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    // Copyright 2020 Joshua J Baker. All rights reserved.
    // Use of this source code is governed by an MIT-style
    // license that can be found in the LICENSE file.
    
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include <stdint.h>
    #include <stddef.h>
    #include "hashmap.h"
    
    static void *(*_malloc)(size_t) = NULL;
    static void *(*_realloc)(void *, size_t) = NULL;
    static void (*_free)(void *) = NULL;
    
    // hashmap_set_allocator allows for configuring a custom allocator for
    // all hashmap library operations. This function, if needed, should be called
    // only once at startup and a prior to calling hashmap_new().
    void hashmap_set_allocator(void *(*malloc)(size_t), void (*free)(void*)) 
    {
        _malloc = malloc;
        _free = free;
    }
    
    #define panic(_msg_) { \
        fprintf(stderr, "panic: %s (%s:%d)\n", (_msg_), __FILE__, __LINE__); \
        exit(1); \
    }
    
    struct bucket {
        uint64_t hash:48;
        uint64_t dib:16;
    };
    
    // hashmap is an open addressed hash map using robinhood hashing.
    struct hashmap {
        void *(*malloc)(size_t);
        void *(*realloc)(void *, size_t);
        void (*free)(void *);
        bool oom;
        size_t elsize;
        size_t cap;
        uint64_t seed0;
        uint64_t seed1;
        uint64_t (*hash)(const void *item, uint64_t seed0, uint64_t seed1);
        int (*compare)(const void *a, const void *b, void *udata);
        void (*elfree)(void *item);
        void *udata;
        size_t bucketsz;
        size_t nbuckets;
        size_t count;
        size_t mask;
        size_t growat;
        size_t shrinkat;
        void *buckets;
        void *spare;
        void *edata;
    };
    
    static struct bucket *bucket_at(struct hashmap *map, size_t index) {
        return (struct bucket*)(((char*)map->buckets)+(map->bucketsz*index));
    }
    
    static void *bucket_item(struct bucket *entry) {
        return ((char*)entry)+sizeof(struct bucket);
    }
    
    static uint64_t get_hash(struct hashmap *map, const void *key) {
        return map->hash(key, map->seed0, map->seed1) << 16 >> 16;
    }
    
    // hashmap_new_with_allocator returns a new hash map using a custom allocator.
    // See hashmap_new for more information information
    struct hashmap *hashmap_new_with_allocator(
                                void *(*_malloc)(size_t), 
                                void *(*_realloc)(void*, size_t), 
                                void (*_free)(void*),
                                size_t elsize, size_t cap, 
                                uint64_t seed0, uint64_t seed1,
                                uint64_t (*hash)(const void *item, 
                                                 uint64_t seed0, uint64_t seed1),
                                int (*compare)(const void *a, const void *b, 
                                               void *udata),
                                void (*elfree)(void *item),
                                void *udata)
    {
        _malloc = _malloc ? _malloc : malloc;
        _realloc = _realloc ? _realloc : realloc;
        _free = _free ? _free : free;
        int ncap = 16;
        if (cap < ncap) {
            cap = ncap;
        } else {
            while (ncap < cap) {
                ncap *= 2;
            }
            cap = ncap;
        }
        size_t bucketsz = sizeof(struct bucket) + elsize;
        while (bucketsz & (sizeof(uintptr_t)-1)) {
            bucketsz++;
        }
        // hashmap + spare + edata
        size_t size = sizeof(struct hashmap)+bucketsz*2;
        struct hashmap *map = _malloc(size);
        if (!map) {
            return NULL;
        }
        memset(map, 0, sizeof(struct hashmap));
        map->elsize = elsize;
        map->bucketsz = bucketsz;
        map->seed0 = seed0;
        map->seed1 = seed1;
        map->hash = hash;
        map->compare = compare;
        map->elfree = elfree;
        map->udata = udata;
        map->spare = ((char*)map)+sizeof(struct hashmap);
        map->edata = (char*)map->spare+bucketsz;
        map->cap = cap;
        map->nbuckets = cap;
        map->mask = map->nbuckets-1;
        map->buckets = _malloc(map->bucketsz*map->nbuckets);
        if (!map->buckets) {
            _free(map);
            return NULL;
        }
        memset(map->buckets, 0, map->bucketsz*map->nbuckets);
        map->growat = map->nbuckets*0.75;
        map->shrinkat = map->nbuckets*0.10;
        map->malloc = _malloc;
        map->realloc = _realloc;
        map->free = _free;
        return map;  
    }
    
