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db_include/lib/rbtree.h

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+/*-------------------------------------------------------------------------
+ *
+ * rbtree.h
+ *	  interface for PostgreSQL generic Red-Black binary tree package
+ *
+ * Copyright (c) 2009-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/include/lib/rbtree.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef RBTREE_H
+#define RBTREE_H
+
+/*
+ * RBTNode is intended to be used as the first field of a larger struct,
+ * whose additional fields carry whatever payload data the caller needs
+ * for a tree entry.  (The total size of that larger struct is passed to
+ * rbt_create.)	RBTNode is declared here to support this usage, but
+ * callers must treat it as an opaque struct.
+ */
+typedef struct RBTNode
+{
+	char color;					/* node's current color, red or black */
+	struct RBTNode *left;		/* left child, or RBTNIL if none */
+	struct RBTNode *right;		/* right child, or RBTNIL if none */
+	struct RBTNode *parent;		/* parent, or NULL (not RBTNIL!) if none */
+} RBTNode;
+
+/* Opaque struct representing a whole tree */
+typedef struct RBTree RBTree;
+
+/* Available tree iteration orderings */
+typedef enum RBTOrderControl
+{
+	LeftRightWalk,				/* inorder: left child, node, right child */
+	RightLeftWalk				/* reverse inorder: right, node, left */
+} RBTOrderControl;
+
+/*
+ * RBTreeIterator holds state while traversing a tree.  This is declared
+ * here so that callers can stack-allocate this, but must otherwise be
+ * treated as an opaque struct.
+ */
+typedef struct RBTreeIterator RBTreeIterator;
+
+struct RBTreeIterator
+{
+	RBTree	   *rbt;
+	RBTNode    *(*iterate) (RBTreeIterator *iter);
+	RBTNode    *last_visited;
+	bool		is_over;
+};
+
+/* Support functions to be provided by caller */
+typedef int (*rbt_comparator) (const RBTNode *a, const RBTNode *b, void *arg);
+typedef void (*rbt_combiner) (RBTNode *existing, const RBTNode *newdata, void *arg);
+typedef RBTNode *(*rbt_allocfunc) (void *arg);
+typedef void (*rbt_freefunc) (RBTNode *x, void *arg);
+
+extern RBTree *rbt_create(Size node_size,
+						  rbt_comparator comparator,
+						  rbt_combiner combiner,
+						  rbt_allocfunc allocfunc,
+						  rbt_freefunc freefunc,
+						  void *arg);
+
+extern RBTNode *rbt_find(RBTree *rbt, const RBTNode *data);
+extern RBTNode *rbt_leftmost(RBTree *rbt);
+
+extern RBTNode *rbt_insert(RBTree *rbt, const RBTNode *data, bool *isNew);
+extern void rbt_delete(RBTree *rbt, RBTNode *node);
+
+extern void rbt_begin_iterate(RBTree *rbt, RBTOrderControl ctrl,
+							  RBTreeIterator *iter);
+extern RBTNode *rbt_iterate(RBTreeIterator *iter);
+
+#endif							/* RBTREE_H */