stuff

1 files changed, 1805 insertions, 0 deletions

diff --git a/src/libbasic/hashmap.c b/src/libbasic/hashmap.c
new file mode 100644
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--- /dev/null
+++ b/src/libbasic/hashmap.c
@@ -0,0 +1,1805 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+  Copyright 2014 Michal Schmidt
+
+  systemd 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 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "alloc-util.h"
+#include "hashmap.h"
+#include "macro.h"
+#include "mempool.h"
+#include "process-util.h"
+#include "random-util.h"
+#include "set.h"
+#include "siphash24.h"
+#include "strv.h"
+#include "util.h"
+
+#ifdef ENABLE_DEBUG_HASHMAP
+#include <pthread.h>
+#include "list.h"
+#endif
+
+/*
+ * Implementation of hashmaps.
+ * Addressing: open
+ *   - uses less RAM compared to closed addressing (chaining), because
+ *     our entries are small (especially in Sets, which tend to contain
+ *     the majority of entries in systemd).
+ * Collision resolution: Robin Hood
+ *   - tends to equalize displacement of entries from their optimal buckets.
+ * Probe sequence: linear
+ *   - though theoretically worse than random probing/uniform hashing/double
+ *     hashing, it is good for cache locality.
+ *
+ * References:
+ * Celis, P. 1986. Robin Hood Hashing.
+ * Ph.D. Dissertation. University of Waterloo, Waterloo, Ont., Canada, Canada.
+ * https://cs.uwaterloo.ca/research/tr/1986/CS-86-14.pdf
+ * - The results are derived for random probing. Suggests deletion with
+ *   tombstones and two mean-centered search methods. None of that works
+ *   well for linear probing.
+ *
+ * Janson, S. 2005. Individual displacements for linear probing hashing with different insertion policies.
+ * ACM Trans. Algorithms 1, 2 (October 2005), 177-213.
+ * DOI=10.1145/1103963.1103964 http://doi.acm.org/10.1145/1103963.1103964
+ * http://www.math.uu.se/~svante/papers/sj157.pdf
+ * - Applies to Robin Hood with linear probing. Contains remarks on
+ *   the unsuitability of mean-centered search with linear probing.
+ *
+ * Viola, A. 2005. Exact distribution of individual displacements in linear probing hashing.
+ * ACM Trans. Algorithms 1, 2 (October 2005), 214-242.
+ * DOI=10.1145/1103963.1103965 http://doi.acm.org/10.1145/1103963.1103965
+ * - Similar to Janson. Note that Viola writes about C_{m,n} (number of probes
+ *   in a successful search), and Janson writes about displacement. C = d + 1.
+ *
+ * Goossaert, E. 2013. Robin Hood hashing: backward shift deletion.
+ * http://codecapsule.com/2013/11/17/robin-hood-hashing-backward-shift-deletion/
+ * - Explanation of backward shift deletion with pictures.
+ *
+ * Khuong, P. 2013. The Other Robin Hood Hashing.
+ * http://www.pvk.ca/Blog/2013/11/26/the-other-robin-hood-hashing/
+ * - Short summary of random vs. linear probing, and tombstones vs. backward shift.
+ */
+
+/*
+ * XXX Ideas for improvement:
+ * For unordered hashmaps, randomize iteration order, similarly to Perl:
+ * http://blog.booking.com/hardening-perls-hash-function.html
+ */
+
+/* INV_KEEP_FREE = 1 / (1 - max_load_factor)
+ * e.g. 1 / (1 - 0.8) = 5 ... keep one fifth of the buckets free. */
+#define INV_KEEP_FREE            5U
+
+/* Fields common to entries of all hashmap/set types */
+struct hashmap_base_entry {
+        const void *key;
+};
+
+/* Entry types for specific hashmap/set types
+ * hashmap_base_entry must be at the beginning of each entry struct. */
+
+struct plain_hashmap_entry {
+        struct hashmap_base_entry b;
+        void *value;
+};
+
+struct ordered_hashmap_entry {
+        struct plain_hashmap_entry p;
+        unsigned iterate_next, iterate_previous;
+};
+
+struct set_entry {
+        struct hashmap_base_entry b;
+};
+
+/* In several functions it is advantageous to have the hash table extended
+ * virtually by a couple of additional buckets. We reserve special index values
+ * for these "swap" buckets. */
+#define _IDX_SWAP_BEGIN     (UINT_MAX - 3)
+#define IDX_PUT             (_IDX_SWAP_BEGIN + 0)
+#define IDX_TMP             (_IDX_SWAP_BEGIN + 1)
+#define _IDX_SWAP_END       (_IDX_SWAP_BEGIN + 2)
+
+#define IDX_FIRST           (UINT_MAX - 1) /* special index for freshly initialized iterators */
+#define IDX_NIL             UINT_MAX       /* special index value meaning "none" or "end" */
+
+assert_cc(IDX_FIRST == _IDX_SWAP_END);
+assert_cc(IDX_FIRST == _IDX_ITERATOR_FIRST);
+
+/* Storage space for the "swap" buckets.
+ * All entry types can fit into a ordered_hashmap_entry. */
+struct swap_entries {
+        struct ordered_hashmap_entry e[_IDX_SWAP_END - _IDX_SWAP_BEGIN];
+};
+
+/* Distance from Initial Bucket */
+typedef uint8_t dib_raw_t;
+#define DIB_RAW_OVERFLOW ((dib_raw_t)0xfdU)   /* indicates DIB value is greater than representable */
+#define DIB_RAW_REHASH   ((dib_raw_t)0xfeU)   /* entry yet to be rehashed during in-place resize */
+#define DIB_RAW_FREE     ((dib_raw_t)0xffU)   /* a free bucket */
+#define DIB_RAW_INIT     ((char)DIB_RAW_FREE) /* a byte to memset a DIB store with when initializing */
+
+#define DIB_FREE UINT_MAX
+
+#ifdef ENABLE_DEBUG_HASHMAP
+struct hashmap_debug_info {
+        LIST_FIELDS(struct hashmap_debug_info, debug_list);
+        unsigned max_entries;  /* high watermark of n_entries */
+
+        /* who allocated this hashmap */
+        int line;
+        const char *file;
+        const char *func;
+
+        /* fields to detect modification while iterating */
+        unsigned put_count;    /* counts puts into the hashmap */
+        unsigned rem_count;    /* counts removals from hashmap */
+        unsigned last_rem_idx; /* remembers last removal index */
+};
+
+/* Tracks all existing hashmaps. Get at it from gdb. See sd_dump_hashmaps.py */
+static LIST_HEAD(struct hashmap_debug_info, hashmap_debug_list);
+static pthread_mutex_t hashmap_debug_list_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+#define HASHMAP_DEBUG_FIELDS struct hashmap_debug_info debug;
+
+#else /* !ENABLE_DEBUG_HASHMAP */
+#define HASHMAP_DEBUG_FIELDS
+#endif /* ENABLE_DEBUG_HASHMAP */
+
+enum HashmapType {
+        HASHMAP_TYPE_PLAIN,
+        HASHMAP_TYPE_ORDERED,
+        HASHMAP_TYPE_SET,
+        _HASHMAP_TYPE_MAX
+};
+
+struct _packed_ indirect_storage {
+        char    *storage;                  /* where buckets and DIBs are stored */
+        uint8_t  hash_key[HASH_KEY_SIZE];  /* hash key; changes during resize */
+
+        unsigned n_entries;                /* number of stored entries */
+        unsigned n_buckets;                /* number of buckets */
+
+        unsigned idx_lowest_entry;         /* Index below which all buckets are free.
+                                              Makes "while(hashmap_steal_first())" loops
+                                              O(n) instead of O(n^2) for unordered hashmaps. */
+        uint8_t  _pad[3];                  /* padding for the whole HashmapBase */
+        /* The bitfields in HashmapBase complete the alignment of the whole thing. */
+};
+
+struct direct_storage {
+        /* This gives us 39 bytes on 64bit, or 35 bytes on 32bit.
