pebblisp/src/hash.c

#include "hash.h"
#include "env.h"

#include <string.h>

struct ObjectTable buildTable(size_t capacity)
{
    struct ObjectTable table = {
        .count = 0,
        .capacity = capacity,
        .elements = capacity ? malloc(sizeof(struct EnvElement) * capacity) : NULL,
    };
    for (int i = 0; i < table.capacity; i++) {
        table.elements[i].symbol = NULL;
    }
    return table;
}

void deleteTable(struct ObjectTable* table)
{
    for (int i = 0; i < table->capacity; i++) {
        if (table->elements[i].symbol) {
            free(table->elements[i].symbol);
            cleanObject(&table->elements[i].object);
        }
    }
    free(table->elements);
}

#ifndef HASHLESS_ENV

static unsigned long hash(const char* str, struct ObjectTable* table)
{
    unsigned long hash = 5381;
    int c;

    while ((c = *str++)) {
        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
    }

    return hash % table->capacity;
}

void extendTable(struct ObjectTable* table)
{
    if (table->capacity < (table->count + 1) * 2) {
        struct ObjectTable newTable = buildTable(table->capacity ? table->capacity * 2 : 4);
        for (int i = 0; i < table->capacity; i++) {
            if (table->elements[i].symbol) {
                addToTable(&newTable, table->elements[i].symbol, table->elements[i].object);
            }
        }
        free(table->elements);
        *table = newTable;
    }
}

Object* getFromTable(struct ObjectTable* table, const char* name)
{
    if (table->capacity == 0) {
        return NULL;
    }
    size_t h = hash(name, table);
    while (table->elements[h].symbol) {
        if (strcmp(name, table->elements[h].symbol) == 0) {
            return &table->elements[h].object;
        }
        h = (h + 1) % table->capacity;
    }
    return NULL;
}

#else

void extendTable(struct ObjectTable* table)
{
    if (table->count == (table->capacity - 1)) {
        struct EnvElement* oldElements = table->elements;
        size_t oldCapacity = table->capacity;
        table->capacity *= 2;
        table->elements = malloc(sizeof(struct EnvElement) * table->capacity);
        for (int i = 0; i < oldCapacity; i++) {
            table->elements[i] = oldElements[i];
        }
        for (size_t i = oldCapacity; i < table->capacity; i++) {
            table->elements[i].symbol = NULL;
        }
        free(oldElements);
    }
}

Object* getFromTable(struct ObjectTable* table, const char* name)
{
    for (size_t i = 0; i < table->count; i++) {
        if (strcmp(name, table->elements[i].symbol) == 0) {
            return &table->elements[i].object;
        }
    }
    return NULL;
}

static unsigned long hash(unused const char* str, struct ObjectTable* table)
{
    return table->count;
}

#endif

///
/// \param table
/// \param name Should be a new allocation
/// \param object Should already be cloned
void addToTable(struct ObjectTable* table, char* name, Object object)
{
    extendTable(table);
    size_t h = hash(name, table);
    while (table->elements[h].symbol) {
        h = (h + 1) % table->capacity;
    }
    table->elements[h].symbol = name;
    table->elements[h].object = object;
    table->count += 1;
}