map.c

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/* =========================================================================
 * Internal slot layout (unchanged from original):
 *   keys_values[i*2]   = key   pointer for slot i  (NULL == empty)
 *   keys_values[i*2+1] = value pointer for slot i
 *   deleted[i]         = REMOVED tombstone marker
 *
 * The Robin Hood implementation repurposes `deleted[]` as a probe-distance
 * (DIB) array: deleted[i] holds the distance-from-initial-bucket for the
 * element stored in slot i.  0 means the element is in its natural slot,
 * 1 means it was displaced by 1, etc.  An empty slot is indicated by
 * keys_values[i*2] == NULL.
 *
 * Because DIB replaces the boolean tombstone, `tombstone_count` is always 0
 * and the 50%-tombstone rehash path is never triggered.
 * ========================================================================= */
#include <limits.h>
#include <stdalign.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define XXH_INLINE_ALL
#include "../include/cmp.h"
#include "../include/lock.h"
#include "../include/map.h"
#include "../include/platform.h"
 
#include <xxhash.h>
 
// Default maximum load factor
#define DEFAULT_MAX_LOAD_FACTOR   0.75f
#define TOMBSTONE_RATIO_THRESHOLD 0.5f  // Rehash when tombstones > 50% of size
#define MIN_CAPACITY              8     // Minimum capacity to avoid frequent resizing
#define MAX(a, b)                 ((a) > (b) ? (a) : (b))
 
/* Distance-from-initial-bucket stored in the (repurposed) deleted[] array. */
#define _RH_DIB(m, i)        ((m)->deleted[i])
#define _RH_SET_DIB(m, i, d) ((m)->deleted[i] = (size_t)(d))
/* Slot is empty when the key pointer is NULL. */
#define _RH_EMPTY(m, i) ((m)->keys_values[(i) * 2] == NULL)
 
/* Compute slot index using capacity bitmask (capacity is always power-of-two). */
static inline size_t _rh_slot(size_t hash, size_t offset, size_t cap_mask) { return (hash + offset) & cap_mask; }
 
// Optimized map structure with better memory layout
typedef struct hash_map {
    void** keys_values;            // Interleaved keys and values for better cache locality
    size_t* deleted;               // DIB (distance-from-initial-bucket) array
    size_t size;                   // Number of active entries
    size_t capacity;               // Map capacity
    float max_load_factor;         // Configurable load factor threshold
    HashFunction hash;             // Hash function
    KeyCmpFunction key_compare;    // Key comparison function
    KeyFreeFunction key_free;      // Key free function (optional)
    ValueFreeFunction value_free;  // Value free function (optional)
    Lock lock;                     // Lock for thread safety
} HashMap;
 
// Fast hash for small keys (up to 8 bytes) - optimized version
static inline uint64_t fast_small_hash(const void* key, size_t size) {
    // Use union to avoid strict aliasing violations
    union {
        uint64_t u64;
        uint32_t u32[2];
        uint16_t u16[4];
        uint8_t u8[8];
    } value = {0};
 
    // Copy only the needed bytes
    const uint8_t* src = (const uint8_t*)key;
    for (size_t i = 0; i < size && i < sizeof(value); i++) {
        value.u8[i] = src[i];
    }
    return value.u64;
}
 
// xxHash implementation with small key optimization
static inline unsigned long xxhash(const void* key, size_t size) {
    if (size <= sizeof(uint64_t)) {
        return fast_small_hash(key, size);
    }
    return XXH3_64bits(key, size);
}
 
// Helper function to calculate next power of two for better hashing
static inline size_t next_power_of_two(size_t n) {
    if (n == 0) return 1;
    n--;
    n |= n >> 1;
    n |= n >> 2;
    n |= n >> 4;
    n |= n >> 8;
    n |= n >> 16;
#if SIZE_MAX > UINT32_MAX
    n |= n >> 32;
#endif
    return n + 1;
}
 
