diff options
| author | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2021-10-05 16:53:47 +0300 |
|---|---|---|
| committer | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2021-10-07 18:58:36 +0300 |
| commit | eb03ac17f16f1bd354482148426353fd35cd879d (patch) | |
| tree | 33978d6fc1d9a392d679ebe1ff2a2673a9154ce3 /newlib | |
| parent | 5f7f27c81736c11c35c119cc5f18231eb8aaecec (diff) | |
sys/tree.h: Red child with black sibling rotations
Add specialized rotations RB_RED_ROTATE_LEFT() and RB_RED_ROTATE_RIGHT() which
may be used if we rotate a red child which has a black sibling. Such a red
node must have at least two child nodes so that the following red-black tree
invariant is fulfilled:
Every path from a given node to any of its descendant NULL nodes goes through
the same number of black nodes.
PARENT
/ \
BLACK RED
/ \
BLACK BLACK
Diffstat (limited to 'newlib')
| -rw-r--r-- | newlib/libc/include/sys/tree.h | 43 |
1 files changed, 41 insertions, 2 deletions
diff --git a/newlib/libc/include/sys/tree.h b/newlib/libc/include/sys/tree.h index f6190f7f4..2d3cec0ec 100644 --- a/newlib/libc/include/sys/tree.h +++ b/newlib/libc/include/sys/tree.h @@ -412,6 +412,45 @@ struct { \ RB_AUGMENT(right); \ } while (/*CONSTCOND*/ 0) +/* + * The RB_RED_ROTATE_LEFT() and RB_RED_ROTATE_RIGHT() rotations are specialized + * versions of RB_ROTATE_LEFT() and RB_ROTATE_RIGHT() which may be used if we + * rotate an element with a red child which has a black sibling. Such a red + * node must have at least two child nodes so that the following red-black tree + * invariant is fulfilled: + * + * Every path from a given node to any of its descendant NULL nodes goes + * through the same number of black nodes. + * + * elm (could be the root) + * / \ + * BLACK RED (left or right child) + * / \ + * BLACK BLACK + */ + +#define RB_RED_ROTATE_LEFT(head, elm, tmp, field) do { \ + (tmp) = RB_RIGHT(elm, field); \ + RB_RIGHT(elm, field) = RB_LEFT(tmp, field); \ + RB_SET_PARENT(RB_RIGHT(elm, field), elm, field); \ + RB_SET_PARENT(tmp, RB_PARENT(elm, field), field); \ + RB_SWAP_CHILD(head, elm, tmp, field); \ + RB_LEFT(tmp, field) = (elm); \ + RB_SET_PARENT(elm, tmp, field); \ + RB_AUGMENT(elm); \ +} while (/*CONSTCOND*/ 0) + +#define RB_RED_ROTATE_RIGHT(head, elm, tmp, field) do { \ + (tmp) = RB_LEFT(elm, field); \ + RB_LEFT(elm, field) = RB_RIGHT(tmp, field); \ + RB_SET_PARENT(RB_LEFT(elm, field), elm, field); \ + RB_SET_PARENT(tmp, RB_PARENT(elm, field), field); \ + RB_SWAP_CHILD(head, elm, tmp, field); \ + RB_RIGHT(tmp, field) = (elm); \ + RB_SET_PARENT(elm, tmp, field); \ + RB_AUGMENT(elm); \ +} while (/*CONSTCOND*/ 0) + /* Generates prototypes and inline functions */ #define RB_PROTOTYPE(name, type, field, cmp) \ RB_PROTOTYPE_INTERNAL(name, type, field, cmp,) @@ -526,7 +565,7 @@ name##_RB_REMOVE_COLOR(struct name *head, struct type *parent) \ tmp = RB_RIGHT(parent, field); \ if (RB_COLOR(tmp, field) == RB_RED) { \ RB_SET_BLACKRED(tmp, parent, field); \ - RB_ROTATE_LEFT(head, parent, tmp, field);\ + RB_RED_ROTATE_LEFT(head, parent, tmp, field); \ tmp = RB_RIGHT(parent, field); \ } \ if (RB_ISRED(RB_RIGHT(tmp, field), field)) \ @@ -552,7 +591,7 @@ name##_RB_REMOVE_COLOR(struct name *head, struct type *parent) \ tmp = RB_LEFT(parent, field); \ if (RB_COLOR(tmp, field) == RB_RED) { \ RB_SET_BLACKRED(tmp, parent, field); \ - RB_ROTATE_RIGHT(head, parent, tmp, field);\ + RB_RED_ROTATE_RIGHT(head, parent, tmp, field); \ tmp = RB_LEFT(parent, field); \ } \ if (RB_ISRED(RB_LEFT(tmp, field), field)) \ |