+ /*
+ Trivial Database 2: hash handling
+ Copyright (C) Rusty Russell 2010
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 3 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+#include "private.h"
+#include <assert.h>
+#include <ccan/hash/hash.h>
+
+static uint64_t jenkins_hash(const void *key, size_t length, uint64_t seed,
+ void *arg)
+{
+ uint64_t ret;
+ /* hash64_stable assumes lower bits are more important; they are a
+ * slightly better hash. We use the upper bits first, so swap them. */
+ ret = hash64_stable((const unsigned char *)key, length, seed);
+ return (ret >> 32) | (ret << 32);
+}
+
+void tdb_hash_init(struct tdb_context *tdb)
+{
+ tdb->khash = jenkins_hash;
+ tdb->hash_priv = NULL;
+}
+
+uint64_t tdb_hash(struct tdb_context *tdb, const void *ptr, size_t len)
+{
+ return tdb->khash(ptr, len, tdb->hash_seed, tdb->hash_priv);
+}
+
+uint64_t hash_record(struct tdb_context *tdb, tdb_off_t off)
+{
+ struct tdb_used_record pad, *r;
+ const void *key;
+ uint64_t klen, hash;
+
+ r = tdb_get(tdb, off, &pad, sizeof(pad));
+ if (!r)
+ /* FIXME */
+ return 0;
+
+ klen = rec_key_length(r);
+ key = tdb_access_read(tdb, off + sizeof(pad), klen, false);
+ if (!key)
+ return 0;
+
+ hash = tdb_hash(tdb, key, klen);
+ tdb_access_release(tdb, key);
+ return hash;
+}
+
+/* Get bits from a value. */
+static uint32_t bits(uint64_t val, unsigned start, unsigned num)
+{
+ assert(num <= 32);
+ return (val >> start) & ((1U << num) - 1);
+}
+
+/* We take bits from the top: that way we can lock whole sections of the hash
+ * by using lock ranges. */
+static uint32_t use_bits(struct hash_info *h, unsigned num)
+{
+ h->hash_used += num;
+ return bits(h->h, 64 - h->hash_used, num);
+}
+
+/* Does entry match? */
+static bool match(struct tdb_context *tdb,
+ struct hash_info *h,
+ const struct tdb_data *key,
+ tdb_off_t val,
+ struct tdb_used_record *rec)
+{
+ bool ret;
+ const unsigned char *rkey;
+ tdb_off_t off;
+
+ /* FIXME: Handle hash value truncated. */
+ if (bits(val, TDB_OFF_HASH_TRUNCATED_BIT, 1))
+ abort();
+
+ /* Desired bucket must match. */
+ if (h->home_bucket != (val & TDB_OFF_HASH_GROUP_MASK))
+ return false;
+
+ /* Top bits of offset == next bits of hash. */
+ if (bits(val, TDB_OFF_HASH_EXTRA_BIT, TDB_OFF_UPPER_STEAL_EXTRA)
+ != bits(h->h, 64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
+ TDB_OFF_UPPER_STEAL_EXTRA))
+ return false;
+
+ off = val & TDB_OFF_MASK;
+ if (tdb_read_convert(tdb, off, rec, sizeof(*rec)) == -1)
+ return false;
+
+ /* FIXME: check extra bits in header? */
+ if (rec_key_length(rec) != key->dsize)
+ return false;
+
+ rkey = tdb_access_read(tdb, off + sizeof(*rec), key->dsize, false);
+ if (!rkey)
+ return false;
+ ret = (memcmp(rkey, key->dptr, key->dsize) == 0);
+ tdb_access_release(tdb, rkey);
+ return ret;
+}
+
+static tdb_off_t hbucket_off(tdb_off_t group_start, unsigned bucket)
+{
+ return group_start
+ + (bucket % (1 << TDB_HASH_GROUP_BITS)) * sizeof(tdb_off_t);
+}
+
+/* Truncated hashes can't be all 1: that's how we spot a sub-hash */
+bool is_subhash(tdb_off_t val)
+{
+ return val >> (64-TDB_OFF_UPPER_STEAL) == (1<<TDB_OFF_UPPER_STEAL) - 1;
+}
+
+/* This is the core routine which searches the hashtable for an entry.
