Use lttng_ prefixed namespace for lttng prio heap

[lttng-modules.git] / lib / prio_heap / lttng_prio_heap.c

diff --git a/lib/prio_heap/lttng_prio_heap.c b/lib/prio_heap/lttng_prio_heap.c
new file mode 100644 (file)
index 0000000..5bbd079
--- /dev/null
+++ b/lib/prio_heap/lttng_prio_heap.c
@@ -0,0 +1,206 @@
+/*
+ * lttng_prio_heap.c
+ *
+ * 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 <linux/slab.h>
+#include "lttng_prio_heap.h"
+
+#ifdef DEBUG_HEAP
+void lttng_check_heap(const struct lttng_ptr_heap *heap)
+{
+       size_t i;
+
+       if (!heap->len)
+               return;
+
+       for (i = 1; i < heap->len; i++)
+               WARN_ON_ONCE(!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 lttng_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 = kmalloc(heap->alloc_len * sizeof(void *), heap->gfpmask);
+       if (!new_ptrs)
+               return -ENOMEM;
+       if (heap->ptrs)
+               memcpy(new_ptrs, heap->ptrs, heap->len * sizeof(void *));
+       kfree(heap->ptrs);
+       heap->ptrs = new_ptrs;
+       return 0;
+}
+
+static
+int heap_set_len(struct lttng_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 lttng_heap_init(struct lttng_ptr_heap *heap, size_t alloc_len,
+             gfp_t gfpmask, 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 lttng_heap_free(struct lttng_ptr_heap *heap)
+{
+       kfree(heap->ptrs);
+}
+
+static void heapify(struct lttng_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 (largest == i)
+                       break;
+               tmp = ptrs[i];
+               ptrs[i] = ptrs[largest];
+               ptrs[largest] = tmp;
+               i = largest;
+       }
+       lttng_check_heap(heap);
+}
+
+void *lttng_heap_replace_max(struct lttng_ptr_heap *heap, void *p)
+{
+       void *res;
+
+       if (!heap->len) {
+               (void) heap_set_len(heap, 1);
+               heap->ptrs[0] = p;
+               lttng_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 lttng_heap_insert(struct lttng_ptr_heap *heap, void *p)
+{
+       void **ptrs;
+       size_t pos;
+       int ret;
+
+       ret = heap_set_len(heap, heap->len + 1);
+       if (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;
+       lttng_check_heap(heap);
+       return 0;
+}
+
+void *lttng_heap_remove(struct lttng_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 lttng_heap_replace_max(heap, heap->ptrs[heap->len]);
+}
+
+void *lttng_heap_cherrypick(struct lttng_ptr_heap *heap, void *p)
+{
+       size_t pos, len = heap->len;
+
+       for (pos = 0; pos < len; pos++)
+               if (heap->ptrs[pos] == p)
+                       goto found;
+       return NULL;
+found:
+       if (heap->len == 1) {
+               (void) heap_set_len(heap, 0);
+               lttng_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;
+}