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/*
*
* Copyright 2015, 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/alarm_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_alarm **first, int i, grpc_alarm *t) {
while (i > 0) {
int parent = (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_alarm **first, int i, int length,
grpc_alarm *t) {
for (;;) {
int left_child = 1 + 2 * i;
int right_child;
int next_i;
if (left_child >= length) break;
right_child = left_child + 1;
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_alarm_heap *heap) {
if (heap->alarm_count >= 8 &&
heap->alarm_count <= heap->alarm_capacity / SHRINK_FULLNESS_FACTOR / 2) {
heap->alarm_capacity = heap->alarm_count * SHRINK_FULLNESS_FACTOR;
heap->alarms =
gpr_realloc(heap->alarms, heap->alarm_capacity * sizeof(grpc_alarm *));
}
}
static void note_changed_priority(grpc_alarm_heap *heap, grpc_alarm *alarm) {
int i = alarm->heap_index;
int parent = (i - 1) / 2;
if (gpr_time_cmp(heap->alarms[parent]->deadline, alarm->deadline) < 0) {
adjust_upwards(heap->alarms, i, alarm);
} else {
adjust_downwards(heap->alarms, i, heap->alarm_count, alarm);
}
}
void grpc_alarm_heap_init(grpc_alarm_heap *heap) {
memset(heap, 0, sizeof(*heap));
}
void grpc_alarm_heap_destroy(grpc_alarm_heap *heap) { gpr_free(heap->alarms); }
int grpc_alarm_heap_add(grpc_alarm_heap *heap, grpc_alarm *alarm) {
if (heap->alarm_count == heap->alarm_capacity) {
heap->alarm_capacity =
GPR_MAX(heap->alarm_capacity + 1, heap->alarm_capacity * 3 / 2);
heap->alarms =
gpr_realloc(heap->alarms, heap->alarm_capacity * sizeof(grpc_alarm *));
}
alarm->heap_index = heap->alarm_count;
adjust_upwards(heap->alarms, heap->alarm_count, alarm);
heap->alarm_count++;
return alarm->heap_index == 0;
}
void grpc_alarm_heap_remove(grpc_alarm_heap *heap, grpc_alarm *alarm) {
int i = alarm->heap_index;
if (i == heap->alarm_count - 1) {
heap->alarm_count--;
maybe_shrink(heap);
return;
}
heap->alarms[i] = heap->alarms[heap->alarm_count - 1];
heap->alarms[i]->heap_index = i;
heap->alarm_count--;
maybe_shrink(heap);
note_changed_priority(heap, heap->alarms[i]);
}
int grpc_alarm_heap_is_empty(grpc_alarm_heap *heap) {
return heap->alarm_count == 0;
}
grpc_alarm *grpc_alarm_heap_top(grpc_alarm_heap *heap) {
return heap->alarms[0];
}
void grpc_alarm_heap_pop(grpc_alarm_heap *heap) {
grpc_alarm_heap_remove(heap, grpc_alarm_heap_top(heap));
}
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