+         * That's room for 4 set_entries + 4 DIB bytes + 3 unused bytes on 64bit,
+         *              or 7 set_entries + 7 DIB bytes + 0 unused bytes on 32bit. */
+        char storage[sizeof(struct indirect_storage)];
+};
+
+#define DIRECT_BUCKETS(entry_t) \
+        (sizeof(struct direct_storage) / (sizeof(entry_t) + sizeof(dib_raw_t)))
+
+/* We should be able to store at least one entry directly. */
+assert_cc(DIRECT_BUCKETS(struct ordered_hashmap_entry) >= 1);
+
+/* We have 3 bits for n_direct_entries. */
+assert_cc(DIRECT_BUCKETS(struct set_entry) < (1 << 3));
+
+/* Hashmaps with directly stored entries all use this shared hash key.
+ * It's no big deal if the key is guessed, because there can be only
+ * a handful of directly stored entries in a hashmap. When a hashmap
+ * outgrows direct storage, it gets its own key for indirect storage. */
+static uint8_t shared_hash_key[HASH_KEY_SIZE];
+static bool shared_hash_key_initialized;
+
+/* Fields that all hashmap/set types must have */
+struct HashmapBase {
+        const struct hash_ops *hash_ops;  /* hash and compare ops to use */
+
+        union _packed_ {
+                struct indirect_storage indirect; /* if  has_indirect */
+                struct direct_storage direct;     /* if !has_indirect */
+        };
+
+        enum HashmapType type:2;     /* HASHMAP_TYPE_* */
+        bool has_indirect:1;         /* whether indirect storage is used */
+        unsigned n_direct_entries:3; /* Number of entries in direct storage.
+                                      * Only valid if !has_indirect. */
+        bool from_pool:1;            /* whether was allocated from mempool */
+        HASHMAP_DEBUG_FIELDS         /* optional hashmap_debug_info */
+};
+
+/* Specific hash types
+ * HashmapBase must be at the beginning of each hashmap struct. */
+
+struct Hashmap {
+        struct HashmapBase b;
+};
+
+struct OrderedHashmap {
+        struct HashmapBase b;
+        unsigned iterate_list_head, iterate_list_tail;
+};
+
+struct Set {
+        struct HashmapBase b;
+};
+
+DEFINE_MEMPOOL(hashmap_pool,         Hashmap,        8);
+DEFINE_MEMPOOL(ordered_hashmap_pool, OrderedHashmap, 8);
+/* No need for a separate Set pool */
+assert_cc(sizeof(Hashmap) == sizeof(Set));
+
+struct hashmap_type_info {
+        size_t head_size;
+        size_t entry_size;
+        struct mempool *mempool;
+        unsigned n_direct_buckets;
+};
+
+static const struct hashmap_type_info hashmap_type_info[_HASHMAP_TYPE_MAX] = {
+        [HASHMAP_TYPE_PLAIN] = {
+                .head_size        = sizeof(Hashmap),
+                .entry_size       = sizeof(struct plain_hashmap_entry),
+                .mempool          = &hashmap_pool,
+                .n_direct_buckets = DIRECT_BUCKETS(struct plain_hashmap_entry),
+        },
+        [HASHMAP_TYPE_ORDERED] = {
+                .head_size        = sizeof(OrderedHashmap),
+                .entry_size       = sizeof(struct ordered_hashmap_entry),
+                .mempool          = &ordered_hashmap_pool,
+                .n_direct_buckets = DIRECT_BUCKETS(struct ordered_hashmap_entry),
+        },
+        [HASHMAP_TYPE_SET] = {
+                .head_size        = sizeof(Set),
+                .entry_size       = sizeof(struct set_entry),
+                .mempool          = &hashmap_pool,
+                .n_direct_buckets = DIRECT_BUCKETS(struct set_entry),
+        },
+};
+
+static unsigned n_buckets(HashmapBase *h) {
+        return h->has_indirect ? h->indirect.n_buckets
+                               : hashmap_type_info[h->type].n_direct_buckets;
+}
+
+static unsigned n_entries(HashmapBase *h) {
+        return h->has_indirect ? h->indirect.n_entries
+                               : h->n_direct_entries;
+}
+
+static void n_entries_inc(HashmapBase *h) {
+        if (h->has_indirect)
+                h->indirect.n_entries++;
+        else
+                h->n_direct_entries++;
+}
+
+static void n_entries_dec(HashmapBase *h) {
+        if (h->has_indirect)
+                h->indirect.n_entries--;
+        else
+                h->n_direct_entries--;
+}
+
+static char *storage_ptr(HashmapBase *h) {
+        return h->has_indirect ? h->indirect.storage
+                               : h->direct.storage;
+}
+
+static uint8_t *hash_key(HashmapBase *h) {
+        return h->has_indirect ? h->indirect.hash_key
+                               : shared_hash_key;
+}
+
+static unsigned base_bucket_hash(HashmapBase *h, const void *p) {
+        struct siphash state;
+        uint64_t hash;
+
+        siphash24_init(&state, hash_key(h));
+
+        h->hash_ops->hash(p, &state);
+
+        hash = siphash24_finalize(&state);
+
+        return (unsigned) (hash % n_buckets(h));
+}
+#define bucket_hash(h, p) base_bucket_hash(HASHMAP_BASE(h), p)
+
+static void get_hash_key(uint8_t hash_key[HASH_KEY_SIZE], bool reuse_is_ok) {
+        static uint8_t current[HASH_KEY_SIZE];
+        static bool current_initialized = false;
+
+        /* Returns a hash function key to use. In order to keep things
+         * fast we will not generate a new key each time we allocate a
+         * new hash table. Instead, we'll just reuse the most recently
+         * generated one, except if we never generated one or when we
+         * are rehashing an entire hash table because we reached a
+         * fill level */
+
+        if (!current_initialized || !reuse_is_ok) {
+                random_bytes(current, sizeof(current));
+                current_initialized = true;
+        }
+
+        memcpy(hash_key, current, sizeof(current));
+}
+
+static struct hashmap_base_entry *bucket_at(HashmapBase *h, unsigned idx) {
+        return (struct hashmap_base_entry*)
+                (storage_ptr(h) + idx * hashmap_type_info[h->type].entry_size);
+}
+
+static struct plain_hashmap_entry *plain_bucket_at(Hashmap *h, unsigned idx) {
+        return (struct plain_hashmap_entry*) bucket_at(HASHMAP_BASE(h), idx);
+}
+
+static struct ordered_hashmap_entry *ordered_bucket_at(OrderedHashmap *h, unsigned idx) {
+        return (struct ordered_hashmap_entry*) bucket_at(HASHMAP_BASE(h), idx);
+}
+
+static struct set_entry *set_bucket_at(Set *h, unsigned idx) {
+        return (struct set_entry*) bucket_at(HASHMAP_BASE(h), idx);
+}
+
+static struct ordered_hashmap_entry *bucket_at_swap(struct swap_entries *swap, unsigned idx) {
+        return &swap->e[idx - _IDX_SWAP_BEGIN];
+}
+
+/* Returns a pointer to the bucket at index idx.
