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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>
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1 parent 402fa75 commit a59b276e18f3d4a548caf549e05188cb1bd3a709 @torvalds torvalds committed with Junio C Hamano Apr 16, 2007
Showing with 116 additions and 65 deletions.
  1. +2 −2 Makefile
  2. +89 −0 decorate.c
  3. +18 −0 decorate.h
  4. +7 −62 object-refs.c
  5. +0 −1 object.h
View
4 Makefile
@@ -283,7 +283,7 @@ LIB_H = \
diff.h object.h pack.h pkt-line.h quote.h refs.h list-objects.h sideband.h \
run-command.h strbuf.h tag.h tree.h git-compat-util.h revision.h \
tree-walk.h log-tree.h dir.h path-list.h unpack-trees.h builtin.h \
- utf8.h reflog-walk.h patch-ids.h
+ utf8.h reflog-walk.h patch-ids.h decorate.h
DIFF_OBJS = \
diff.o diff-lib.o diffcore-break.o diffcore-order.o \
@@ -305,7 +305,7 @@ LIB_OBJS = \
write_or_die.o trace.o list-objects.o grep.o match-trees.o \
alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS) \
color.o wt-status.o archive-zip.o archive-tar.o shallow.o utf8.o \
- convert.o
+ convert.o decorate.o
BUILTIN_OBJS = \
builtin-add.o \
View
89 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;
+ }
+}
View
18 decorate.h
@@ -0,0 +1,18 @@
+#ifndef DECORATE_H
+#define DECORATE_H
+
+struct object_decoration {
+ struct object *base;
+ void *decoration;
+};
+
+struct decoration {
+ const char *name;
+ unsigned int size, nr;
+ struct object_decoration *hash;
+};
+
+extern void *add_decoration(struct decoration *n, struct object *obj, void *decoration);
+extern void *lookup_decoration(struct decoration *n, struct object *obj);
+
+#endif
View
69 object-refs.c
@@ -1,75 +1,20 @@
#include "cache.h"
#include "object.h"
+#include "decorate.h"
int track_object_refs = 0;
-static unsigned int refs_hash_size, nr_object_refs;
-static struct object_refs **refs_hash;
+static struct decoration ref_decorate;
-static unsigned int hash_obj(struct object *obj, unsigned int n)
+struct object_refs *lookup_object_refs(struct object *base)
{
- unsigned int hash = *(unsigned int *)obj->sha1;
- return hash % n;
+ return lookup_decoration(&ref_decorate, base);
}
-static void insert_ref_hash(struct object_refs *ref, struct object_refs **hash, unsigned int size)
+static void add_object_refs(struct object *obj, struct object_refs *refs)
{
- int j = hash_obj(ref->base, size);
-
- while (hash[j]) {
- j++;
- if (j >= size)
- j = 0;
- }
- hash[j] = ref;
-}
-
-static void grow_refs_hash(void)
-{
- int i;
- int new_hash_size = (refs_hash_size + 1000) * 3 / 2;
- struct object_refs **new_hash;
-
- new_hash = xcalloc(new_hash_size, sizeof(struct object_refs *));
- for (i = 0; i < refs_hash_size; i++) {
- struct object_refs *ref = refs_hash[i];
- if (!ref)
- continue;
- insert_ref_hash(ref, new_hash, new_hash_size);
- }
- free(refs_hash);
- refs_hash = new_hash;
- refs_hash_size = new_hash_size;
-}
-
-static void add_object_refs(struct object *obj, struct object_refs *ref)
-{
- int nr = nr_object_refs + 1;
-
- if (nr > refs_hash_size * 2 / 3)
- grow_refs_hash();
- ref->base = obj;
- insert_ref_hash(ref, refs_hash, refs_hash_size);
- nr_object_refs = nr;
-}
-
-struct object_refs *lookup_object_refs(struct object *obj)
-{
- struct object_refs *ref;
- int j;
-
- /* nothing to lookup */
- if (!refs_hash_size)
- return NULL;
- j = hash_obj(obj, refs_hash_size);
- while ((ref = refs_hash[j]) != NULL) {
- if (ref->base == obj)
- break;
- j++;
- if (j >= refs_hash_size)
- j = 0;
- }
- return ref;
+ 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)
View
1 object.h
@@ -8,7 +8,6 @@ struct object_list {
struct object_refs {
unsigned count;
- struct object *base;
struct object *ref[FLEX_ARRAY]; /* more */
};

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