Cleanup: Move headers from lib/ to include/lttng/

[lttng-modules.git] / include / lttng / prio_heap.h

diff --git a/include/lttng/prio_heap.h b/include/lttng/prio_heap.h
new file mode 100644 (file)
index 0000000..d01cbe6
--- /dev/null
+++ b/include/lttng/prio_heap.h
@@ -0,0 +1,108 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * lttng/prio_heap.h
+ *
+ * Priority heap containing pointers. Based on CLRS, chapter 6.
+ *
+ * Copyright 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#ifndef _LTTNG_PRIO_HEAP_H
+#define _LTTNG_PRIO_HEAP_H
+
+#include <linux/gfp.h>
+
+struct lttng_ptr_heap {
+       size_t len, alloc_len;
+       void **ptrs;
+       int (*gt)(void *a, void *b);
+       gfp_t gfpmask;
+};
+
+#ifdef DEBUG_HEAP
+void lttng_check_heap(const struct lttng_ptr_heap *heap);
+#else
+static inline
+void lttng_check_heap(const struct lttng_ptr_heap *heap)
+{
+}
+#endif
+
+/**
+ * lttng_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 *lttng_heap_maximum(const struct lttng_ptr_heap *heap)
+{
+       lttng_check_heap(heap);
+       return heap->len ? heap->ptrs[0] : NULL;
+}
+
+/**
+ * lttng_heap_init - initialize the heap
+ * @heap: the heap to initialize
+ * @alloc_len: number of elements initially allocated
+ * @gfp: allocation flags
+ * @gt: function to compare the elements
+ *
+ * Returns -ENOMEM if out of memory.
+ */
+extern int lttng_heap_init(struct lttng_ptr_heap *heap,
+                    size_t alloc_len, gfp_t gfpmask,
+                    int gt(void *a, void *b));
+
+/**
+ * lttng_heap_free - free the heap
+ * @heap: the heap to free
+ */
+extern void lttng_heap_free(struct lttng_ptr_heap *heap);
+
+/**
+ * lttng_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 lttng_heap_insert(struct lttng_ptr_heap *heap, void *p);
+
+/**
+ * lttng_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 *lttng_heap_remove(struct lttng_ptr_heap *heap);
+
+/**
+ * lttng_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 *lttng_heap_cherrypick(struct lttng_ptr_heap *heap, void *p);
+
+/**
+ * lttng_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 heap_remove() and then heap_insert(), but
+ * it only rebalances the heap once. It never allocates memory.
+ */
+extern void *lttng_heap_replace_max(struct lttng_ptr_heap *heap, void *p);
+
+#endif /* _LTTNG_PRIO_HEAP_H */