+ * On error, no locks are held and TDB_OFF_ERR is returned.
+ * Otherwise, hinfo is filled in.
+ * If not found, the return value is 0.
+ * If found, the return value is the offset, and *rec is the record. */
+tdb_off_t find_and_lock(struct tdb_context *tdb,
+ struct tdb_data key,
+ int ltype,
+ struct hash_info *h,
+ struct tdb_used_record *rec)
+{
+ uint32_t i, group;
+ tdb_off_t hashtable;
+
+ h->h = tdb_hash(tdb, key.dptr, key.dsize);
+ h->hash_used = 0;
+ group = use_bits(h, TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
+ h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
+
+ /* FIXME: Guess the depth, don't over-lock! */
+ h->hlock_start = (tdb_off_t)group
+ << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
+ h->hlock_range = 1ULL << (64 - (TDB_TOPLEVEL_HASH_BITS
+ - TDB_HASH_GROUP_BITS));
+ if (tdb_lock_hashes(tdb, h->hlock_start, h->hlock_range, ltype,
+ TDB_LOCK_WAIT))
+ return TDB_OFF_ERR;
+
+ hashtable = offsetof(struct tdb_header, hashtable);
+
+ while (likely(h->hash_used < 64)) {
+ /* Read in the hash group. */
+ h->group_start = hashtable
+ + group * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
+
+ if (tdb_read_convert(tdb, h->group_start, &h->group,
+ sizeof(h->group)) == -1)
+ goto fail;
+
+ /* Pointer to another hash table? Go down... */
+ if (is_subhash(h->group[h->home_bucket])) {
+ hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
+ + sizeof(struct tdb_used_record);
+ group = use_bits(h, TDB_SUBLEVEL_HASH_BITS
+ - TDB_HASH_GROUP_BITS);
+ h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
+ continue;
+ }
+
+ /* It's in this group: search (until 0 or all searched) */
+ for (i = 0, h->found_bucket = h->home_bucket;
+ i < (1 << TDB_HASH_GROUP_BITS);
+ i++, h->found_bucket = ((h->found_bucket+1)
+ % (1 << TDB_HASH_GROUP_BITS))) {
+ if (is_subhash(h->group[h->found_bucket]))
+ continue;
+
+ if (!h->group[h->found_bucket])
+ break;
+
+ if (match(tdb, h, &key, h->group[h->found_bucket], rec))
+ return h->group[h->found_bucket] & TDB_OFF_MASK;
+ }
+ /* Didn't find it: h indicates where it would go. */
+ return 0;
+ }
+
+ /* FIXME: We hit the bottom. Chain! */
+ abort();
+
+fail:
+ tdb_unlock_hashes(tdb, h->hlock_start, h->hlock_range, ltype);
+ return TDB_OFF_ERR;
+}
+
+/* I wrote a simple test, expanding a hash to 2GB, for the following
+ * cases:
+ * 1) Expanding all the buckets at once,
+ * 2) Expanding the most-populated bucket,
+ * 3) Expanding the bucket we wanted to place the new entry ito.
+ *
+ * I measured the worst/average/best density during this process.
+ * 1) 3%/16%/30%
+ * 2) 4%/20%/38%
+ * 3) 6%/22%/41%
+ *
+ * So we figure out the busiest bucket for the moment.
