--- /dev/null
+#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.
+ */
+
+#include <unistd.h>
+
+struct ptr_heap {
+ size_t len, alloc_len;
+ void **ptrs;
+ int (*gt)(void *a, void *b);
+};
+
+/**
+ * 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 *heap_maximum(const struct ptr_heap *heap)
+{
+ return heap->len ? heap->ptrs[0] : NULL;
+}
+
+/**
+ * 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 heap_init(struct ptr_heap *heap,
+ size_t alloc_len,
+ int gt(void *a, void *b));
+
+/**
+ * heap_free - free the heap
+ * @heap: the heap to free
+ */
+extern void heap_free(struct ptr_heap *heap);
+
+/**
+ * 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 heap_insert(struct ptr_heap *heap, void *p);
+
+/**
+ * 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 *heap_remove(struct ptr_heap *heap);
+
+/**
+ * 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 *heap_cherrypick(struct ptr_heap *heap, void *p);
+
+/**
+ * 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 *heap_replace_max(struct ptr_heap *heap, void *p);
+
+#endif /* _BABELTRACE_PRIO_HEAP_H */
--- /dev/null
+/*
+ * prio_heap.c
+ *
+ * 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.
+ */
+
+#include <babeltrace/prio_heap.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef max_t
+#define max_t(type, a, b) \
+ ((type) (a) > (type) (b) ? (type) (a) : (type) (b))
+#endif
+
+static __attribute__((unused))
+size_t parent(size_t i)
+{
+ return i >> 1;
+}
+
+static
+size_t left(size_t i)
+{
+ return i << 1;
+}
+
+static
+size_t right(size_t i)
+{
+ return (i << 1) + 1;
+}
+
+static
+int heap_grow(struct ptr_heap *heap, size_t new_len)
+{
+ void **new_ptrs;
+
+ if (heap->alloc_len >= new_len)
+ return 0;
+
+ heap->alloc_len = max_t(size_t, new_len, heap->alloc_len << 1);
+ new_ptrs = calloc(heap->alloc_len, sizeof(void *));
+ if (!new_ptrs)
+ return -ENOMEM;
+ if (heap->ptrs)
+ memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *));
+ free(heap->ptrs);
+ heap->ptrs = new_ptrs;
+ return 0;
+}
+
+static
+int heap_set_len(struct ptr_heap *heap, size_t new_len)
+{
+ int ret;
+
+ ret = heap_grow(heap, new_len);
+ if (ret)
+ return ret;
+ heap->len = new_len;
+ return 0;
+}
+
+int heap_init(struct ptr_heap *heap, size_t alloc_len,
+ int gt(void *a, void *b))
+{
+ heap->ptrs = NULL;
+ heap->len = 0;
+ heap->alloc_len = 0;
+ heap->gt = gt;
+ /*
+ * Minimum size allocated is 1 entry to ensure memory allocation
+ * never fails within heap_replace_max.
+ */
+ return heap_grow(heap, max_t(size_t, 1, alloc_len));
+}
+
+void heap_free(struct ptr_heap *heap)
+{
+ free(heap->ptrs);
+}
+
+static void heapify(struct ptr_heap *heap, size_t i)
+{
+ void **ptrs = heap->ptrs;
+ size_t l, r, largest;
+
+ for (;;) {
+ l = left(i);
+ r = right(i);
+ if (l <= heap->len && ptrs[l] > ptrs[i])
+ largest = l;
+ else
+ largest = i;
+ if (r <= heap->len && ptrs[r] > ptrs[largest])
+ largest = r;
+ if (largest != i) {
+ void *tmp;
+
+ tmp = ptrs[i];
+ ptrs[i] = ptrs[largest];
+ ptrs[largest] = tmp;
+ i = largest;
+ continue;
+ } else {
+ break;
+ }
+ }
+}
+
+void *heap_replace_max(struct ptr_heap *heap, void *p)
+{
+ void *res;
+ void **ptrs = heap->ptrs;
+
+ if (!heap->len) {
+ (void) heap_set_len(heap, 1);
+ ptrs[0] = p;
+ return NULL;
+ }
+
+ /* Replace the current max and heapify */
+ res = ptrs[0];
+ ptrs[0] = p;
+ heapify(heap, 0);
+ return res;
+}
+
+int heap_insert(struct ptr_heap *heap, void *p)
+{
+ void **ptrs = heap->ptrs;
+ int ret;
+
+ ret = heap_set_len(heap, heap->len + 1);
+ if (ret)
+ return ret;
+ /* Add the element to the end */
+ ptrs[heap->len - 1] = p;
+ /* rebalance */
+ heapify(heap, 0);
+ return 0;
+}
+
+void *heap_remove(struct ptr_heap *heap)
+{
+ void **ptrs = heap->ptrs;
+
+ switch (heap->len) {
+ case 0:
+ return NULL;
+ case 1:
+ (void) heap_set_len(heap, 0);
+ return ptrs[0];
+ }
+ /* Shrink, replace the current max by previous last entry and heapify */
+ heap_set_len(heap, heap->len - 1);
+ return heap_replace_max(heap, ptrs[heap->len - 1]);
+}
+
+void *heap_cherrypick(struct ptr_heap *heap, void *p)
+{
+ void **ptrs = heap->ptrs;
+ size_t pos, len = heap->len;
+
+ for (pos = 0; pos < len; pos++)
+ if (ptrs[pos] == p)
+ goto found;
+ return NULL;
+found:
+ if (heap->len == 1) {
+ (void) heap_set_len(heap, 0);
+ return ptrs[0];
+ }
+ /* Replace p with previous last entry and heapify. */
+ heap_set_len(heap, heap->len - 1);
+ ptrs[pos] = ptrs[heap->len - 1];
+ heapify(heap, pos);
+ return p;
+}
projects / babeltrace.git / commitdiff
