Initial checkin of gRPC to third_party/

third_party/grpc/src/core/iomgr/timer_heap.c

+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/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 (gpr_time_cmp(first[parent]->deadline, t->deadline) <= 0) 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 &&
+                              gpr_time_cmp(first[left_child]->deadline,
+                                           first[right_child]->deadline) > 0
+                          ? right_child
+                          : left_child;
+    if (gpr_time_cmp(t->deadline, first[next_i]->deadline) <= 0) 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 =
+        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 (gpr_time_cmp(heap->timers[parent]->deadline, timer->deadline) > 0) {
+    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 =
+        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));
+}