From f72b184e3ec8161db914ee0a4cdc02e0216909c1 Mon Sep 17 00:00:00 2001
From: Zdenek Kabelac <zkabelac@redhat.com>
Date: Thu, 23 Feb 2012 18:05:12 +0000
Subject: [PATCH] Limit number of mem allocs and copies

If we have good enough glibc to return number of needed chars, do not
loop try to reach good size, but use this size directly for allocation,
saving also last strdup.

Since now we start with 16 bytes - skip buffer realloc for shorter string.
---
 WHATS_NEW_DM         |  1 +
 libdm/libdm-string.c | 32 ++++++++++++++++++--------------
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/WHATS_NEW_DM b/WHATS_NEW_DM
index 8f2071ada..cc4e79fcf 100644
--- a/WHATS_NEW_DM
+++ b/WHATS_NEW_DM
@@ -1,5 +1,6 @@
 Version 1.02.72 - 
 ====================================
+  Avoid memory reallocation for dm_asprintf.
 
 Version 1.02.71 - 20th February 2012
 ====================================
diff --git a/libdm/libdm-string.c b/libdm/libdm-string.c
index d9b444c1c..42efcf717 100644
--- a/libdm/libdm-string.c
+++ b/libdm/libdm-string.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2007 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2006-2012 Red Hat, Inc. All rights reserved.
  *
  * This file is part of the device-mapper userspace tools.
  *
@@ -131,7 +131,7 @@ const char *dm_basename(const char *path)
 
 int dm_asprintf(char **result, const char *format, ...)
 {
-	int n, ok = 0, size = 32;
+	int i, n, size = 16;
 	va_list ap;
 	char *buf = dm_malloc(size);
 
@@ -140,26 +140,30 @@ int dm_asprintf(char **result, const char *format, ...)
 	if (!buf)
 		return -1;
 
-	while (!ok) {
+	for (i = 0;; i++) {
 		va_start(ap, format);
 		n = vsnprintf(buf, size, format, ap);
 		va_end(ap);
 
 		if (0 <= n && n < size)
-			ok = 1;
-		else {
-			dm_free(buf);
-			size *= 2;
-			buf = dm_malloc(size);
-			if (!buf)
-				return -1;
-		}
+			break;
+
+		dm_free(buf);
+		/* Up to glibc 2.0.6 returns -1 */
+		size = (n < 0) ? size * 2 : n + 1;
+		if (!(buf = dm_malloc(size)))
+			return -1;
 	}
 
-	if (!(*result = dm_strdup(buf)))
-		n = -2; /* return -1 */
+	if (i > 1) {
+		/* Reallocating more then once? */
+		if (!(*result = dm_strdup(buf))) {
+			dm_free(buf);
+			return -1;
+		}
+	} else
+		*result = buf;
 
-	dm_free(buf);
 	return n + 1;
 }