    
    // hashmap_new returns a new hash map. 
    // Param `elsize` is the size of each element in the tree. Every element that
    // is inserted, deleted, or retrieved will be this size.
    // Param `cap` is the default lower capacity of the hashmap. Setting this to
    // zero will default to 16.
    // Params `seed0` and `seed1` are optional seed values that are passed to the 
    // following `hash` function. These can be any value you wish but it's often 
    // best to use randomly generated values.
    // Param `hash` is a function that generates a hash value for an item. It's
    // important that you provide a good hash function, otherwise it will perform
    // poorly or be vulnerable to Denial-of-service attacks. This implementation
    // comes with two helper functions `hashmap_sip()` and `hashmap_murmur()`.
    // Param `compare` is a function that compares items in the tree. See the 
    // qsort stdlib function for an example of how this function works.
    // The hashmap must be freed with hashmap_free(). 
    // Param `elfree` is a function that frees a specific item. This should be NULL
    // unless you're storing some kind of reference data in the hash.
    struct hashmap *hashmap_new(size_t elsize, size_t cap, 
                                uint64_t seed0, uint64_t seed1,
                                uint64_t (*hash)(const void *item, 
                                                 uint64_t seed0, uint64_t seed1),
                                int (*compare)(const void *a, const void *b, 
                                               void *udata),
                                void (*elfree)(void *item),
                                void *udata)
    {
        return hashmap_new_with_allocator(
            (_malloc?_malloc:malloc),
            (_realloc?_realloc:realloc),
            (_free?_free:free),
            elsize, cap, seed0, seed1, hash, compare, elfree, udata
        );
    }
    
    static void free_elements(struct hashmap *map) {
        if (map->elfree) {
            for (size_t i = 0; i < map->nbuckets; i++) {
                struct bucket *bucket = bucket_at(map, i);
                if (bucket->dib) map->elfree(bucket_item(bucket));
            }
        }
    }
    
    
    // hashmap_clear quickly clears the map. 
    // Every item is called with the element-freeing function given in hashmap_new,
    // if present, to free any data referenced in the elements of the hashmap.
    // When the update_cap is provided, the map's capacity will be updated to match
    // the currently number of allocated buckets. This is an optimization to ensure
    // that this operation does not perform any allocations.
    void hashmap_clear(struct hashmap *map, bool update_cap) {
        map->count = 0;
        free_elements(map);
        if (update_cap) {
            map->cap = map->nbuckets;
        } else if (map->nbuckets != map->cap) {
            void *new_buckets = map->malloc(map->bucketsz*map->cap);
            if (new_buckets) {
                map->free(map->buckets);
                map->buckets = new_buckets;
            }
            map->nbuckets = map->cap;
        }
        memset(map->buckets, 0, map->bucketsz*map->nbuckets);
        map->mask = map->nbuckets-1;
        map->growat = map->nbuckets*0.75;
        map->shrinkat = map->nbuckets*0.10;
    }
    
    
    static bool resize(struct hashmap *map, size_t new_cap) {
        struct hashmap *map2 = hashmap_new_with_allocator(map->malloc, map->realloc, map->free,
                                                          map->elsize, new_cap, map->seed0, 
                                                          map->seed1, map->hash, map->compare,
                                                          map->elfree, map->udata);
        if (!map2) {
            return false;
        }
        for (size_t i = 0; i < map->nbuckets; i++) {
            struct bucket *entry = bucket_at(map, i);
            if (!entry->dib) {
                continue;
            }
            entry->dib = 1;
            size_t j = entry->hash & map2->mask;
            for (;;) {
                struct bucket *bucket = bucket_at(map2, j);
                if (bucket->dib == 0) {
                    memcpy(bucket, entry, map->bucketsz);
                    break;
                }
                if (bucket->dib < entry->dib) {
                    memcpy(map2->spare, bucket, map->bucketsz);
                    memcpy(bucket, entry, map->bucketsz);
                    memcpy(entry, map2->spare, map->bucketsz);
                }
                j = (j + 1) & map2->mask;
                entry->dib += 1;
            }
    	}
        map->free(map->buckets);
        map->buckets = map2->buckets;
        map->nbuckets = map2->nbuckets;
        map->mask = map2->mask;
        map->growat = map2->growat;
        map->shrinkat = map2->shrinkat;
        map->free(map2);
        return true;
    }
    
