42sh/src/parser/grammar.c

// === Includes
#include "grammar.h"

#include <stdio.h>
#include <stdlib.h>

#include "grammar_basic.h"

// === Static variables

// rule-indexed array containing firsts
static struct firsts_list *firsts_map = NULL;

// === Static functions

/* @brief get the first accepted tokens of a rule
 *
 * @arg r the rule
 * @return the accepted tokens as a firsts_list struct
 */
static struct firsts_list *first(enum rule r)
{
    if (firsts_map == NULL || firsts_map[r].tokens == NULL)
    {
        puts("Internal error: attempted to get the firsts of a rule without "
             "properly initializing the firsts map");
        return NULL;
    }

    return &firsts_map[r];
}

/* @brief Add a token to a rule's firsts (in firsts_map)
 *
 * @arg rule the rule to which add a first
 * @arg token the token to add to the rule's firsts
 * @return true on success, false on error
 */
static bool add_first(enum rule rule, struct token token)
{
    struct firsts_list *item = &firsts_map[rule];
    if (item->tokens != NULL)
    {
        // Check for duplicates
        for (size_t i = 0; i < item->list_length; i++)
        {
            if (item->tokens[i].type == token.type)
                return true;
        }

        // Append
        item->list_length++;
        item->tokens = realloc(
            item->tokens, (item->list_length) * sizeof(struct firsts_list));
    }
    else
    {
        // Create entry
        item->tokens =
            calloc(item->list_length + 1, sizeof(struct firsts_list));
    }

    // Check for alloc error
    if (item->tokens == NULL)
    {
        item->list_length = 0;
        return false;
    }

    // Fill
    item->list_length++;
    item->tokens[item->list_length - 1] = token;

    return true;
}

/* @brief initializes the firsts_map static variable (does not populate it)
 * @return true on success, false on error
 */
static bool init_firsts_map(void)
{
    firsts_map = calloc(NUMBER_OF_RULES, sizeof(struct firsts_list));
    if (firsts_map == NULL)
    {
        puts("Internal error: couldn't create the firsts_map (is your memory "
             "full ?)");
        return false;
    }

    return true;
}

// === Functions

bool grammar_init(void)
{
    // Initialize the firsts map
    bool success = init_firsts_map();
    if (success != true)
        return false;

    // Populate the firsts map
    // TODO

    return true;
}

void grammar_close(void)
{
    // Deep free firsts map
    for (int i = 0; i < NUMBER_OF_RULES; i++)
    {
        if (firsts_map[i].tokens != NULL)
        {
            free(firsts_map[i].tokens);
        }
    }
    free(firsts_map);
    firsts_map = NULL;
}

struct ast *parse_input(struct lexer_context *ctx)
{
    return parse_list(ctx);
}