| /* |
| * |
| * 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, gpr_uint32 i, grpc_alarm * t) |
| { |
| while (i > 0) |
| { |
| gpr_uint32 parent = (gpr_uint32) (((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_alarm ** first, gpr_uint32 i, gpr_uint32 length, grpc_alarm * t) |
| { |
| for (;;) |
| { |
| gpr_uint32 left_child = 1u + 2u * i; |
| gpr_uint32 right_child; |
| gpr_uint32 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) |
| { |
| gpr_uint32 i = alarm->heap_index; |
| gpr_uint32 parent = (gpr_uint32) (((int) 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) |
| { |
| gpr_uint32 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)); |
| } |