/*

 * Copyright 2024-2025 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 *

 *

 *

 * Notes On hash table design and layout

 * This hashtable uses a hopscotch algorithm to do indexing.  The data structure

 * looks as follows:

 *

 *   hash          +--------------+

 *   value+------->+ HT_VALUE     |

 *      +          +--------------+

 *  +-------+

 *  |       |

 *  +---------------------------------------------------------+

 *  |       |       |       |       |                         |

 *  | entry | entry | entry | entry |                         |

 *  |       |       |       |       |                         |

 *  +---------------------------------------------------------+

 *  |                               |                         |

 *  |                               |                         |

 *  +---------------------------------------------------------+

 *  |              +                             +            +

 *  |        neighborhood[0]               neighborhood[1]    |

 *  |                                                         |

 *  |                                                         |

 *  +---------------------------------------------------------+

 *                              |

 *                              +

 *                         neighborhoods

 *

 * On lookup/insert/delete, the items key is hashed to a 64 bit value

 * and the result is masked to provide an index into the neighborhoods

 * table.  Once a neighborhood is determined, an in-order search is done

 * of the elements in the neighborhood indexes entries for a matching hash

 * value, if found, the corresponding HT_VALUE is used for the respective

 * operation.  The number of entries in a neighborhood is determined at build

 * time based on the cacheline size of the target CPU.  The intent is for a

 * neighborhood to have all entries in the neighborhood fit into a single cache

 * line to speed up lookups.  If all entries in a neighborhood are in use at the

 * time of an insert, the table is expanded and rehashed.

 *

 * Lockless reads hash table is based on the same design but does not

 * allow growing and deletion. Thus subsequent neighborhoods are always

 * searched for a match until an empty entry is found.

 */

#include <string.h>

#include <internal/rcu.h>

#include <internal/hashtable.h>

#include <internal/hashfunc.h>

#include <openssl/rand.h>

/*

 * gcc defines __SANITIZE_THREAD__

 * but clang uses the feature attributes api

 * map the latter to the former

 */

#if defined(__clang__) && defined(__has_feature)

# if __has_feature(thread_sanitizer)

#  define __SANITIZE_THREADS__

# endif

#endif

#ifdef __SANITIZE_THREADS__

# include <sanitizer/tsan_interface.h>

#endif

#include "internal/numbers.h"

/*

 * When we do a lookup/insert/delete, there is a high likelihood

 * that we will iterate over at least part of the neighborhood list

 * As such, because we design a neighborhood entry to fit into a single

 * cache line it is advantageous, when supported to fetch the entire

 * structure for faster lookups

 */

#if defined(__GNUC__) || defined(__CLANG__)

# define PREFETCH_NEIGHBORHOOD(x) __builtin_prefetch(x.entries)

# define PREFETCH(x) __builtin_prefetch(x)

#else

# define PREFETCH_NEIGHBORHOOD(x)

# define PREFETCH(x)

#endif

/*

 * Define our neighborhood list length

 * Note: It should always be a power of 2

 */

#define DEFAULT_NEIGH_LEN_LOG 4

#define DEFAULT_NEIGH_LEN (1 << DEFAULT_NEIGH_LEN_LOG)

/*

 * For now assume cache line size is 64 bytes

 */

#define CACHE_LINE_BYTES 64

#define CACHE_LINE_ALIGNMENT CACHE_LINE_BYTES

#define NEIGHBORHOOD_LEN (CACHE_LINE_BYTES / sizeof(struct ht_neighborhood_entry_st))

/*

 * Defines our chains of values

 */

struct ht_internal_value_st {

    HT_VALUE value;

    HT *ht;

};

struct ht_neighborhood_entry_st {

    uint64_t hash;

    struct ht_internal_value_st *value;

};

struct ht_neighborhood_st {

    struct ht_neighborhood_entry_st entries[NEIGHBORHOOD_LEN];

};

/*

 * Updates to data in this struct

 * require an rcu sync after modification

 * prior to free

 */

struct ht_mutable_data_st {

    struct ht_neighborhood_st *neighborhoods;

    void *neighborhood_ptr_to_free;

    uint64_t neighborhood_mask;

