src/common/index-allocator.c

   1 /*
   2  * Copyright (C) 2020 Francis Deslauriers <francis.deslauriers@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #include <assert.h>
   9 #include <inttypes.h>
  10
  11 #include <urcu.h>
  12 #include <urcu/list.h>
  13
  14 #include "macros.h"
  15 #include "error.h"
  16
  17 #include "index-allocator.h"
  18
  19 struct lttng_index_allocator {
  20         struct cds_list_head unused_list;
  21         uint64_t size;
  22         uint64_t position;
  23 };
  24
  25 struct lttng_index {
  26         uint64_t index;
  27         struct cds_list_head head;
  28 };
  29
  30 struct lttng_index_allocator *lttng_index_allocator_create(
  31                 uint64_t index_count)
  32 {
  33         struct lttng_index_allocator *allocator = NULL;
  34
  35         allocator = zmalloc(sizeof(*allocator));
  36         if (!allocator) {
  37                 PERROR("Failed to allocate free index queue");
  38                 goto end;
  39         }
  40         allocator->size = index_count;
  41         allocator->position = 0;
  42
  43         CDS_INIT_LIST_HEAD(&allocator->unused_list);
  44
  45 end:
  46         return allocator;
  47 }
  48
  49 uint64_t lttng_index_allocator_get_index_count(struct lttng_index_allocator *allocator)
  50 {
  51         return allocator->size;
  52 }
  53
  54 enum lttng_index_allocator_status lttng_index_allocator_alloc(
  55                 struct lttng_index_allocator *allocator,
  56                 uint64_t *allocated_index)
  57 {
  58         enum lttng_index_allocator_status status =
  59                         LTTNG_INDEX_ALLOCATOR_STATUS_OK;
  60
  61         if (cds_list_empty(&allocator->unused_list)) {
  62                 if (allocator->position >= allocator->size) {
  63                         /* No indices left. */
  64                         status = LTTNG_INDEX_ALLOCATOR_STATUS_EMPTY;
  65                         goto end;
  66                 }
  67
  68                 *allocated_index = allocator->position++;
  69         } else {
  70                 struct lttng_index *index;
  71
  72                 index = cds_list_first_entry(&allocator->unused_list,
  73                                 typeof(*index), head);
  74                 cds_list_del(&index->head);
  75                 *allocated_index = index->index;
  76                 free(index);
  77         }
  78
  79 end:
  80         return status;
  81 }
  82
  83 enum lttng_index_allocator_status lttng_index_allocator_release(
  84                 struct lttng_index_allocator *allocator, uint64_t idx)
  85 {
  86         struct lttng_index *index = NULL;
  87         enum lttng_index_allocator_status status =
  88                         LTTNG_INDEX_ALLOCATOR_STATUS_OK;
  89
  90         assert(idx < allocator->size);
  91
  92         index = zmalloc(sizeof(*index));
  93         if (!index) {
  94                 PERROR("Failed to allocate free index queue");
  95                 status = LTTNG_INDEX_ALLOCATOR_STATUS_ERROR;
  96                 goto end;
  97         }
  98
  99         index->index = idx;
 100         cds_list_add_tail(&index->head, &allocator->unused_list);
 101
 102 end:
 103         return status;
 104 }
 105
 106 void lttng_index_allocator_destroy(struct lttng_index_allocator *allocator)
 107 {
 108         struct lttng_index *index = NULL, *tmp_index = NULL;
 109
 110         if (!allocator) {
 111                 return;
 112         }
 113
 114         cds_list_for_each_entry_safe(index, tmp_index,
 115                         &allocator->unused_list, head) {
 116                 cds_list_del(&index->head);
 117                 free(index);
 118         }
 119
 120         free(allocator);
 121 }