libbpf: add resizable non-thread safe internal hashmap
There is a need for fast point lookups inside libbpf for multiple use cases (e.g., name resolution for BTF-to-C conversion, by-name lookups in BTF for upcoming BPF CO-RE relocation support, etc). This patch implements simple resizable non-thread safe hashmap using single linked list chains. Four different insert strategies are supported: - HASHMAP_ADD - only add key/value if key doesn't exist yet; - HASHMAP_SET - add key/value pair if key doesn't exist yet; otherwise, update value; - HASHMAP_UPDATE - update value, if key already exists; otherwise, do nothing and return -ENOENT; - HASHMAP_APPEND - always add key/value pair, even if key already exists. This turns hashmap into a multimap by allowing multiple values to be associated with the same key. Most useful read API for such hashmap is hashmap__for_each_key_entry() iteration. If hashmap__find() is still used, it will return last inserted key/value entry (first in a bucket chain). For HASHMAP_SET and HASHMAP_UPDATE, old key/value pair is returned, so that calling code can handle proper memory management, if necessary. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko
Alexei Starovoitov
parent
9db324314d
commit
e3b9242240
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@ -1 +1 @@
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libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o
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libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o
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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
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/*
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* Generic non-thread safe hash map implementation.
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*
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* Copyright (c) 2019 Facebook
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include <linux/err.h>
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#include "hashmap.h"
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/* start with 4 buckets */
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#define HASHMAP_MIN_CAP_BITS 2
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static void hashmap_add_entry(struct hashmap_entry **pprev,
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struct hashmap_entry *entry)
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{
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entry->next = *pprev;
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*pprev = entry;
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}
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static void hashmap_del_entry(struct hashmap_entry **pprev,
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struct hashmap_entry *entry)
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{
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*pprev = entry->next;
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entry->next = NULL;
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}
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void hashmap__init(struct hashmap *map, hashmap_hash_fn hash_fn,
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hashmap_equal_fn equal_fn, void *ctx)
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{
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map->hash_fn = hash_fn;
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map->equal_fn = equal_fn;
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map->ctx = ctx;
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map->buckets = NULL;
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map->cap = 0;
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map->cap_bits = 0;
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map->sz = 0;
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}
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struct hashmap *hashmap__new(hashmap_hash_fn hash_fn,
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hashmap_equal_fn equal_fn,
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void *ctx)
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{
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struct hashmap *map = malloc(sizeof(struct hashmap));
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if (!map)
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return ERR_PTR(-ENOMEM);
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hashmap__init(map, hash_fn, equal_fn, ctx);
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return map;
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}
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void hashmap__clear(struct hashmap *map)
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{
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free(map->buckets);
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map->cap = map->cap_bits = map->sz = 0;
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}
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void hashmap__free(struct hashmap *map)
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{
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if (!map)
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return;
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hashmap__clear(map);
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free(map);
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}
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size_t hashmap__size(const struct hashmap *map)
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{
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return map->sz;
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}
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size_t hashmap__capacity(const struct hashmap *map)
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{
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return map->cap;
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}
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static bool hashmap_needs_to_grow(struct hashmap *map)
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{
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/* grow if empty or more than 75% filled */
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return (map->cap == 0) || ((map->sz + 1) * 4 / 3 > map->cap);
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}
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static int hashmap_grow(struct hashmap *map)
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{
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struct hashmap_entry **new_buckets;
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struct hashmap_entry *cur, *tmp;
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size_t new_cap_bits, new_cap;
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size_t h;
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int bkt;
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new_cap_bits = map->cap_bits + 1;
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if (new_cap_bits < HASHMAP_MIN_CAP_BITS)
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new_cap_bits = HASHMAP_MIN_CAP_BITS;
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new_cap = 1UL << new_cap_bits;
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new_buckets = calloc(new_cap, sizeof(new_buckets[0]));
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if (!new_buckets)
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return -ENOMEM;
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hashmap__for_each_entry_safe(map, cur, tmp, bkt) {
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h = hash_bits(map->hash_fn(cur->key, map->ctx), new_cap_bits);
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hashmap_add_entry(&new_buckets[h], cur);
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}
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map->cap = new_cap;
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map->cap_bits = new_cap_bits;
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free(map->buckets);
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map->buckets = new_buckets;
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return 0;
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}
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static bool hashmap_find_entry(const struct hashmap *map,
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const void *key, size_t hash,
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struct hashmap_entry ***pprev,
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struct hashmap_entry **entry)
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{
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struct hashmap_entry *cur, **prev_ptr;
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if (!map->buckets)
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return false;
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for (prev_ptr = &map->buckets[hash], cur = *prev_ptr;
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cur;
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prev_ptr = &cur->next, cur = cur->next) {
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if (map->equal_fn(cur->key, key, map->ctx)) {
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if (pprev)
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*pprev = prev_ptr;
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*entry = cur;
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return true;
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}
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}
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return false;
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}
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int hashmap__insert(struct hashmap *map, const void *key, void *value,