// Safe capacity growth calculation
static inline size_t calculate_new_capacity(size_t current) {
    if (current > SIZE_MAX / 2) {
        return SIZE_MAX;
    }
    size_t new_cap = current * 2;
    return (new_cap < current) ? SIZE_MAX : new_cap;
}
 
// Wrapper to match HashFunction signature
static inline size_t xxhash_wrapper(const void* key, size_t len) { return (size_t)xxhash(key, (size_t)len); }
 
// Map creation with better error handling and memory optimization
HashMap* map_create(const MapConfig* config) {
    if (!config || !config->key_compare) {
        return NULL;
    }
 
    size_t capacity = MAX(
        MIN_CAPACITY, config->initial_capacity > 0 ? next_power_of_two(config->initial_capacity) : INITIAL_MAP_SIZE);
 
    if (capacity > SIZE_MAX / 2) {
        return NULL;
    }
 
    float max_load_factor = config->max_load_factor > 0.1f && config->max_load_factor <= 0.95f
                                ? config->max_load_factor
                                : DEFAULT_MAX_LOAD_FACTOR;
 
    HashMap* m = (HashMap*)malloc(sizeof(HashMap));
    if (!m) {
        return NULL;
    }
 
    // Allocate interleaved keys and values for better cache locality
    m->keys_values = (void**)calloc(capacity * 2, sizeof(void*));
    m->deleted     = (size_t*)calloc(capacity, sizeof(size_t));
 
    if (!m->keys_values || !m->deleted) {
        free(m->keys_values);
        free(m->deleted);
        free(m);
        return NULL;
    }
 
    m->size            = 0;
    m->capacity        = capacity;
    m->max_load_factor = max_load_factor;
    m->hash            = config->hash_func ? config->hash_func : xxhash_wrapper;
    m->key_compare     = config->key_compare;
    m->key_free        = config->key_free;
    m->value_free      = config->value_free;
 
    lock_init(&m->lock);
    return m;
}
 
// Helper to get key pointer from interleaved array
static inline void** get_key_ptr(HashMap* m, size_t index) { return &m->keys_values[index * 2]; }
 
// Helper to get value pointer from interleaved array
static inline void** get_value_ptr(HashMap* m, size_t index) { return &m->keys_values[index * 2 + 1]; }
 
// Resize the map with optimized rehashing and error handling
static bool map_resize(HashMap* m, size_t new_capacity, size_t key_len) {
    if (new_capacity <= m->capacity || new_capacity > SIZE_MAX / 2) {
        return false;
    }
 
    void** new_keys_values = (void**)calloc(new_capacity * 2, sizeof(void*));
    size_t* new_deleted    = (size_t*)calloc(new_capacity, sizeof(size_t));
 
    if (!new_keys_values || !new_deleted) {
        free(new_keys_values);
        free(new_deleted);
        return false;
    }
 
    // Save old data
    void** old_keys_values = m->keys_values;
    size_t* old_deleted    = m->deleted;
    size_t old_capacity    = m->capacity;
 
    // Swap in new arrays
    m->keys_values  = new_keys_values;
    m->deleted      = new_deleted;
    m->capacity     = new_capacity;
    size_t old_size = m->size;
    m->size         = 0;
 
    // Rehash all active entries using Robin Hood linear probing (matching map_set)
    bool success      = true;
    const size_t mask = new_capacity - 1;
    for (size_t i = 0; i < old_capacity; i++) {
        if (old_keys_values[i * 2] && old_keys_values[i * 2] != NULL) {
            void* ins_key   = old_keys_values[i * 2];
            void* ins_value = old_keys_values[i * 2 + 1];
 
            size_t hash     = m->hash(ins_key, key_len);
            size_t idx      = hash & mask;
            size_t ins_dist = 0;
 
            for (size_t j = 0; j < new_capacity; j++) {
                if (_RH_EMPTY(m, idx)) {
                    *get_key_ptr(m, idx)   = ins_key;
                    *get_value_ptr(m, idx) = ins_value;
                    _RH_SET_DIB(m, idx, ins_dist);
                    m->size++;
                    break;
                }
 