+ * Understands real indexes and swap indexes, hence "_virtual". */
+static struct hashmap_base_entry *bucket_at_virtual(HashmapBase *h, struct swap_entries *swap,
+                                                    unsigned idx) {
+        if (idx < _IDX_SWAP_BEGIN)
+                return bucket_at(h, idx);
+
+        if (idx < _IDX_SWAP_END)
+                return &bucket_at_swap(swap, idx)->p.b;
+
+        assert_not_reached("Invalid index");
+}
+
+static dib_raw_t *dib_raw_ptr(HashmapBase *h) {
+        return (dib_raw_t*)
+                (storage_ptr(h) + hashmap_type_info[h->type].entry_size * n_buckets(h));
+}
+
+static unsigned bucket_distance(HashmapBase *h, unsigned idx, unsigned from) {
+        return idx >= from ? idx - from
+                           : n_buckets(h) + idx - from;
+}
+
+static unsigned bucket_calculate_dib(HashmapBase *h, unsigned idx, dib_raw_t raw_dib) {
+        unsigned initial_bucket;
+
+        if (raw_dib == DIB_RAW_FREE)
+                return DIB_FREE;
+
+        if (_likely_(raw_dib < DIB_RAW_OVERFLOW))
+                return raw_dib;
+
+        /*
+         * Having an overflow DIB value is very unlikely. The hash function
+         * would have to be bad. For example, in a table of size 2^24 filled
+         * to load factor 0.9 the maximum observed DIB is only about 60.
+         * In theory (assuming I used Maxima correctly), for an infinite size
+         * hash table with load factor 0.8 the probability of a given entry
+         * having DIB > 40 is 1.9e-8.
+         * This returns the correct DIB value by recomputing the hash value in
+         * the unlikely case. XXX Hitting this case could be a hint to rehash.
+         */
+        initial_bucket = bucket_hash(h, bucket_at(h, idx)->key);
+        return bucket_distance(h, idx, initial_bucket);
+}
+
+static void bucket_set_dib(HashmapBase *h, unsigned idx, unsigned dib) {
+        dib_raw_ptr(h)[idx] = dib != DIB_FREE ? MIN(dib, DIB_RAW_OVERFLOW) : DIB_RAW_FREE;
+}
+
+static unsigned skip_free_buckets(HashmapBase *h, unsigned idx) {
+        dib_raw_t *dibs;
+
+        dibs = dib_raw_ptr(h);
+
+        for ( ; idx < n_buckets(h); idx++)
+                if (dibs[idx] != DIB_RAW_FREE)
+                        return idx;
+
+        return IDX_NIL;
+}
+
+static void bucket_mark_free(HashmapBase *h, unsigned idx) {
+        memzero(bucket_at(h, idx), hashmap_type_info[h->type].entry_size);
+        bucket_set_dib(h, idx, DIB_FREE);
+}
+
+static void bucket_move_entry(HashmapBase *h, struct swap_entries *swap,
+                              unsigned from, unsigned to) {
+        struct hashmap_base_entry *e_from, *e_to;
+
+        assert(from != to);
+
+        e_from = bucket_at_virtual(h, swap, from);
+        e_to   = bucket_at_virtual(h, swap, to);
+
+        memcpy(e_to, e_from, hashmap_type_info[h->type].entry_size);
+
+        if (h->type == HASHMAP_TYPE_ORDERED) {
+                OrderedHashmap *lh = (OrderedHashmap*) h;
+                struct ordered_hashmap_entry *le, *le_to;
+
+                le_to = (struct ordered_hashmap_entry*) e_to;
+
+                if (le_to->iterate_next != IDX_NIL) {
+                        le = (struct ordered_hashmap_entry*)
+                             bucket_at_virtual(h, swap, le_to->iterate_next);
+                        le->iterate_previous = to;
+                }
+
+                if (le_to->iterate_previous != IDX_NIL) {
+                        le = (struct ordered_hashmap_entry*)
+                             bucket_at_virtual(h, swap, le_to->iterate_previous);
+                        le->iterate_next = to;
+                }
+
+                if (lh->iterate_list_head == from)
+                        lh->iterate_list_head = to;
+                if (lh->iterate_list_tail == from)
+                        lh->iterate_list_tail = to;
+        }
+}
+
+static unsigned next_idx(HashmapBase *h, unsigned idx) {
+        return (idx + 1U) % n_buckets(h);
+}
+
+static unsigned prev_idx(HashmapBase *h, unsigned idx) {
+        return (n_buckets(h) + idx - 1U) % n_buckets(h);
+}
+
+static void *entry_value(HashmapBase *h, struct hashmap_base_entry *e) {
+        switch (h->type) {
+
+        case HASHMAP_TYPE_PLAIN:
+        case HASHMAP_TYPE_ORDERED:
+                return ((struct plain_hashmap_entry*)e)->value;
+
+        case HASHMAP_TYPE_SET:
+                return (void*) e->key;
+
+        default:
+                assert_not_reached("Unknown hashmap type");
+        }
+}
+
+static void base_remove_entry(HashmapBase *h, unsigned idx) {
+        unsigned left, right, prev, dib;
+        dib_raw_t raw_dib, *dibs;
+
+        dibs = dib_raw_ptr(h);
+        assert(dibs[idx] != DIB_RAW_FREE);
+
+#ifdef ENABLE_DEBUG_HASHMAP
+        h->debug.rem_count++;
+        h->debug.last_rem_idx = idx;
+#endif
+
+        left = idx;
+        /* Find the stop bucket ("right"). It is either free or has DIB == 0. */
+        for (right = next_idx(h, left); ; right = next_idx(h, right)) {
+                raw_dib = dibs[right];
+                if (raw_dib == 0 || raw_dib == DIB_RAW_FREE)
+                        break;
+
+                /* The buckets are not supposed to be all occupied and with DIB > 0.
+                 * That would mean we could make everyone better off by shifting them
+                 * backward. This scenario is impossible. */
+                assert(left != right);
+        }
+
+        if (h->type == HASHMAP_TYPE_ORDERED) {
+                OrderedHashmap *lh = (OrderedHashmap*) h;
+                struct ordered_hashmap_entry *le = ordered_bucket_at(lh, idx);
+
+                if (le->iterate_next != IDX_NIL)
+                        ordered_bucket_at(lh, le->iterate_next)->iterate_previous = le->iterate_previous;
+                else
+                        lh->iterate_list_tail = le->iterate_previous;
+
+                if (le->iterate_previous != IDX_NIL)
+                        ordered_bucket_at(lh, le->iterate_previous)->iterate_next = le->iterate_next;
+                else
+                        lh->iterate_list_head = le->iterate_next;
+        }
+
+        /* Now shift all buckets in the interval (left, right) one step backwards */
+        for (prev = left, left = next_idx(h, left); left != right;
+             prev = left, left = next_idx(h, left)) {
+                dib = bucket_calculate_dib(h, left, dibs[left]);
+                assert(dib != 0);
+                bucket_move_entry(h, NULL, left, prev);
+                bucket_set_dib(h, prev, dib - 1);
+        }
+
+        bucket_mark_free(h, prev);
+        n_entries_dec(h);
+}
+#define remove_entry(h, idx) base_remove_entry(HASHMAP_BASE(h), idx)
+
+static unsigned hashmap_iterate_in_insertion_order(OrderedHashmap *h, Iterator *i) {
+        struct ordered_hashmap_entry *e;
+        unsigned idx;
+
+        assert(h);
+        assert(i);
+
+        if (i->idx == IDX_NIL)
+                goto at_end;
+
+        if (i->idx == IDX_FIRST && h->iterate_list_head == IDX_NIL)
+                goto at_end;
+
+        if (i->idx == IDX_FIRST) {
+                idx = h->iterate_list_head;
+                e = ordered_bucket_at(h, idx);
+        } else {
+                idx = i->idx;
+                e = ordered_bucket_at(h, idx);
+                /*
+                 * We allow removing the current entry while iterating, but removal may cause
+                 * a backward shift. The next entry may thus move one bucket to the left.
+                 * To detect when it happens, we remember the key pointer of the entry we were
+                 * going to iterate next. If it does not match, there was a backward shift.