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enum hashmap_insert_strategy strategy,
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const void **old_key, void **old_value)
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{
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struct hashmap_entry *entry;
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size_t h;
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int err;
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if (old_key)
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*old_key = NULL;
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if (old_value)
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*old_value = NULL;
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h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
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if (strategy != HASHMAP_APPEND &&
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hashmap_find_entry(map, key, h, NULL, &entry)) {
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if (old_key)
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*old_key = entry->key;
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if (old_value)
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*old_value = entry->value;
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if (strategy == HASHMAP_SET || strategy == HASHMAP_UPDATE) {
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entry->key = key;
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entry->value = value;
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return 0;
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} else if (strategy == HASHMAP_ADD) {
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return -EEXIST;
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}
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}
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if (strategy == HASHMAP_UPDATE)
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return -ENOENT;
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if (hashmap_needs_to_grow(map)) {
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err = hashmap_grow(map);
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if (err)
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return err;
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h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
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}
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entry = malloc(sizeof(struct hashmap_entry));
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if (!entry)
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return -ENOMEM;
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entry->key = key;
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entry->value = value;
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hashmap_add_entry(&map->buckets[h], entry);
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map->sz++;
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return 0;
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}
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bool hashmap__find(const struct hashmap *map, const void *key, void **value)
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{
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struct hashmap_entry *entry;
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size_t h;
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h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
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if (!hashmap_find_entry(map, key, h, NULL, &entry))
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return false;
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if (value)
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*value = entry->value;
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return true;
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}
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bool hashmap__delete(struct hashmap *map, const void *key,
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const void **old_key, void **old_value)
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{
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struct hashmap_entry **pprev, *entry;
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size_t h;
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h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
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if (!hashmap_find_entry(map, key, h, &pprev, &entry))
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return false;
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if (old_key)
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*old_key = entry->key;
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if (old_value)
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*old_value = entry->value;
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hashmap_del_entry(pprev, entry);
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free(entry);
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map->sz--;
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return true;
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}
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@ -0,0 +1,173 @@
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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/*
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* Generic non-thread safe hash map implementation.
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*
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* Copyright (c) 2019 Facebook
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*/
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#ifndef __LIBBPF_HASHMAP_H
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#define __LIBBPF_HASHMAP_H
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#include <stdbool.h>
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#include <stddef.h>
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#include "libbpf_internal.h"
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static inline size_t hash_bits(size_t h, int bits)
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{
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/* shuffle bits and return requested number of upper bits */
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return (h * 11400714819323198485llu) >> (__WORDSIZE - bits);
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}
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typedef size_t (*hashmap_hash_fn)(const void *key, void *ctx);
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typedef bool (*hashmap_equal_fn)(const void *key1, const void *key2, void *ctx);
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struct hashmap_entry {
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const void *key;
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void *value;
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struct hashmap_entry *next;
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};
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struct hashmap {
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hashmap_hash_fn hash_fn;
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hashmap_equal_fn equal_fn;
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void *ctx;
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struct hashmap_entry **buckets;
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size_t cap;
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size_t cap_bits;
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size_t sz;
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};
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#define HASHMAP_INIT(hash_fn, equal_fn, ctx) { \
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.hash_fn = (hash_fn), \
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.equal_fn = (equal_fn), \
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.ctx = (ctx), \
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.buckets = NULL, \
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.cap = 0, \
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.cap_bits = 0, \
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.sz = 0, \
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}
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void hashmap__init(struct hashmap *map, hashmap_hash_fn hash_fn,
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hashmap_equal_fn equal_fn, void *ctx);
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struct hashmap *hashmap__new(hashmap_hash_fn hash_fn,
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hashmap_equal_fn equal_fn,
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void *ctx);
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void hashmap__clear(struct hashmap *map);
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void hashmap__free(struct hashmap *map);
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size_t hashmap__size(const struct hashmap *map);
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size_t hashmap__capacity(const struct hashmap *map);
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/*
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* Hashmap insertion strategy:
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* - HASHMAP_ADD - only add key/value if key doesn't exist yet;
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* - HASHMAP_SET - add key/value pair if key doesn't exist yet; otherwise,
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* update value;
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* - HASHMAP_UPDATE - update value, if key already exists; otherwise, do
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* nothing and return -ENOENT;
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* - HASHMAP_APPEND - always add key/value pair, even if key already exists.
