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>

diff --git a/Makefile b/Makefile
index b8e603094050377fb8ca2988c2558c76fe113e70..251fc31fc05035bf85265d3ea56c8b3ab24c895f 100644 (file)
--- a/Makefile
+++ b/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 \

diff --git a/decorate.c b/decorate.c
new file mode 100644 (file)
index 0000000..396b413
--- /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;
+       }
+}

diff --git a/decorate.h b/decorate.h
new file mode 100644 (file)
index 0000000..1fa4ad9
--- /dev/null
+++ b/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

diff --git a/object-refs.c b/object-refs.c
index 98ea10005a851c3879c6e65929e3e34068dc9e8b..022e8d841c7f5498b6f008647ed37c430826b443 100644 (file)
--- a/object-refs.c
+++ b/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)

diff --git a/object.h b/object.h
index bdbf0facd47015b61a6fbf25eb358b6e256c86b6..bdbbc1889c0227519de0ba02439f0e94dfcd1651 100644 (file)
--- a/object.h
+++ b/object.h
@@ -8,7 +8,6 @@ struct object_list {
 
 struct object_refs {
        unsigned count;
-       struct object *base;
        struct object *ref[FLEX_ARRAY]; /* more */
 };