Add RB_REINSERT(3), a low overhead alternative to

removing a node and reinserting it back with an updated key.

This is one of dependencies for the upcoming stats(3) code.

Reviewed by:	cem
Obtained from:	Netflix
MFC after:	2 weeks
Sponsored by:	Klara Inc, Netflix
Differential Revision:	https://reviews.freebsd.org/D21786

diff --git a/newlib/libc/include/sys/tree.h b/newlib/libc/include/sys/tree.h
index fd66ceba1cefe37699e37b49b2c84d654031fd3b..0eacf951d5c5628041d252c99eafeffce7c0d4b7 100644 (file)
--- a/newlib/libc/include/sys/tree.h
+++ b/newlib/libc/include/sys/tree.h
@@ -393,7 +393,8 @@ struct {                                                            \
        RB_PROTOTYPE_NFIND(name, type, attr);                           \
        RB_PROTOTYPE_NEXT(name, type, attr);                            \
        RB_PROTOTYPE_PREV(name, type, attr);                            \
-       RB_PROTOTYPE_MINMAX(name, type, attr);
+       RB_PROTOTYPE_MINMAX(name, type, attr);                          \
+       RB_PROTOTYPE_REINSERT(name, type, attr);
 #define RB_PROTOTYPE_INSERT_COLOR(name, type, attr)                    \
        attr void name##_RB_INSERT_COLOR(struct name *, struct type *)
 #define RB_PROTOTYPE_REMOVE_COLOR(name, type, attr)                    \
@@ -412,6 +413,8 @@ struct {                                                            \
        attr struct type *name##_RB_PREV(struct type *)
 #define RB_PROTOTYPE_MINMAX(name, type, attr)                          \
        attr struct type *name##_RB_MINMAX(struct name *, int)
+#define RB_PROTOTYPE_REINSERT(name, type, attr)                        \
+       attr struct type *name##_RB_REINSERT(struct name *, struct type *)
 
 /* Main rb operation.
  * Moves node close to the key of elm to top
@@ -429,7 +432,9 @@ struct {                                                            \
        RB_GENERATE_NFIND(name, type, field, cmp, attr)                 \
        RB_GENERATE_NEXT(name, type, field, attr)                       \
        RB_GENERATE_PREV(name, type, field, attr)                       \
-       RB_GENERATE_MINMAX(name, type, field, attr)
+       RB_GENERATE_MINMAX(name, type, field, attr)                     \
+       RB_GENERATE_REINSERT(name, type, field, cmp, attr)
+
 
 #define RB_GENERATE_INSERT_COLOR(name, type, field, attr)              \
 attr void                                                              \
@@ -758,6 +763,22 @@ name##_RB_MINMAX(struct name *head, int val)                               \
        return (parent);                                                \
 }
 
+#define        RB_GENERATE_REINSERT(name, type, field, cmp, attr)              \
+attr struct type *                                                     \
+name##_RB_REINSERT(struct name *head, struct type *elm)                        \
+{                                                                      \
+       struct type *cmpelm;                                            \
+       if (((cmpelm = RB_PREV(name, head, elm)) != NULL &&             \
+           cmp(cmpelm, elm) >= 0) ||                                   \
+           ((cmpelm = RB_NEXT(name, head, elm)) != NULL &&             \
+           cmp(elm, cmpelm) >= 0)) {                                   \
+               /* XXXLAS: Remove/insert is heavy handed. */            \
+               RB_REMOVE(name, head, elm);                             \
+               return (RB_INSERT(name, head, elm));                    \
+       }                                                               \
+       return (NULL);                                                  \
+}                                                                      \
+
 #define RB_NEGINF      -1
 #define RB_INF 1
 
@@ -769,6 +790,7 @@ name##_RB_MINMAX(struct name *head, int val)                                \
 #define RB_PREV(name, x, y)    name##_RB_PREV(y)
 #define RB_MIN(name, x)                name##_RB_MINMAX(x, RB_NEGINF)
 #define RB_MAX(name, x)                name##_RB_MINMAX(x, RB_INF)
+#define RB_REINSERT(name, x, y)        name##_RB_REINSERT(x, y)
 
 #define RB_FOREACH(x, name, head)                                      \
        for ((x) = RB_MIN(name, head);                                  \