    // hashmap_set inserts or replaces an item in the hash map. If an item is
    // replaced then it is returned otherwise NULL is returned. This operation
    // may allocate memory. If the system is unable to allocate additional
    // memory then NULL is returned and hashmap_oom() returns true.
    void *hashmap_set(struct hashmap *map, const void *item) {
        if (!item) {
            panic("item is null");
        }
        map->oom = false;
        if (map->count == map->growat) {
            if (!resize(map, map->nbuckets*2)) {
                map->oom = true;
                return NULL;
            }
        }
    
        
        struct bucket *entry = map->edata;
        entry->hash = get_hash(map, item);
        entry->dib = 1;
        memcpy(bucket_item(entry), item, map->elsize);
        
        size_t i = entry->hash & map->mask;
    	for (;;) {
            struct bucket *bucket = bucket_at(map, i);
            if (bucket->dib == 0) {
                memcpy(bucket, entry, map->bucketsz);
                map->count++;
    			return NULL;
    		}
            if (entry->hash == bucket->hash && 
                map->compare(bucket_item(entry), bucket_item(bucket), 
                             map->udata) == 0)
            {
                memcpy(map->spare, bucket_item(bucket), map->elsize);
                memcpy(bucket_item(bucket), bucket_item(entry), map->elsize);
                return map->spare;
    		}
            if (bucket->dib < entry->dib) {
                memcpy(map->spare, bucket, map->bucketsz);
                memcpy(bucket, entry, map->bucketsz);
                memcpy(entry, map->spare, map->bucketsz);
    		}
    		i = (i + 1) & map->mask;
            entry->dib += 1;
    	}
    }
    
    // hashmap_get returns the item based on the provided key. If the item is not
    // found then NULL is returned.
    void *hashmap_get(struct hashmap *map, const void *key) {
        if (!key) {
            panic("key is null");
        }
        uint64_t hash = get_hash(map, key);
    	size_t i = hash & map->mask;
    	for (;;) {
            struct bucket *bucket = bucket_at(map, i);
    		if (!bucket->dib) {
    			return NULL;
    		}
    		if (bucket->hash == hash && 
                map->compare(key, bucket_item(bucket), map->udata) == 0)
            {
                return bucket_item(bucket);
    		}
    		i = (i + 1) & map->mask;
    	}
    }
    
    // hashmap_probe returns the item in the bucket at position or NULL if an item
    // is not set for that bucket. The position is 'moduloed' by the number of 
    // buckets in the hashmap.
    void *hashmap_probe(struct hashmap *map, uint64_t position) {
        size_t i = position & map->mask;
        struct bucket *bucket = bucket_at(map, i);
        if (!bucket->dib) {
    		return NULL;
    	}
        return bucket_item(bucket);
    }
    
    
    // hashmap_delete removes an item from the hash map and returns it. If the
    // item is not found then NULL is returned.
    void *hashmap_delete(struct hashmap *map, void *key) {
        if (!key) {
            panic("key is null");
        }
        map->oom = false;
        uint64_t hash = get_hash(map, key);
    	size_t i = hash & map->mask;
    	for (;;) {
            struct bucket *bucket = bucket_at(map, i);
    		if (!bucket->dib) {
    			return NULL;
    		}
    		if (bucket->hash == hash && 
                map->compare(key, bucket_item(bucket), map->udata) == 0)
            {
                memcpy(map->spare, bucket_item(bucket), map->elsize);
                bucket->dib = 0;
                for (;;) {
                    struct bucket *prev = bucket;
                    i = (i + 1) & map->mask;
                    bucket = bucket_at(map, i);
                    if (bucket->dib <= 1) {
                        prev->dib = 0;
                        break;
                    }
                    memcpy(prev, bucket, map->bucketsz);
                    prev->dib--;
                }
                map->count--;
                if (map->nbuckets > map->cap && map->count <= map->shrinkat) {
                    // Ignore the return value. It's ok for the resize operation to
                    // fail to allocate enough memory because a shrink operation
                    // does not change the integrity of the data.
                    resize(map, map->nbuckets/2);
                }
    			return map->spare;
    		}
    		i = (i + 1) & map->mask;
    	}
    }
    
    // hashmap_count returns the number of items in the hash map.
    size_t hashmap_count(struct hashmap *map) {
        return map->count;
    }
    
    // hashmap_free frees the hash map
    // Every item is called with the element-freeing function given in hashmap_new,
    // if present, to free any data referenced in the elements of the hashmap.
    void hashmap_free(struct hashmap *map) {
        if (!map) return;
        free_elements(map);
        map->free(map->buckets);
        map->free(map);
    }
    
