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authorLinus Torvalds <torvalds@linux-foundation.org>2007-04-16 16:03:15 -0700
committerJunio C Hamano <junkio@cox.net>2007-04-16 16:51:09 -0700
commita59b276e18f3d4a548caf549e05188cb1bd3a709 (patch)
tree2633d6fd7b33dddee9c1d7ed35d6061bffc957ba /decorate.c
parent402fa75eed29c104ae5392ce88560f6bffc64ce7 (diff)
downloadgit-a59b276e18f3d4a548caf549e05188cb1bd3a709.tar.gz
Add a generic "object decorator" interface, and make object refs use it
This allows you to add an arbitrary "decoration" of your choice to any object. It's a space- and time-efficient way to add information to arbitrary objects, especially if most objects probably do not have the decoration. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
Diffstat (limited to 'decorate.c')
-rw-r--r--decorate.c89
1 files changed, 89 insertions, 0 deletions
diff --git a/decorate.c b/decorate.c
new file mode 100644
index 0000000000..396b41311a
--- /dev/null
+++ b/decorate.c
@@ -0,0 +1,89 @@
+/*
+ * decorate.c - decorate a git object with some arbitrary
+ * data.
+ */
+#include "cache.h"
+#include "object.h"
+#include "decorate.h"
+
+static unsigned int hash_obj(struct object *obj, unsigned int n)
+{
+ unsigned int hash = *(unsigned int *)obj->sha1;
+ return hash % n;
+}
+
+static void *insert_decoration(struct decoration *n, struct object *base, void *decoration)
+{
+ int size = n->size;
+ struct object_decoration *hash = n->hash;
+ int j = hash_obj(base, size);
+
+ while (hash[j].base) {
+ if (hash[j].base == base) {
+ void *old = hash[j].decoration;
+ hash[j].decoration = decoration;
+ return old;
+ }
+ j++;
+ if (++j >= size)
+ j = 0;
+ }
+ hash[j].base = base;
+ hash[j].decoration = decoration;
+ n->nr++;
+ return NULL;
+}
+
+static void grow_decoration(struct decoration *n)
+{
+ int i;
+ int old_size = n->size;
+ struct object_decoration *old_hash;
+
+ old_size = n->size;
+ old_hash = n->hash;
+
+ n->size = (old_size + 1000) * 3 / 2;
+ n->hash = xcalloc(n->size, sizeof(struct object_decoration));
+ n->nr = 0;
+
+ for (i = 0; i < old_size; i++) {
+ struct object *base = old_hash[i].base;
+ void *decoration = old_hash[i].decoration;
+
+ if (!base)
+ continue;
+ insert_decoration(n, base, decoration);
+ }
+ free(old_hash);
+}
+
+/* Add a decoration pointer, return any old one */
+void *add_decoration(struct decoration *n, struct object *obj, void *decoration)
+{
+ int nr = n->nr + 1;
+
+ if (nr > n->size * 2 / 3)
+ grow_decoration(n);
+ return insert_decoration(n, obj, decoration);
+}
+
+/* Lookup a decoration pointer */
+void *lookup_decoration(struct decoration *n, struct object *obj)
+{
+ int j;
+
+ /* nothing to lookup */
+ if (!n->size)
+ return NULL;
+ j = hash_obj(obj, n->size);
+ for (;;) {
+ struct object_decoration *ref = n->hash + j;
+ if (ref->base == obj)
+ return ref->decoration;
+ if (!ref->base)
+ return NULL;
+ if (++j == n->size)
+ j = 0;
+ }
+}