X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Fhtable%2Fhtable.c;h=b7e65d11966acc96be83dffbb25a273fec153145;hp=938d410ace7d2f638dde6a4f5f9e3b2b19ccfd13;hb=c321a1d02755a77ae790d6e8976b2ff15edba89d;hpb=198d85adf5e8d9a44b7436bdd046dbffce66b23a diff --git a/ccan/htable/htable.c b/ccan/htable/htable.c index 938d410a..b7e65d11 100644 --- a/ccan/htable/htable.c +++ b/ccan/htable/htable.c @@ -1,26 +1,14 @@ +/* Licensed under LGPLv2+ - see LICENSE file for details */ #include #include -#include #include +#include #include #include -/* This means a struct htable takes at least 512 bytes / 1k (32/64 bits). */ -#define HTABLE_BASE_BITS 7 - /* We use 0x1 as deleted marker. */ #define HTABLE_DELETED (0x1) -struct htable { - size_t (*rehash)(const void *elem, void *priv); - void *priv; - unsigned int bits; - size_t elems, max; - /* These are the bits which are the same in all pointers. */ - uintptr_t common_mask, common_bits; - uintptr_t *table; -}; - /* We clear out the bits which are always the same, and put metadata there. */ static inline uintptr_t get_extra_ptr_bits(const struct htable *ht, uintptr_t e) @@ -50,35 +38,25 @@ static inline uintptr_t get_hash_ptr_bits(const struct htable *ht, /* Shuffling the extra bits (as specified in mask) down the * end is quite expensive. But the lower bits are redundant, so * we fold the value first. */ - return (hash ^ (hash >> ht->bits)) & ht->common_mask; + return (hash ^ (hash >> ht->bits)) + & ht->common_mask & ~ht->perfect_bit; } -struct htable *htable_new(size_t (*rehash)(const void *elem, void *priv), - void *priv) +void htable_init(struct htable *ht, + size_t (*rehash)(const void *elem, void *priv), void *priv) { - struct htable *ht = malloc(sizeof(struct htable)); - if (ht) { - ht->bits = HTABLE_BASE_BITS; - ht->rehash = rehash; - ht->priv = priv; - ht->elems = 0; - ht->max = (1 << ht->bits) * 3 / 4; - /* This guarantees we enter update_common first add. */ - ht->common_mask = -1; - ht->common_bits = 0; - ht->table = calloc(1 << ht->bits, sizeof(uintptr_t)); - if (!ht->table) { - free(ht); - ht = NULL; - } - } - return ht; + struct htable empty = HTABLE_INITIALIZER(empty, NULL, NULL); + *ht = empty; + ht->rehash = rehash; + ht->priv = priv; + ht->table = &ht->perfect_bit; } -void htable_free(const struct htable *ht) +void htable_clear(struct htable *ht) { - free((void *)ht->table); - free((void *)ht); + if (ht->table != &ht->perfect_bit) + free((void *)ht->table); + htable_init(ht, ht->rehash, ht->priv); } static size_t hash_bucket(const struct htable *ht, size_t h) @@ -87,9 +65,9 @@ static size_t hash_bucket(const struct htable *ht, size_t h) } static void *htable_val(const struct htable *ht, - struct htable_iter *i, size_t hash) + struct htable_iter *i, size_t hash, uintptr_t perfect) { - uintptr_t h2 = get_hash_ptr_bits(ht, hash); + uintptr_t h2 = get_hash_ptr_bits(ht, hash) | perfect; while (ht->table[i->off]) { if (ht->table[i->off] != HTABLE_DELETED) { @@ -97,6 +75,7 @@ static void *htable_val(const struct htable *ht, return get_raw_ptr(ht, ht->table[i->off]); } i->off = (i->off + 1) & ((1 << ht->bits)-1); + h2 &= ~perfect; } return NULL; } @@ -105,14 +84,14 @@ void *htable_firstval(const struct htable *ht, struct htable_iter *i, size_t hash) { i->off = hash_bucket(ht, hash); - return htable_val(ht, i, hash); + return htable_val(ht, i, hash, ht->perfect_bit); } void *htable_nextval(const struct htable *ht, struct htable_iter *i, size_t hash) { i->off = (i->off + 1) & ((1 << ht->bits)-1); - return htable_val(ht, i, hash); + return htable_val(ht, i, hash, 0); } void *htable_first(const struct htable *ht, struct htable_iter *i) @@ -137,20 +116,22 @@ void *htable_next(const struct htable *ht, struct htable_iter *i) static void ht_add(struct htable *ht, const void *new, size_t h) { size_t i; + uintptr_t perfect = ht->perfect_bit; i = hash_bucket(ht, h); - while (entry_is_valid(ht->table[i])) + while (entry_is_valid(ht->table[i])) { + perfect = 0; i = (i + 1) & ((1 << ht->bits)-1); - - ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)); + } + ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect); } -static COLD_ATTRIBUTE bool double_table(struct htable *ht) +static COLD bool double_table(struct htable *ht) { unsigned int i; size_t oldnum = (size_t)1 << ht->bits; - size_t *oldtable, e; + uintptr_t *oldtable, e; oldtable = ht->table; ht->table = calloc(1 << (ht->bits+1), sizeof(size_t)); @@ -159,27 +140,75 @@ static COLD_ATTRIBUTE bool double_table(struct htable *ht) return false; } ht->bits++; - ht->max *= 2; + ht->max = ((size_t)3 << ht->bits) / 4; + ht->max_with_deleted = ((size_t)9 << ht->bits) / 10; + + /* If we lost our "perfect bit", get it back now. */ + if (!ht->perfect_bit && ht->common_mask) { + for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) { + if (ht->common_mask & ((size_t)1 << i)) { + ht->perfect_bit = (size_t)1 << i; + break; + } + } + } + + if (oldtable != &ht->perfect_bit) { + for (i = 0; i < oldnum; i++) { + if (entry_is_valid(e = oldtable[i])) { + void *p = get_raw_ptr(ht, e); + ht_add(ht, p, ht->rehash(p, ht->priv)); + } + } + free(oldtable); + } + ht->deleted = 0; + return true; +} + +static COLD void rehash_table(struct htable *ht) +{ + size_t start, i; + uintptr_t e; + + /* Beware wrap cases: we need to start from first empty bucket. */ + for (start = 0; ht->table[start]; start++); - for (i = 0; i < oldnum; i++) { - if (entry_is_valid(e = oldtable[i])) { + for (i = 0; i < (size_t)1 << ht->bits; i++) { + size_t h = (i + start) & ((1 << ht->bits)-1); + e = ht->table[h]; + if (!e) + continue; + if (e == HTABLE_DELETED) + ht->table[h] = 0; + else if (!(e & ht->perfect_bit)) { void *p = get_raw_ptr(ht, e); + ht->table[h] = 0; ht_add(ht, p, ht->rehash(p, ht->priv)); } } - free(oldtable); - return true; + ht->deleted = 0; } /* We stole some bits, now we need to put them back... */ -static COLD_ATTRIBUTE void update_common(struct htable *ht, const void *p) +static COLD void update_common(struct htable *ht, const void *p) { unsigned int i; uintptr_t maskdiff, bitsdiff; if (ht->elems == 0) { - ht->common_mask = -1; - ht->common_bits = (uintptr_t)p; + /* Always reveal one bit of the pointer in the bucket, + * so it's not zero or HTABLE_DELETED (1), even if + * hash happens to be 0. Assumes (void *)1 is not a + * valid pointer. */ + for (i = sizeof(uintptr_t)*CHAR_BIT - 1; i > 0; i--) { + if ((uintptr_t)p & ((uintptr_t)1 << i)) + break; + } + + ht->common_mask = ~((uintptr_t)1 << i); + ht->common_bits = ((uintptr_t)p & ht->common_mask); + ht->perfect_bit = 1; return; } @@ -198,15 +227,18 @@ static COLD_ATTRIBUTE void update_common(struct htable *ht, const void *p) ht->table[i] |= bitsdiff; } - /* Take away those bits from our mask and set. */ + /* Take away those bits from our mask, bits and perfect bit. */ ht->common_mask &= ~maskdiff; ht->common_bits &= ~maskdiff; + ht->perfect_bit &= ~maskdiff; } bool htable_add(struct htable *ht, size_t hash, const void *p) { if (ht->elems+1 > ht->max && !double_table(ht)) return false; + if (ht->elems+1 + ht->deleted > ht->max_with_deleted) + rehash_table(ht); assert(p); if (((uintptr_t)p & ht->common_mask) != ht->common_bits) update_common(ht, p); @@ -216,26 +248,6 @@ bool htable_add(struct htable *ht, size_t hash, const void *p) return true; } -/* If every one of the following buckets are DELETED (up to the next unused - one), we can actually mark them all unused. */ -static void delete_run(struct htable *ht, unsigned int num) -{ - unsigned int i, last = num + 1; - size_t mask = (((size_t)1 << ht->bits)-1); - - while (ht->table[last & mask]) { - if (entry_is_valid(ht->table[last & mask])) - return; - last++; - } - - /* Now see if we can step backwards to find previous deleted ones. */ - for (i = num-1; ht->table[i & mask] == HTABLE_DELETED; i--); - - for (i++; i < last; i++) - ht->table[i & ((1 << ht->bits)-1)] = 0; -} - bool htable_del(struct htable *ht, size_t h, const void *p) { struct htable_iter i; @@ -257,5 +269,5 @@ void htable_delval(struct htable *ht, struct htable_iter *i) ht->elems--; ht->table[i->off] = HTABLE_DELETED; - delete_run(ht, i->off); + ht->deleted++; }