+                 */
+                if (e->p.b.key != i->next_key) {
+                        idx = prev_idx(HASHMAP_BASE(h), idx);
+                        e = ordered_bucket_at(h, idx);
+                }
+                assert(e->p.b.key == i->next_key);
+        }
+
+#ifdef ENABLE_DEBUG_HASHMAP
+        i->prev_idx = idx;
+#endif
+
+        if (e->iterate_next != IDX_NIL) {
+                struct ordered_hashmap_entry *n;
+                i->idx = e->iterate_next;
+                n = ordered_bucket_at(h, i->idx);
+                i->next_key = n->p.b.key;
+        } else
+                i->idx = IDX_NIL;
+
+        return idx;
+
+at_end:
+        i->idx = IDX_NIL;
+        return IDX_NIL;
+}
+
+static unsigned hashmap_iterate_in_internal_order(HashmapBase *h, Iterator *i) {
+        unsigned idx;
+
+        assert(h);
+        assert(i);
+
+        if (i->idx == IDX_NIL)
+                goto at_end;
+
+        if (i->idx == IDX_FIRST) {
+                /* fast forward to the first occupied bucket */
+                if (h->has_indirect) {
+                        i->idx = skip_free_buckets(h, h->indirect.idx_lowest_entry);
+                        h->indirect.idx_lowest_entry = i->idx;
+                } else
+                        i->idx = skip_free_buckets(h, 0);
+
+                if (i->idx == IDX_NIL)
+                        goto at_end;
+        } else {
+                struct hashmap_base_entry *e;
+
+                assert(i->idx > 0);
+
+                e = bucket_at(h, i->idx);
+                /*
+                 * We allow removing the current entry while iterating, but removal may cause
+                 * a backward shift. The next entry may thus move one bucket to the left.
+                 * To detect when it happens, we remember the key pointer of the entry we were
+                 * going to iterate next. If it does not match, there was a backward shift.
+                 */
+                if (e->key != i->next_key)
+                        e = bucket_at(h, --i->idx);
+
+                assert(e->key == i->next_key);
+        }
+
+        idx = i->idx;
+#ifdef ENABLE_DEBUG_HASHMAP
+        i->prev_idx = idx;
+#endif
+
+        i->idx = skip_free_buckets(h, i->idx + 1);
+        if (i->idx != IDX_NIL)
+                i->next_key = bucket_at(h, i->idx)->key;
+        else
+                i->idx = IDX_NIL;
+
+        return idx;
+
+at_end:
+        i->idx = IDX_NIL;
+        return IDX_NIL;
+}
+
+static unsigned hashmap_iterate_entry(HashmapBase *h, Iterator *i) {
+        if (!h) {
+                i->idx = IDX_NIL;
+                return IDX_NIL;
+        }
+
+#ifdef ENABLE_DEBUG_HASHMAP
+        if (i->idx == IDX_FIRST) {
+                i->put_count = h->debug.put_count;
+                i->rem_count = h->debug.rem_count;
+        } else {
+                /* While iterating, must not add any new entries */
+                assert(i->put_count == h->debug.put_count);
+                /* ... or remove entries other than the current one */
+                assert(i->rem_count == h->debug.rem_count ||
+                       (i->rem_count == h->debug.rem_count - 1 &&
+                        i->prev_idx == h->debug.last_rem_idx));
+                /* Reset our removals counter */
+                i->rem_count = h->debug.rem_count;
+        }
+#endif
+
+        return h->type == HASHMAP_TYPE_ORDERED ? hashmap_iterate_in_insertion_order((OrderedHashmap*) h, i)
+                                               : hashmap_iterate_in_internal_order(h, i);
+}
+
+bool internal_hashmap_iterate(HashmapBase *h, Iterator *i, void **value, const void **key) {
+        struct hashmap_base_entry *e;
+        void *data;
+        unsigned idx;
+
+        idx = hashmap_iterate_entry(h, i);
+        if (idx == IDX_NIL) {
+                if (value)
+                        *value = NULL;
+                if (key)
+                        *key = NULL;
+
+                return false;
+        }
+
+        e = bucket_at(h, idx);
+        data = entry_value(h, e);
+        if (value)
+                *value = data;
+        if (key)
+                *key = e->key;
+
+        return true;
+}
+
+bool set_iterate(Set *s, Iterator *i, void **value) {
+        return internal_hashmap_iterate(HASHMAP_BASE(s), i, value, NULL);
+}
+
+#define HASHMAP_FOREACH_IDX(idx, h, i) \
+        for ((i) = ITERATOR_FIRST, (idx) = hashmap_iterate_entry((h), &(i)); \
+             (idx != IDX_NIL); \
+             (idx) = hashmap_iterate_entry((h), &(i)))
+
+static void reset_direct_storage(HashmapBase *h) {
+        const struct hashmap_type_info *hi = &hashmap_type_info[h->type];
+        void *p;
+
+        assert(!h->has_indirect);
+
+        p = mempset(h->direct.storage, 0, hi->entry_size * hi->n_direct_buckets);
+        memset(p, DIB_RAW_INIT, sizeof(dib_raw_t) * hi->n_direct_buckets);
+}
+
+static struct HashmapBase *hashmap_base_new(const struct hash_ops *hash_ops, enum HashmapType type HASHMAP_DEBUG_PARAMS) {
+        HashmapBase *h;
+        const struct hashmap_type_info *hi = &hashmap_type_info[type];
+        bool use_pool;
+
+        use_pool = is_main_thread();
+
+        h = use_pool ? mempool_alloc0_tile(hi->mempool) : malloc0(hi->head_size);
+
+        if (!h)
+                return NULL;
+
+        h->type = type;
+        h->from_pool = use_pool;
+        h->hash_ops = hash_ops ? hash_ops : &trivial_hash_ops;
+
+        if (type == HASHMAP_TYPE_ORDERED) {
+                OrderedHashmap *lh = (OrderedHashmap*)h;
+                lh->iterate_list_head = lh->iterate_list_tail = IDX_NIL;
+        }
+
+        reset_direct_storage(h);
+
+        if (!shared_hash_key_initialized) {
+                random_bytes(shared_hash_key, sizeof(shared_hash_key));
+                shared_hash_key_initialized= true;
+        }
+
+#ifdef ENABLE_DEBUG_HASHMAP
+        h->debug.func = func;
+        h->debug.file = file;
+        h->debug.line = line;
+        assert_se(pthread_mutex_lock(&hashmap_debug_list_mutex) == 0);
+        LIST_PREPEND(debug_list, hashmap_debug_list, &h->debug);
+        assert_se(pthread_mutex_unlock(&hashmap_debug_list_mutex) == 0);
+#endif
+
+        return h;
+}
+
+Hashmap *internal_hashmap_new(const struct hash_ops *hash_ops  HASHMAP_DEBUG_PARAMS) {
+        return (Hashmap*)        hashmap_base_new(hash_ops, HASHMAP_TYPE_PLAIN HASHMAP_DEBUG_PASS_ARGS);
+}
+
+OrderedHashmap *internal_ordered_hashmap_new(const struct hash_ops *hash_ops  HASHMAP_DEBUG_PARAMS) {
+        return (OrderedHashmap*) hashmap_base_new(hash_ops, HASHMAP_TYPE_ORDERED HASHMAP_DEBUG_PASS_ARGS);
+}
+
+Set *internal_set_new(const struct hash_ops *hash_ops  HASHMAP_DEBUG_PARAMS) {
+        return (Set*)            hashmap_base_new(hash_ops, HASHMAP_TYPE_SET HASHMAP_DEBUG_PASS_ARGS);
+}
+
+static int hashmap_base_ensure_allocated(HashmapBase **h, const struct hash_ops *hash_ops,
+                                         enum HashmapType type HASHMAP_DEBUG_PARAMS) {
+        HashmapBase *q;
+
+        assert(h);
+
+        if (*h)
+                return 0;
+
+        q = hashmap_base_new(hash_ops, type HASHMAP_DEBUG_PASS_ARGS);
+        if (!q)
+                return -ENOMEM;
+
+        *h = q;
+        return 0;
+}
+
+int internal_hashmap_ensure_allocated(Hashmap **h, const struct hash_ops *hash_ops  HASHMAP_DEBUG_PARAMS) {
+        return hashmap_base_ensure_allocated((HashmapBase**)h, hash_ops, HASHMAP_TYPE_PLAIN HASHMAP_DEBUG_PASS_ARGS);
+}
+