    // hashmap_oom returns true if the last hashmap_set() call failed due to the 
    // system being out of memory.
    bool hashmap_oom(struct hashmap *map) {
        return map->oom;
    }
    
    // hashmap_scan iterates over all items in the hash map
    // Param `iter` can return false to stop iteration early.
    // Returns false if the iteration has been stopped early.
    bool hashmap_scan(struct hashmap *map, 
                      bool (*iter)(const void *item, void *udata), void *udata)
    {
        for (size_t i = 0; i < map->nbuckets; i++) {
            struct bucket *bucket = bucket_at(map, i);
            if (bucket->dib) {
                if (!iter(bucket_item(bucket), udata)) {
                    return false;
                }
            }
        }
        return true;
    }
    
    
    // hashmap_iter iterates one key at a time yielding a reference to an
    // entry at each iteration. Useful to write simple loops and avoid writing
    // dedicated callbacks and udata structures, as in hashmap_scan.
    //
    // map is a hash map handle. i is a pointer to a size_t cursor that
    // should be initialized to 0 at the beginning of the loop. item is a void
    // pointer pointer that is populated with the retrieved item. Note that this
    // is NOT a copy of the item stored in the hash map and can be directly
    // modified.
    //
    // Note that if hashmap_delete() is called on the hashmap being iterated,
    // the buckets are rearranged and the iterator must be reset to 0, otherwise
    // unexpected results may be returned after deletion.
    //
    // This function has not been tested for thread safety.
    //
    // The function returns true if an item was retrieved; false if the end of the
    // iteration has been reached.
    bool hashmap_iter(struct hashmap *map, size_t *i, void **item)
    {
        struct bucket *bucket;
    
        do {
            if (*i >= map->nbuckets) return false;
    
            bucket = bucket_at(map, *i);
            (*i)++;
        } while (!bucket->dib);
    
        *item = bucket_item(bucket);
    
        return true;
    }
    
    
    //-----------------------------------------------------------------------------
    // SipHash reference C implementation
    //
    // Copyright (c) 2012-2016 Jean-Philippe Aumasson
    // <jeanphilippe.aumasson@gmail.com>
    // Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>
    //
    // To the extent possible under law, the author(s) have dedicated all copyright
    // and related and neighboring rights to this software to the public domain
    // worldwide. This software is distributed without any warranty.
    //
    // You should have received a copy of the CC0 Public Domain Dedication along
    // with this software. If not, see
    // <http://creativecommons.org/publicdomain/zero/1.0/>.
    //
    // default: SipHash-2-4
    //-----------------------------------------------------------------------------
    static uint64_t SIP64(const uint8_t *in, const size_t inlen, 
                          uint64_t seed0, uint64_t seed1) 
    {
    #define U8TO64_LE(p) \
        {  (((uint64_t)((p)[0])) | ((uint64_t)((p)[1]) << 8) | \
            ((uint64_t)((p)[2]) << 16) | ((uint64_t)((p)[3]) << 24) | \
            ((uint64_t)((p)[4]) << 32) | ((uint64_t)((p)[5]) << 40) | \
            ((uint64_t)((p)[6]) << 48) | ((uint64_t)((p)[7]) << 56)) }
    #define U64TO8_LE(p, v) \
        { U32TO8_LE((p), (uint32_t)((v))); \
          U32TO8_LE((p) + 4, (uint32_t)((v) >> 32)); }
    #define U32TO8_LE(p, v) \
        { (p)[0] = (uint8_t)((v)); \
          (p)[1] = (uint8_t)((v) >> 8); \
          (p)[2] = (uint8_t)((v) >> 16); \
          (p)[3] = (uint8_t)((v) >> 24); }
    #define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
    #define SIPROUND \
        { v0 += v1; v1 = ROTL(v1, 13); \
          v1 ^= v0; v0 = ROTL(v0, 32); \
          v2 += v3; v3 = ROTL(v3, 16); \
          v3 ^= v2; \
          v0 += v3; v3 = ROTL(v3, 21); \
          v3 ^= v0; \
          v2 += v1; v1 = ROTL(v1, 17); \
          v1 ^= v2; v2 = ROTL(v2, 32); }
        uint64_t k0 = U8TO64_LE((uint8_t*)&seed0);
        uint64_t k1 = U8TO64_LE((uint8_t*)&seed1);
        uint64_t v3 = UINT64_C(0x7465646279746573) ^ k1;
        uint64_t v2 = UINT64_C(0x6c7967656e657261) ^ k0;
        uint64_t v1 = UINT64_C(0x646f72616e646f6d) ^ k1;
        uint64_t v0 = UINT64_C(0x736f6d6570736575) ^ k0;
        const uint8_t *end = in + inlen - (inlen % sizeof(uint64_t));
        for (; in != end; in += 8) {
            uint64_t m = U8TO64_LE(in);
            v3 ^= m;
            SIPROUND; SIPROUND;
            v0 ^= m;
        }
        const int left = inlen & 7;
        uint64_t b = ((uint64_t)inlen) << 56;
        switch (left) {
        case 7: b |= ((uint64_t)in[6]) << 48;
        case 6: b |= ((uint64_t)in[5]) << 40;
        case 5: b |= ((uint64_t)in[4]) << 32;
        case 4: b |= ((uint64_t)in[3]) << 24;
        case 3: b |= ((uint64_t)in[2]) << 16;
        case 2: b |= ((uint64_t)in[1]) << 8;
        case 1: b |= ((uint64_t)in[0]); break;
        case 0: break;
        }
        v3 ^= b;
        SIPROUND; SIPROUND;
        v0 ^= b;
        v2 ^= 0xff;
        SIPROUND; SIPROUND; SIPROUND; SIPROUND;
        b = v0 ^ v1 ^ v2 ^ v3;
        uint64_t out = 0;
        U64TO8_LE((uint8_t*)&out, b);
        return out;
    }
    
