From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1921) id 2188D385802D; Thu, 7 Oct 2021 16:02:35 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2188D385802D Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Sebastian Huber To: newlib-cvs@sourceware.org Subject: [newlib-cygwin] sys/tree.h: Red child with black sibling rotations X-Act-Checkin: newlib-cygwin X-Git-Author: Sebastian Huber X-Git-Refname: refs/heads/master X-Git-Oldrev: 5f7f27c81736c11c35c119cc5f18231eb8aaecec X-Git-Newrev: eb03ac17f16f1bd354482148426353fd35cd879d Message-Id: <20211007160235.2188D385802D@sourceware.org> Date: Thu, 7 Oct 2021 16:02:35 +0000 (GMT) X-BeenThere: newlib-cvs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Newlib GIT logs List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Oct 2021 16:02:35 -0000 https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=eb03ac17f16f1bd354482148426353fd35cd879d commit eb03ac17f16f1bd354482148426353fd35cd879d Author: Sebastian Huber Date: Tue Oct 5 15:53:47 2021 +0200 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 Diff: --- newlib/libc/include/sys/tree.h | 43 ++++++++++++++++++++++++++++++++++++++++-- 1 file 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)) \