};

/*

 * Private data may be updated on the write

 * side only, and so do not require rcu sync

 */

struct ht_write_private_data_st {

    size_t neighborhood_len;

    size_t value_count;

    int need_sync;

};

struct ht_internal_st {

    HT_CONFIG config;

    CRYPTO_RCU_LOCK *lock;

    CRYPTO_RWLOCK *atomic_lock;

    struct ht_mutable_data_st *md;

    struct ht_write_private_data_st wpd;

};

static void free_value(struct ht_internal_value_st *v);

static struct ht_neighborhood_st *alloc_new_neighborhood_list(size_t len,

                                                              void **freeptr)

{

    struct ht_neighborhood_st *ret;

    ret = OPENSSL_aligned_alloc(sizeof(struct ht_neighborhood_st) * len,

                                CACHE_LINE_BYTES, freeptr);

    /* fall back to regular malloc */

    if (ret == NULL) {

        ret = *freeptr = OPENSSL_malloc(sizeof(struct ht_neighborhood_st) * len);

        if (ret == NULL)

            return NULL;

    }

    memset(ret, 0, sizeof(struct ht_neighborhood_st) * len);

    return ret;

}

static void internal_free_nop(HT_VALUE *v)

{

    return;

}

HT *ossl_ht_new(const HT_CONFIG *conf)

{

    HT *new = OPENSSL_zalloc(sizeof(*new));

    if (new == NULL)

        return NULL;

    new->atomic_lock = CRYPTO_THREAD_lock_new();

    if (new->atomic_lock == NULL)

        goto err;

    memcpy(&new->config, conf, sizeof(*conf));

    if (new->config.init_neighborhoods != 0) {

        new->wpd.neighborhood_len = new->config.init_neighborhoods;

        /* round up to the next power of 2 */

        new->wpd.neighborhood_len--;

        new->wpd.neighborhood_len |= new->wpd.neighborhood_len >> 1;

        new->wpd.neighborhood_len |= new->wpd.neighborhood_len >> 2;

        new->wpd.neighborhood_len |= new->wpd.neighborhood_len >> 4;

        new->wpd.neighborhood_len |= new->wpd.neighborhood_len >> 8;

        new->wpd.neighborhood_len |= new->wpd.neighborhood_len >> 16;

        new->wpd.neighborhood_len++;

    } else {

        new->wpd.neighborhood_len = DEFAULT_NEIGH_LEN;

    }

    if (new->config.ht_free_fn == NULL)

        new->config.ht_free_fn = internal_free_nop;

    new->md = OPENSSL_zalloc(sizeof(*new->md));

    if (new->md == NULL)

        goto err;

    new->md->neighborhoods =

        alloc_new_neighborhood_list(new->wpd.neighborhood_len,

                                    &new->md->neighborhood_ptr_to_free);

    if (new->md->neighborhoods == NULL)

        goto err;

    new->md->neighborhood_mask = new->wpd.neighborhood_len - 1;

    new->lock = ossl_rcu_lock_new(1, conf->ctx);

    if (new->lock == NULL)

        goto err;

    if (new->config.ht_hash_fn == NULL)

        new->config.ht_hash_fn = ossl_fnv1a_hash;

    return new;

err:

    CRYPTO_THREAD_lock_free(new->atomic_lock);

    ossl_rcu_lock_free(new->lock);

    if (new->md != NULL)

        OPENSSL_free(new->md->neighborhood_ptr_to_free);

    OPENSSL_free(new->md);

    OPENSSL_free(new);

    return NULL;

}

void ossl_ht_read_lock(HT *htable)

{

    ossl_rcu_read_lock(htable->lock);

}

void ossl_ht_read_unlock(HT *htable)

{

    ossl_rcu_read_unlock(htable->lock);

}

void ossl_ht_write_lock(HT *htable)

{

    ossl_rcu_write_lock(htable->lock);

    htable->wpd.need_sync = 0;

}

void ossl_ht_write_unlock(HT *htable)

{

    int need_sync = htable->wpd.need_sync;

    htable->wpd.need_sync = 0;

    ossl_rcu_write_unlock(htable->lock);

    if (need_sync)

        ossl_synchronize_rcu(htable->lock);

