--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/ucx/cx/tree.h Sat Dec 07 18:56:37 2024 +0100
@@ -0,0 +1,398 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2024 Mike Becker, Olaf Wintermann All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+/**
+ * \file tree.h
+ * \brief Interface for tree implementations.
+ * \author Mike Becker
+ * \author Olaf Wintermann
+ * \copyright 2-Clause BSD License
+ */
+
+#ifndef UCX_TREE_H
+#define UCX_TREE_H
+
+#include "common.h"
+
+#include "iterator.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * A depth-first tree iterator.
+ *
+ * This iterator is not position-aware in a strict sense, as it does not assume a particular order of elements in the
+ * tree. However, the iterator keeps track of the number of nodes it has passed in a counter variable.
+ * Each node, regardless of the number of passes, is counted only once.
+ *
+ * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
+ * underlying data structure is mutated by other means than this iterator (e.g. elements added or removed),
+ * the iterator becomes invalid (regardless of what cxIteratorValid() returns).
+ *
+ * @see CxIterator
+ */
+typedef struct cx_tree_iterator_s {
+ /**
+ * Base members.
+ */
+ CX_ITERATOR_BASE;
+ /**
+ * Indicates whether the subtree below the current node shall be skipped.
+ */
+ bool skip;
+ /**
+ * Set to true, when the iterator shall visit a node again
+ * when all it's children have been processed.
+ */
+ bool visit_on_exit;
+ /**
+ * True, if this iterator is currently leaving the node.
+ */
+ bool exiting;
+ /**
+ * Offset in the node struct for the children linked list.
+ */
+ ptrdiff_t loc_children;
+ /**
+ * Offset in the node struct for the next pointer.
+ */
+ ptrdiff_t loc_next;
+ /**
+ * The total number of distinct nodes that have been passed so far.
+ */
+ size_t counter;
+ /**
+ * The currently observed node.
+ *
+ * This is the same what cxIteratorCurrent() would return.
+ */
+ void *node;
+ /**
+ * Stores a copy of the next pointer of the visited node.
+ * Allows freeing a node on exit without corrupting the iteration.
+ */
+ void *node_next;
+ /**
+ * Internal stack.
+ * Will be automatically freed once the iterator becomes invalid.
+ *
+ * If you want to discard the iterator before, you need to manually
+ * call cxTreeIteratorDispose().
+ */
+ void **stack;
+ /**
+ * Internal capacity of the stack.
+ */
+ size_t stack_capacity;
+ union {
+ /**
+ * Internal stack size.
+ */
+ size_t stack_size;
+ /**
+ * The current depth in the tree.
+ */
+ size_t depth;
+ };
+} CxTreeIterator;
+
+/**
+ * An element in a visitor queue.
+ */
+struct cx_tree_visitor_queue_s {
+ /**
+ * The tree node to visit.
+ */
+ void *node;
+ /**
+ * The depth of the node.
+ */
+ size_t depth;
+ /**
+ * The next element in the queue or \c NULL.
+ */
+ struct cx_tree_visitor_queue_s *next;
+};
+
+/**
+ * A breadth-first tree iterator.
+ *
+ * This iterator needs to maintain a visitor queue that will be automatically freed once the iterator becomes invalid.
+ * If you want to discard the iterator before, you MUST manually call cxTreeVisitorDispose().
+ *
+ * This iterator is not position-aware in a strict sense, as it does not assume a particular order of elements in the
+ * tree. However, the iterator keeps track of the number of nodes it has passed in a counter variable.
+ * Each node, regardless of the number of passes, is counted only once.
+ *
+ * @note Objects that are pointed to by an iterator are mutable through that iterator. However, if the
+ * underlying data structure is mutated by other means than this iterator (e.g. elements added or removed),
+ * the iterator becomes invalid (regardless of what cxIteratorValid() returns).
+ *
+ * @see CxIterator
+ */
+typedef struct cx_tree_visitor_s {
+ /**
+ * Base members.
