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

> 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);