}

static void free_oldmd(void *arg)

{

    struct ht_mutable_data_st *oldmd = arg;

    size_t i, j;

    size_t neighborhood_len = (size_t)oldmd->neighborhood_mask + 1;

    struct ht_internal_value_st *v;

    for (i = 0; i < neighborhood_len; i++) {

        PREFETCH_NEIGHBORHOOD(oldmd->neighborhoods[i + 1]);

        for (j = 0; j < NEIGHBORHOOD_LEN; j++) {

            if (oldmd->neighborhoods[i].entries[j].value != NULL) {

                v = oldmd->neighborhoods[i].entries[j].value;

                v->ht->config.ht_free_fn((HT_VALUE *)v);

                free_value(v);

            }

        }

    }

    OPENSSL_free(oldmd->neighborhood_ptr_to_free);

    OPENSSL_free(oldmd);

}

static int ossl_ht_flush_internal(HT *h)

{

    struct ht_mutable_data_st *newmd = NULL;

    struct ht_mutable_data_st *oldmd = NULL;

    newmd = OPENSSL_zalloc(sizeof(*newmd));

    if (newmd == NULL)

        return 0;

    newmd->neighborhoods = alloc_new_neighborhood_list(DEFAULT_NEIGH_LEN,

                                                       &newmd->neighborhood_ptr_to_free);

    if (newmd->neighborhoods == NULL) {

        OPENSSL_free(newmd);

        return 0;

    }

    newmd->neighborhood_mask = DEFAULT_NEIGH_LEN - 1;

    /* Swap the old and new mutable data sets */

    oldmd = ossl_rcu_deref(&h->md);

    ossl_rcu_assign_ptr(&h->md, &newmd);

    /* Set the number of entries to 0 */

    h->wpd.value_count = 0;

    h->wpd.neighborhood_len = DEFAULT_NEIGH_LEN;

    ossl_rcu_call(h->lock, free_oldmd, oldmd);

    h->wpd.need_sync = 1;

    return 1;

}

int ossl_ht_flush(HT *h)

{

    return ossl_ht_flush_internal(h);

}

void ossl_ht_free(HT *h)

{

    if (h == NULL)

        return;

    ossl_ht_write_lock(h);

    ossl_ht_flush_internal(h);

    ossl_ht_write_unlock(h);

    /* Freeing the lock does a final sync for us */

    CRYPTO_THREAD_lock_free(h->atomic_lock);

    ossl_rcu_lock_free(h->lock);

    OPENSSL_free(h->md->neighborhood_ptr_to_free);

    OPENSSL_free(h->md);

    OPENSSL_free(h);

    return;

}

size_t ossl_ht_count(HT *h)

{

    size_t count;

    count = h->wpd.value_count;

    return count;

}

void ossl_ht_foreach_until(HT *h, int (*cb)(HT_VALUE *obj, void *arg),

                           void *arg)

{

    size_t i, j;

    struct ht_mutable_data_st *md;

    md = ossl_rcu_deref(&h->md);

    for (i = 0; i < md->neighborhood_mask + 1; i++) {

        PREFETCH_NEIGHBORHOOD(md->neighborhoods[i + 1]);

        for (j = 0; j < NEIGHBORHOOD_LEN; j++) {

            if (md->neighborhoods[i].entries[j].value != NULL) {

                if (!cb((HT_VALUE *)md->neighborhoods[i].entries[j].value, arg))

                    goto out;

            }

        }

    }

out:

    return;

}

HT_VALUE_LIST *ossl_ht_filter(HT *h, size_t max_len,

                                     int (*filter)(HT_VALUE *obj, void *arg),

                                     void *arg)

{

    struct ht_mutable_data_st *md;

    HT_VALUE_LIST *list = OPENSSL_zalloc(sizeof(HT_VALUE_LIST)

                                         + (sizeof(HT_VALUE *) * max_len));

    size_t i, j;

    struct ht_internal_value_st *v;

    if (list == NULL)

        return NULL;

