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/*
*
* 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));
}
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