+ */
+ CX_ITERATOR_BASE;
+ /**
+ * Indicates whether the subtree below the current node shall be skipped.
+ */
+ bool skip;
+ /**
+ * Offset in the node struct for the children linked list.
+ */
+ ptrdiff_t loc_children;
+ /**
+ * Offset in the node struct for the next pointer.
+ */
+ ptrdiff_t loc_next;
+ /**
+ * The total number of distinct nodes that have been passed so far.
+ */
+ size_t counter;
+ /**
+ * The currently observed node.
+ *
+ * This is the same what cxIteratorCurrent() would return.
+ */
+ void *node;
+ /**
+ * The current depth in the tree.
+ */
+ size_t depth;
+ /**
+ * The next element in the visitor queue.
+ */
+ struct cx_tree_visitor_queue_s *queue_next;
+ /**
+ * The last element in the visitor queue.
+ */
+ struct cx_tree_visitor_queue_s *queue_last;
+} CxTreeVisitor;
+
+/**
+ * Releases internal memory of the given tree iterator.
+ * @param iter the iterator
+ */
+ __attribute__((__nonnull__))
+static inline void cxTreeIteratorDispose(CxTreeIterator *iter) {
+ free(iter->stack);
+ iter->stack = NULL;
+}
+
+/**
+ * Releases internal memory of the given tree visitor.
+ * @param visitor the visitor
+ */
+__attribute__((__nonnull__))
+static inline void cxTreeVisitorDispose(CxTreeVisitor *visitor) {
+ struct cx_tree_visitor_queue_s *q = visitor->queue_next;
+ while (q != NULL) {
+ struct cx_tree_visitor_queue_s *next = q->next;
+ free(q);
+ q = next;
+ }
+}
+
+/**
+ * Advises the iterator to skip the subtree below the current node and
+ * also continues the current loop.
+ *
+ * @param iterator the iterator
+ */
+#define cxTreeIteratorContinue(iterator) (iterator).skip = true; continue
+
+/**
+ * Advises the visitor to skip the subtree below the current node and
+ * also continues the current loop.
+ *
+ * @param visitor the visitor
+ */
+#define cxTreeVisitorContinue(visitor) cxTreeIteratorContinue(visitor)
+
+/**
+ * Links a node to a (new) parent.
+ *
+ * If the node has already a parent, it is unlinked, first.
+ * If the parent has children already, the node is \em prepended to the list
+ * of all currently existing children.
+ *
+ * @param parent the parent node
+ * @param node the node that shall be linked
+ * @param loc_parent offset in the node struct for the parent pointer
+ * @param loc_children offset in the node struct for the children linked list
+ * @param loc_prev offset in the node struct for the prev pointer
+ * @param loc_next offset in the node struct for the next pointer
+ * @see cx_tree_unlink()
+ */
+__attribute__((__nonnull__))
+void cx_tree_link(
+ void * restrict parent,
+ void * restrict node,
+ ptrdiff_t loc_parent,
+ ptrdiff_t loc_children,
+ ptrdiff_t loc_prev,
+ ptrdiff_t loc_next
+);
+
+/**
+ * Unlinks a node from its parent.
+ *
+ * If the node has no parent, this function does nothing.
+ *
+ * @param node the node that shall be unlinked from its parent
+ * @param loc_parent offset in the node struct for the parent pointer
+ * @param loc_children offset in the node struct for the children linked list
+ * @param loc_prev offset in the node struct for the prev pointer
+ * @param loc_next offset in the node struct for the next pointer
+ * @see cx_tree_link()
+ */
+__attribute__((__nonnull__))
+void cx_tree_unlink(
+ void *node,
+ ptrdiff_t loc_parent,
+ ptrdiff_t loc_children,
+ ptrdiff_t loc_prev,
+ ptrdiff_t loc_next
+);
+
+/**
+ * Function pointer for a search function.
+ *
+ * A function of this kind shall check if the specified \p node
+ * contains the given \p data or if one of the children might contain
+ * the data.