    /*

     * The list array lives just beyond the end of

     * the struct

     */

    list->list = (HT_VALUE **)(list + 1);

    md = ossl_rcu_deref(&h->md);

    for (i = 0; i < md->neighborhood_mask + 1; i++) {

        PREFETCH_NEIGHBORHOOD(md->neighborhoods[i+1]);

        for (j = 0; j < NEIGHBORHOOD_LEN; j++) {

            v = md->neighborhoods[i].entries[j].value;

            if (v != NULL && filter((HT_VALUE *)v, arg)) {

                list->list[list->list_len++] = (HT_VALUE *)v;

                if (list->list_len == max_len)

                    goto out;

            }

        }

    }

out:

    return list;

}

void ossl_ht_value_list_free(HT_VALUE_LIST *list)

{

    OPENSSL_free(list);

}

static int compare_hash(uint64_t hash1, uint64_t hash2)

{

    return (hash1 == hash2);

}

static void free_old_neigh_table(void *arg)

{

    struct ht_mutable_data_st *oldmd = arg;

    OPENSSL_free(oldmd->neighborhood_ptr_to_free);

    OPENSSL_free(oldmd);

}

/*

 * Increase hash table bucket list

 * must be called with write_lock held

 */

static int grow_hashtable(HT *h, size_t oldsize)

{

    struct ht_mutable_data_st *newmd;

    struct ht_mutable_data_st *oldmd = ossl_rcu_deref(&h->md);

    int rc = 0;

    uint64_t oldi, oldj, newi, newj;

    uint64_t oldhash;

    struct ht_internal_value_st *oldv;

    int rehashed;

    size_t newsize = oldsize * 2;

    if (h->config.lockless_reads)

        goto out;

    if ((newmd = OPENSSL_zalloc(sizeof(*newmd))) == NULL)

        goto out;

    /* bucket list is always a power of 2 */

    newmd->neighborhoods = alloc_new_neighborhood_list(oldsize * 2,

                                                       &newmd->neighborhood_ptr_to_free);

    if (newmd->neighborhoods == NULL)

        goto out_free;

    /* being a power of 2 makes for easy mask computation */

    newmd->neighborhood_mask = (newsize - 1);

    /*

     * Now we need to start rehashing entries

     * Note we don't need to use atomics here as the new

     * mutable data hasn't been published

     */

    for (oldi = 0; oldi < h->wpd.neighborhood_len; oldi++) {

        PREFETCH_NEIGHBORHOOD(oldmd->neighborhoods[oldi + 1]);

        for (oldj = 0; oldj < NEIGHBORHOOD_LEN; oldj++) {

            oldv = oldmd->neighborhoods[oldi].entries[oldj].value;

            if (oldv == NULL)

                continue;

            oldhash = oldmd->neighborhoods[oldi].entries[oldj].hash;

            newi = oldhash & newmd->neighborhood_mask;

            rehashed = 0;

            for (newj = 0; newj < NEIGHBORHOOD_LEN; newj++) {

                if (newmd->neighborhoods[newi].entries[newj].value == NULL) {

                    newmd->neighborhoods[newi].entries[newj].value = oldv;

                    newmd->neighborhoods[newi].entries[newj].hash = oldhash;

                    rehashed = 1;

                    break;

                }

            }

            if (rehashed == 0) {

                /* we ran out of space in a neighborhood, grow again */

                OPENSSL_free(newmd->neighborhoods);

                OPENSSL_free(newmd);

                return grow_hashtable(h, newsize);

            }

        }

    }

    /*

     * Now that our entries are all hashed into the new bucket list

     * update our bucket_len and target_max_load

     */

    h->wpd.neighborhood_len = newsize;

    /*

     * Now we replace the old mutable data with the new

     */

    ossl_rcu_assign_ptr(&h->md, &newmd);

    ossl_rcu_call(h->lock, free_old_neigh_table, oldmd);

    h->wpd.need_sync = 1;

    /*

     * And we're done

     */

    rc = 1;

out:

    return rc;

out_free:

    OPENSSL_free(newmd->neighborhoods);

    OPENSSL_free(newmd);

    goto out;

}

static void free_old_ht_value(void *arg)

{

    HT_VALUE *h = (HT_VALUE *)arg;