                // Robin Hood: steal from richer elements
                size_t cur_dist = _RH_DIB(m, idx);
                if (cur_dist < ins_dist) {
                    void* tmp_k            = *get_key_ptr(m, idx);
                    void* tmp_v            = *get_value_ptr(m, idx);
                    *get_key_ptr(m, idx)   = ins_key;
                    *get_value_ptr(m, idx) = ins_value;
                    _RH_SET_DIB(m, idx, ins_dist);
                    ins_key   = tmp_k;
                    ins_value = tmp_v;
                    ins_dist  = cur_dist;
                }
 
                idx = (idx + 1) & mask;
                ins_dist++;
            }
        }
    }
 
    if (success) {
        // Free old arrays
        free(old_keys_values);
        free(old_deleted);
    } else {
        // Restore original state on failure
        m->keys_values = old_keys_values;
        m->deleted     = old_deleted;
        m->capacity    = old_capacity;
        m->size        = old_size;
        free(new_keys_values);
        free(new_deleted);
        return false;
    }
 
    return true;
}
 
size_t map_length(HashMap* m) { return m->size; }
 
// Set a key-value pair with optimizations and better error handling
bool map_set(HashMap* m, void* key, size_t key_len, void* value) {
    if (!m || !key) return false;
 
    /* Grow before inserting if load would exceed threshold. */
    size_t total_used = m->size; /* no tombstones in Robin Hood */
    if ((float)total_used / (float)m->capacity >= m->max_load_factor) {
        size_t new_cap = calculate_new_capacity(m->capacity);
        if (new_cap <= m->capacity || !map_resize(m, new_cap, key_len)) return false;
    }
 
    const size_t mask = m->capacity - 1;
    size_t hash       = m->hash(key, key_len);
    size_t idx        = hash & mask;
 
    /* The element we're about to insert. */
    void* ins_key   = key;
    void* ins_value = value;
    size_t ins_dist = 0;
 
    for (size_t i = 0; i < m->capacity; i++) {
        if (_RH_EMPTY(m, idx)) {
            /* Empty slot — place the element here. */
            *get_key_ptr(m, idx)   = ins_key;
            *get_value_ptr(m, idx) = ins_value;
            _RH_SET_DIB(m, idx, ins_dist);
            m->size++;
            return true;
        }
 
        /* Slot occupied.  Check for key match (update). */
        void** cur_kp = get_key_ptr(m, idx);
        if (m->key_compare(*cur_kp, ins_key)) {
            /* Key already exists — update value. */
            if (m->value_free) m->value_free(*get_value_ptr(m, idx));
            *get_value_ptr(m, idx) = ins_value;
            return true;
        }
 
        /* Robin Hood: if resident has smaller DIB ("richer"), steal its slot. */
        size_t cur_dist = _RH_DIB(m, idx);
        if (cur_dist < ins_dist) {
            /* Swap incoming element with resident. */
            void* tmp_k = *cur_kp;
            void* tmp_v = *get_value_ptr(m, idx);
 
            *get_key_ptr(m, idx)   = ins_key;
            *get_value_ptr(m, idx) = ins_value;
            _RH_SET_DIB(m, idx, ins_dist);
 
            ins_key   = tmp_k;
            ins_value = tmp_v;
            ins_dist  = cur_dist;
        }
 
        idx = (idx + 1) & mask;
        ins_dist++;
    }
 
    return false; /* table full (shouldn't happen at <75% load) */
}
 
// Get a value by key with optimized probing
void* map_get(HashMap* m, void* key, size_t key_len) {
    if (!m || !key) return NULL;
 
    const size_t hash = m->hash(key, key_len);
    const size_t mask = m->capacity - 1;
    size_t idx        = hash & mask;
 
    for (size_t dist = 0; dist < m->capacity; dist++) {
        if (_RH_EMPTY(m, idx)) return NULL;
 
