mem-pool.c

   1 /*
   2  * Memory Pool implementation logic.
   3  */
   4
   5 #include "git-compat-util.h"
   6 #include "mem-pool.h"
   7
   8 #define BLOCK_GROWTH_SIZE (1024 * 1024 - sizeof(struct mp_block))
   9
  10 /*
  11  * The inner union is an approximation for C11's max_align_t, and the
  12  * struct + offsetof computes _Alignof. This can all just be replaced
  13  * with _Alignof(max_align_t) if/when C11 is part of the baseline.
  14  * Note that _Alignof(X) need not be the same as sizeof(X); it's only
  15  * required to be a (possibly trivial) factor. They are the same for
  16  * most architectures, but m68k for example has only 2-byte alignment
  17  * for its 4-byte and 8-byte types, so using sizeof would waste space.
  18  *
  19  * Add more types to the union if the current set is insufficient.
  20  */
  21 struct git_max_alignment {
  22         char unalign;
  23         union {
  24                 uintmax_t max_align_uintmax;
  25                 void *max_align_pointer;
  26         } aligned;
  27 };
  28 #define GIT_MAX_ALIGNMENT offsetof(struct git_max_alignment, aligned)
  29
  30 /*
  31  * Allocate a new mp_block and insert it after the block specified in
  32  * `insert_after`. If `insert_after` is NULL, then insert block at the
  33  * head of the linked list.
  34  */
  35 static struct mp_block *mem_pool_alloc_block(struct mem_pool *pool,
  36                                              size_t block_alloc,
  37                                              struct mp_block *insert_after)
  38 {
  39         struct mp_block *p;
  40
  41         pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
  42         p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
  43
  44         p->next_free = (char *)p->space;
  45         p->end = p->next_free + block_alloc;
  46
  47         if (insert_after) {
  48                 p->next_block = insert_after->next_block;
  49                 insert_after->next_block = p;
  50         } else {
  51                 p->next_block = pool->mp_block;
  52                 pool->mp_block = p;
  53         }
  54
  55         return p;
  56 }
  57
  58 void mem_pool_init(struct mem_pool *pool, size_t initial_size)
  59 {
  60         memset(pool, 0, sizeof(*pool));
  61         pool->block_alloc = BLOCK_GROWTH_SIZE;
  62
  63         if (initial_size > 0)
  64                 mem_pool_alloc_block(pool, initial_size, NULL);
  65 }
  66
  67 void mem_pool_discard(struct mem_pool *pool, int invalidate_memory)
  68 {
  69         struct mp_block *block, *block_to_free;
  70
  71         block = pool->mp_block;
  72         while (block)
  73         {
  74                 block_to_free = block;
  75                 block = block->next_block;
  76
  77                 if (invalidate_memory)
  78                         memset(block_to_free->space, 0xDD, ((char *)block_to_free->end) - ((char *)block_to_free->space));
  79
  80                 free(block_to_free);
  81         }
  82
  83         pool->mp_block = NULL;
  84         pool->pool_alloc = 0;
  85 }
  86
  87 void *mem_pool_alloc(struct mem_pool *pool, size_t len)
  88 {
  89         struct mp_block *p = NULL;
  90         void *r;
  91
  92         /* round up to a 'GIT_MAX_ALIGNMENT' alignment */
  93         if (len & (GIT_MAX_ALIGNMENT - 1))
  94                 len += GIT_MAX_ALIGNMENT - (len & (GIT_MAX_ALIGNMENT - 1));
  95
  96         if (pool->mp_block &&
  97             pool->mp_block->end - pool->mp_block->next_free >= len)
  98                 p = pool->mp_block;
  99
 100         if (!p) {
 101                 if (len >= (pool->block_alloc / 2))
 102                         return mem_pool_alloc_block(pool, len, pool->mp_block);
 103
 104                 p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
 105         }
 106
 107         r = p->next_free;
 108         p->next_free += len;
 109         return r;
 110 }
 111
 112 void *mem_pool_calloc(struct mem_pool *pool, size_t count, size_t size)
 113 {
 114         size_t len = st_mult(count, size);
 115         void *r = mem_pool_alloc(pool, len);
 116         memset(r, 0, len);
 117         return r;
 118 }
 119
 120 char *mem_pool_strdup(struct mem_pool *pool, const char *str)
 121 {
 122         size_t len = strlen(str) + 1;
 123         char *ret = mem_pool_alloc(pool, len);
 124
 125         return memcpy(ret, str, len);
 126 }
 127
 128 char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
 129 {
 130         char *p = memchr(str, '\0', len);
 131         size_t actual_len = (p ? p - str : len);
 132         char *ret = mem_pool_alloc(pool, actual_len+1);
 133
 134         ret[actual_len] = '\0';
 135         return memcpy(ret, str, actual_len);
 136 }
 137
 138 int mem_pool_contains(struct mem_pool *pool, void *mem)
 139 {
 140         struct mp_block *p;
 141
 142         /* Check if memory is allocated in a block */
 143         for (p = pool->mp_block; p; p = p->next_block)
 144                 if ((mem >= ((void *)p->space)) &&
 145                     (mem < ((void *)p->end)))
 146                         return 1;
 147
 148         return 0;
 149 }
 150
 151 void mem_pool_combine(struct mem_pool *dst, struct mem_pool *src)
 152 {
 153         struct mp_block *p;
 154
 155         /* Append the blocks from src to dst */
 156         if (dst->mp_block && src->mp_block) {
 157                 /*
 158                  * src and dst have blocks, append
 159                  * blocks from src to dst.
 160                  */
 161                 p = dst->mp_block;
 162                 while (p->next_block)
 163                         p = p->next_block;
 164
 165                 p->next_block = src->mp_block;
 166         } else if (src->mp_block) {
 167                 /*
 168                  * src has blocks, dst is empty.
 169                  */
 170                 dst->mp_block = src->mp_block;
 171         } else {
 172                 /* src is empty, nothing to do. */
 173         }
 174
 175         dst->pool_alloc += src->pool_alloc;
 176         src->pool_alloc = 0;
 177         src->mp_block = NULL;
 178 }