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From: Marcel Moolenaar <marcel@FreeBSD.org>
Date: Fri, 21 Nov 2014 19:13:55 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-user@freebsd.org
Subject: svn commit: r274809 - user/marcel/libvdsk/libvdsk
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Author: marcel
Date: Fri Nov 21 19:13:54 2014
New Revision: 274809
URL: https://svnweb.freebsd.org/changeset/base/274809

Log:
  Improve vdsk_open():
  1.  Use calloc(3) instead of malloc(3) so that the user context is
      always pre-initialized.
  2.  Wrap the sequence of steps in a `do { ... } while (0)' block so
      that we can use break to exit. Introduce ctx as the variable to
      return and use it to determine success or failure.
  
  With a single entry and a single exit, we can more easily add some
  kind of tracing or logging in the future.

Modified:
  user/marcel/libvdsk/libvdsk/vdsk.c

Modified: user/marcel/libvdsk/libvdsk/vdsk.c
==============================================================================
--- user/marcel/libvdsk/libvdsk/vdsk.c	Fri Nov 21 18:35:50 2014	(r274808)
+++ user/marcel/libvdsk/libvdsk/vdsk.c	Fri Nov 21 19:13:54 2014	(r274809)
@@ -52,37 +52,50 @@ vdskctx
 vdsk_open(const char *path, int flags, size_t size)
 {
 	struct stat sb;
+	vdskctx ctx;
 	struct vdsk *vdsk;
 
-	size += sizeof(struct vdsk);
-	vdsk = malloc(size);
-	if (vdsk == NULL)
-		return (NULL);
-
-	vdsk->fd = open(path, flags);
-	if (vdsk->fd == -1) {
-		free(vdsk);
-		return (NULL);
-	}
+	ctx = NULL;
 
-	if (fstat(vdsk->fd, &sb) == -1) {
-		close(vdsk->fd);
-		free(vdsk);
-		return (NULL);
-	}
+	do {
+		size += sizeof(struct vdsk);
+		vdsk = calloc(1, size);
+		if (vdsk == NULL)
+			break;
+
+		vdsk->fd = open(path, flags);
+		if (vdsk->fd == -1)
+			break;
+
+		if (fstat(vdsk->fd, &sb) == -1)
+			break;
+
+		if (S_ISCHR(sb.st_mode)) {
+			if (ioctl(vdsk->fd, DIOCGMEDIASIZE,
+			    &vdsk->capacity) < 0)
+				break;
+			if (ioctl(vdsk->fd, DIOCGSECTORSIZE,
+			    &vdsk->sectorsize) < 0)
+				break;
+		} else {
+			vdsk->capacity = sb.st_size;
+			vdsk->sectorsize = DEV_BSIZE;
+		}
 
-	if (S_ISCHR(sb.st_mode)) {
-		if (ioctl(vdsk->fd, DIOCGMEDIASIZE, &vdsk->capacity) < 0 ||
-		    ioctl(vdsk->fd, DIOCGSECTORSIZE, &vdsk->sectorsize) < 0) {
-			close(vdsk->fd);
+		/* Complete... */
+		ctx = vdsk + 1;
+	} while (0);
+
+	if (ctx == NULL) {
+		if (vdsk != NULL) {
+			if (vdsk->fd != -1)
+				close(vdsk->fd);
 			free(vdsk);
-			return (NULL);
+			vdsk = NULL;
 		}
-	} else {
-		vdsk->capacity = sb.st_size;
-		vdsk->sectorsize = DEV_BSIZE;
 	}
-	return (vdsk + 1);
+
+	return (ctx);
 }
 
 int