        /* Robin Hood early exit: element would have robbed this slot. */
        if (_RH_DIB(m, idx) < dist) return NULL;
 
        void** kp = get_key_ptr(m, idx);
        if (m->key_compare(*kp, key)) return *get_value_ptr(m, idx);
 
        idx = (idx + 1) & mask;
    }
    return NULL;
}
 
// Remove a key-value pair with tombstone optimization
bool map_remove(HashMap* m, void* key, size_t key_len) {
    if (!m || !key) return false;
 
    const size_t mask = m->capacity - 1;
    size_t hash       = m->hash(key, key_len);
    size_t idx        = hash & mask;
 
    /* Locate the element. */
    size_t pos = SIZE_MAX;
    for (size_t dist = 0; dist < m->capacity; dist++) {
        if (_RH_EMPTY(m, idx)) return false;
        if (_RH_DIB(m, idx) < dist) return false; /* Robin Hood miss */
 
        if (m->key_compare(*get_key_ptr(m, idx), key)) {
            pos = idx;
            break;
        }
        idx = (idx + 1) & mask;
    }
    if (pos == SIZE_MAX) return false;
 
    /* Free key/value if cleanup functions were provided. */
    if (m->key_free) m->key_free(*get_key_ptr(m, pos));
    if (m->value_free) m->value_free(*get_value_ptr(m, pos));
 
    /* Backward-shift: pull forward any displaced neighbours. */
    size_t hole = pos;
    for (;;) {
        size_t next = (hole + 1) & mask;
        if (_RH_EMPTY(m, next) || _RH_DIB(m, next) == 0) break;
 
        /* Move next into hole and decrement its DIB. */
        *get_key_ptr(m, hole)   = *get_key_ptr(m, next);
        *get_value_ptr(m, hole) = *get_value_ptr(m, next);
        _RH_SET_DIB(m, hole, _RH_DIB(m, next) - 1);
 
        hole = next;
    }
 
    /* Mark the last vacated slot as empty. */
    *get_key_ptr(m, hole)   = NULL;
    *get_value_ptr(m, hole) = NULL;
    _RH_SET_DIB(m, hole, 0);
    m->size--;
    return true;
}
 
void map_destroy(HashMap* m) {
    if (!m) return;
 
    // no cleanup functions are provided
    if (!m->key_free && !m->value_free) {
        goto cleanup;
    }
 
    void** keys_values           = m->keys_values;
    size_t capacity              = m->capacity;
    KeyFreeFunction key_free     = m->key_free;
    ValueFreeFunction value_free = m->value_free;
 
    for (size_t i = 0; i < capacity; i++) {
        void* key = keys_values[i * 2];
        if (key) {
            if (key_free) key_free(key);
            if (value_free) value_free(keys_values[i * 2 + 1]);
        }
    }
 
cleanup:
    free(m->keys_values);
    free(m->deleted);
    lock_free(&m->lock);
    free(m);
}
 
map_iterator map_iter(HashMap* map) {
    map_iterator it = {.map = map, .index = 0};
    return it;
}
 
bool map_next(map_iterator* it, void** key, void** value) {
    HashMap* map       = it->map;
    size_t capacity    = map->capacity;
    void** keys_values = map->keys_values;
    size_t index       = it->index;
 
    while (index < capacity) {
        void* current_key = keys_values[index * 2];
        if (current_key) {
            if (key) *key = current_key;
            if (value) *value = keys_values[index * 2 + 1];
            it->index = index + 1;
            return true;
        }
        index++;
    }
    it->index = capacity;
    return false;
}
 
// Thread-safe operations
bool map_set_safe(HashMap* m, void* key, size_t key_len, void* value) {
    lock_acquire(&m->lock);
    bool result = map_set(m, key, key_len, value);
    lock_release(&m->lock);
    return result;
}
 
void* map_get_safe(HashMap* m, void* key, size_t key_len) {
    lock_acquire(&m->lock);
    void* value = map_get(m, key, key_len);
    lock_release(&m->lock);
    return value;
}
 
bool map_remove_safe(HashMap* m, void* key, size_t key_len) {
    lock_acquire(&m->lock);
    bool result = map_remove(m, key, key_len);
    lock_release(&m->lock);
    return result;
}