src/st-heap.c

   1 /*
   2  * st-heap.c
   3  *
   4  * Copyright (C) 2008 Vincent Geddes
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23 */
  24
  25
  26 #include "st-heap.h"
  27 #include "st-utils.h"
  28 #include "st-system.h"
  29
  30 #define PAGE_SIZE (st_system_pagesize ())
  31
  32 static inline st_uint
  33 round_pagesize (st_uint size)
  34 {
  35     return ((size + PAGE_SIZE - 1) / PAGE_SIZE) * PAGE_SIZE;
  36 }
  37
  38 st_heap *
  39 st_heap_new (st_uint reserved_size)
  40 {
  41     /* Create a new heap with a reserved address space.
  42      * Returns NULL if address space could not be reserved
  43      */
  44     st_pointer result;
  45     st_heap   *heap;
  46     st_uint    size;
  47
  48     st_assert (reserved_size > 0);
  49     size = round_pagesize (reserved_size);
  50
  51     result = st_system_reserve_memory (NULL, size);
  52     if (result == NULL)
  53         return NULL;
  54
  55     heap = st_new0 (st_heap);
  56
  57     heap->start = result;
  58     heap->end = result + size;
  59     heap->p = result;
  60
  61     return heap;
  62 }
  63
  64 bool
  65 st_heap_grow (st_heap *heap, st_uint grow_size)
  66 {
  67     /* Grows the heap by the specified amount (in bytes).
  68      * The primitive will not succeed if the heap runs out
  69      * of reserved address space.
  70      */
  71     st_pointer result;
  72     st_uint    size;
  73
  74     st_assert (grow_size > 0);
  75     size = round_pagesize (grow_size);
  76
  77     if ((heap->p + size) >= heap->end)
  78         return false;
  79
  80     result = st_system_commit_memory (heap->p, size);
  81     if (result == NULL)
  82         return false;
  83
  84     heap->p += size;
  85
  86     return true;
  87 }
  88
  89 bool
  90 st_heap_shrink (st_heap *heap, st_uint shrink_size)
  91 {
  92     /* Shrinks the heap by the specified amount (in bytes).
  93      */
  94     st_pointer result;
  95     st_uint    size;
  96
  97     st_assert (shrink_size > 0);
  98     size = round_pagesize (shrink_size);
  99
 100     if ((heap->p - size) < heap->start)
 101         return false;
 102
 103     result = st_system_decommit_memory (heap->p - size, size);
 104     if (result == NULL)
 105         return false;
 106
 107     heap->p -= size;
 108
 109     return true;
 110 }
 111
 112 void
 113 st_heap_destroy (st_heap *heap)
 114 {
 115     st_system_release_memory (heap->start, heap->end - heap->start);
 116     st_free (heap);
 117 }