    //-----------------------------------------------------------------------------
    // MurmurHash3 was written by Austin Appleby, and is placed in the public
    // domain. The author hereby disclaims copyright to this source code.
    //
    // Murmur3_86_128
    //-----------------------------------------------------------------------------
    static void MM86128(const void *key, const int len, uint32_t seed, void *out) {
    #define	ROTL32(x, r) ((x << r) | (x >> (32 - r)))
    #define FMIX32(h) h^=h>>16; h*=0x85ebca6b; h^=h>>13; h*=0xc2b2ae35; h^=h>>16;
        const uint8_t * data = (const uint8_t*)key;
        const int nblocks = len / 16;
        uint32_t h1 = seed;
        uint32_t h2 = seed;
        uint32_t h3 = seed;
        uint32_t h4 = seed;
        uint32_t c1 = 0x239b961b; 
        uint32_t c2 = 0xab0e9789;
        uint32_t c3 = 0x38b34ae5; 
        uint32_t c4 = 0xa1e38b93;
        const uint32_t * blocks = (const uint32_t *)(data + nblocks*16);
        for (int i = -nblocks; i; i++) {
            uint32_t k1 = blocks[i*4+0];
            uint32_t k2 = blocks[i*4+1];
            uint32_t k3 = blocks[i*4+2];
            uint32_t k4 = blocks[i*4+3];
            k1 *= c1; k1  = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
            h1 = ROTL32(h1,19); h1 += h2; h1 = h1*5+0x561ccd1b;
            k2 *= c2; k2  = ROTL32(k2,16); k2 *= c3; h2 ^= k2;
            h2 = ROTL32(h2,17); h2 += h3; h2 = h2*5+0x0bcaa747;
            k3 *= c3; k3  = ROTL32(k3,17); k3 *= c4; h3 ^= k3;
            h3 = ROTL32(h3,15); h3 += h4; h3 = h3*5+0x96cd1c35;
            k4 *= c4; k4  = ROTL32(k4,18); k4 *= c1; h4 ^= k4;
            h4 = ROTL32(h4,13); h4 += h1; h4 = h4*5+0x32ac3b17;
        }
        const uint8_t * tail = (const uint8_t*)(data + nblocks*16);
        uint32_t k1 = 0;
        uint32_t k2 = 0;
        uint32_t k3 = 0;
        uint32_t k4 = 0;
        switch(len & 15) {
        case 15: k4 ^= tail[14] << 16;
        case 14: k4 ^= tail[13] << 8;
        case 13: k4 ^= tail[12] << 0;
                 k4 *= c4; k4  = ROTL32(k4,18); k4 *= c1; h4 ^= k4;
        case 12: k3 ^= tail[11] << 24;
        case 11: k3 ^= tail[10] << 16;
        case 10: k3 ^= tail[ 9] << 8;
        case  9: k3 ^= tail[ 8] << 0;
                 k3 *= c3; k3  = ROTL32(k3,17); k3 *= c4; h3 ^= k3;
        case  8: k2 ^= tail[ 7] << 24;
        case  7: k2 ^= tail[ 6] << 16;
        case  6: k2 ^= tail[ 5] << 8;
        case  5: k2 ^= tail[ 4] << 0;
                 k2 *= c2; k2  = ROTL32(k2,16); k2 *= c3; h2 ^= k2;
        case  4: k1 ^= tail[ 3] << 24;
        case  3: k1 ^= tail[ 2] << 16;
        case  2: k1 ^= tail[ 1] << 8;
        case  1: k1 ^= tail[ 0] << 0;
                 k1 *= c1; k1  = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
        };
        h1 ^= len; h2 ^= len; h3 ^= len; h4 ^= len;
        h1 += h2; h1 += h3; h1 += h4;
        h2 += h1; h3 += h1; h4 += h1;
        FMIX32(h1); FMIX32(h2); FMIX32(h3); FMIX32(h4);
        h1 += h2; h1 += h3; h1 += h4;
        h2 += h1; h3 += h1; h4 += h1;
        ((uint32_t*)out)[0] = h1;
        ((uint32_t*)out)[1] = h2;
        ((uint32_t*)out)[2] = h3;
        ((uint32_t*)out)[3] = h4;
    }
    
