1 files changed, 87 insertions, 0 deletions
diff --git a/object-refs.c b/object-refs.c
new file mode 100644
index 0000000000..5345671569
--- /dev/null
+++ b/object-refs.c
@@ -0,0 +1,87 @@
+#include "cache.h"
+#include "object.h"
+#include "decorate.h"
+
+int track_object_refs = 0;
+
+static struct decoration ref_decorate;
+
+struct object_refs *lookup_object_refs(struct object *base)
+{
+	return lookup_decoration(&ref_decorate, base);
+}
+
+static void add_object_refs(struct object *obj, struct object_refs *refs)
+{
+	if (add_decoration(&ref_decorate, obj, refs))
+		die("object %s tried to add refs twice!", sha1_to_hex(obj->sha1));
+}
+
+struct object_refs *alloc_object_refs(unsigned count)
+{
+	struct object_refs *refs;
+	size_t size = sizeof(*refs) + count*sizeof(struct object *);
+
+	refs = xcalloc(1, size);
+	refs->count = count;
+	return refs;
+}
+
+static int compare_object_pointers(const void *a, const void *b)
+{
+	const struct object * const *pa = a;
+	const struct object * const *pb = b;
+	if (*pa == *pb)
+		return 0;
+	else if (*pa < *pb)
+		return -1;
+	else
+		return 1;
+}
+
+void set_object_refs(struct object *obj, struct object_refs *refs)
+{
+	unsigned int i, j;
+
+	/* Do not install empty list of references */
+	if (refs->count < 1) {
+		free(refs);
+		return;
+	}
+
+	/* Sort the list and filter out duplicates */
+	qsort(refs->ref, refs->count, sizeof(refs->ref[0]),
+	      compare_object_pointers);
+	for (i = j = 1; i < refs->count; i++) {
+		if (refs->ref[i] != refs->ref[i - 1])
+			refs->ref[j++] = refs->ref[i];
+	}
+	if (j < refs->count) {
+		/* Duplicates were found - reallocate list */
+		size_t size = sizeof(*refs) + j*sizeof(struct object *);
+		refs->count = j;
+		refs = xrealloc(refs, size);
+	}
+
+	for (i = 0; i < refs->count; i++)
+		refs->ref[i]->used = 1;
+	add_object_refs(obj, refs);
+}
+
+void mark_reachable(struct object *obj, unsigned int mask)
+{
+	const struct object_refs *refs;
+
+	if (!track_object_refs)
+		die("cannot do reachability with object refs turned off");
+	/* If we've been here already, don't bother */
+	if (obj->flags & mask)
+		return;
+	obj->flags |= mask;
+	refs = lookup_object_refs(obj);
+	if (refs) {
+		unsigned i;
+		for (i = 0; i < refs->count; i++)
+			mark_reachable(refs->ref[i], mask);
+	}
+}