[PATCH v5 04/13] csum-file: add CSUM_KEEP_OPEN flag

[Derrick Stolee <stolee@gmail.com>]

This patch is new to the series due to the interactions with the lockfile API
and the hashfile API. I need to ensure the hashfile writes the hash value at
the end of the file, but keep the file descriptor open so the lock is valid.

I welcome any susggestions to this patch or to the way I use it in the commit
that follows.

-- >8 --

If we want to use a hashfile on the temporary file for a lockfile, then
we need hashclose() to fully write the trailing hash but also keep the
file descriptor open.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 csum-file.c | 10 +++++++---
 csum-file.h |  1 +
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/csum-file.c b/csum-file.c
index 5eda7fb..302e6ae 100644
--- a/csum-file.c
+++ b/csum-file.c
@@ -66,9 +66,13 @@ int hashclose(struct hashfile *f, unsigned char *result, unsigned int flags)
 		flush(f, f->buffer, the_hash_algo->rawsz);
 		if (flags & CSUM_FSYNC)
 			fsync_or_die(f->fd, f->name);
-		if (close(f->fd))
-			die_errno("%s: sha1 file error on close", f->name);
-		fd = 0;
+		if (flags & CSUM_KEEP_OPEN)
+			fd = f->fd;
+		else {
+			if (close(f->fd))
+				die_errno("%s: sha1 file error on close", f->name);
+			fd = 0;
+		}
 	} else
 		fd = f->fd;
 	if (0 <= f->check_fd) {
diff --git a/csum-file.h b/csum-file.h
index 992e5c0..b7c0e48 100644
--- a/csum-file.h
+++ b/csum-file.h
@@ -29,6 +29,7 @@ extern int hashfile_truncate(struct hashfile *, struct hashfile_checkpoint *);
 /* hashclose flags */
 #define CSUM_CLOSE	1
 #define CSUM_FSYNC	2
+#define CSUM_KEEP_OPEN	4
 
 extern struct hashfile *hashfd(int fd, const char *name);
 extern struct hashfile *hashfd_check(const char *name);
-- 
2.7.4