    // hashmap_sip returns a hash value for `data` using SipHash-2-4.
    uint64_t hashmap_sip(const void *data, size_t len, 
                         uint64_t seed0, uint64_t seed1)
    {
        return SIP64((uint8_t*)data, len, seed0, seed1);
    }
    
    // hashmap_murmur returns a hash value for `data` using Murmur3_86_128.
    uint64_t hashmap_murmur(const void *data, size_t len, 
                            uint64_t seed0, uint64_t seed1)
    {
        char out[16];
        MM86128(data, len, seed0, &out);
        return *(uint64_t*)out;
    }
    
    //==============================================================================
    // TESTS AND BENCHMARKS
    // $ cc -DHASHMAP_TEST hashmap.c && ./a.out              # run tests
    // $ cc -DHASHMAP_TEST -O3 hashmap.c && BENCH=1 ./a.out  # run benchmarks
    //==============================================================================
    #ifdef HASHMAP_TEST
    
    static size_t deepcount(struct hashmap *map) {
        size_t count = 0;
        for (size_t i = 0; i < map->nbuckets; i++) {
            if (bucket_at(map, i)->dib) {
                count++;
            }
        }
        return count;
    }
    
    
    #pragma GCC diagnostic ignored "-Wextra"
    
    
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    #include <assert.h>
    #include <stdio.h>
    #include "hashmap.h"
    
    static bool rand_alloc_fail = false;
    static int rand_alloc_fail_odds = 3; // 1 in 3 chance malloc will fail.
    static uintptr_t total_allocs = 0;
    static uintptr_t total_mem = 0;
    
    static void *xmalloc(size_t size) {
        if (rand_alloc_fail && rand()%rand_alloc_fail_odds == 0) {
            return NULL;
        }
        void *mem = malloc(sizeof(uintptr_t)+size);
        assert(mem);
        *(uintptr_t*)mem = size;
        total_allocs++;
        total_mem += size;
        return (char*)mem+sizeof(uintptr_t);
    }
    
    static void xfree(void *ptr) {
        if (ptr) {
            total_mem -= *(uintptr_t*)((char*)ptr-sizeof(uintptr_t));
            free((char*)ptr-sizeof(uintptr_t));
            total_allocs--;
        }
    }
    
    static void shuffle(void *array, size_t numels, size_t elsize) {
        char tmp[elsize];
        char *arr = array;
        for (size_t i = 0; i < numels - 1; i++) {
            int j = i + rand() / (RAND_MAX / (numels - i) + 1);
            memcpy(tmp, arr + j * elsize, elsize);
            memcpy(arr + j * elsize, arr + i * elsize, elsize);
            memcpy(arr + i * elsize, tmp, elsize);
        }
    }
    
    static bool iter_ints(const void *item, void *udata) {
        int *vals = *(int**)udata;
        vals[*(int*)item] = 1;
        return true;
    }
    
    static int compare_ints(const void *a, const void *b) {
        return *(int*)a - *(int*)b;
    }
    
    static int compare_ints_udata(const void *a, const void *b, void *udata) {
        return *(int*)a - *(int*)b;
    }
    
    static int compare_strs(const void *a, const void *b, void *udata) {
        return strcmp(*(char**)a, *(char**)b);
    }
    
    static uint64_t hash_int(const void *item, uint64_t seed0, uint64_t seed1) {
        return hashmap_murmur(item, sizeof(int), seed0, seed1);
    }
    
    static uint64_t hash_str(const void *item, uint64_t seed0, uint64_t seed1) {
        return hashmap_murmur(*(char**)item, strlen(*(char**)item), seed0, seed1);
    }
    
    static void free_str(void *item) {
        xfree(*(char**)item);
    }
    
    static void all() {
        int seed = getenv("SEED")?atoi(getenv("SEED")):time(NULL);
        int N = getenv("N")?atoi(getenv("N")):2000;
        printf("seed=%d, count=%d, item_size=%zu\n", seed, N, sizeof(int));
        srand(seed);
    
        rand_alloc_fail = true;
    
