X-Git-Url: http://git.efficios.com/?p=babeltrace.git;a=blobdiff_plain;f=lib%2Fprio_heap%2Fprio_heap.c;fp=lib%2Fprio_heap%2Fprio_heap.c;h=a37e64c89542d10f017f8da835e01272dab2e2ef;hp=0000000000000000000000000000000000000000;hb=74f21e2d288b83a1e810a20eaa6503bb25b7059f;hpb=6f3077a2db5bfeb47ed75b1c7c731a5e8e60aa43

diff --git a/lib/prio_heap/prio_heap.c b/lib/prio_heap/prio_heap.c
new file mode 100644
index 00000000..a37e64c8
--- /dev/null
+++ b/lib/prio_heap/prio_heap.c
@@ -0,0 +1,216 @@
+/*
+ * 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 <babeltrace/babeltrace-internal.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#ifndef max_t
+#define max_t(type, a, b)	\
+	((type) (a) > (type) (b) ? (type) (a) : (type) (b))
+#endif
+
+#ifdef DEBUG_HEAP
+void check_heap(const struct ptr_heap *heap)
+{
+	size_t i;
+
+	if (!heap->len)
+		return;
+
+	for (i = 1; i < heap->len; i++)
+		assert(!heap->gt(heap->ptrs[i], heap->ptrs[0]));
+}
+#endif
+
+static
+size_t parent(size_t i)
+{
+	return (i - 1) >> 1;
+}
+
+static
+size_t left(size_t i)
+{
+	return (i << 1) + 1;
+}
+
+static
+size_t right(size_t i)
+{
+	return (i << 1) + 2;
+}
+
+/*
+ * Copy of heap->ptrs pointer is invalid after heap_grow.
+ */
+static
+int heap_grow(struct ptr_heap *heap, size_t new_len)
+{
+	void **new_ptrs;
+
+	if (likely(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 (unlikely(!new_ptrs))
+		return -ENOMEM;
+	if (likely(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 (unlikely(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 (;;) {
+		void *tmp;
+
+		l = left(i);
+		r = right(i);
+		if (l < heap->len && heap->gt(ptrs[l], ptrs[i]))
+			largest = l;
+		else
+			largest = i;
+		if (r < heap->len && heap->gt(ptrs[r], ptrs[largest]))
+			largest = r;
+		if (unlikely(largest == i))
+			break;
+		tmp = ptrs[i];
+		ptrs[i] = ptrs[largest];
+		ptrs[largest] = tmp;
+		i = largest;
+	}
+	check_heap(heap);
+}
+
+void *heap_replace_max(struct ptr_heap *heap, void *p)
+{
+	void *res;
+
+	if (unlikely(!heap->len)) {
+		(void) heap_set_len(heap, 1);
+		heap->ptrs[0] = p;
+		check_heap(heap);
+		return NULL;
+	}
+
+	/* Replace the current max and heapify */
+	res = heap->ptrs[0];
+	heap->ptrs[0] = p;
+	heapify(heap, 0);
+	return res;
+}
+
+int heap_insert(struct ptr_heap *heap, void *p)
+{
+	void **ptrs;
+	size_t pos;
+	int ret;
+
+	ret = heap_set_len(heap, heap->len + 1);
+	if (unlikely(ret))
+		return ret;
+	ptrs = heap->ptrs;
+	pos = heap->len - 1;
+	while (pos > 0 && heap->gt(p, ptrs[parent(pos)])) {
+		/* Move parent down until we find the right spot */
+		ptrs[pos] = ptrs[parent(pos)];
+		pos = parent(pos);
+	}
+	ptrs[pos] = p;
+	check_heap(heap);
+	return 0;
+}
+
+void *heap_remove(struct ptr_heap *heap)
+{
+	switch (heap->len) {
+	case 0:
+		return NULL;
+	case 1:
+		(void) heap_set_len(heap, 0);
+		return heap->ptrs[0];
+	}
+	/* Shrink, replace the current max by previous last entry and heapify */
+	heap_set_len(heap, heap->len - 1);
+	/* len changed. previous last entry is at heap->len */
+	return heap_replace_max(heap, heap->ptrs[heap->len]);
+}
+
+void *heap_cherrypick(struct ptr_heap *heap, void *p)
+{
+	size_t pos, len = heap->len;
+
+	for (pos = 0; pos < len; pos++)
+		if (unlikely(heap->ptrs[pos] == p))
+			goto found;
+	return NULL;
+found:
+	if (unlikely(heap->len == 1)) {
+		(void) heap_set_len(heap, 0);
+		check_heap(heap);
+		return heap->ptrs[0];
+	}
+	/* Replace p with previous last entry and heapify. */
+	heap_set_len(heap, heap->len - 1);
+	/* len changed. previous last entry is at heap->len */
+	heap->ptrs[pos] = heap->ptrs[heap->len];
+	heapify(heap, pos);
+	return p;
+}