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* This turns hashmap into a multimap by allowing multiple values to be
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* associated with the same key. Most useful read API for such hashmap is
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* hashmap__for_each_key_entry() iteration. If hashmap__find() is still
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* used, it will return last inserted key/value entry (first in a bucket
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* chain).
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*/
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enum hashmap_insert_strategy {
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HASHMAP_ADD,
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HASHMAP_SET,
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HASHMAP_UPDATE,
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HASHMAP_APPEND,
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};
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/*
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* hashmap__insert() adds key/value entry w/ various semantics, depending on
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* provided strategy value. If a given key/value pair replaced already
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* existing key/value pair, both old key and old value will be returned
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* through old_key and old_value to allow calling code do proper memory
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* management.
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*/
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int hashmap__insert(struct hashmap *map, const void *key, void *value,
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enum hashmap_insert_strategy strategy,
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const void **old_key, void **old_value);
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static inline int hashmap__add(struct hashmap *map,
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const void *key, void *value)
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{
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return hashmap__insert(map, key, value, HASHMAP_ADD, NULL, NULL);
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}
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static inline int hashmap__set(struct hashmap *map,
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const void *key, void *value,
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const void **old_key, void **old_value)
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{
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return hashmap__insert(map, key, value, HASHMAP_SET,
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old_key, old_value);
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}
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static inline int hashmap__update(struct hashmap *map,
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const void *key, void *value,
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const void **old_key, void **old_value)
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{
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return hashmap__insert(map, key, value, HASHMAP_UPDATE,
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old_key, old_value);
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}
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static inline int hashmap__append(struct hashmap *map,
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const void *key, void *value)
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{
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return hashmap__insert(map, key, value, HASHMAP_APPEND, NULL, NULL);
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}
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bool hashmap__delete(struct hashmap *map, const void *key,
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const void **old_key, void **old_value);
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bool hashmap__find(const struct hashmap *map, const void *key, void **value);
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/*
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* hashmap__for_each_entry - iterate over all entries in hashmap
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* @map: hashmap to iterate
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* @cur: struct hashmap_entry * used as a loop cursor
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* @bkt: integer used as a bucket loop cursor
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*/
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#define hashmap__for_each_entry(map, cur, bkt) \
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for (bkt = 0; bkt < map->cap; bkt++) \
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for (cur = map->buckets[bkt]; cur; cur = cur->next)
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/*
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* hashmap__for_each_entry_safe - iterate over all entries in hashmap, safe
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* against removals
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* @map: hashmap to iterate
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* @cur: struct hashmap_entry * used as a loop cursor
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* @tmp: struct hashmap_entry * used as a temporary next cursor storage
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* @bkt: integer used as a bucket loop cursor
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*/
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#define hashmap__for_each_entry_safe(map, cur, tmp, bkt) \
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for (bkt = 0; bkt < map->cap; bkt++) \
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for (cur = map->buckets[bkt]; \
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cur && ({tmp = cur->next; true; }); \
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cur = tmp)
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/*
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* hashmap__for_each_key_entry - iterate over entries associated with given key
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* @map: hashmap to iterate
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* @cur: struct hashmap_entry * used as a loop cursor
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* @key: key to iterate entries for
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*/
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#define hashmap__for_each_key_entry(map, cur, _key) \
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for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\
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map->cap_bits); \
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map->buckets ? map->buckets[bkt] : NULL; }); \
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cur; \
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cur = cur->next) \
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if (map->equal_fn(cur->key, (_key), map->ctx))
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#define hashmap__for_each_key_entry_safe(map, cur, tmp, _key) \
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for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\
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map->cap_bits); \
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cur = map->buckets ? map->buckets[bkt] : NULL; }); \
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cur && ({ tmp = cur->next; true; }); \
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cur = tmp) \
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if (map->equal_fn(cur->key, (_key), map->ctx))
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#endif /* __LIBBPF_HASHMAP_H */
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