+ */
+static unsigned fullest_bucket(struct tdb_context *tdb,
+ const tdb_off_t *group,
+ unsigned new_bucket)
+{
+ unsigned counts[1 << TDB_HASH_GROUP_BITS] = { 0 };
+ unsigned int i, best_bucket;
+
+ /* Count the new entry. */
+ counts[new_bucket]++;
+ best_bucket = new_bucket;
+
+ for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
+ unsigned this_bucket;
+
+ if (is_subhash(group[i]))
+ continue;
+ this_bucket = group[i] & TDB_OFF_HASH_GROUP_MASK;
+ if (++counts[this_bucket] > counts[best_bucket])
+ best_bucket = this_bucket;
+ }
+
+ return best_bucket;
+}
+
+static bool put_into_group(tdb_off_t *group,
+ unsigned bucket, tdb_off_t encoded)
+{
+ unsigned int i;
+
+ for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
+ unsigned b = (bucket + i) % (1 << TDB_HASH_GROUP_BITS);
+
+ if (group[b] == 0) {
+ group[b] = encoded;
+ return true;
+ }
+ }
+ return false;
+}
+
+static void force_into_group(tdb_off_t *group,
+ unsigned bucket, tdb_off_t encoded)
+{
+ if (!put_into_group(group, bucket, encoded))
+ abort();
+}
+
+static tdb_off_t encode_offset(tdb_off_t new_off, struct hash_info *h)
+{
+ return h->home_bucket
+ | new_off
+ | ((uint64_t)bits(h->h,
+ 64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
+ TDB_OFF_UPPER_STEAL_EXTRA)
+ << TDB_OFF_HASH_EXTRA_BIT);
+}
+
+/* Simply overwrite the hash entry we found before. */
+int replace_in_hash(struct tdb_context *tdb,
+ struct hash_info *h,
+ tdb_off_t new_off)
+{
+ return tdb_write_off(tdb, hbucket_off(h->group_start, h->found_bucket),
+ encode_offset(new_off, h));
+}
+
+/* Add into a newly created subhash. */
+static int add_to_subhash(struct tdb_context *tdb, tdb_off_t subhash,
+ unsigned hash_used, tdb_off_t val)
+{
+ tdb_off_t off = (val & TDB_OFF_MASK), *group;
+ struct hash_info h;
+ unsigned int gnum;
+
+ h.hash_used = hash_used;
+
+ /* FIXME chain if hash_used == 64 */
+ if (hash_used + TDB_SUBLEVEL_HASH_BITS > 64)
+ abort();
+
+ /* FIXME: Do truncated hash bits if we can! */
+ h.h = hash_record(tdb, off);
+ gnum = use_bits(&h, TDB_SUBLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS);
+ h.group_start = subhash + sizeof(struct tdb_used_record)
+ + gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
+ h.home_bucket = use_bits(&h, TDB_HASH_GROUP_BITS);
+
+ group = tdb_access_write(tdb, h.group_start,
+ sizeof(*group) << TDB_HASH_GROUP_BITS, true);
+ if (!group)
+ return -1;
+ force_into_group(group, h.home_bucket, encode_offset(off, &h));
+ return tdb_access_commit(tdb, group);
+}
+
+static int expand_group(struct tdb_context *tdb, struct hash_info *h)
+{
+ unsigned bucket, num_vals, i;
+ tdb_off_t subhash;
+ tdb_off_t vals[1 << TDB_HASH_GROUP_BITS];
+
+ /* Attach new empty subhash under fullest bucket. */
+ bucket = fullest_bucket(tdb, h->group, h->home_bucket);
+
+ subhash = alloc(tdb, 0, sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS,
+ 0, false);
+ if (subhash == TDB_OFF_ERR)
+ return -1;
+
+ if (zero_out(tdb, subhash + sizeof(struct tdb_used_record),
+ sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS) == -1)
+ return -1;
+
+ /* Remove any which are destined for bucket or are in wrong place. */
+ num_vals = 0;
+ for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
+ unsigned home_bucket = h->group[i] & TDB_OFF_HASH_GROUP_MASK;
+ if (!h->group[i] || is_subhash(h->group[i]))
+ continue;
+ if (home_bucket == bucket || home_bucket != i) {
+ vals[num_vals++] = h->group[i];
+ h->group[i] = 0;
+ }
+ }
