1 files changed, 137 insertions, 0 deletions
diff --git a/src/core/lib/iomgr/timer_heap.cc b/src/core/lib/iomgr/timer_heap.cc
new file mode 100644
index 0000000000..2648d5da5d
--- /dev/null
+++ b/src/core/lib/iomgr/timer_heap.cc
@@ -0,0 +1,137 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_TIMER_USE_GENERIC
+
+#include "src/core/lib/iomgr/timer_heap.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/useful.h>
+
+/* Adjusts a heap so as to move a hole at position i closer to the root,
+   until a suitable position is found for element t. Then, copies t into that
+   position. This functor is called each time immediately after modifying a
+   value in the underlying container, with the offset of the modified element as
+   its argument. */
+static void adjust_upwards(grpc_timer **first, uint32_t i, grpc_timer *t) {
+  while (i > 0) {
+    uint32_t parent = (uint32_t)(((int)i - 1) / 2);
+    if (first[parent]->deadline <= t->deadline) break;
+    first[i] = first[parent];
+    first[i]->heap_index = i;
+    i = parent;
+  }
+  first[i] = t;
+  t->heap_index = i;
+}
+
+/* Adjusts a heap so as to move a hole at position i farther away from the root,
+   until a suitable position is found for element t.  Then, copies t into that
+   position. */
+static void adjust_downwards(grpc_timer **first, uint32_t i, uint32_t length,
+                             grpc_timer *t) {
+  for (;;) {
+    uint32_t left_child = 1u + 2u * i;
+    if (left_child >= length) break;
+    uint32_t right_child = left_child + 1;
+    uint32_t next_i =
+        right_child < length &&
+                first[left_child]->deadline > first[right_child]->deadline
+            ? right_child
+            : left_child;
+    if (t->deadline <= first[next_i]->deadline) break;
+    first[i] = first[next_i];
+    first[i]->heap_index = i;
+    i = next_i;
+  }
+  first[i] = t;
+  t->heap_index = i;
+}
+
+#define SHRINK_MIN_ELEMS 8
+#define SHRINK_FULLNESS_FACTOR 2
+
+static void maybe_shrink(grpc_timer_heap *heap) {
+  if (heap->timer_count >= 8 &&
+      heap->timer_count <= heap->timer_capacity / SHRINK_FULLNESS_FACTOR / 2) {
+    heap->timer_capacity = heap->timer_count * SHRINK_FULLNESS_FACTOR;
+    heap->timers = (grpc_timer **)gpr_realloc(
+        heap->timers, heap->timer_capacity * sizeof(grpc_timer *));
+  }
+}
+
+static void note_changed_priority(grpc_timer_heap *heap, grpc_timer *timer) {
+  uint32_t i = timer->heap_index;
+  uint32_t parent = (uint32_t)(((int)i - 1) / 2);
+  if (heap->timers[parent]->deadline > timer->deadline) {
+    adjust_upwards(heap->timers, i, timer);
+  } else {
+    adjust_downwards(heap->timers, i, heap->timer_count, timer);
+  }
+}
+
+void grpc_timer_heap_init(grpc_timer_heap *heap) {
+  memset(heap, 0, sizeof(*heap));
+}
+
+void grpc_timer_heap_destroy(grpc_timer_heap *heap) { gpr_free(heap->timers); }
+
+int grpc_timer_heap_add(grpc_timer_heap *heap, grpc_timer *timer) {
+  if (heap->timer_count == heap->timer_capacity) {
+    heap->timer_capacity =
+        GPR_MAX(heap->timer_capacity + 1, heap->timer_capacity * 3 / 2);
+    heap->timers = (grpc_timer **)gpr_realloc(
+        heap->timers, heap->timer_capacity * sizeof(grpc_timer *));
+  }
+  timer->heap_index = heap->timer_count;
+  adjust_upwards(heap->timers, heap->timer_count, timer);
+  heap->timer_count++;
+  return timer->heap_index == 0;
+}
+
+void grpc_timer_heap_remove(grpc_timer_heap *heap, grpc_timer *timer) {
+  uint32_t i = timer->heap_index;
+  if (i == heap->timer_count - 1) {
+    heap->timer_count--;
+    maybe_shrink(heap);
+    return;
+  }
+  heap->timers[i] = heap->timers[heap->timer_count - 1];
+  heap->timers[i]->heap_index = i;
+  heap->timer_count--;
+  maybe_shrink(heap);
+  note_changed_priority(heap, heap->timers[i]);
+}
+
+int grpc_timer_heap_is_empty(grpc_timer_heap *heap) {
+  return heap->timer_count == 0;
+}
+
+grpc_timer *grpc_timer_heap_top(grpc_timer_heap *heap) {
+  return heap->timers[0];
+}
+
+void grpc_timer_heap_pop(grpc_timer_heap *heap) {
+  grpc_timer_heap_remove(heap, grpc_timer_heap_top(heap));
+}
+
+#endif /* GRPC_TIMER_USE_GENERIC */