/* Partial red-black tree implementation for rs6000-gen-builtins.cc. Copyright (C) 2020-2022 Free Software Foundation, Inc. Contributed by Bill Schmidt, IBM This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see . */ #include #include #include #include #include "rbtree.h" /* Initialize a red-black tree. */ void rbt_new (struct rbt_strings *t) { t->rbt_nil = (rbt_string_node *) malloc (sizeof (rbt_string_node)); t->rbt_nil->color = RBT_BLACK; t->rbt_root = t->rbt_nil; } /* Create a new node to be inserted into the red-black tree. An inserted node starts out red. */ static struct rbt_string_node * rbt_create_node (struct rbt_strings *t, char *str) { struct rbt_string_node *nodeptr = (struct rbt_string_node *) malloc (sizeof (rbt_string_node)); nodeptr->str = str; nodeptr->left = t->rbt_nil; nodeptr->right = t->rbt_nil; nodeptr->par = NULL; nodeptr->color = RBT_RED; return nodeptr; } /* Perform a left-rotate operation on NODE in the red-black tree. */ static void rbt_left_rotate (struct rbt_strings *t, struct rbt_string_node *node) { struct rbt_string_node *right = node->right; assert (right); /* Turn RIGHT's left subtree into NODE's right subtree. */ node->right = right->left; if (right->left != t->rbt_nil) right->left->par = node; /* Link NODE's parent to RIGHT. */ right->par = node->par; if (node->par == t->rbt_nil) t->rbt_root = right; else if (node == node->par->left) node->par->left = right; else node->par->right = right; /* Put NODE on RIGHT's left. */ right->left = node; node->par = right; } /* Perform a right-rotate operation on NODE in the red-black tree. */ static void rbt_right_rotate (struct rbt_strings *t, struct rbt_string_node *node) { struct rbt_string_node *left = node->left; assert (left); /* Turn LEFT's right subtree into NODE's left subtree. */ node->left = left->right; if (left->right != t->rbt_nil) left->right->par = node; /* Link NODE's parent to LEFT. */ left->par = node->par; if (node->par == t->rbt_nil) t->rbt_root = left; else if (node == node->par->right) node->par->right = left; else node->par->left = left; /* Put NODE on LEFT's right. */ left->right = node; node->par = left; } /* Insert STR into the tree, returning 1 for success and 0 if STR already appears in the tree. */ int rbt_insert (struct rbt_strings *t, char *str) { struct rbt_string_node *curr = t->rbt_root; struct rbt_string_node *trail = t->rbt_nil; while (curr != t->rbt_nil) { trail = curr; int cmp = strcmp (str, curr->str); if (cmp < 0) curr = curr->left; else if (cmp > 0) curr = curr->right; else return 0; } struct rbt_string_node *fresh = rbt_create_node (t, str); fresh->par = trail; if (trail == t->rbt_nil) t->rbt_root = fresh; else if (strcmp (fresh->str, trail->str) < 0) trail->left = fresh; else trail->right = fresh; fresh->left = t->rbt_nil; fresh->right = t->rbt_nil; /* FRESH has now been inserted as a red leaf. If we have invalidated one of the following preconditions, we must fix things up: (a) If a node is red, both of its children are black. (b) The root must be black. Note that only (a) or (b) applies at any given time during the process. This algorithm works up the tree from NEW looking for a red child with a red parent, and cleaning that up. If the root ends up red, it gets turned black at the end. */ curr = fresh; while (curr->par->color == RBT_RED) if (curr->par == curr->par->par->left) { struct rbt_string_node *uncle = curr->par->par->right; if (uncle->color == RBT_RED) { curr->par->color = RBT_BLACK; uncle->color = RBT_BLACK; curr->par->par->color = RBT_RED; curr = curr->par->par; } else if (curr == curr->par->right) { curr = curr->par; rbt_left_rotate (t, curr); } else { curr->par->color = RBT_BLACK; curr->par->par->color = RBT_RED; rbt_right_rotate (t, curr->par->par); } } else /* curr->par == curr->par->par->right */ { /* Gender-neutral formations are awkward, so let's be fair. ;-) ("Parent-sibling" is just awful.) */ struct rbt_string_node *aunt = curr->par->par->left; if (aunt->color == RBT_RED) { curr->par->color = RBT_BLACK; aunt->color = RBT_BLACK; curr->par->par->color = RBT_RED; curr = curr->par->par; } else if (curr == curr->par->left) { curr = curr->par; rbt_right_rotate (t, curr); } else { curr->par->color = RBT_BLACK; curr->par->par->color = RBT_RED; rbt_left_rotate (t, curr->par->par); } } t->rbt_root->color = RBT_BLACK; return 1; } /* Return 1 if STR is in the red-black tree, else 0. */ int rbt_find (struct rbt_strings *t, char *str) { struct rbt_string_node *curr = t->rbt_root; while (curr != t->rbt_nil) { int cmp = strcmp (str, curr->str); if (cmp < 0) curr = curr->left; else if (cmp > 0) curr = curr->right; else return 1; } return 0; } /* Inorder dump of the binary search tree. */ void rbt_dump (struct rbt_strings *t, struct rbt_string_node *subtree) { if (subtree != t->rbt_nil) { rbt_dump (t, subtree->left); fprintf (stderr, "%s\n", subtree->str); rbt_dump (t, subtree->right); } } /* Inorder call-back for iteration over the tree. */ void rbt_inorder_callback (struct rbt_strings *t, struct rbt_string_node *subtree, void (*fn) (char *)) { if (subtree != t->rbt_nil) { rbt_inorder_callback (t, subtree->left, fn); (*fn) (subtree->str); rbt_inorder_callback (t, subtree->right, fn); } }