hashmap.c

// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

/*
 * Generic non-thread safe hash map implementation.
 *
 * Copyright (c) 2019 Facebook
 */
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include "hashmap.h"

/* make sure libbpf doesn't use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64

/* prevent accidental re-addition of reallocarray() */
#pragma GCC poison reallocarray

/* start with 4 buckets */
#define HASHMAP_MIN_CAP_BITS 2

static void hashmap_add_entry(struct hashmap_entry **pprev,
                  struct hashmap_entry *entry)
{
    entry->next = *pprev;
    *pprev = entry;
}

static void hashmap_del_entry(struct hashmap_entry **pprev,
                  struct hashmap_entry *entry)
{
    *pprev = entry->next;
    entry->next = NULL;
}

void hashmap__init(struct hashmap *map, hashmap_hash_fn hash_fn,
           hashmap_equal_fn equal_fn, void *ctx)
{
    map->hash_fn = hash_fn;
    map->equal_fn = equal_fn;
    map->ctx = ctx;

    map->buckets = NULL;
    map->cap = 0;
    map->cap_bits = 0;
    map->sz = 0;
}

struct hashmap *hashmap__new(hashmap_hash_fn hash_fn,
                 hashmap_equal_fn equal_fn,
                 void *ctx)
{
    struct hashmap *map = malloc(sizeof(struct hashmap));

    if (!map) {
        errno = ENOMEM;
        return 0;
    }
    hashmap__init(map, hash_fn, equal_fn, ctx);
    return map;
}

void hashmap__clear(struct hashmap *map)
{
    struct hashmap_entry *cur, *tmp;
    size_t bkt;

    hashmap__for_each_entry_safe(map, cur, tmp, bkt) {
        free(cur);
    }
    free(map->buckets);
    map->buckets = NULL;
    map->cap = map->cap_bits = map->sz = 0;
}

void hashmap__free(struct hashmap *map)
{
    if (!map)
        return;

    hashmap__clear(map);
    free(map);
}

size_t hashmap__size(const struct hashmap *map)
{
    return map->sz;
}

size_t hashmap__capacity(const struct hashmap *map)
{
    return map->cap;
}

static bool hashmap_needs_to_grow(struct hashmap *map)
{
    /* grow if empty or more than 75% filled */
    return (map->cap == 0) || ((map->sz + 1) * 4 / 3 > map->cap);
}

static int hashmap_grow(struct hashmap *map)
{
    struct hashmap_entry **new_buckets;
    struct hashmap_entry *cur, *tmp;
    size_t new_cap_bits, new_cap;
    size_t h, bkt;

    new_cap_bits = map->cap_bits + 1;
    if (new_cap_bits < HASHMAP_MIN_CAP_BITS)
        new_cap_bits = HASHMAP_MIN_CAP_BITS;

    new_cap = 1UL << new_cap_bits;
    new_buckets = calloc(new_cap, sizeof(new_buckets[0]));
    if (!new_buckets)
        return -ENOMEM;

    hashmap__for_each_entry_safe(map, cur, tmp, bkt) {
        h = hash_bits(map->hash_fn(cur->key, map->ctx), new_cap_bits);
        hashmap_add_entry(&new_buckets[h], cur);
    }

    map->cap = new_cap;
    map->cap_bits = new_cap_bits;
    free(map->buckets);
    map->buckets = new_buckets;

    return 0;
}

static bool hashmap_find_entry(const struct hashmap *map,
                   const long key, size_t hash,
                   struct hashmap_entry ***pprev,
                   struct hashmap_entry **entry)
{
    struct hashmap_entry *cur, **prev_ptr;

    if (!map->buckets)
        return false;

    for (prev_ptr = &map->buckets[hash], cur = *prev_ptr;
         cur;
         prev_ptr = &cur->next, cur = cur->next) {
        if (map->equal_fn(cur->key, key, map->ctx)) {
            if (pprev)
                *pprev = prev_ptr;
            *entry = cur;
            return true;
        }
    }

    return false;
}

int hashmap_insert(struct hashmap *map, long key, long value,
           enum hashmap_insert_strategy strategy,
           long *old_key, long *old_value)
{
    struct hashmap_entry *entry;
    size_t h;
    int err;

    if (old_key)
        *old_key = 0;
    if (old_value)
        *old_value = 0;

    h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
    if (strategy != HASHMAP_APPEND &&
        hashmap_find_entry(map, key, h, NULL, &entry)) {
        if (old_key)
            *old_key = entry->key;
        if (old_value)
            *old_value = entry->value;

        if (strategy == HASHMAP_SET || strategy == HASHMAP_UPDATE) {
            entry->key = key;
            entry->value = value;
            return 0;
        } else if (strategy == HASHMAP_ADD) {
            return -EEXIST;
        }
    }

    if (strategy == HASHMAP_UPDATE)
        return -ENOENT;

    if (hashmap_needs_to_grow(map)) {
        err = hashmap_grow(map);
        if (err)
            return err;
        h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
    }

    entry = malloc(sizeof(struct hashmap_entry));
    if (!entry)
        return -ENOMEM;

    entry->key = key;
    entry->value = value;
    hashmap_add_entry(&map->buckets[h], entry);
    map->sz++;

    return 0;
}

bool hashmap_find(const struct hashmap *map, long key, long *value)
{
    struct hashmap_entry *entry;
    size_t h;

    h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
    if (!hashmap_find_entry(map, key, h, NULL, &entry))
        return false;

    if (value)
        *value = entry->value;
    return true;
}

bool hashmap_delete(struct hashmap *map, long key,
            long *old_key, long *old_value)
{
    struct hashmap_entry **pprev, *entry;
    size_t h;

    h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);
    if (!hashmap_find_entry(map, key, h, &pprev, &entry))
        return false;

    if (old_key)
        *old_key = entry->key;
    if (old_value)
        *old_value = entry->value;

    hashmap_del_entry(pprev, entry);
    free(entry);
    map->sz--;

    return true;
}