+int internal_ordered_hashmap_ensure_allocated(OrderedHashmap **h, const struct hash_ops *hash_ops  HASHMAP_DEBUG_PARAMS) {
+        return hashmap_base_ensure_allocated((HashmapBase**)h, hash_ops, HASHMAP_TYPE_ORDERED HASHMAP_DEBUG_PASS_ARGS);
+}
+
+int internal_set_ensure_allocated(Set **s, const struct hash_ops *hash_ops  HASHMAP_DEBUG_PARAMS) {
+        return hashmap_base_ensure_allocated((HashmapBase**)s, hash_ops, HASHMAP_TYPE_SET HASHMAP_DEBUG_PASS_ARGS);
+}
+
+static void hashmap_free_no_clear(HashmapBase *h) {
+        assert(!h->has_indirect);
+        assert(!h->n_direct_entries);
+
+#ifdef ENABLE_DEBUG_HASHMAP
+        assert_se(pthread_mutex_lock(&hashmap_debug_list_mutex) == 0);
+        LIST_REMOVE(debug_list, hashmap_debug_list, &h->debug);
+        assert_se(pthread_mutex_unlock(&hashmap_debug_list_mutex) == 0);
+#endif
+
+        if (h->from_pool)
+                mempool_free_tile(hashmap_type_info[h->type].mempool, h);
+        else
+                free(h);
+}
+
+HashmapBase *internal_hashmap_free(HashmapBase *h) {
+
+        /* Free the hashmap, but nothing in it */
+
+        if (h) {
+                internal_hashmap_clear(h);
+                hashmap_free_no_clear(h);
+        }
+
+        return NULL;
+}
+
+HashmapBase *internal_hashmap_free_free(HashmapBase *h) {
+
+        /* Free the hashmap and all data objects in it, but not the
+         * keys */
+
+        if (h) {
+                internal_hashmap_clear_free(h);
+                hashmap_free_no_clear(h);
+        }
+
+        return NULL;
+}
+
+Hashmap *hashmap_free_free_free(Hashmap *h) {
+
+        /* Free the hashmap and all data and key objects in it */
+
+        if (h) {
+                hashmap_clear_free_free(h);
+                hashmap_free_no_clear(HASHMAP_BASE(h));
+        }
+
+        return NULL;
+}
+
+void internal_hashmap_clear(HashmapBase *h) {
+        if (!h)
+                return;
+
+        if (h->has_indirect) {
+                free(h->indirect.storage);
+                h->has_indirect = false;
+        }
+
+        h->n_direct_entries = 0;
+        reset_direct_storage(h);
+
+        if (h->type == HASHMAP_TYPE_ORDERED) {
+                OrderedHashmap *lh = (OrderedHashmap*) h;
+                lh->iterate_list_head = lh->iterate_list_tail = IDX_NIL;
+        }
+}
+
+void internal_hashmap_clear_free(HashmapBase *h) {
+        unsigned idx;
+
+        if (!h)
+                return;
+
+        for (idx = skip_free_buckets(h, 0); idx != IDX_NIL;
+             idx = skip_free_buckets(h, idx + 1))
+                free(entry_value(h, bucket_at(h, idx)));
+
+        internal_hashmap_clear(h);
+}
+
+void hashmap_clear_free_free(Hashmap *h) {
+        unsigned idx;
+
+        if (!h)
+                return;
+
+        for (idx = skip_free_buckets(HASHMAP_BASE(h), 0); idx != IDX_NIL;
+             idx = skip_free_buckets(HASHMAP_BASE(h), idx + 1)) {
+                struct plain_hashmap_entry *e = plain_bucket_at(h, idx);
+                free((void*)e->b.key);
+                free(e->value);
+        }
+
+        internal_hashmap_clear(HASHMAP_BASE(h));
+}
+
+static int resize_buckets(HashmapBase *h, unsigned entries_add);
+
+/*
+ * Finds an empty bucket to put an entry into, starting the scan at 'idx'.
+ * Performs Robin Hood swaps as it goes. The entry to put must be placed
+ * by the caller into swap slot IDX_PUT.
+ * If used for in-place resizing, may leave a displaced entry in swap slot
+ * IDX_PUT. Caller must rehash it next.
+ * Returns: true if it left a displaced entry to rehash next in IDX_PUT,
+ *          false otherwise.
+ */
+static bool hashmap_put_robin_hood(HashmapBase *h, unsigned idx,
+                                   struct swap_entries *swap) {
+        dib_raw_t raw_dib, *dibs;
+        unsigned dib, distance;
+
+#ifdef ENABLE_DEBUG_HASHMAP
+        h->debug.put_count++;
+#endif
+
+        dibs = dib_raw_ptr(h);
+
+        for (distance = 0; ; distance++) {
+                raw_dib = dibs[idx];
+                if (raw_dib == DIB_RAW_FREE || raw_dib == DIB_RAW_REHASH) {
+                        if (raw_dib == DIB_RAW_REHASH)
+                                bucket_move_entry(h, swap, idx, IDX_TMP);
+
+                        if (h->has_indirect && h->indirect.idx_lowest_entry > idx)
+                                h->indirect.idx_lowest_entry = idx;
+
+                        bucket_set_dib(h, idx, distance);
+                        bucket_move_entry(h, swap, IDX_PUT, idx);
+                        if (raw_dib == DIB_RAW_REHASH) {
+                                bucket_move_entry(h, swap, IDX_TMP, IDX_PUT);
+                                return true;
+                        }
+
+                        return false;
+                }
+
+                dib = bucket_calculate_dib(h, idx, raw_dib);
+
+                if (dib < distance) {
+                        /* Found a wealthier entry. Go Robin Hood! */
+                        bucket_set_dib(h, idx, distance);
+
+                        /* swap the entries */
+                        bucket_move_entry(h, swap, idx, IDX_TMP);
+                        bucket_move_entry(h, swap, IDX_PUT, idx);
+                        bucket_move_entry(h, swap, IDX_TMP, IDX_PUT);
+
+                        distance = dib;
+                }
+
+                idx = next_idx(h, idx);
+        }
+}
+
+/*
+ * Puts an entry into a hashmap, boldly - no check whether key already exists.
+ * The caller must place the entry (only its key and value, not link indexes)
+ * in swap slot IDX_PUT.
+ * Caller must ensure: the key does not exist yet in the hashmap.
+ *                     that resize is not needed if !may_resize.
+ * Returns: 1 if entry was put successfully.
+ *          -ENOMEM if may_resize==true and resize failed with -ENOMEM.
+ *          Cannot return -ENOMEM if !may_resize.
+ */
+static int hashmap_base_put_boldly(HashmapBase *h, unsigned idx,
+                                   struct swap_entries *swap, bool may_resize) {
+        struct ordered_hashmap_entry *new_entry;
+        int r;
+
+        assert(idx < n_buckets(h));
+
+        new_entry = bucket_at_swap(swap, IDX_PUT);
+
+        if (may_resize) {
+                r = resize_buckets(h, 1);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        idx = bucket_hash(h, new_entry->p.b.key);
+        }
+        assert(n_entries(h) < n_buckets(h));
+
+        if (h->type == HASHMAP_TYPE_ORDERED) {
+                OrderedHashmap *lh = (OrderedHashmap*) h;
+
+                new_entry->iterate_next = IDX_NIL;
+                new_entry->iterate_previous = lh->iterate_list_tail;
+
+                if (lh->iterate_list_tail != IDX_NIL) {
+                        struct ordered_hashmap_entry *old_tail;
+
+                        old_tail = ordered_bucket_at(lh, lh->iterate_list_tail);
+                        assert(old_tail->iterate_next == IDX_NIL);
+                        old_tail->iterate_next = IDX_PUT;
+                }
+
+                lh->iterate_list_tail = IDX_PUT;
+                if (lh->iterate_list_head == IDX_NIL)
+                        lh->iterate_list_head = IDX_PUT;
+        }
+
+        assert_se(hashmap_put_robin_hood(h, idx, swap) == false);
+
+        n_entries_inc(h);
+#ifdef ENABLE_DEBUG_HASHMAP
+        h->debug.max_entries = MAX(h->debug.max_entries, n_entries(h));
+#endif
+
+        return 1;
+}
+#define hashmap_put_boldly(h, idx, swap, may_resize) \
+        hashmap_base_put_boldly(HASHMAP_BASE(h), idx, swap, may_resize)
+
+/*
+ * Returns 0 if resize is not needed.
