1 /*
2 *
3 * Copyright 2015 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19 #include <grpc/support/port_platform.h>
20
21 #include "src/core/lib/iomgr/port.h"
22
23 #include "src/core/lib/iomgr/timer_heap.h"
24
25 #include <string.h>
26
27 #include <grpc/support/alloc.h>
28
29 #include "src/core/lib/gpr/useful.h"
30
31 /* Adjusts a heap so as to move a hole at position i closer to the root,
32 until a suitable position is found for element t. Then, copies t into that
33 position. This functor is called each time immediately after modifying a
34 value in the underlying container, with the offset of the modified element as
35 its argument. */
adjust_upwards(grpc_timer ** first,uint32_t i,grpc_timer * t)36 static void adjust_upwards(grpc_timer** first, uint32_t i, grpc_timer* t) {
37 while (i > 0) {
38 uint32_t parent = static_cast<uint32_t>((static_cast<int>(i) - 1) / 2);
39 if (first[parent]->deadline <= t->deadline) break;
40 first[i] = first[parent];
41 first[i]->heap_index = i;
42 i = parent;
43 }
44 first[i] = t;
45 t->heap_index = i;
46 }
47
48 /* Adjusts a heap so as to move a hole at position i farther away from the root,
49 until a suitable position is found for element t. Then, copies t into that
50 position. */
adjust_downwards(grpc_timer ** first,uint32_t i,uint32_t length,grpc_timer * t)51 static void adjust_downwards(grpc_timer** first, uint32_t i, uint32_t length,
52 grpc_timer* t) {
53 for (;;) {
54 uint32_t left_child = 1u + 2u * i;
55 if (left_child >= length) break;
56 uint32_t right_child = left_child + 1;
57 uint32_t next_i = right_child < length && first[left_child]->deadline >
58 first[right_child]->deadline
59 ? right_child
60 : left_child;
61 if (t->deadline <= first[next_i]->deadline) break;
62 first[i] = first[next_i];
63 first[i]->heap_index = i;
64 i = next_i;
65 }
66 first[i] = t;
67 t->heap_index = i;
68 }
69
70 #define SHRINK_MIN_ELEMS 8
71 #define SHRINK_FULLNESS_FACTOR 2
72
maybe_shrink(grpc_timer_heap * heap)73 static void maybe_shrink(grpc_timer_heap* heap) {
74 if (heap->timer_count >= 8 &&
75 heap->timer_count <= heap->timer_capacity / SHRINK_FULLNESS_FACTOR / 2) {
76 heap->timer_capacity = heap->timer_count * SHRINK_FULLNESS_FACTOR;
77 heap->timers = static_cast<grpc_timer**>(
78 gpr_realloc(heap->timers, heap->timer_capacity * sizeof(grpc_timer*)));
79 }
80 }
81
note_changed_priority(grpc_timer_heap * heap,grpc_timer * timer)82 static void note_changed_priority(grpc_timer_heap* heap, grpc_timer* timer) {
83 uint32_t i = timer->heap_index;
84 uint32_t parent = static_cast<uint32_t>((static_cast<int>(i) - 1) / 2);
85 if (heap->timers[parent]->deadline > timer->deadline) {
86 adjust_upwards(heap->timers, i, timer);
87 } else {
88 adjust_downwards(heap->timers, i, heap->timer_count, timer);
89 }
90 }
91
grpc_timer_heap_init(grpc_timer_heap * heap)92 void grpc_timer_heap_init(grpc_timer_heap* heap) {
93 memset(heap, 0, sizeof(*heap));
94 }
95
grpc_timer_heap_destroy(grpc_timer_heap * heap)96 void grpc_timer_heap_destroy(grpc_timer_heap* heap) { gpr_free(heap->timers); }
97
grpc_timer_heap_add(grpc_timer_heap * heap,grpc_timer * timer)98 int grpc_timer_heap_add(grpc_timer_heap* heap, grpc_timer* timer) {
99 if (heap->timer_count == heap->timer_capacity) {
100 heap->timer_capacity =
101 GPR_MAX(heap->timer_capacity + 1, heap->timer_capacity * 3 / 2);
102 heap->timers = static_cast<grpc_timer**>(
103 gpr_realloc(heap->timers, heap->timer_capacity * sizeof(grpc_timer*)));
104 }
105 timer->heap_index = heap->timer_count;
106 adjust_upwards(heap->timers, heap->timer_count, timer);
107 heap->timer_count++;
108 return timer->heap_index == 0;
109 }
110
grpc_timer_heap_remove(grpc_timer_heap * heap,grpc_timer * timer)111 void grpc_timer_heap_remove(grpc_timer_heap* heap, grpc_timer* timer) {
112 uint32_t i = timer->heap_index;
113 if (i == heap->timer_count - 1) {
114 heap->timer_count--;
115 maybe_shrink(heap);
116 return;
117 }
118 heap->timers[i] = heap->timers[heap->timer_count - 1];
119 heap->timers[i]->heap_index = i;
120 heap->timer_count--;
121 maybe_shrink(heap);
122 note_changed_priority(heap, heap->timers[i]);
123 }
124
grpc_timer_heap_is_empty(grpc_timer_heap * heap)125 int grpc_timer_heap_is_empty(grpc_timer_heap* heap) {
126 return heap->timer_count == 0;
127 }
128
grpc_timer_heap_top(grpc_timer_heap * heap)129 grpc_timer* grpc_timer_heap_top(grpc_timer_heap* heap) {
130 return heap->timers[0];
131 }
132
grpc_timer_heap_pop(grpc_timer_heap * heap)133 void grpc_timer_heap_pop(grpc_timer_heap* heap) {
134 grpc_timer_heap_remove(heap, grpc_timer_heap_top(heap));
135 }
136