lib/ccan/htable/htable.c

   1 #include <ccan/htable/htable.h>
   2 #include <ccan/compiler/compiler.h>
   3 #include <stdint.h>
   4 #include <stdlib.h>
   5 #include <limits.h>
   6 #include <stdbool.h>
   7 #include <assert.h>
   8
   9 /* This means a struct htable takes at least 512 bytes / 1k (32/64 bits). */
  10 #define HTABLE_BASE_BITS 7
  11
  12 /* We use 0x1 as deleted marker. */
  13 #define HTABLE_DELETED (0x1)
  14
  15 struct htable {
  16         size_t (*rehash)(const void *elem, void *priv);
  17         void *priv;
  18         unsigned int bits;
  19         size_t elems, deleted, max, max_with_deleted;
  20         /* These are the bits which are the same in all pointers. */
  21         uintptr_t common_mask, common_bits;
  22         uintptr_t perfect_bit;
  23         uintptr_t *table;
  24 };
  25
  26 /* We clear out the bits which are always the same, and put metadata there. */
  27 static inline uintptr_t get_extra_ptr_bits(const struct htable *ht,
  28                                            uintptr_t e)
  29 {
  30         return e & ht->common_mask;
  31 }
  32
  33 static inline void *get_raw_ptr(const struct htable *ht, uintptr_t e)
  34 {
  35         return (void *)((e & ~ht->common_mask) | ht->common_bits);
  36 }
  37
  38 static inline uintptr_t make_hval(const struct htable *ht,
  39                                   const void *p, uintptr_t bits)
  40 {
  41         return ((uintptr_t)p & ~ht->common_mask) | bits;
  42 }
  43
  44 static inline bool entry_is_valid(uintptr_t e)
  45 {
  46         return e > HTABLE_DELETED;
  47 }
  48
  49 static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
  50                                           size_t hash)
  51 {
  52         /* Shuffling the extra bits (as specified in mask) down the
  53          * end is quite expensive.  But the lower bits are redundant, so
  54          * we fold the value first. */
  55         return (hash ^ (hash >> ht->bits))
  56                 & ht->common_mask & ~ht->perfect_bit;
  57 }
  58
  59 struct htable *htable_new(size_t (*rehash)(const void *elem, void *priv),
  60                           void *priv)
  61 {
  62         struct htable *ht = malloc(sizeof(struct htable));
  63         if (ht) {
  64                 ht->bits = HTABLE_BASE_BITS;
  65                 ht->rehash = rehash;
  66                 ht->priv = priv;
  67                 ht->elems = 0;
  68                 ht->deleted = 0;
  69                 ht->max = ((size_t)1 << ht->bits) * 3 / 4;
  70                 ht->max_with_deleted = ((size_t)1 << ht->bits) * 9 / 10;
  71                 /* This guarantees we enter update_common first add. */
  72                 ht->common_mask = -1;
  73                 ht->common_bits = 0;
  74                 ht->perfect_bit = 0;
  75                 ht->table = calloc(1 << ht->bits, sizeof(uintptr_t));
  76                 if (!ht->table) {
  77                         free(ht);
  78                         ht = NULL;
  79                 }
  80         }
  81         return ht;
  82 }
  83
  84 void htable_free(const struct htable *ht)
  85 {
  86         free((void *)ht->table);
  87         free((void *)ht);
  88 }
  89
  90 static size_t hash_bucket(const struct htable *ht, size_t h)
  91 {
  92         return h & ((1 << ht->bits)-1);
  93 }
  94
  95 static void *htable_val(const struct htable *ht,
  96                         struct htable_iter *i, size_t hash, uintptr_t perfect)
  97 {
  98         uintptr_t h2 = get_hash_ptr_bits(ht, hash) | perfect;
  99
 100         while (ht->table[i->off]) {
 101                 if (ht->table[i->off] != HTABLE_DELETED) {
 102                         if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)
 103                                 return get_raw_ptr(ht, ht->table[i->off]);
 104                 }
 105                 i->off = (i->off + 1) & ((1 << ht->bits)-1);
 106                 h2 &= ~perfect;
 107         }
 108         return NULL;
 109 }
 110
 111 void *htable_firstval(const struct htable *ht,
 112                       struct htable_iter *i, size_t hash)
 113 {
 114         i->off = hash_bucket(ht, hash);
 115         return htable_val(ht, i, hash, ht->perfect_bit);
 116 }
 117
 118 void *htable_nextval(const struct htable *ht,
 119                      struct htable_iter *i, size_t hash)
 120 {
 121         i->off = (i->off + 1) & ((1 << ht->bits)-1);
 122         return htable_val(ht, i, hash, 0);
 123 }
 124
 125 void *htable_first(const struct htable *ht, struct htable_iter *i)
 126 {
 127         for (i->off = 0; i->off < (size_t)1 << ht->bits; i->off++) {
 128                 if (entry_is_valid(ht->table[i->off]))
 129                         return get_raw_ptr(ht, ht->table[i->off]);
 130         }
 131         return NULL;
 132 }
 133
 134 void *htable_next(const struct htable *ht, struct htable_iter *i)
 135 {
 136         for (i->off++; i->off < (size_t)1 << ht->bits; i->off++) {
 137                 if (entry_is_valid(ht->table[i->off]))
 138                         return get_raw_ptr(ht, ht->table[i->off]);
 139         }
 140         return NULL;
 141 }
 142
 143 /* This does not expand the hash table, that's up to caller. */
