make add_object_array_with_context interface more sane

When you resolve a sha1, you can optionally keep any context
found during the resolution, including the path and mode of
a tree entry (e.g., when looking up "HEAD:subdir/file.c").

The add_object_array_with_context function lets you then
attach that context to an entry in a list. Unfortunately,
the interface for doing so is horrible. The object_context
structure is large and most object_array users do not use
it. Therefore we keep a pointer to the structure to avoid
burdening other users too much. But that means when we do
use it that we must allocate the struct ourselves. And the
struct contains a fixed PATH_MAX-sized buffer, which makes
this wholly unsuitable for any large arrays.

We can observe that there is only a single user of the
"with_context" variant: builtin/grep.c. And in that use
case, the only element we care about is the path. We can
therefore store only the path as a pointer (the context's
mode field was redundant with the object_array_entry itself,
and nobody actually cared about the surrounding tree). This
still requires a strdup of the pathname, but at least we are
only consuming the minimum amount of memory for each string.

We can also handle the copying ourselves in
add_object_array_*, and free it as appropriate in
object_array_release_entry.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 14 deletions

diff --git a/object.c b/object.c
index 6aeb1bbbe3..df86bdd5a5 100644
--- a/object.c
+++ b/object.c
@@ -307,10 +307,9 @@ int object_list_contains(struct object_list *list, struct object *obj)
  */
 static char object_array_slopbuf[1];
 
-static void add_object_array_with_mode_context(struct object *obj, const char *name,
-					       struct object_array *array,
-					       unsigned mode,
-					       struct object_context *context)
+void add_object_array_with_path(struct object *obj, const char *name,
+				struct object_array *array,
+				unsigned mode, const char *path)
 {
 	unsigned nr = array->nr;
 	unsigned alloc = array->alloc;
@@ -333,7 +332,10 @@ static void add_object_array_with_mode_context(struct object *obj, const char *n
 	else
 		entry->name = xstrdup(name);
 	entry->mode = mode;
-	entry->context = context;
+	if (path)
+		entry->path = xstrdup(path);
+	else
+		entry->path = NULL;
 	array->nr = ++nr;
 }
 
@@ -344,15 +346,7 @@ void add_object_array(struct object *obj, const char *name, struct object_array
 
 void add_object_array_with_mode(struct object *obj, const char *name, struct object_array *array, unsigned mode)
 {
-	add_object_array_with_mode_context(obj, name, array, mode, NULL);
-}
-
-void add_object_array_with_context(struct object *obj, const char *name, struct object_array *array, struct object_context *context)
-{
-	if (context)
-		add_object_array_with_mode_context(obj, name, array, context->mode, context);
-	else
-		add_object_array_with_mode_context(obj, name, array, S_IFINVALID, context);
+	add_object_array_with_path(obj, name, array, mode, NULL);
 }
 
 /*
@@ -363,6 +357,7 @@ static void object_array_release_entry(struct object_array_entry *ent)
 {
 	if (ent->name != object_array_slopbuf)
 		free(ent->name);
+	free(ent->path);
 }
 
 void object_array_filter(struct object_array *array,