+ /* FIXME: This assert is valid, but we do this during unit test :( */
+ /* assert(num_vals); */
+
+ /* Overwrite expanded bucket with subhash pointer. */
+ h->group[bucket] = subhash | ~((1ULL << (64 - TDB_OFF_UPPER_STEAL))-1);
+
+ /* Put values back. */
+ for (i = 0; i < num_vals; i++) {
+ unsigned this_bucket = vals[i] & TDB_OFF_HASH_GROUP_MASK;
+
+ if (this_bucket == bucket) {
+ if (add_to_subhash(tdb, subhash, h->hash_used, vals[i]))
+ return -1;
+ } else {
+ /* There should be room to put this back. */
+ force_into_group(h->group, this_bucket, vals[i]);
+ }
+ }
+ return 0;
+}
+
+int delete_from_hash(struct tdb_context *tdb, struct hash_info *h)
+{
+ unsigned int i, num_movers = 0;
+ tdb_off_t movers[1 << TDB_HASH_GROUP_BITS];
+
+ h->group[h->found_bucket] = 0;
+ for (i = 1; i < (1 << TDB_HASH_GROUP_BITS); i++) {
+ unsigned this_bucket;
+
+ this_bucket = (h->found_bucket+i) % (1 << TDB_HASH_GROUP_BITS);
+ /* Empty bucket? We're done. */
+ if (!h->group[this_bucket])
+ break;
+
+ /* Ignore subhashes. */
+ if (is_subhash(h->group[this_bucket]))
+ continue;
+
+ /* If this one is not happy where it is, we'll move it. */
+ if ((h->group[this_bucket] & TDB_OFF_HASH_GROUP_MASK)
+ != this_bucket) {
+ movers[num_movers++] = h->group[this_bucket];
+ h->group[this_bucket] = 0;
+ }
+ }
+
+ /* Put back the ones we erased. */
+ for (i = 0; i < num_movers; i++) {
+ force_into_group(h->group, movers[i] & TDB_OFF_HASH_GROUP_MASK,
+ movers[i]);
+ }
+
+ /* Now we write back the hash group */
+ return tdb_write_convert(tdb, h->group_start,
+ h->group, sizeof(h->group));
+}
+
+int add_to_hash(struct tdb_context *tdb, struct hash_info *h, tdb_off_t new_off)
+{
+ /* FIXME: chain! */
+ if (h->hash_used >= 64)
+ abort();
+
+ /* We hit an empty bucket during search? That's where it goes. */
+ if (!h->group[h->found_bucket]) {
+ h->group[h->found_bucket] = encode_offset(new_off, h);
+ /* Write back the modified group. */
+ return tdb_write_convert(tdb, h->group_start,
+ h->group, sizeof(h->group));
+ }
+
+ /* We're full. Expand. */
+ if (expand_group(tdb, h) == -1)
+ return -1;
+
+ if (is_subhash(h->group[h->home_bucket])) {
+ /* We were expanded! */
+ tdb_off_t hashtable;
+ unsigned int gnum;
+
+ /* Write back the modified group. */
+ if (tdb_write_convert(tdb, h->group_start, h->group,
+ sizeof(h->group)))
+ return -1;
+
+ /* Move hashinfo down a level. */
+ hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
+ + sizeof(struct tdb_used_record);
+ gnum = use_bits(h,TDB_SUBLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
+ h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
+ h->group_start = hashtable
+ + gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
+ if (tdb_read_convert(tdb, h->group_start, &h->group,
+ sizeof(h->group)) == -1)
+ return -1;
+ }
+
+ /* Expanding the group must have made room if it didn't choose this
+ * bucket. */
+ if (put_into_group(h->group, h->home_bucket, encode_offset(new_off, h)))
+ return tdb_write_convert(tdb, h->group_start,
+ h->group, sizeof(h->group));
+
+ /* This can happen if all hashes in group (and us) dropped into same
+ * group in subhash. */
+ return add_to_hash(tdb, h, new_off);
+}
+
+/* No point holding references/copies of db once we drop lock. */
+static void release_entries(struct tdb_context *tdb,
+ struct traverse_info *tinfo)
+{
+ unsigned int i;
+
+ for (i = 0; i < tinfo->num_levels; i++) {
+ if (tinfo->levels[i].entries) {
+ tdb_access_release(tdb, tinfo->levels[i].entries);
