOT_DIR)/mk/spdk.common.mk
 
 CFLAGS += $(DPDK_INC)
 
-C_SRCS = pci.c
+C_SRCS = string.c pci.c
 
 C_OBJS := $(patsubst %.c,%.o,$(C_SRCS))
 

lib/util/string.c

@@ -0,0 +1,82 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2015 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 THE COPYRIGHT
+ *   OWNER 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 <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "spdk/string.h"
+
+char *
+sprintf_alloc(const char *format, ...)
+{
+	va_list args;
+	char *buf;
+	size_t bufsize;
+	int rc;
+
+	/* Try with a small buffer first. */
+	bufsize = 32;
+
+	/* Limit maximum buffer size to something reasonable so we don't loop forever. */
+	while (bufsize <= 1024 * 1024) {
+		buf = malloc(bufsize);
+		if (buf == NULL) {
+			return NULL;
+		}
+
+		va_start(args, format);
+		rc = vsnprintf(buf, bufsize, format, args);
+		va_end(args);
+
+		/*
+		 * If vsnprintf() returned a count within our current buffer size, we are done.
+		 * The count does not include the \0 terminator, so rc == bufsize is not OK.
+		 */
+		if (rc >= 0 && rc < bufsize) {
+			return buf;
+		}
+
+		/*
+		 * vsnprintf() should return the required space, but some libc versions do not
+		 * implement this correctly, so just double the buffer size and try again.
+		 *
+		 * We don't need the data in buf, so rather than realloc(), use free() and malloc()
+		 * again to avoid a copy.
+		 */
+		free(buf);
+		bufsize *= 2;
+	}
+
+	return NULL;
+}