+ *         1 if successfully resized.
+ *         -ENOMEM on allocation failure.
+ */
+static int resize_buckets(HashmapBase *h, unsigned entries_add) {
+        struct swap_entries swap;
+        char *new_storage;
+        dib_raw_t *old_dibs, *new_dibs;
+        const struct hashmap_type_info *hi;
+        unsigned idx, optimal_idx;
+        unsigned old_n_buckets, new_n_buckets, n_rehashed, new_n_entries;
+        uint8_t new_shift;
+        bool rehash_next;
+
+        assert(h);
+
+        hi = &hashmap_type_info[h->type];
+        new_n_entries = n_entries(h) + entries_add;
+
+        /* overflow? */
+        if (_unlikely_(new_n_entries < entries_add))
+                return -ENOMEM;
+
+        /* For direct storage we allow 100% load, because it's tiny. */
+        if (!h->has_indirect && new_n_entries <= hi->n_direct_buckets)
+                return 0;
+
+        /*
+         * Load factor = n/m = 1 - (1/INV_KEEP_FREE).
+         * From it follows: m = n + n/(INV_KEEP_FREE - 1)
+         */
+        new_n_buckets = new_n_entries + new_n_entries / (INV_KEEP_FREE - 1);
+        /* overflow? */
+        if (_unlikely_(new_n_buckets < new_n_entries))
+                return -ENOMEM;
+
+        if (_unlikely_(new_n_buckets > UINT_MAX / (hi->entry_size + sizeof(dib_raw_t))))
+                return -ENOMEM;
+
+        old_n_buckets = n_buckets(h);
+
+        if (_likely_(new_n_buckets <= old_n_buckets))
+                return 0;
+
+        new_shift = log2u_round_up(MAX(
+                        new_n_buckets * (hi->entry_size + sizeof(dib_raw_t)),
+                        2 * sizeof(struct direct_storage)));
+
+        /* Realloc storage (buckets and DIB array). */
+        new_storage = realloc(h->has_indirect ? h->indirect.storage : NULL,
+                              1U << new_shift);
+        if (!new_storage)
+                return -ENOMEM;
+
+        /* Must upgrade direct to indirect storage. */
+        if (!h->has_indirect) {
+                memcpy(new_storage, h->direct.storage,
+                       old_n_buckets * (hi->entry_size + sizeof(dib_raw_t)));
+                h->indirect.n_entries = h->n_direct_entries;
+                h->indirect.idx_lowest_entry = 0;
+                h->n_direct_entries = 0;
+        }
+
+        /* Get a new hash key. If we've just upgraded to indirect storage,
+         * allow reusing a previously generated key. It's still a different key
+         * from the shared one that we used for direct storage. */
+        get_hash_key(h->indirect.hash_key, !h->has_indirect);
+
+        h->has_indirect = true;
+        h->indirect.storage = new_storage;
+        h->indirect.n_buckets = (1U << new_shift) /
+                                (hi->entry_size + sizeof(dib_raw_t));
+
+        old_dibs = (dib_raw_t*)(new_storage + hi->entry_size * old_n_buckets);
+        new_dibs = dib_raw_ptr(h);
+
+        /*
+         * Move the DIB array to the new place, replacing valid DIB values with
+         * DIB_RAW_REHASH to indicate all of the used buckets need rehashing.
+         * Note: Overlap is not possible, because we have at least doubled the
+         * number of buckets and dib_raw_t is smaller than any entry type.
+         */
+        for (idx = 0; idx < old_n_buckets; idx++) {
+                assert(old_dibs[idx] != DIB_RAW_REHASH);
+                new_dibs[idx] = old_dibs[idx] == DIB_RAW_FREE ? DIB_RAW_FREE
+                                                              : DIB_RAW_REHASH;
+        }
+
+        /* Zero the area of newly added entries (including the old DIB area) */
+        memzero(bucket_at(h, old_n_buckets),
+               (n_buckets(h) - old_n_buckets) * hi->entry_size);
+
+        /* The upper half of the new DIB array needs initialization */
+        memset(&new_dibs[old_n_buckets], DIB_RAW_INIT,
+               (n_buckets(h) - old_n_buckets) * sizeof(dib_raw_t));
+
+        /* Rehash entries that need it */
+        n_rehashed = 0;
+        for (idx = 0; idx < old_n_buckets; idx++) {
+                if (new_dibs[idx] != DIB_RAW_REHASH)
+                        continue;
+
+                optimal_idx = bucket_hash(h, bucket_at(h, idx)->key);
+
+                /*
+                 * Not much to do if by luck the entry hashes to its current
+                 * location. Just set its DIB.
+                 */
+                if (optimal_idx == idx) {
+                        new_dibs[idx] = 0;
+                        n_rehashed++;
+                        continue;
+                }
+
+                new_dibs[idx] = DIB_RAW_FREE;
+                bucket_move_entry(h, &swap, idx, IDX_PUT);
+                /* bucket_move_entry does not clear the source */
+                memzero(bucket_at(h, idx), hi->entry_size);
+
+                do {
+                        /*
+                         * Find the new bucket for the current entry. This may make
+                         * another entry homeless and load it into IDX_PUT.
+                         */
+                        rehash_next = hashmap_put_robin_hood(h, optimal_idx, &swap);
+                        n_rehashed++;
+
+                        /* Did the current entry displace another one? */
+                        if (rehash_next)
+                                optimal_idx = bucket_hash(h, bucket_at_swap(&swap, IDX_PUT)->p.b.key);
+                } while (rehash_next);
+        }
+
+        assert(n_rehashed == n_entries(h));
+
+        return 1;
+}
+
+/*
+ * Finds an entry with a matching key
+ * Returns: index of the found entry, or IDX_NIL if not found.