 144 static void ht_add(struct htable *ht, const void *new, size_t h)
 145 {
 146         size_t i;
 147         uintptr_t perfect = ht->perfect_bit;
 148
 149         i = hash_bucket(ht, h);
 150
 151         while (entry_is_valid(ht->table[i])) {
 152                 perfect = 0;
 153                 i = (i + 1) & ((1 << ht->bits)-1);
 154         }
 155         ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);
 156 }
 157
 158 static COLD bool double_table(struct htable *ht)
 159 {
 160         unsigned int i;
 161         size_t oldnum = (size_t)1 << ht->bits;
 162         uintptr_t *oldtable, e;
 163
 164         oldtable = ht->table;
 165         ht->table = calloc(1 << (ht->bits+1), sizeof(size_t));
 166         if (!ht->table) {
 167                 ht->table = oldtable;
 168                 return false;
 169         }
 170         ht->bits++;
 171         ht->max *= 2;
 172         ht->max_with_deleted *= 2;
 173
 174         /* If we lost our "perfect bit", get it back now. */
 175         if (!ht->perfect_bit && ht->common_mask) {
 176                 for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) {
 177                         if (ht->common_mask & ((size_t)1 << i)) {
 178                                 ht->perfect_bit = (size_t)1 << i;
 179                                 break;
 180                         }
 181                 }
 182         }
 183
 184         for (i = 0; i < oldnum; i++) {
 185                 if (entry_is_valid(e = oldtable[i])) {
 186                         void *p = get_raw_ptr(ht, e);
 187                         ht_add(ht, p, ht->rehash(p, ht->priv));
 188                 }
 189         }
 190         ht->deleted = 0;
 191         free(oldtable);
 192         return true;
 193 }
 194
 195 static COLD void rehash_table(struct htable *ht)
 196 {
 197         size_t start, i;
 198         uintptr_t e;
 199
 200         /* Beware wrap cases: we need to start from first empty bucket. */
 201         for (start = 0; ht->table[start]; start++);
 202
 203         for (i = 0; i < (size_t)1 << ht->bits; i++) {
 204                 size_t h = (i + start) & ((1 << ht->bits)-1);
 205                 e = ht->table[h];
 206                 if (!e)
 207                         continue;
 208                 if (e == HTABLE_DELETED)
 209                         ht->table[h] = 0;
 210                 else if (!(e & ht->perfect_bit)) {
 211                         void *p = get_raw_ptr(ht, e);
 212                         ht->table[h] = 0;
 213                         ht_add(ht, p, ht->rehash(p, ht->priv));
 214                 }
 215         }
 216         ht->deleted = 0;
 217 }
 218
 219 /* We stole some bits, now we need to put them back... */
 220 static COLD void update_common(struct htable *ht, const void *p)
 221 {
 222         unsigned int i;
 223         uintptr_t maskdiff, bitsdiff;
 224
 225         if (ht->elems == 0) {
 226                 ht->common_mask = -1;
 227                 ht->common_bits = (uintptr_t)p;
 228                 ht->perfect_bit = 1;
 229                 return;
 230         }
 231
 232         /* Find bits which are unequal to old common set. */
 233         maskdiff = ht->common_bits ^ ((uintptr_t)p & ht->common_mask);
 234
 235         /* These are the bits which go there in existing entries. */
 236         bitsdiff = ht->common_bits & maskdiff;
 237
 238         for (i = 0; i < (size_t)1 << ht->bits; i++) {
 239                 if (!entry_is_valid(ht->table[i]))
 240                         continue;
 241                 /* Clear the bits no longer in the mask, set them as
 242                  * expected. */
 243                 ht->table[i] &= ~maskdiff;
 244                 ht->table[i] |= bitsdiff;
 245         }
 246
 247         /* Take away those bits from our mask, bits and perfect bit. */
 248         ht->common_mask &= ~maskdiff;
 249         ht->common_bits &= ~maskdiff;
 250         ht->perfect_bit &= ~maskdiff;
 251 }
 252
 253 bool htable_add(struct htable *ht, size_t hash, const void *p)
 254 {
 255         if (ht->elems+1 > ht->max && !double_table(ht))
 256                 return false;
 257         if (ht->elems+1 + ht->deleted > ht->max_with_deleted)
 258                 rehash_table(ht);
 259         assert(p);
 260         if (((uintptr_t)p & ht->common_mask) != ht->common_bits)
 261                 update_common(ht, p);
 262
 263         ht_add(ht, p, hash);
 264         ht->elems++;
 265         return true;
 266 }
 267
 268 bool htable_del(struct htable *ht, size_t h, const void *p)
 269 {
 270         struct htable_iter i;
 271         void *c;
 272
 273         for (c = htable_firstval(ht,&i,h); c; c = htable_nextval(ht,&i,h)) {
 274                 if (c == p) {
 275                         htable_delval(ht, &i);
 276                         return true;
 277                 }
 278         }
 279         return false;
 280 }
 281
 282 void htable_delval(struct htable *ht, struct htable_iter *i)
 283 {
 284         assert(i->off < (size_t)1 << ht->bits);
 285         assert(entry_is_valid(ht->table[i->off]));
 286
 287         ht->elems--;
 288         ht->table[i->off] = HTABLE_DELETED;
 289         ht->deleted++;
 290 }