        // test sip and murmur hashes
        assert(hashmap_sip("hello", 5, 1, 2) == 2957200328589801622);
        assert(hashmap_murmur("hello", 5, 1, 2) == 1682575153221130884);
    
        int *vals;
        while (!(vals = xmalloc(N * sizeof(int)))) {}
        for (int i = 0; i < N; i++) {
            vals[i] = i;
        }
    
        struct hashmap *map;
    
        while (!(map = hashmap_new(sizeof(int), 0, seed, seed, 
                                   hash_int, compare_ints_udata, NULL, NULL))) {}
        shuffle(vals, N, sizeof(int));
        for (int i = 0; i < N; i++) {
            // // printf("== %d ==\n", vals[i]);
            assert(map->count == i);
            assert(map->count == hashmap_count(map));
            assert(map->count == deepcount(map));
            int *v;
            assert(!hashmap_get(map, &vals[i]));
            assert(!hashmap_delete(map, &vals[i]));
            while (true) {
                assert(!hashmap_set(map, &vals[i]));
                if (!hashmap_oom(map)) {
                    break;
                }
            }
            
            for (int j = 0; j < i; j++) {
                v = hashmap_get(map, &vals[j]);
                assert(v && *v == vals[j]);
            }
            while (true) {
                v = hashmap_set(map, &vals[i]);
                if (!v) {
                    assert(hashmap_oom(map));
                    continue;
                } else {
                    assert(!hashmap_oom(map));
                    assert(v && *v == vals[i]);
                    break;
                }
            }
            v = hashmap_get(map, &vals[i]);
            assert(v && *v == vals[i]);
            v = hashmap_delete(map, &vals[i]);
            assert(v && *v == vals[i]);
            assert(!hashmap_get(map, &vals[i]));
            assert(!hashmap_delete(map, &vals[i]));
            assert(!hashmap_set(map, &vals[i]));
            assert(map->count == i+1);
            assert(map->count == hashmap_count(map));
            assert(map->count == deepcount(map));
        }
    
        int *vals2;
        while (!(vals2 = xmalloc(N * sizeof(int)))) {}
        memset(vals2, 0, N * sizeof(int));
        assert(hashmap_scan(map, iter_ints, &vals2));
    
        // Test hashmap_iter. This does the same as hashmap_scan above.
        size_t iter = 0;
        void *iter_val;
        while (hashmap_iter (map, &iter, &iter_val)) {
            assert (iter_ints(iter_val, &vals2));
        }
        for (int i = 0; i < N; i++) {
            assert(vals2[i] == 1);
        }
        xfree(vals2);
    
        shuffle(vals, N, sizeof(int));
        for (int i = 0; i < N; i++) {
            int *v;
            v = hashmap_delete(map, &vals[i]);
            assert(v && *v == vals[i]);
            assert(!hashmap_get(map, &vals[i]));
            assert(map->count == N-i-1);
            assert(map->count == hashmap_count(map));
            assert(map->count == deepcount(map));
            for (int j = N-1; j > i; j--) {
                v = hashmap_get(map, &vals[j]);
                assert(v && *v == vals[j]);
            }
        }
    
        for (int i = 0; i < N; i++) {
            while (true) {
                assert(!hashmap_set(map, &vals[i]));
                if (!hashmap_oom(map)) {
                    break;
                }
            }
        }
    
        assert(map->count != 0);
        size_t prev_cap = map->cap;
        hashmap_clear(map, true);
        assert(prev_cap < map->cap);
        assert(map->count == 0);
    
    
        for (int i = 0; i < N; i++) {
            while (true) {
                assert(!hashmap_set(map, &vals[i]));
                if (!hashmap_oom(map)) {
                    break;
                }
            }
        }
    
        prev_cap = map->cap;
        hashmap_clear(map, false);
        assert(prev_cap == map->cap);
    
        hashmap_free(map);
    
        xfree(vals);
    