+ */
+static unsigned base_bucket_scan(HashmapBase *h, unsigned idx, const void *key) {
+        struct hashmap_base_entry *e;
+        unsigned dib, distance;
+        dib_raw_t *dibs = dib_raw_ptr(h);
+
+        assert(idx < n_buckets(h));
+
+        for (distance = 0; ; distance++) {
+                if (dibs[idx] == DIB_RAW_FREE)
+                        return IDX_NIL;
+
+                dib = bucket_calculate_dib(h, idx, dibs[idx]);
+
+                if (dib < distance)
+                        return IDX_NIL;
+                if (dib == distance) {
+                        e = bucket_at(h, idx);
+                        if (h->hash_ops->compare(e->key, key) == 0)
+                                return idx;
+                }
+
+                idx = next_idx(h, idx);
+        }
+}
+#define bucket_scan(h, idx, key) base_bucket_scan(HASHMAP_BASE(h), idx, key)
+
+int hashmap_put(Hashmap *h, const void *key, void *value) {
+        struct swap_entries swap;
+        struct plain_hashmap_entry *e;
+        unsigned hash, idx;
+
+        assert(h);
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx != IDX_NIL) {
+                e = plain_bucket_at(h, idx);
+                if (e->value == value)
+                        return 0;
+                return -EEXIST;
+        }
+
+        e = &bucket_at_swap(&swap, IDX_PUT)->p;
+        e->b.key = key;
+        e->value = value;
+        return hashmap_put_boldly(h, hash, &swap, true);
+}
+
+int set_put(Set *s, const void *key) {
+        struct swap_entries swap;
+        struct hashmap_base_entry *e;
+        unsigned hash, idx;
+
+        assert(s);
+
+        hash = bucket_hash(s, key);
+        idx = bucket_scan(s, hash, key);
+        if (idx != IDX_NIL)
+                return 0;
+
+        e = &bucket_at_swap(&swap, IDX_PUT)->p.b;
+        e->key = key;
+        return hashmap_put_boldly(s, hash, &swap, true);
+}
+
+int hashmap_replace(Hashmap *h, const void *key, void *value) {
+        struct swap_entries swap;
+        struct plain_hashmap_entry *e;
+        unsigned hash, idx;
+
+        assert(h);
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx != IDX_NIL) {
+                e = plain_bucket_at(h, idx);
+#ifdef ENABLE_DEBUG_HASHMAP
+                /* Although the key is equal, the key pointer may have changed,
+                 * and this would break our assumption for iterating. So count
+                 * this operation as incompatible with iteration. */
+                if (e->b.key != key) {
+                        h->b.debug.put_count++;
+                        h->b.debug.rem_count++;
+                        h->b.debug.last_rem_idx = idx;
+                }
+#endif
+                e->b.key = key;
+                e->value = value;
+                return 0;
+        }
+
+        e = &bucket_at_swap(&swap, IDX_PUT)->p;
+        e->b.key = key;
+        e->value = value;
+        return hashmap_put_boldly(h, hash, &swap, true);
+}
+
+int hashmap_update(Hashmap *h, const void *key, void *value) {
+        struct plain_hashmap_entry *e;
+        unsigned hash, idx;
+
+        assert(h);
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL)
+                return -ENOENT;
+
+        e = plain_bucket_at(h, idx);
+        e->value = value;
+        return 0;
+}
+
+void *internal_hashmap_get(HashmapBase *h, const void *key) {
+        struct hashmap_base_entry *e;
+        unsigned hash, idx;
+
+        if (!h)
+                return NULL;
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = bucket_at(h, idx);
+        return entry_value(h, e);
+}
+
+void *hashmap_get2(Hashmap *h, const void *key, void **key2) {
+        struct plain_hashmap_entry *e;
+        unsigned hash, idx;
+
+        if (!h)
+                return NULL;
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = plain_bucket_at(h, idx);
+        if (key2)
+                *key2 = (void*) e->b.key;
+
+        return e->value;
+}
+
+bool internal_hashmap_contains(HashmapBase *h, const void *key) {
+        unsigned hash;
+
+        if (!h)
+                return false;
+
+        hash = bucket_hash(h, key);
+        return bucket_scan(h, hash, key) != IDX_NIL;
+}
+
+void *internal_hashmap_remove(HashmapBase *h, const void *key) {
+        struct hashmap_base_entry *e;
+        unsigned hash, idx;
+        void *data;
+
+        if (!h)
+                return NULL;
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = bucket_at(h, idx);
+        data = entry_value(h, e);
+        remove_entry(h, idx);
+
+        return data;
+}
+
+void *hashmap_remove2(Hashmap *h, const void *key, void **rkey) {
+        struct plain_hashmap_entry *e;
+        unsigned hash, idx;
+        void *data;
+
+        if (!h) {
+                if (rkey)
+                        *rkey = NULL;
+                return NULL;
+        }
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL) {
+                if (rkey)
+                        *rkey = NULL;
+                return NULL;
+        }
+
+        e = plain_bucket_at(h, idx);
+        data = e->value;
+        if (rkey)
+                *rkey = (void*) e->b.key;
+
+        remove_entry(h, idx);
+
+        return data;
+}
+
+int hashmap_remove_and_put(Hashmap *h, const void *old_key, const void *new_key, void *value) {
+        struct swap_entries swap;
+        struct plain_hashmap_entry *e;
+        unsigned old_hash, new_hash, idx;
+
+        if (!h)
+                return -ENOENT;
+
+        old_hash = bucket_hash(h, old_key);
+        idx = bucket_scan(h, old_hash, old_key);
+        if (idx == IDX_NIL)
+                return -ENOENT;
+
+        new_hash = bucket_hash(h, new_key);
+        if (bucket_scan(h, new_hash, new_key) != IDX_NIL)
+                return -EEXIST;
+
+        remove_entry(h, idx);
+
+        e = &bucket_at_swap(&swap, IDX_PUT)->p;
+        e->b.key = new_key;
+        e->value = value;
+        assert_se(hashmap_put_boldly(h, new_hash, &swap, false) == 1);
+
+        return 0;
+}
+
+int set_remove_and_put(Set *s, const void *old_key, const void *new_key) {
+        struct swap_entries swap;
+        struct hashmap_base_entry *e;
+        unsigned old_hash, new_hash, idx;
+
+        if (!s)
+                return -ENOENT;
+
+        old_hash = bucket_hash(s, old_key);
+        idx = bucket_scan(s, old_hash, old_key);
+        if (idx == IDX_NIL)
+                return -ENOENT;
+
+        new_hash = bucket_hash(s, new_key);
+        if (bucket_scan(s, new_hash, new_key) != IDX_NIL)
+                return -EEXIST;
+
+        remove_entry(s, idx);
+
+        e = &bucket_at_swap(&swap, IDX_PUT)->p.b;
+        e->key = new_key;
+        assert_se(hashmap_put_boldly(s, new_hash, &swap, false) == 1);
+
+        return 0;
+}
+
+int hashmap_remove_and_replace(Hashmap *h, const void *old_key, const void *new_key, void *value) {
+        struct swap_entries swap;
+        struct plain_hashmap_entry *e;
+        unsigned old_hash, new_hash, idx_old, idx_new;
+
+        if (!h)
+                return -ENOENT;
+
+        old_hash = bucket_hash(h, old_key);
+        idx_old = bucket_scan(h, old_hash, old_key);
+        if (idx_old == IDX_NIL)
+                return -ENOENT;
+
+        old_key = bucket_at(HASHMAP_BASE(h), idx_old)->key;
+
+        new_hash = bucket_hash(h, new_key);
+        idx_new = bucket_scan(h, new_hash, new_key);
+        if (idx_new != IDX_NIL)
+                if (idx_old != idx_new) {
+                        remove_entry(h, idx_new);
+                        /* Compensate for a possible backward shift. */
+                        if (old_key != bucket_at(HASHMAP_BASE(h), idx_old)->key)
+                                idx_old = prev_idx(HASHMAP_BASE(h), idx_old);
+                        assert(old_key == bucket_at(HASHMAP_BASE(h), idx_old)->key);
+                }
+
+        remove_entry(h, idx_old);
+
+        e = &bucket_at_swap(&swap, IDX_PUT)->p;
+        e->b.key = new_key;
+        e->value = value;
+        assert_se(hashmap_put_boldly(h, new_hash, &swap, false) == 1);
+
+        return 0;
+}
+
+void *hashmap_remove_value(Hashmap *h, const void *key, void *value) {
