mem-pool.c

   1 /*
   2  * Memory Pool implementation logic.
   3  */
   4
   5 #include "cache.h"
   6 #include "mem-pool.h"
   7
   8 #define BLOCK_GROWTH_SIZE 1024*1024 - sizeof(struct mp_block);
   9
  10 /*
  11  * Allocate a new mp_block and insert it after the block specified in
  12  * `insert_after`. If `insert_after` is NULL, then insert block at the
  13  * head of the linked list.
  14  */
  15 static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t block_alloc, struct mp_block *insert_after)
  16 {
  17         struct mp_block *p;
  18
  19         mem_pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
  20         p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
  21
  22         p->next_free = (char *)p->space;
  23         p->end = p->next_free + block_alloc;
  24
  25         if (insert_after) {
  26                 p->next_block = insert_after->next_block;
  27                 insert_after->next_block = p;
  28         } else {
  29                 p->next_block = mem_pool->mp_block;
  30                 mem_pool->mp_block = p;
  31         }
  32
  33         return p;
  34 }
  35
  36 void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size)
  37 {
  38         struct mem_pool *pool;
  39
  40         if (*mem_pool)
  41                 return;
  42
  43         pool = xcalloc(1, sizeof(*pool));
  44
  45         pool->block_alloc = BLOCK_GROWTH_SIZE;
  46
  47         if (initial_size > 0)
  48                 mem_pool_alloc_block(pool, initial_size, NULL);
  49
  50         *mem_pool = pool;
  51 }
  52
  53 void mem_pool_discard(struct mem_pool *mem_pool)
  54 {
  55         struct mp_block *block, *block_to_free;
  56
  57         while ((block = mem_pool->mp_block))
  58         {
  59                 block_to_free = block;
  60                 block = block->next_block;
  61                 free(block_to_free);
  62         }
  63
  64         free(mem_pool);
  65 }
  66
  67 void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
  68 {
  69         struct mp_block *p = NULL;
  70         void *r;
  71
  72         /* round up to a 'uintmax_t' alignment */
  73         if (len & (sizeof(uintmax_t) - 1))
  74                 len += sizeof(uintmax_t) - (len & (sizeof(uintmax_t) - 1));
  75
  76         if (mem_pool->mp_block &&
  77             mem_pool->mp_block->end - mem_pool->mp_block->next_free >= len)
  78                 p = mem_pool->mp_block;
  79
  80         if (!p) {
  81                 if (len >= (mem_pool->block_alloc / 2))
  82                         return mem_pool_alloc_block(mem_pool, len, mem_pool->mp_block);
  83
  84                 p = mem_pool_alloc_block(mem_pool, mem_pool->block_alloc, NULL);
  85         }
  86
  87         r = p->next_free;
  88         p->next_free += len;
  89         return r;
  90 }
  91
  92 void *mem_pool_calloc(struct mem_pool *mem_pool, size_t count, size_t size)
  93 {
  94         size_t len = st_mult(count, size);
  95         void *r = mem_pool_alloc(mem_pool, len);
  96         memset(r, 0, len);
  97         return r;
  98 }