+ tinfo->levels[i].entries = NULL;
+ }
+ }
+}
+
+/* Traverse support: returns offset of record, or 0 or TDB_OFF_ERR. */
+static tdb_off_t iterate_hash(struct tdb_context *tdb,
+ struct traverse_info *tinfo)
+{
+ tdb_off_t off;
+ unsigned int i;
+ struct traverse_level *tlevel;
+
+ tlevel = &tinfo->levels[tinfo->num_levels-1];
+
+again:
+ if (!tlevel->entries) {
+ tlevel->entries = tdb_access_read(tdb, tlevel->hashtable,
+ sizeof(tdb_off_t)
+ * tlevel->total_buckets,
+ true);
+ if (!tlevel->entries)
+ return TDB_OFF_ERR;
+ }
+
+ /* FIXME: Use tdb_find_nonzero_off? */
+ for (i = tlevel->entry; i < tlevel->total_buckets; i++) {
+ if (!tlevel->entries[i] || tlevel->entries[i] == tinfo->prev)
+ continue;
+
+ tlevel->entry = i;
+ off = tlevel->entries[i] & TDB_OFF_MASK;
+
+ if (!is_subhash(tlevel->entries[i])) {
+ /* Found one. */
+ tinfo->prev = tlevel->entries[i];
+ release_entries(tdb, tinfo);
+ return off;
+ }
+
+ /* When we come back, we want tne next one */
+ tlevel->entry++;
+ tinfo->num_levels++;
+ tlevel++;
+ tlevel->hashtable = off + sizeof(struct tdb_used_record);
+ tlevel->entry = 0;
+ tlevel->entries = NULL;
+ tlevel->total_buckets = (1 << TDB_SUBLEVEL_HASH_BITS);
+ goto again;
+ }
+
+ /* Nothing there? */
+ if (tinfo->num_levels == 1) {
+ release_entries(tdb, tinfo);
+ return 0;
+ }
+
+ /* Go back up and keep searching. */
+ tdb_access_release(tdb, tlevel->entries);
+ tinfo->num_levels--;
+ tlevel--;
+ goto again;
+}
+
+/* Return 1 if we find something, 0 if not, -1 on error. */
+int next_in_hash(struct tdb_context *tdb, int ltype,
+ struct traverse_info *tinfo,
+ TDB_DATA *kbuf, unsigned int *dlen)
+{
+ const unsigned group_bits = TDB_TOPLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS;
+ tdb_off_t hlock_start, hlock_range, off;
+
+ while (tinfo->toplevel_group < (1 << group_bits)) {
+ hlock_start = (tdb_off_t)tinfo->toplevel_group
+ << (64 - group_bits);
+ hlock_range = 1ULL << group_bits;
+ if (tdb_lock_hashes(tdb, hlock_start, hlock_range, ltype,
+ TDB_LOCK_WAIT) != 0)
+ return -1;
+
+ off = iterate_hash(tdb, tinfo);
+ if (off) {
+ struct tdb_used_record rec;
+
+ if (tdb_read_convert(tdb, off, &rec, sizeof(rec))) {
+ tdb_unlock_hashes(tdb,
+ hlock_start, hlock_range,
+ ltype);
+ return -1;
+ }
+ kbuf->dsize = rec_key_length(&rec);
+
+ /* They want data as well? */
+ if (dlen) {
+ *dlen = rec_data_length(&rec);
+ kbuf->dptr = tdb_alloc_read(tdb,
+ off + sizeof(rec),
+ kbuf->dsize
+ + *dlen);
+ } else {
+ kbuf->dptr = tdb_alloc_read(tdb,
+ off + sizeof(rec),
+ kbuf->dsize);
+ }
+ tdb_unlock_hashes(tdb, hlock_start, hlock_range, ltype);
+ return kbuf->dptr ? 1 : -1;
+ }
+
+ tdb_unlock_hashes(tdb, hlock_start, hlock_range, ltype);
+
+ tinfo->toplevel_group++;
+ tinfo->levels[0].hashtable
+ += (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
+ tinfo->levels[0].entry = 0;
+ }
+ return 0;
+}
+
+/* Return 1 if we find something, 0 if not, -1 on error. */
+int first_in_hash(struct tdb_context *tdb, int ltype,
+ struct traverse_info *tinfo,
+ TDB_DATA *kbuf, unsigned int *dlen)
+{
+ tinfo->prev = 0;
+ tinfo->toplevel_group = 0;
+ tinfo->num_levels = 1;
+ tinfo->levels[0].hashtable = offsetof(struct tdb_header, hashtable);
+ tinfo->levels[0].entries = NULL;
+ tinfo->levels[0].entry = 0;
+ tinfo->levels[0].total_buckets = (1 << TDB_HASH_GROUP_BITS);
+
+ return next_in_hash(tdb, ltype, tinfo, kbuf, dlen);
+}
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