--- /dev/null
+/*
+ *
+ * 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 <grpc/support/port_platform.h>
+
+#include "src/core/lib/iomgr/port.h"
+
+#include "src/core/lib/iomgr/timer_heap.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+
+#include "src/core/lib/gpr/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 = static_cast<uint32_t>((static_cast<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 = static_cast<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 = static_cast<uint32_t>((static_cast<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); }
+
+bool 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 = static_cast<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]);
+}
+
+bool 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));
+}