mem-pool.c

   1 /*
   2  * Memory Pool implementation logic.
   3  */
   4
   5 #include "git-compat-util.h"
   6 #include "mem-pool.h"
   7 #include "gettext.h"
   8
   9 #define BLOCK_GROWTH_SIZE (1024 * 1024 - sizeof(struct mp_block))
  10
  11 /*
  12  * The inner union is an approximation for C11's max_align_t, and the
  13  * struct + offsetof computes _Alignof. This can all just be replaced
  14  * with _Alignof(max_align_t) if/when C11 is part of the baseline.
  15  * Note that _Alignof(X) need not be the same as sizeof(X); it's only
  16  * required to be a (possibly trivial) factor. They are the same for
  17  * most architectures, but m68k for example has only 2-byte alignment
  18  * for its 4-byte and 8-byte types, so using sizeof would waste space.
  19  *
  20  * Add more types to the union if the current set is insufficient.
  21  */
  22 struct git_max_alignment {
  23         char unalign;
  24         union {
  25                 uintmax_t max_align_uintmax;
  26                 void *max_align_pointer;
  27         } aligned;
  28 };
  29 #define GIT_MAX_ALIGNMENT offsetof(struct git_max_alignment, aligned)
  30
  31 /*
  32  * Allocate a new mp_block and insert it after the block specified in
  33  * `insert_after`. If `insert_after` is NULL, then insert block at the
  34  * head of the linked list.
  35  */
  36 static struct mp_block *mem_pool_alloc_block(struct mem_pool *pool,
  37                                              size_t block_alloc,
  38                                              struct mp_block *insert_after)
  39 {
  40         struct mp_block *p;
  41
  42         pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
  43         p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
  44
  45         p->next_free = (char *)p->space;
  46         p->end = p->next_free + block_alloc;
  47
  48         if (insert_after) {
  49                 p->next_block = insert_after->next_block;
  50                 insert_after->next_block = p;
  51         } else {
  52                 p->next_block = pool->mp_block;
  53                 pool->mp_block = p;
  54         }
  55
  56         return p;
  57 }
  58
  59 void mem_pool_init(struct mem_pool *pool, size_t initial_size)
  60 {
  61         memset(pool, 0, sizeof(*pool));
  62         pool->block_alloc = BLOCK_GROWTH_SIZE;
  63
  64         if (initial_size > 0)
  65                 mem_pool_alloc_block(pool, initial_size, NULL);
  66 }
  67
  68 void mem_pool_discard(struct mem_pool *pool, int invalidate_memory)
  69 {
  70         struct mp_block *block, *block_to_free;
  71
  72         block = pool->mp_block;
  73         while (block)
  74         {
  75                 block_to_free = block;
  76                 block = block->next_block;
  77
  78                 if (invalidate_memory)
  79                         memset(block_to_free->space, 0xDD, ((char *)block_to_free->end) - ((char *)block_to_free->space));
  80
  81                 free(block_to_free);
  82         }
  83
  84         pool->mp_block = NULL;
  85         pool->pool_alloc = 0;
  86 }
  87
  88 void *mem_pool_alloc(struct mem_pool *pool, size_t len)
  89 {
  90         struct mp_block *p = NULL;
  91         void *r;
  92
  93         len = DIV_ROUND_UP(len, GIT_MAX_ALIGNMENT) * GIT_MAX_ALIGNMENT;
  94
  95         if (pool->mp_block &&
  96             pool->mp_block->end - pool->mp_block->next_free >= len)
  97                 p = pool->mp_block;
  98
  99         if (!p) {
 100                 if (len >= (pool->block_alloc / 2))
 101                         p = mem_pool_alloc_block(pool, len, pool->mp_block);
 102                 else
 103                         p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
 104         }
 105
 106         r = p->next_free;
 107         p->next_free += len;
 108         return r;
 109 }
 110
 111 static char *mem_pool_strvfmt(struct mem_pool *pool, const char *fmt,
 112                               va_list ap)
 113 {
 114         struct mp_block *block = pool->mp_block;
 115         char *next_free = block ? block->next_free : NULL;
 116         size_t available = block ? block->end - block->next_free : 0;
 117         va_list cp;
 118         int len, len2;
 119         size_t size;
 120         char *ret;
 121
 122         va_copy(cp, ap);
 123         len = vsnprintf(next_free, available, fmt, cp);
 124         va_end(cp);
 125         if (len < 0)
 126                 die(_("unable to format message: %s"), fmt);
 127
 128         size = st_add(len, 1); /* 1 for NUL */
 129         ret = mem_pool_alloc(pool, size);
 130
 131         /* Shortcut; relies on mem_pool_alloc() not touching buffer contents. */
 132         if (ret == next_free)
 133                 return ret;
 134
 135         len2 = vsnprintf(ret, size, fmt, ap);
 136         if (len2 != len)
 137                 BUG("your vsnprintf is broken (returns inconsistent lengths)");
 138         return ret;
 139 }
 140
 141 char *mem_pool_strfmt(struct mem_pool *pool, const char *fmt, ...)
 142 {
 143         va_list ap;
 144         char *ret;
 145
 146         va_start(ap, fmt);
 147         ret = mem_pool_strvfmt(pool, fmt, ap);
 148         va_end(ap);
 149         return ret;
 150 }
 151
 152 void *mem_pool_calloc(struct mem_pool *pool, size_t count, size_t size)
 153 {
 154         size_t len = st_mult(count, size);
 155         void *r = mem_pool_alloc(pool, len);
 156         memset(r, 0, len);
 157         return r;
 158 }
 159
 160 char *mem_pool_strdup(struct mem_pool *pool, const char *str)
 161 {
 162         size_t len = strlen(str) + 1;
 163         char *ret = mem_pool_alloc(pool, len);
 164
 165         return memcpy(ret, str, len);
 166 }
 167
 168 char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
 169 {
 170         char *p = memchr(str, '\0', len);
 171         size_t actual_len = (p ? p - str : len);
 172         char *ret = mem_pool_alloc(pool, actual_len+1);
 173
 174         ret[actual_len] = '\0';
 175         return memcpy(ret, str, actual_len);
 176 }
 177
 178 int mem_pool_contains(struct mem_pool *pool, void *mem)
 179 {
 180         struct mp_block *p;
 181
 182         /* Check if memory is allocated in a block */
 183         for (p = pool->mp_block; p; p = p->next_block)
 184                 if ((mem >= ((void *)p->space)) &&
 185                     (mem < ((void *)p->end)))
 186                         return 1;
 187
 188         return 0;
 189 }
 190
 191 void mem_pool_combine(struct mem_pool *dst, struct mem_pool *src)
 192 {
 193         struct mp_block *p;
 194
 195         /* Append the blocks from src to dst */
 196         if (dst->mp_block && src->mp_block) {
 197                 /*
 198                  * src and dst have blocks, append
 199                  * blocks from src to dst.
 200                  */
 201                 p = dst->mp_block;
 202                 while (p->next_block)
 203                         p = p->next_block;
 204
 205                 p->next_block = src->mp_block;
 206         } else if (src->mp_block) {
 207                 /*
 208                  * src has blocks, dst is empty.
 209                  */
 210                 dst->mp_block = src->mp_block;
 211         } else {
 212                 /* src is empty, nothing to do. */
 213         }
 214
 215         dst->pool_alloc += src->pool_alloc;
 216         src->pool_alloc = 0;
 217         src->mp_block = NULL;
 218 }