    
        while (!(map = hashmap_new(sizeof(char*), 0, seed, seed,
                                   hash_str, compare_strs, free_str, NULL)));
    
        for (int i = 0; i < N; i++) {
            char *str;
            while (!(str = xmalloc(16)));
            sprintf(str, "s%i", i);
            while(!hashmap_set(map, &str));
        }
    
        hashmap_clear(map, false);
        assert(hashmap_count(map) == 0);
    
        for (int i = 0; i < N; i++) {
            char *str;
            while (!(str = xmalloc(16)));
            sprintf(str, "s%i", i);
            while(!hashmap_set(map, &str));
        }
    
        hashmap_free(map);
    
        if (total_allocs != 0) {
            fprintf(stderr, "total_allocs: expected 0, got %lu\n", total_allocs);
            exit(1);
        }
    }
    
    #define bench(name, N, code) {{ \
        if (strlen(name) > 0) { \
            printf("%-14s ", name); \
        } \
        size_t tmem = total_mem; \
        size_t tallocs = total_allocs; \
        uint64_t bytes = 0; \
        clock_t begin = clock(); \
        for (int i = 0; i < N; i++) { \
            (code); \
        } \
        clock_t end = clock(); \
        double elapsed_secs = (double)(end - begin) / CLOCKS_PER_SEC; \
        double bytes_sec = (double)bytes/elapsed_secs; \
        printf("%d ops in %.3f secs, %.0f ns/op, %.0f op/sec", \
            N, elapsed_secs, \
            elapsed_secs/(double)N*1e9, \
            (double)N/elapsed_secs \
        ); \
        if (bytes > 0) { \
            printf(", %.1f GB/sec", bytes_sec/1024/1024/1024); \
        } \
        if (total_mem > tmem) { \
            size_t used_mem = total_mem-tmem; \
            printf(", %.2f bytes/op", (double)used_mem/N); \
        } \
        if (total_allocs > tallocs) { \
            size_t used_allocs = total_allocs-tallocs; \
            printf(", %.2f allocs/op", (double)used_allocs/N); \
        } \
        printf("\n"); \
    }}
    
    static void benchmarks() {
        int seed = getenv("SEED")?atoi(getenv("SEED")):time(NULL);
        int N = getenv("N")?atoi(getenv("N")):5000000;
        printf("seed=%d, count=%d, item_size=%zu\n", seed, N, sizeof(int));
        srand(seed);
    
    
        int *vals = xmalloc(N * sizeof(int));
        for (int i = 0; i < N; i++) {
            vals[i] = i;
        }
    
        shuffle(vals, N, sizeof(int));
    
        struct hashmap *map;
        shuffle(vals, N, sizeof(int));
    
        map = hashmap_new(sizeof(int), 0, seed, seed, hash_int, compare_ints_udata, 
                          NULL, NULL);
        bench("set", N, {
            int *v = hashmap_set(map, &vals[i]);
            assert(!v);
        })
        shuffle(vals, N, sizeof(int));
        bench("get", N, {
            int *v = hashmap_get(map, &vals[i]);
            assert(v && *v == vals[i]);
        })
        shuffle(vals, N, sizeof(int));
        bench("delete", N, {
            int *v = hashmap_delete(map, &vals[i]);
            assert(v && *v == vals[i]);
        })
        hashmap_free(map);
    
        map = hashmap_new(sizeof(int), N, seed, seed, hash_int, compare_ints_udata, 
                          NULL, NULL);
        bench("set (cap)", N, {
            int *v = hashmap_set(map, &vals[i]);
            assert(!v);
        })
        shuffle(vals, N, sizeof(int));
        bench("get (cap)", N, {
            int *v = hashmap_get(map, &vals[i]);
            assert(v && *v == vals[i]);
        })
        shuffle(vals, N, sizeof(int));
        bench("delete (cap)" , N, {
            int *v = hashmap_delete(map, &vals[i]);
            assert(v && *v == vals[i]);
        })
    
        hashmap_free(map);
    
        
        xfree(vals);
    
        if (total_allocs != 0) {
            fprintf(stderr, "total_allocs: expected 0, got %lu\n", total_allocs);
            exit(1);
        }
    }
    
    int main() {
        hashmap_set_allocator(xmalloc, xfree);
    
        if (getenv("BENCH")) {
            printf("Running hashmap.c benchmarks...\n");
            benchmarks();
        } else {
            printf("Running hashmap.c tests...\n");
            all();
            printf("PASSED\n");
        }
    }
    
    
    #endif