table.c

#include "table.h"
#include <string.h>
#include "memory.h"

#define TABLE_MAX_LOAD 0.75


static Entry* findEntry(Entry* entries, int capacity, 
    ObjString* key) {
        
    uint32_t index = key->hash % capacity;
    Entry* tombStone = NULL;
    for(;;) {
        Entry* entry = &entries[index];

        if (entry->key == NULL) {
            if (IS_NIL(entry->value)) { 
                return tombStone != NULL ? tombStone : entry;
            } else {
                if (tombStone == NULL) tombStone = entry;
            }
        } else if (entry->key == key) {
            return entry;
        }

        index = (index + 1) % capacity;
    }        
}

static void adjustCapacity(Table* table, int capacity) {
    Entry* entries = ALLOCATE(Entry, capacity);
    for (int i = 0; i < capacity; i++) {
        entries[i].key = NULL;
        entries[i].value = NIL_VAL;
    }

    table->count = 0;
    for (int i = 0; i < table->capacity; i++) {
        Entry* entry = &table->entries[i];
        if (entry->key == NULL) continue;

        Entry* dest = findEntry(entries, capacity, entry->key);
        dest->key = entry->key;
        dest->value = entry->value;
        table->count++;
    }

    FREE_ARRAY(Entry, table->entries, table->capacity);

    table->entries = entries;
    table->capacity = capacity;
}

void initTable(Table* table) {
    table->count = 0;
    table->capacity = 0;
    table->entries = NULL;
}

void freeTable(Table* table) {
    FREE_ARRAY(Entry, table->entries, table->capacity);
    initTable(table);
}

bool tableSet(Table* table, ObjString* key, Value value) {
    if (table->count + 1 > table->capacity * TABLE_MAX_LOAD) {
        int newCapacity = GROW_CAPACITY(table->capacity);
        adjustCapacity(table, newCapacity);
    }

    Entry* entry = findEntry(table->entries, table->capacity, key);

    bool isNewKey = entry->key == NULL;
    if (isNewKey && IS_NIL(entry->value)) table->count++;

    entry->key = key;
    entry->value = value;
    return isNewKey;
}


void tableAdd(Table* from, Table* to) {
    for (int i = 0; i < from->capacity; i++) {
        Entry* entry = &from->entries[i];

        if(!entry->key) {
            tableSet(to, entry->key, entry->value);
        }
    } 
}

bool tableGet(Table* table, ObjString* key, Value* value) {
    if (table->count == 0) return false;
    
    Entry* entry = findEntry(table->entries, table->capacity, key);
    if (entry->key == NULL) return false;

    *value = entry->value; //copy
    return true;
}


bool tableDelete(Table* table, ObjString* key) {
    if (table->count == 0) return false;

    Entry* entry = findEntry(table->entries, table->capacity, key);
    if (entry->key == NULL) return false;

    entry->key = NULL;
    entry->value = BOOL_VAL(true);
    return true;
}

ObjString* tableFindString(Table* table, const char* chars,
    int length, uint32_t hash) {
        if (table->count == 0) return NULL;
        
        uint32_t index = hash % table->capacity;
        for(;;) {
            Entry* entry = &table->entries[index];
            
            if(entry->key == NULL) {
                if (IS_NIL(entry->value)) return NULL;
            } else if (entry->key->length == length &&
                entry->key->hash == hash &&
                memcmp(entry->key->chars, chars, length) == 0) {
                    return entry->key;
            }

            index = (index + 1) % table->capacity;
        }
}