+        struct plain_hashmap_entry *e;
+        unsigned hash, idx;
+
+        if (!h)
+                return NULL;
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = plain_bucket_at(h, idx);
+        if (e->value != value)
+                return NULL;
+
+        remove_entry(h, idx);
+
+        return value;
+}
+
+static unsigned find_first_entry(HashmapBase *h) {
+        Iterator i = ITERATOR_FIRST;
+
+        if (!h || !n_entries(h))
+                return IDX_NIL;
+
+        return hashmap_iterate_entry(h, &i);
+}
+
+void *internal_hashmap_first(HashmapBase *h) {
+        unsigned idx;
+
+        idx = find_first_entry(h);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        return entry_value(h, bucket_at(h, idx));
+}
+
+void *internal_hashmap_first_key(HashmapBase *h) {
+        struct hashmap_base_entry *e;
+        unsigned idx;
+
+        idx = find_first_entry(h);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = bucket_at(h, idx);
+        return (void*) e->key;
+}
+
+void *internal_hashmap_steal_first(HashmapBase *h) {
+        struct hashmap_base_entry *e;
+        void *data;
+        unsigned idx;
+
+        idx = find_first_entry(h);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = bucket_at(h, idx);
+        data = entry_value(h, e);
+        remove_entry(h, idx);
+
+        return data;
+}
+
+void *internal_hashmap_steal_first_key(HashmapBase *h) {
+        struct hashmap_base_entry *e;
+        void *key;
+        unsigned idx;
+
+        idx = find_first_entry(h);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = bucket_at(h, idx);
+        key = (void*) e->key;
+        remove_entry(h, idx);
+
+        return key;
+}
+
+unsigned internal_hashmap_size(HashmapBase *h) {
+
+        if (!h)
+                return 0;
+
+        return n_entries(h);
+}
+
+unsigned internal_hashmap_buckets(HashmapBase *h) {
+
+        if (!h)
+                return 0;
+
+        return n_buckets(h);
+}
+
+int internal_hashmap_merge(Hashmap *h, Hashmap *other) {
+        Iterator i;
+        unsigned idx;
+
+        assert(h);
+
+        HASHMAP_FOREACH_IDX(idx, HASHMAP_BASE(other), i) {
+                struct plain_hashmap_entry *pe = plain_bucket_at(other, idx);
+                int r;
+
+                r = hashmap_put(h, pe->b.key, pe->value);
+                if (r < 0 && r != -EEXIST)
+                        return r;
+        }
+
+        return 0;
+}
+
+int set_merge(Set *s, Set *other) {
+        Iterator i;
+        unsigned idx;
+
+        assert(s);
+
+        HASHMAP_FOREACH_IDX(idx, HASHMAP_BASE(other), i) {
+                struct set_entry *se = set_bucket_at(other, idx);
+                int r;
+
+                r = set_put(s, se->b.key);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int internal_hashmap_reserve(HashmapBase *h, unsigned entries_add) {
+        int r;
+
+        assert(h);
+
+        r = resize_buckets(h, entries_add);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+/*
+ * The same as hashmap_merge(), but every new item from other is moved to h.
+ * Keys already in h are skipped and stay in other.
+ * Returns: 0 on success.
+ *          -ENOMEM on alloc failure, in which case no move has been done.
+ */
+int internal_hashmap_move(HashmapBase *h, HashmapBase *other) {
+        struct swap_entries swap;
+        struct hashmap_base_entry *e, *n;
+        Iterator i;
+        unsigned idx;
+        int r;
+
+        assert(h);
+
+        if (!other)
+                return 0;
+
+        assert(other->type == h->type);
+
+        /*
+         * This reserves buckets for the worst case, where none of other's
+         * entries are yet present in h. This is preferable to risking
+         * an allocation failure in the middle of the moving and having to
+         * rollback or return a partial result.
+         */
+        r = resize_buckets(h, n_entries(other));
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH_IDX(idx, other, i) {
+                unsigned h_hash;
+
+                e = bucket_at(other, idx);
+                h_hash = bucket_hash(h, e->key);
+                if (bucket_scan(h, h_hash, e->key) != IDX_NIL)
+                        continue;
+
+                n = &bucket_at_swap(&swap, IDX_PUT)->p.b;
+                n->key = e->key;
+                if (h->type != HASHMAP_TYPE_SET)
+                        ((struct plain_hashmap_entry*) n)->value =
+                                ((struct plain_hashmap_entry*) e)->value;
+                assert_se(hashmap_put_boldly(h, h_hash, &swap, false) == 1);
+
+                remove_entry(other, idx);
+        }
+
+        return 0;
+}
+
+int internal_hashmap_move_one(HashmapBase *h, HashmapBase *other, const void *key) {
+        struct swap_entries swap;
+        unsigned h_hash, other_hash, idx;
+        struct hashmap_base_entry *e, *n;
+        int r;
+
+        assert(h);
+
+        h_hash = bucket_hash(h, key);
+        if (bucket_scan(h, h_hash, key) != IDX_NIL)
+                return -EEXIST;
+
+        if (!other)
+                return -ENOENT;
+
+        assert(other->type == h->type);
+
+        other_hash = bucket_hash(other, key);
+        idx = bucket_scan(other, other_hash, key);
+        if (idx == IDX_NIL)
+                return -ENOENT;
+
+        e = bucket_at(other, idx);
+
+        n = &bucket_at_swap(&swap, IDX_PUT)->p.b;
+        n->key = e->key;
+        if (h->type != HASHMAP_TYPE_SET)
+                ((struct plain_hashmap_entry*) n)->value =
+                        ((struct plain_hashmap_entry*) e)->value;
+        r = hashmap_put_boldly(h, h_hash, &swap, true);
+        if (r < 0)
+                return r;
+
+        remove_entry(other, idx);
+        return 0;
+}
+
+HashmapBase *internal_hashmap_copy(HashmapBase *h) {
+        HashmapBase *copy;
+        int r;
+
+        assert(h);
+
+        copy = hashmap_base_new(h->hash_ops, h->type  HASHMAP_DEBUG_SRC_ARGS);
+        if (!copy)
+                return NULL;
+
+        switch (h->type) {
+        case HASHMAP_TYPE_PLAIN:
+        case HASHMAP_TYPE_ORDERED:
+                r = hashmap_merge((Hashmap*)copy, (Hashmap*)h);
+                break;
+        case HASHMAP_TYPE_SET:
+                r = set_merge((Set*)copy, (Set*)h);
+                break;
+        default:
+                assert_not_reached("Unknown hashmap type");
+        }
+
+        if (r < 0) {
+                internal_hashmap_free(copy);
+                return NULL;
+        }
+
+        return copy;
+}
+
+char **internal_hashmap_get_strv(HashmapBase *h) {
+        char **sv;
+        Iterator i;
+        unsigned idx, n;
+
+        sv = new(char*, n_entries(h)+1);
+        if (!sv)
+                return NULL;
+
+        n = 0;
+        HASHMAP_FOREACH_IDX(idx, h, i)
+                sv[n++] = entry_value(h, bucket_at(h, idx));
+        sv[n] = NULL;
+
+        return sv;
+}
+
+void *ordered_hashmap_next(OrderedHashmap *h, const void *key) {
+        struct ordered_hashmap_entry *e;
+        unsigned hash, idx;
+
+        if (!h)
+                return NULL;
+
+        hash = bucket_hash(h, key);
+        idx = bucket_scan(h, hash, key);
+        if (idx == IDX_NIL)
+                return NULL;
+
+        e = ordered_bucket_at(h, idx);
+        if (e->iterate_next == IDX_NIL)
+                return NULL;
+        return ordered_bucket_at(h, e->iterate_next)->p.value;
+}
+
+int set_consume(Set *s, void *value) {
+        int r;
+
+        r = set_put(s, value);
+        if (r <= 0)
+                free(value);
+
+        return r;
+}
+
+int set_put_strdup(Set *s, const char *p) {
+        char *c;
+        int r;
+
+        assert(s);
+        assert(p);
+
+        c = strdup(p);
+        if (!c)
+                return -ENOMEM;
+
+        r = set_consume(s, c);
+        if (r == -EEXIST)
+                return 0;
+
+        return r;
+}
+
+int set_put_strdupv(Set *s, char **l) {
+        int n = 0, r;
+        char **i;
+
+        STRV_FOREACH(i, l) {
+                r = set_put_strdup(s, *i);
+                if (r < 0)
+                        return r;
+
+                n += r;
+        }
+
+        return n;
+}