+ *
+ * The function should use the returned integer to indicate how close the
+ * match is, where a negative number means that it does not match at all.
+ *
+ * For example if a tree stores file path information, a node that is
+ * describing a parent directory of a filename that is searched, shall
+ * return a positive number to indicate that a child node might contain the
+ * searched item. On the other hand, if the node denotes a path that is not a
+ * prefix of the searched filename, the function would return -1 to indicate
+ * that * the search does not need to be continued in that branch.
+ *
+ * @param node the node that is currently investigated
+ * @param data the data that is searched for
+ *
+ * @return 0 if the node contains the data,
+ * positive if one of the children might contain the data,
+ * negative if neither the node, nor the children contains the data
+ */
+typedef int (*cx_tree_search_func)(void const *node, void const* data);
+
+
+/**
+ * Searches for data in a tree.
+ *
+ * When the data cannot be found exactly, the search function might return a
+ * closest result which might be a good starting point for adding a new node
+ * to the tree.
+ *
+ * Depending on the tree structure it is not necessarily guaranteed that the
+ * "closest" match is uniquely defined. This function will search for a node
+ * with the best match according to the \p sfunc (meaning: the return value of
+ * \p sfunc which is closest to zero). If that is also ambiguous, an arbitrary
+ * node matching the criteria is returned.
+ *
+ * @param root the root node
+ * @param data the data to search for
+ * @param sfunc the search function
+ * @param result where the result shall be stored
+ * @param loc_children offset in the node struct for the children linked list
+ * @param loc_next offset in the node struct for the next pointer
+ * @return zero if the node was found exactly, positive if a node was found that
+ * could contain the node (but doesn't right now), negative if the tree does not
+ * contain any node that might be related to the searched data
+ */
+__attribute__((__nonnull__))
+int cx_tree_search(
+ void const *root,
+ void const *data,
+ cx_tree_search_func sfunc,
+ void **result,
+ ptrdiff_t loc_children,
+ ptrdiff_t loc_next
+);
+
+/**
+ * Creates a depth-first iterator for a tree with the specified root node.
+ *
+ * @note A tree iterator needs to maintain a stack of visited nodes, which is allocated using stdlib malloc().
+ * When the iterator becomes invalid, this memory is automatically released. However, if you wish to cancel the
+ * iteration before the iterator becomes invalid by itself, you MUST call cxTreeIteratorDispose() manually to release
+ * the memory.
+ *
+ * @remark The returned iterator does not support cxIteratorFlagRemoval().
+ *
+ * @param root the root node
+ * @param visit_on_exit set to true, when the iterator shall visit a node again after processing all children
+ * @param loc_children offset in the node struct for the children linked list
+ * @param loc_next offset in the node struct for the next pointer
+ * @return the new tree iterator
+ * @see cxTreeIteratorDispose()
+ */
+__attribute__((__nonnull__))
+CxTreeIterator cx_tree_iterator(
+ void *root,
+ bool visit_on_exit,
+ ptrdiff_t loc_children,
+ ptrdiff_t loc_next
+);
+
+/**
+ * Creates a breadth-first iterator for a tree with the specified root node.
+ *
+ * @note A tree visitor needs to maintain a queue of to be visited nodes, which is allocated using stdlib malloc().
+ * When the visitor becomes invalid, this memory is automatically released. However, if you wish to cancel the
+ * iteration before the visitor becomes invalid by itself, you MUST call cxTreeVisitorDispose() manually to release
+ * the memory.
+ *
+ * @remark The returned iterator does not support cxIteratorFlagRemoval().
+ *
+ * @param root the root node
+ * @param loc_children offset in the node struct for the children linked list
+ * @param loc_next offset in the node struct for the next pointer
+ * @return the new tree visitor
+ * @see cxTreeVisitorDispose()
+ */
+__attribute__((__nonnull__))
+CxTreeVisitor cx_tree_visitor(
+ void *root,
+ ptrdiff_t loc_children,
+ ptrdiff_t loc_next
+);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif //UCX_TREE_H