Re: [PATCH v5 4/8] convert: Separate generic structures and variables from the filter specific ones

[Lars Schneider <larsxschneider@gmail.com>]

> On 07 Apr 2017, at 14:03, Ben Peart <peartben@gmail.com> wrote:
> 
> To enable future reuse of the filter.<driver>.process infrastructure,
> split the cmd2process structure into two separate parts.
> 
> subprocess_entry will now contain the generic data required to manage
> the creation and tracking of the child process in a hashmap. Also move
> all knowledge of the hashmap into the generic functions.
> 
> cmd2process is a filter protocol specific structure that is used to
> track the negotiated capabilities of the filter.
> 
> Signed-off-by: Ben Peart <benpeart@microsoft.com>
> ---
> convert.c | 57 +++++++++++++++++++++++++++++++--------------------------
> 1 file changed, 31 insertions(+), 26 deletions(-)
> 
> diff --git a/convert.c b/convert.c
> index 404757eac9..f569026511 100644
> --- a/convert.c
> +++ b/convert.c
> @@ -496,29 +496,40 @@ static int apply_single_file_filter(const char *path, const char *src, size_t le
> #define CAP_CLEAN    (1u<<0)
> #define CAP_SMUDGE   (1u<<1)
> 
> -struct cmd2process {
> +struct subprocess_entry {
> 	struct hashmap_entry ent; /* must be the first member! */
> -	unsigned int supported_capabilities;
> 	const char *cmd;
> 	struct child_process process;
> };
> 
> +struct cmd2process {
> +	struct subprocess_entry subprocess; /* must be the first member! */
> +	unsigned int supported_capabilities;
> +};
> +
> static int cmd_process_map_initialized;
> static struct hashmap cmd_process_map;
> 
> -static int cmd2process_cmp(const struct cmd2process *e1,
> -			   const struct cmd2process *e2,
> +static int cmd2process_cmp(const struct subprocess_entry *e1,
> +			   const struct subprocess_entry *e2,
> 			   const void *unused)
> {
> 	return strcmp(e1->cmd, e2->cmd);
> }
> 
> -static struct cmd2process *find_multi_file_filter_entry(struct hashmap *hashmap, const char *cmd)
> +static struct subprocess_entry *find_multi_file_filter_entry(const char *cmd)

I am curious why you removed the hashmap parameter (here and in other pars of this patch). 
I know the parameter is not strictly necessary as the hashmap is a global variable anyways. 
However, I think it eases code maintainability in the long run if a function is "as pure as 
possible" (IOW does rely on global state as less as possible).

As I consider this personal preference I think either way is fine.


> {
> -	struct cmd2process key;
> +	struct subprocess_entry key;
> +
> +	if (!cmd_process_map_initialized) {
> +		cmd_process_map_initialized = 1;
> +		hashmap_init(&cmd_process_map, (hashmap_cmp_fn)cmd2process_cmp, 0);
> +		return NULL;
> +	}
> +

I am a bit in doubt about this one. If the process map was not initialized yet, then
I would expect "find_multi_file_filter_entry" to return NULL. Creating the hash
map as side effect seems a bit unexpected to me. 

The rest of the patch looks good to me.

Thanks,
Lars