convert: refactor capabilities negotiation

The code to negotiate long running filter capabilities was very
repetitive for new capabilities. Replace the repetitive conditional
statements with a table-driven approach. This is useful for the
subsequent patch 'convert: add "status=delayed" to filter process
protocol'.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/convert.c b/convert.c
index e55c034..d13e505 100644 (file)
--- a/convert.c
+++ b/convert.c
@@ -507,7 +507,7 @@ static struct hashmap subprocess_map;
 
 static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
 {
-       int err;
+       int err, i;
        struct cmd2process *entry = (struct cmd2process *)subprocess;
        struct string_list cap_list = STRING_LIST_INIT_NODUP;
        char *cap_buf;
@@ -515,6 +515,14 @@ static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
        struct child_process *process = &subprocess->process;
        const char *cmd = subprocess->cmd;
 
+       static const struct {
+               const char *name;
+               unsigned int cap;
+       } known_caps[] = {
+               { "clean",  CAP_CLEAN  },
+               { "smudge", CAP_SMUDGE },
+       };
+
        sigchain_push(SIGPIPE, SIG_IGN);
 
        err = packet_writel(process->in, "git-filter-client", "version=2", NULL);
@@ -533,7 +541,15 @@ static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
        if (err)
                goto done;
 
-       err = packet_writel(process->in, "capability=clean", "capability=smudge", NULL);
+       for (i = 0; i < ARRAY_SIZE(known_caps); ++i) {
+               err = packet_write_fmt_gently(
+                       process->in, "capability=%s\n", known_caps[i].name);
+               if (err)
+                       goto done;
+       }
+       err = packet_flush_gently(process->in);
+       if (err)
+               goto done;
 
        for (;;) {
                cap_buf = packet_read_line(process->out, NULL);
@@ -545,16 +561,15 @@ static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
                        continue;
 
                cap_name = cap_list.items[1].string;
-               if (!strcmp(cap_name, "clean")) {
-                       entry->supported_capabilities |= CAP_CLEAN;
-               } else if (!strcmp(cap_name, "smudge")) {
-                       entry->supported_capabilities |= CAP_SMUDGE;
-               } else {
-                       warning(
-                               "external filter '%s' requested unsupported filter capability '%s'",
-                               cmd, cap_name
-                       );
-               }
+               i = ARRAY_SIZE(known_caps) - 1;
+               while (i >= 0 && strcmp(cap_name, known_caps[i].name))
+                       i--;
+
+               if (i >= 0)
+                       entry->supported_capabilities |= known_caps[i].cap;
+               else
+                       warning("external filter '%s' requested unsupported filter capability '%s'",
+                       cmd, cap_name);
 
                string_list_clear(&cap_list, 0);
        }