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         len = DIV_ROUND_UP(len, GIT_MAX_ALIGNMENT) * GIT_MAX_ALIGNMENT;
  93
  94         if (pool->mp_block &&
  95             pool->mp_block->end - pool->mp_block->next_free >= len)
  96                 p = pool->mp_block;
  97
  98         if (!p) {
  99                 if (len >= (pool->block_alloc / 2))
 100                         p = mem_pool_alloc_block(pool, len, pool->mp_block);
 101                 else
 102                         p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
 103         }
 104
 105         r = p->next_free;
 106         p->next_free += len;
 107         return r;
 108 }
 109
 110 static char *mem_pool_strvfmt(struct mem_pool *pool, const char *fmt,
 111                               va_list ap)
 112 {
 113         struct mp_block *block = pool->mp_block;
 114         char *next_free = block ? block->next_free : NULL;
 115         size_t available = block ? block->end - block->next_free : 0;
 116         va_list cp;
 117         int len, len2;
 118         size_t size;
 119         char *ret;
 120
 121         va_copy(cp, ap);
 122         len = vsnprintf(next_free, available, fmt, cp);
 123         va_end(cp);
 124         if (len < 0)
 125                 BUG("your vsnprintf is broken (returned %d)", len);
 126
 127         size = st_add(len, 1); /* 1 for NUL */
 128         ret = mem_pool_alloc(pool, size);
 129
 130         /* Shortcut; relies on mem_pool_alloc() not touching buffer contents. */
 131         if (ret == next_free)
 132                 return ret;
 133
 134         len2 = vsnprintf(ret, size, fmt, ap);
 135         if (len2 != len)
 136                 BUG("your vsnprintf is broken (returns inconsistent lengths)");
 137         return ret;
 138 }
 139
 140 char *mem_pool_strfmt(struct mem_pool *pool, const char *fmt, ...)
 141 {
 142         va_list ap;
 143         char *ret;
 144
 145         va_start(ap, fmt);
 146         ret = mem_pool_strvfmt(pool, fmt, ap);
 147         va_end(ap);
 148         return ret;
 149 }
 150
 151 void *mem_pool_calloc(struct mem_pool *pool, size_t count, size_t size)
 152 {
 153         size_t len = st_mult(count, size);
 154         void *r = mem_pool_alloc(pool, len);
 155         memset(r, 0, len);
 156         return r;
 157 }
 158
 159 char *mem_pool_strdup(struct mem_pool *pool, const char *str)
 160 {
 161         size_t len = strlen(str) + 1;
 162         char *ret = mem_pool_alloc(pool, len);
 163
 164         return memcpy(ret, str, len);
 165 }
 166
 167 char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
 168 {
 169         char *p = memchr(str, '\0', len);
 170         size_t actual_len = (p ? p - str : len);
 171         char *ret = mem_pool_alloc(pool, actual_len+1);
 172
 173         ret[actual_len] = '\0';
 174         return memcpy(ret, str, actual_len);
 175 }
 176
 177 int mem_pool_contains(struct mem_pool *pool, void *mem)
 178 {
 179         struct mp_block *p;
 180
 181         /* Check if memory is allocated in a block */
 182         for (p = pool->mp_block; p; p = p->next_block)
 183                 if ((mem >= ((void *)p->space)) &&
 184                     (mem < ((void *)p->end)))
 185                         return 1;
 186
 187         return 0;
 188 }
 189
 190 void mem_pool_combine(struct mem_pool *dst, struct mem_pool *src)
 191 {
 192         struct mp_block *p;
 193
 194         /* Append the blocks from src to dst */
 195         if (dst->mp_block && src->mp_block) {
 196                 /*
 197                  * src and dst have blocks, append
 198                  * blocks from src to dst.
 199                  */
 200                 p = dst->mp_block;
 201                 while (p->next_block)
 202                         p = p->next_block;
 203
 204                 p->next_block = src->mp_block;
 205         } else if (src->mp_block) {
 206                 /*
 207                  * src has blocks, dst is empty.
 208                  */
 209                 dst->mp_block = src->mp_block;
 210         } else {
 211                 /* src is empty, nothing to do. */
 212         }
 213
 214         dst->pool_alloc += src->pool_alloc;
 215         src->pool_alloc = 0;
 216         src->mp_block = NULL;
 217 }