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Diffstat (limited to 'src/core/lib/iomgr/timer_heap.c')
-rw-r--r-- | src/core/lib/iomgr/timer_heap.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/src/core/lib/iomgr/timer_heap.c b/src/core/lib/iomgr/timer_heap.c new file mode 100644 index 0000000000..d43b6ccf75 --- /dev/null +++ b/src/core/lib/iomgr/timer_heap.c @@ -0,0 +1,146 @@ +/* + * + * Copyright 2015-2016, 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/lib/iomgr/timer_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_timer **first, uint32_t i, grpc_timer *t) { + while (i > 0) { + uint32_t parent = (uint32_t)(((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_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 && + 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_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 = + 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 = (uint32_t)(((int)i - 1) / 2); + if (gpr_time_cmp(heap->timers[parent]->deadline, timer->deadline) > 0) { + 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); } + +int 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 = + 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]); +} + +int 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)); +} |