    /*

     * Note, this is only called on replacement,

     * the caller is responsible for freeing the

     * held data, we just need to free the wrapping

     * struct here

     */

    OPENSSL_free(h);

}

static ossl_inline int match_key(HT_KEY *a, HT_KEY *b)

{

    /*

     * keys match if they are both present, the same size

     * and compare equal in memory

     */

    PREFETCH(a->keybuf);

    PREFETCH(b->keybuf);

    if (a->keybuf != NULL && b->keybuf != NULL && a->keysize == b->keysize)

        return !memcmp(a->keybuf, b->keybuf, a->keysize);

    return 1;

}

static int ossl_ht_insert_locked(HT *h, uint64_t hash,

                                 struct ht_internal_value_st *newval,

                                 HT_VALUE **olddata)

{

    struct ht_mutable_data_st *md = h->md;

    uint64_t neigh_idx_start = hash & md->neighborhood_mask;

    uint64_t neigh_idx = neigh_idx_start;

    size_t j;

    uint64_t ihash;

    HT_VALUE *ival;

    size_t empty_idx = SIZE_MAX;

    int lockless_reads = h->config.lockless_reads;

    do {

        PREFETCH_NEIGHBORHOOD(md->neighborhoods[neigh_idx]);

        for (j = 0; j < NEIGHBORHOOD_LEN; j++) {

            ival = ossl_rcu_deref(&md->neighborhoods[neigh_idx].entries[j].value);

            if (ival == NULL) {

                empty_idx = j;

                /* lockless_reads implies no deletion, we can break out */

                if (lockless_reads)

                    goto not_found;

                continue;

            }

            if (!CRYPTO_atomic_load(&md->neighborhoods[neigh_idx].entries[j].hash,

                                    &ihash, h->atomic_lock))

                return 0;

            if (compare_hash(hash, ihash) && match_key(&newval->value.key,

                                                       &ival->key)) {

                if (olddata == NULL) {

                    /* This would insert a duplicate -> fail */

                    return 0;

                }

                /* Do a replacement */

                if (!CRYPTO_atomic_store(&md->neighborhoods[neigh_idx].entries[j].hash,

                                         hash, h->atomic_lock))

                    return 0;

                *olddata = (HT_VALUE *)md->neighborhoods[neigh_idx].entries[j].value;

                ossl_rcu_assign_ptr(&md->neighborhoods[neigh_idx].entries[j].value,

                                    &newval);

                ossl_rcu_call(h->lock, free_old_ht_value, *olddata);

                h->wpd.need_sync = 1;

                return 1;

            }

        }

        if (!lockless_reads)

            break;

        /* Continue search in subsequent neighborhoods */

        neigh_idx = (neigh_idx + 1) & md->neighborhood_mask;

    } while (neigh_idx != neigh_idx_start);

 not_found:

    /* If we get to here, its just an insert */

    if (empty_idx == SIZE_MAX)

        return -1; /* out of space */

    if (!CRYPTO_atomic_store(&md->neighborhoods[neigh_idx].entries[empty_idx].hash,

                             hash, h->atomic_lock))

        return 0;

    h->wpd.value_count++;

    ossl_rcu_assign_ptr(&md->neighborhoods[neigh_idx].entries[empty_idx].value,

                        &newval);

    return 1;

}

static struct ht_internal_value_st *alloc_new_value(HT *h, HT_KEY *key,

                                                    void *data,

                                                    uintptr_t *type)

{

    struct ht_internal_value_st *tmp;

    size_t nvsize = sizeof(*tmp);

    if (h->config.collision_check == 1)

        nvsize += key->keysize;

    tmp = OPENSSL_malloc(nvsize);

    if (tmp == NULL)

        return NULL;

    tmp->ht = h;

    tmp->value.value = data;

    tmp->value.type_id = type;

    tmp->value.key.keybuf = NULL;

    if (h->config.collision_check) {

        tmp->value.key.keybuf = (uint8_t *)(tmp + 1);

        tmp->value.key.keysize = key->keysize;

        memcpy(tmp->value.key.keybuf, key->keybuf, key->keysize);

    }

    return tmp;

}

static void free_value(struct ht_internal_value_st *v)

