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[lttngtop.git] / lib / babeltrace / prio_heap.h

diff --git a/lib/babeltrace/prio_heap.h b/lib/babeltrace/prio_heap.h
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+#ifndef _BABELTRACE_PRIO_HEAP_H
+#define _BABELTRACE_PRIO_HEAP_H
+
+/*
+ * prio_heap.h
+ *
+ * Static-sized priority heap containing pointers. Based on CLRS,
+ * chapter 6.
+ *
+ * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <unistd.h>
+#include <babeltrace/babeltrace-internal.h>
+
+struct ptr_heap {
+       size_t len, alloc_len;
+       void **ptrs;
+       int (*gt)(void *a, void *b);
+};
+
+#ifdef DEBUG_HEAP
+void check_heap(const struct ptr_heap *heap);
+#else
+static inline
+void check_heap(const struct ptr_heap *heap)
+{
+}
+#endif
+
+/**
+ * bt_heap_maximum - return the largest element in the heap
+ * @heap: the heap to be operated on
+ *
+ * Returns the largest element in the heap, without performing any modification
+ * to the heap structure. Returns NULL if the heap is empty.
+ */
+static inline void *bt_heap_maximum(const struct ptr_heap *heap)
+{
+       check_heap(heap);
+       return likely(heap->len) ? heap->ptrs[0] : NULL;
+}
+
+/**
+ * bt_heap_init - initialize the heap
+ * @heap: the heap to initialize
+ * @alloc_len: number of elements initially allocated
+ * @gt: function to compare the elements
+ *
+ * Returns -ENOMEM if out of memory.
+ */
+extern int bt_heap_init(struct ptr_heap *heap,
+                    size_t alloc_len,
+                    int gt(void *a, void *b));
+
+/**
+ * bt_heap_free - free the heap
+ * @heap: the heap to free
+ */
+extern void bt_heap_free(struct ptr_heap *heap);
+
+/**
+ * bt_heap_insert - insert an element into the heap
+ * @heap: the heap to be operated on
+ * @p: the element to add
+ *
+ * Insert an element into the heap.
+ *
+ * Returns -ENOMEM if out of memory.
+ */
+extern int bt_heap_insert(struct ptr_heap *heap, void *p);
+
+/**
+ * bt_heap_remove - remove the largest element from the heap
+ * @heap: the heap to be operated on
+ *
+ * Returns the largest element in the heap. It removes this element from the
+ * heap. Returns NULL if the heap is empty.
+ */
+extern void *bt_heap_remove(struct ptr_heap *heap);
+
+/**
+ * bt_heap_cherrypick - remove a given element from the heap
+ * @heap: the heap to be operated on
+ * @p: the element
+ *
+ * Remove the given element from the heap. Return the element if present, else
+ * return NULL. This algorithm has a complexity of O(n), which is higher than
+ * O(log(n)) provided by the rest of this API.
+ */
+extern void *bt_heap_cherrypick(struct ptr_heap *heap, void *p);
+
+/**
+ * bt_heap_replace_max - replace the the largest element from the heap
+ * @heap: the heap to be operated on
+ * @p: the pointer to be inserted as topmost element replacement
+ *
+ * Returns the largest element in the heap. It removes this element from the
+ * heap. The heap is rebalanced only once after the insertion. Returns NULL if
+ * the heap is empty.
+ *
+ * This is the equivalent of calling bt_heap_remove() and then bt_heap_insert(), but
+ * it only rebalances the heap once. It never allocates memory.
+ */
+extern void *bt_heap_replace_max(struct ptr_heap *heap, void *p);
+
+/**
+ * bt_heap_copy - copy a heap
+ * @dst: the destination heap (must be allocated)
+ * @src: the source heap
+ *
+ * Returns -ENOMEM if out of memory.
+ */
+extern int bt_heap_copy(struct ptr_heap *dst, struct ptr_heap *src);
+
+#endif /* _BABELTRACE_PRIO_HEAP_H */