diff options
Diffstat (limited to 'debian/htdig/htdig-3.2.0b6/db/db_shash.c')
| -rw-r--r-- | debian/htdig/htdig-3.2.0b6/db/db_shash.c | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/debian/htdig/htdig-3.2.0b6/db/db_shash.c b/debian/htdig/htdig-3.2.0b6/db/db_shash.c new file mode 100644 index 00000000..265d6723 --- /dev/null +++ b/debian/htdig/htdig-3.2.0b6/db/db_shash.c @@ -0,0 +1,124 @@ +/*- + * See the file LICENSE for redistribution information. + * + * Copyright (c) 1996, 1997, 1998, 1999 + * Sleepycat Software. All rights reserved. + */ + +#include "db_config.h" + +#ifndef lint +static const char sccsid[] = "@(#)db_shash.c 11.1 (Sleepycat) 7/25/99"; +#endif /* not lint */ + +#ifndef NO_SYSTEM_INCLUDES +#include <sys/types.h> +#endif + +#include "db_int.h" + +/* + * Table of good hash values. Up to ~250,000 buckets, we use powers of 2. + * After that, we slow the rate of increase by half. For each choice, we + * then use a nearby prime number as the hash value. + * + * If a terabyte is the maximum cache we'll see, and we assume there are + * 10 1K buckets on each hash chain, then 107374182 is the maximum number + * of buckets we'll ever need. + */ +static const struct { + u_int32_t power; + u_int32_t prime; +} list[] = { + { 64, 67}, /* 2^6 */ + { 128, 131}, /* 2^7 */ + { 256, 257}, /* 2^8 */ + { 512, 521}, /* 2^9 */ + { 1024, 1031}, /* 2^10 */ + { 2048, 2053}, /* 2^11 */ + { 4096, 4099}, /* 2^12 */ + { 8192, 8191}, /* 2^13 */ + { 16384, 16381}, /* 2^14 */ + { 32768, 32771}, /* 2^15 */ + { 65536, 65537}, /* 2^16 */ + { 131072, 131071}, /* 2^17 */ + { 262144, 262147}, /* 2^18 */ + { 393216, 393209}, /* 2^18 + 2^18/2 */ + { 524288, 524287}, /* 2^19 */ + { 786432, 786431}, /* 2^19 + 2^19/2 */ + { 1048576, 1048573}, /* 2^20 */ + { 1572864, 1572869}, /* 2^20 + 2^20/2 */ + { 2097152, 2097169}, /* 2^21 */ + { 3145728, 3145721}, /* 2^21 + 2^21/2 */ + { 4194304, 4194301}, /* 2^22 */ + { 6291456, 6291449}, /* 2^22 + 2^22/2 */ + { 8388608, 8388617}, /* 2^23 */ + { 12582912, 12582917}, /* 2^23 + 2^23/2 */ + { 16777216, 16777213}, /* 2^24 */ + { 25165824, 25165813}, /* 2^24 + 2^24/2 */ + { 33554432, 33554393}, /* 2^25 */ + { 50331648, 50331653}, /* 2^25 + 2^25/2 */ + { 67108864, 67108859}, /* 2^26 */ + { 100663296, 100663291}, /* 2^26 + 2^26/2 */ + { 134217728, 134217757}, /* 2^27 */ + { 201326592, 201326611}, /* 2^27 + 2^27/2 */ + { 268435456, 268435459}, /* 2^28 */ + { 402653184, 402653189}, /* 2^28 + 2^28/2 */ + { 536870912, 536870909}, /* 2^29 */ + { 805306368, 805306357}, /* 2^29 + 2^29/2 */ + {1073741824, 1073741827}, /* 2^30 */ + {0, 0} +}; + +/* + * CDB___db_tablesize -- + * Choose a size for the hash table. + * + * PUBLIC: int CDB___db_tablesize __P((u_int32_t)); + */ +int +CDB___db_tablesize(n_buckets) + u_int32_t n_buckets; +{ + int i; + + /* + * We try to be clever about how big we make the hash tables. Use a + * prime number close to the "suggested" number of elements that will + * be in the hash table. Use 64 as the minimum hash table size. + * + * Ref: Sedgewick, Algorithms in C, "Hash Functions" + */ + if (n_buckets < 64) + n_buckets = 64; + + for (i = 0;; ++i) { + if (list[i].power == 0) { + --i; + break; + } + if (list[i].power >= n_buckets) + break; + } + return (list[i].prime); +} + +/* + * CDB___db_hashinit -- + * Initialize a hash table that resides in shared memory. + * + * PUBLIC: void CDB___db_hashinit __P((void *, u_int32_t)); + */ +void +CDB___db_hashinit(begin, nelements) + void *begin; + u_int32_t nelements; +{ + u_int32_t i; + SH_TAILQ_HEAD(hash_head) *headp; + + headp = (struct hash_head *)begin; + + for (i = 0; i < nelements; i++, headp++) + SH_TAILQ_INIT(headp); +} |