{

    OPENSSL_free(v);

}

int ossl_ht_insert(HT *h, HT_KEY *key, HT_VALUE *data, HT_VALUE **olddata)

{

    struct ht_internal_value_st *newval = NULL;

    uint64_t hash;

    int rc = 0;

    int i;

    if (data->value == NULL)

        goto out;

    newval = alloc_new_value(h, key, data->value, data->type_id);

    if (newval == NULL)

        goto out;

    /*

     * we have to take our lock here to prevent other changes

     * to the bucket list

     */

    hash = h->config.ht_hash_fn(key->keybuf, key->keysize);

    for (i = 0;

         (rc = ossl_ht_insert_locked(h, hash, newval, olddata)) == -1

         && i < 4;

         ++i)

        if (!grow_hashtable(h, h->wpd.neighborhood_len)) {

            rc = -1;

            break;

        }

    if (rc <= 0)

        free_value(newval);

out:

    return rc;

}

HT_VALUE *ossl_ht_get(HT *h, HT_KEY *key)

{

    struct ht_mutable_data_st *md;

    uint64_t hash;

    uint64_t neigh_idx_start;

    uint64_t neigh_idx;

    struct ht_internal_value_st *ival = NULL;

    size_t j;

    uint64_t ehash;

    int lockless_reads = h->config.lockless_reads;

    hash = h->config.ht_hash_fn(key->keybuf, key->keysize);

    md = ossl_rcu_deref(&h->md);

    neigh_idx = neigh_idx_start = hash & md->neighborhood_mask;

    do {

        PREFETCH_NEIGHBORHOOD(md->neighborhoods[neigh_idx]);

        for (j = 0; j < NEIGHBORHOOD_LEN; j++) {

            ival = ossl_rcu_deref(&md->neighborhoods[neigh_idx].entries[j].value);

            if (ival == NULL) {

                if (lockless_reads)

                    /* lockless_reads implies no deletion, we can break out */

                    return NULL;

                continue;

            }

            if (!CRYPTO_atomic_load(&md->neighborhoods[neigh_idx].entries[j].hash,

                                    &ehash, h->atomic_lock))

                return NULL;

            if (compare_hash(hash, ehash) && match_key(&ival->value.key, key))

                return (HT_VALUE *)ival;

        }

        if (!lockless_reads)

            break;

        /* Continue search in subsequent neighborhoods */

        neigh_idx = (neigh_idx + 1) & md->neighborhood_mask;

    } while (neigh_idx != neigh_idx_start);

    return NULL;

}

static void free_old_entry(void *arg)

{

    struct ht_internal_value_st *v = arg;

    v->ht->config.ht_free_fn((HT_VALUE *)v);

    free_value(v);

}

int ossl_ht_delete(HT *h, HT_KEY *key)

{

    uint64_t hash;

    uint64_t neigh_idx;

    size_t j;

    struct ht_internal_value_st *v = NULL;

    HT_VALUE *nv = NULL;

    int rc = 0;

    if (h->config.lockless_reads)

        return 0;

    hash = h->config.ht_hash_fn(key->keybuf, key->keysize);

    neigh_idx = hash & h->md->neighborhood_mask;

    PREFETCH_NEIGHBORHOOD(h->md->neighborhoods[neigh_idx]);

    for (j = 0; j < NEIGHBORHOOD_LEN; j++) {

        v = (struct ht_internal_value_st *)h->md->neighborhoods[neigh_idx].entries[j].value;

        if (v == NULL)

            continue;

        if (compare_hash(hash, h->md->neighborhoods[neigh_idx].entries[j].hash)

            && match_key(key, &v->value.key)) {

            if (!CRYPTO_atomic_store(&h->md->neighborhoods[neigh_idx].entries[j].hash,

                                     0, h->atomic_lock))

                break;

            h->wpd.value_count--;

            ossl_rcu_assign_ptr(&h->md->neighborhoods[neigh_idx].entries[j].value,

                                &nv);

            rc = 1;

            break;

        }

    }

    if (rc == 1) {

        ossl_rcu_call(h->lock, free_old_entry, v);

        h->wpd.need_sync = 1;

    }

    return rc;

}