42sh/src/parser/grammar.c

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

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

#include "../lexer/lexer.h"
#include "grammar_basic.h"

// === Static variables

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

// === Static functions

/* @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, enum token_type 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] == token)
                return true;
        }

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

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

    // Fill
    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)
    {
        perror("Internal error: couldn't create the firsts_map (is your memory "
               "full ?)");
        return false;
    }

    return true;
}

/* @brief: add all the redirection token_types to the first of [rule].
 *          this also contains IONUMBER
 */
static void add_first_redir(enum rule rule)
{
    add_first(rule, TOKEN_IONUMBER);
    add_first(rule, TOKEN_REDIR_LEFT);
    add_first(rule, TOKEN_REDIR_RIGHT);
    add_first(rule, TOKEN_REDIR_LEFT_RIGHT);
    add_first(rule, TOKEN_REDIR_DOUBLE_RIGHT);
    add_first(rule, TOKEN_REDIR_LEFT_AMP);
    add_first(rule, TOKEN_REDIR_RIGHT_AMP);
    add_first(rule, TOKEN_REDIR_RIGHT_PIPE);
}

// === Functions

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

    // Populate the firsts map
    add_first(RULE_INPUT, TOKEN_WORD);
    add_first(RULE_INPUT, TOKEN_IF);
    add_first(RULE_COMMAND, TOKEN_NEGATION);
    add_first(RULE_INPUT, TOKEN_NEWLINE);
    add_first(RULE_INPUT, TOKEN_EOF);

    add_first(RULE_LIST, TOKEN_WORD);
    add_first(RULE_LIST, TOKEN_IF);
    add_first(RULE_COMMAND, TOKEN_NEGATION);

    add_first(RULE_AND_OR, TOKEN_WORD);
    add_first(RULE_AND_OR, TOKEN_IF);
    add_first(RULE_COMMAND, TOKEN_NEGATION);

    add_first(RULE_PIPELINE, TOKEN_WORD);
    add_first(RULE_PIPELINE, TOKEN_IF);
    add_first(RULE_COMMAND, TOKEN_NEGATION);

    add_first(RULE_COMMAND, TOKEN_WORD);
    add_first(RULE_COMMAND, TOKEN_IF);

    add_first(RULE_SIMPLE_COMMAND, TOKEN_WORD);

    add_first(RULE_SHELL_COMMAND, TOKEN_IF);

    add_first(RULE_IF, TOKEN_IF);

    add_first(RULE_COMPOUND_LIST, TOKEN_NEWLINE);
    add_first(RULE_COMPOUND_LIST, TOKEN_WORD);
    add_first(RULE_COMPOUND_LIST, TOKEN_IF);

    add_first(RULE_ELSE_CLAUSE, TOKEN_ELSE);
    add_first(RULE_ELSE_CLAUSE, TOKEN_ELIF);

    add_first(RULE_ELEMENT, TOKEN_WORD);
    add_first_redir(RULE_ELEMENT);

    add_first_redir(RULE_REDIRECTION);

    add_first_redir(RULE_PREFIX);

    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 firsts_list *first(enum rule rule)
{
    if (firsts_map == NULL || firsts_map[rule].tokens == NULL)
    {
        perror("Internal error: attempted to get the firsts of a rule without "
               "properly initializing the firsts map");
        return NULL;
    }

    return &firsts_map[rule];
}

bool is_first(struct token token, enum rule rule)
{
    struct firsts_list *firsts = &firsts_map[rule];
    for (size_t i = 0; i < firsts->list_length; i++)
    {
        if (firsts->tokens[i] == token.type)
            return true;
    }

    return false;
}

struct ast *parse_input(struct lexer_context *ctx)
{
    struct token *token = PEEK_TOKEN();

    if (token->type == TOKEN_EOF)
    {
        POP_TOKEN();
        return ast_create_end();
    }

    if (token->type == TOKEN_NEWLINE)
    {
        POP_TOKEN();
        return ast_create_list(NULL);
    }

    struct ast *ast = parse_list(ctx);
    if (ast == NULL)
        return NULL;

    token = PEEK_TOKEN();
    if (token->type == TOKEN_NEWLINE || token->type == TOKEN_EOF)
    {
        if (token->type == TOKEN_NEWLINE)
        {
            POP_TOKEN();
        }
        return ast;
    }

    perror("Syntax error: expected newline or EOF after list");
    ast_free(&ast);
    return NULL;
}