vis

commit fcd06b3d31af9c149dc8b73efe12d1efee0b0179
parent 3ba0be3dd450744b6b9513603c9bd3d774fa67b4
Author: Marc André Tanner <mat@brain-dump.org>
Date:   Wed, 25 Apr 2018 19:22:18 +0200

text: use mkstemp(3) for temporary file creation in atomic saves

Instead of simply appending a tilde to the original file name, we now
create an unique temporary file based on the pattern `.filename.vis.XXXXXX`.

In case the file does not yet exist, we use 0666 & ~umask as permission,
(this should match the previous `open(2)` based behavior).

Diffstat:
M
text.c
 | 
31
+++++++++++++++++++++++++------
M
text.h
 | 
7
++++---

2 files changed, 29 insertions(+), 9 deletions(-)
diff --git a/text.c b/text.c
@@ -815,7 +815,8 @@ static bool preserve_selinux_context(int src, int dest) {
 	return true;
 }
 
-/* Create a new file named `filename~` and try to preserve all important
+/* Create a new file named `.filename.vis.XXXXXX` (where `XXXXXX` is a
+ * randomly generated, unique suffix) and try to preserve all important
  * meta data. After the file content has been written to this temporary
  * file, text_save_commit_atomic will atomically move it to  its final
  * (possibly already existing) destination using rename(2).
@@ -844,14 +845,32 @@ static bool text_save_begin_atomic(TextSave *ctx) {
 			goto err;
 	}
 
-	size_t namelen = strlen(ctx->filename) + 1 /* ~ */ + 1 /* \0 */;
-	if (!(ctx->tmpname = calloc(1, namelen)))
+	char suffix[] = ".vis.XXXXXX";
+	size_t len = strlen(ctx->filename) + sizeof("./.") + sizeof(suffix);
+	char *dir = strdup(ctx->filename);
+	char *base = strdup(ctx->filename);
+
+	if (!(ctx->tmpname = malloc(len)) || !dir || !base) {
+		free(dir);
+		free(base);
 		goto err;
-	snprintf(ctx->tmpname, namelen, "%s~", ctx->filename);
+	}
 
-	if ((ctx->fd = open(ctx->tmpname, O_CREAT|O_EXCL|O_WRONLY|O_TRUNC, oldfd == -1 ? 0666 : oldmeta.st_mode)) == -1)
+	snprintf(ctx->tmpname, len, "%s/.%s%s", dirname(dir), basename(base), suffix);
+	free(dir);
+	free(base);
+
+	if ((ctx->fd = mkstemp(ctx->tmpname)) == -1)
 		goto err;
-	if (oldfd != -1) {
+
+	if (oldfd == -1) {
+		mode_t mask = umask(0);
+		umask(mask);
+		if (fchmod(ctx->fd, 0666 & ~mask) == -1)
+			goto err;
+	} else {
+		if (fchmod(ctx->fd, oldmeta.st_mode) == -1)
+			goto err;
 		if (!preserve_acl(oldfd, ctx->fd) || !preserve_selinux_context(oldfd, ctx->fd))
 			goto err;
 		/* change owner if necessary */
diff --git a/text.h b/text.h
@@ -280,9 +280,10 @@ enum TextSaveMethod {
 	/**
 	 * Save file atomically using `rename(2)`.
 	 *
-	 * Creates a new file named `filename~` and tries to restore all important
-	 * meta data. After which it is atomically moved to its final
-	 * (possibly already existing) destination using `rename(2)`.
+	 * Creates a temporary file, restores all important meta data,
+	 * before moving it atomically to its final (possibly already
+	 * existing) destination using `rename(2)`. For new files,
+	 * permissions are set to `0666 & ~umask`.
 	 *
 	 * @rst
 	 * .. warning:: This approach does not work if: