path: root/clr-table.c

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

#ifndef XCALLOC_IMPLEMENTED
#define XCALLOC_IMPLEMENTED
void *xcalloc(size_t n, size_t size) { void *addr = calloc(n, size); return addr ? addr : (exit(1), NULL); }
#else
extern void *xcalloc(size_t n, size_t size);
#endif

typedef unsigned int symbol;
extern const size_t total_symbols;

extern int symbol_is_terminal(symbol s);
extern int symbol_is_input_end(symbol s);

extern struct production {
    symbol LHS;
    symbol *RHS;
    size_t nRHS;
} grammar[];
extern const size_t total_productions;

void grammar_print()
{
    for(size_t i = 0; i < total_productions; i++) {
        printf("%d --> ", grammar[i].LHS);
        for(size_t j = 0; j < grammar[i].nRHS; j++)
            printf("%d ", grammar[i].RHS[j]);
        printf("\n");
    }
}

extern int **first;
extern int **follow;

struct action {
    enum action_type {
        ACTION_NOT_SET = 0, ACTION_SHIFT,
        ACTION_GOTO, ACTION_REDUCE,
        ACTION_ACCEPT
    } type;
    size_t arg;
};

#define TABLE_CAP 64
struct action *table[TABLE_CAP];
size_t table_states = 0;

void table_allocate() { for(size_t i = 0; i < TABLE_CAP; i++) table[i] = xcalloc(total_symbols, sizeof(*table[i])); }
void table_free() { for(size_t i = 0; i < TABLE_CAP; i++) free(table[i]); }
int table_insert(size_t state, symbol sym, struct action a);
void table_print();

struct item {
    size_t prod_idx;
    size_t dot;
    symbol lookahead;
};

int item_eq(struct item *i1, struct item *i2) { return (i1->dot == i2->dot && i1->prod_idx == i2->prod_idx && i1->lookahead == i2->lookahead) ? 1 : 0; }

#define SEEN_SETS_CAP 64
static struct {
    struct item *items;
    size_t nitems;
    size_t state;
} seen_sets[SEEN_SETS_CAP];
static size_t nseen_sets;

void seen_sets_free() { for(size_t i = 0; i < nseen_sets; i++) free(seen_sets[i].items);}

size_t itemset_handle(struct item *set, size_t nset);
int itemset_insert(size_t state, struct item *initial_set, size_t ninitial);
size_t itemset_closure(struct item *in_set, size_t nin, struct item *out_set, size_t nout);
void itemset_print(struct item *set, size_t nset)
{
    printf("{");
    for(size_t i = 0; i < nset; i++)
        printf("{%zu, %zu, %d}, ", set[i].prod_idx, set[i].dot, set[i].lookahead);
    printf("}\n");
}

size_t itemset_handle(struct item *set, size_t nset)
{
    // 1. is set in seen_sets
    for(size_t i = 0; i < nseen_sets; i++) {
        if(seen_sets[i].nitems != nset) continue;

        int _seen = 0;
        for(size_t j = 0; j < nset; j++) {
            _seen = 0;
            for(size_t k = 0; k < nset; k++)
                if(item_eq(&seen_sets[i].items[k], &set[j])) _seen = 1;
            if(!_seen) break;
        }
        if(_seen) return seen_sets[i].state;
    }

    // 2. add set to seen_sets
    if(nseen_sets >= SEEN_SETS_CAP) {
        fprintf(stderr, "ERROR: SEEN_SET_CAP exceeded\n");
        exit(1);
    }

    seen_sets[nseen_sets].items = xcalloc(nset, sizeof(*set));
    seen_sets[nseen_sets].nitems = nset;
    for(size_t i = 0; i < nset; i++)
        seen_sets[nseen_sets].items[i] = set[i];

    // 3. insert new state
    size_t new_state = seen_sets[nseen_sets++].state = table_states++;
    if(new_state >= TABLE_CAP) {
        fprintf(stderr, "ERROR: TABLE_CAP exceeded\n");
        exit(1);
    }

    if(itemset_insert(new_state, set, nset)) {
        fprintf(stderr, "ERROR: itemset_insert failed\n");
        exit(1);
    }

    return new_state;
}

#define CLOSURE_SET_CAP 64
#define GOTO_SET_CAP 32
int itemset_insert(size_t state, struct item *initial_set, size_t ninitial)
{
    struct item closure_set[CLOSURE_SET_CAP];

    size_t nclosure = itemset_closure(initial_set, ninitial, closure_set, CLOSURE_SET_CAP);
    if(nclosure > CLOSURE_SET_CAP) {
        fprintf(stderr, "ERROR: CLOSURE_SET_CAP exceeded\n");
        return 1;
    }

    for(size_t sym = 0; sym < total_symbols; sym++) {
        struct item goto_set[GOTO_SET_CAP];
        size_t ngoto = 0;

        for(size_t j = 0; j < nclosure; j++) {
            struct production *p = &grammar[closure_set[j].prod_idx];
            size_t dot = closure_set[j].dot;

            if(dot == p->nRHS) {
                if(sym != 0) continue;
                if(table_insert(state, closure_set[j].lookahead, (struct action) {
                            ACTION_REDUCE, closure_set[j].prod_idx}))
                    return 1;
                continue;
            }

            if(p->RHS[dot] == sym) {
                if(ngoto >= GOTO_SET_CAP) {
                    fprintf(stderr, "ERROR: GOTO_SET_CAP exceeded\n");
                    return 1;
                }
                goto_set[ngoto] = closure_set[j];
                goto_set[ngoto++].dot++;
            }
        }

        if(ngoto == 0) continue;
    
        if(symbol_is_input_end(sym)) {
            if(table_insert(state, sym, (struct action){ACTION_ACCEPT, 0}))
                return 1;
            continue;
        }

        size_t new_state = itemset_handle(goto_set, ngoto);

        if(table_insert(state, sym, (struct action){
                    symbol_is_terminal(sym) ? ACTION_SHIFT : ACTION_GOTO,
                    new_state})) return 1;
    }

    return 0;
}

size_t itemset_closure(struct item *in_set, size_t nin, struct item *out_set, size_t nout_max)
{
    size_t nout = nin;

    if(nout > nout_max) return nout;
    for(size_t i = 0; i < nin; i++) out_set[i] = in_set[i];

    int **is_in_closure = xcalloc(total_productions, sizeof(*is_in_closure));
    for(size_t i = 0; i < total_productions; i++)
        is_in_closure[i] = xcalloc(total_symbols, sizeof(**is_in_closure));
    
#define add_item(prod_idx, lookahead, ...) do {          \
        if(is_in_closure[prod_idx][lookahead]) break;    \
        is_in_closure[prod_idx][lookahead] = 1;          \
        if(nout++ >= nout_max) goto cleanup;             \
        out_set[nout-1] = __VA_ARGS__;                   \
    } while(0)    

    for(size_t i = 0; i < nout; i++)
    {
        struct production *p = &grammar[out_set[i].prod_idx];
        if(out_set[i].dot == p->nRHS) continue;
        symbol sym = p->RHS[out_set[i].dot];

        for(size_t j = 0; j < total_productions; j++)
            if(grammar[j].LHS == sym) {
                if(out_set[i].dot + 1 == p->nRHS) {
                    add_item(j, out_set[i].lookahead,
                             (struct item){j, 0, out_set[i].lookahead});
                    continue;
                }
                
                symbol next_symbol = p->RHS[out_set[i].dot+1];
                for(size_t terminal = 0; terminal < total_symbols; terminal++) {
                    if(!symbol_is_terminal(terminal)) continue;
                    if(first[next_symbol][terminal])
                        add_item(j, terminal, (struct item){j, 0, terminal});
                }
            }
    }

cleanup:
    for(size_t i = 0; i < total_productions; i++) free(is_in_closure[i]);
    free(is_in_closure);
    return nout;
}

int table_insert(size_t state, symbol sym, struct action a)
{
    if(table[state][sym].type != ACTION_NOT_SET) {
        fprintf(stderr, "TABLE COLLISION on state '%zu' sym '%d'\n", state, sym);
        fprintf(stderr, "\t{%d %zu} vs {%d %zu}\n",
                table[state][sym].type, table[state][sym].arg,
                a.type, a.arg);
        return 1;
    }

    table[state][sym] = a;
    return 0;
}

void table_print()
{
    printf("    ");
    for(size_t sym = 0; sym < total_symbols; sym++) printf("%2zu  ", sym);
    printf("\n");

    char action_to_char[] = {[ACTION_SHIFT] = 's', [ACTION_REDUCE] = 'r', [ACTION_GOTO] = 'g'};
    for(size_t i = 0; i < table_states; i++) {
        printf("%2zu  ", i);
        for(size_t sym = 0; sym < total_symbols; sym++)
            if(table[i][sym].type == ACTION_ACCEPT) printf(" a  ");
            else if(table[i][sym].type) printf("%c%-2zu ", action_to_char[table[i][sym].type], table[i][sym].arg);
            else printf("    ");
        printf("\n");
    }
}

#ifdef _CLR_TABLE_STANDALONE

#include "util-tables.c"

#ifndef CHOOSE_GRAMMAR
#define CHOOSE_GRAMMAR 1 // 0 or 1
#endif

enum symbol {
#if (CHOOSE_GRAMMAR == 0)    
    ID, EQUAL, STAR,
    END_INPUT,
    EP, E, L, R,
    SYMBOLS_END,
#else
    SC, SD,
    END_INPUT,
    EP, E, C,
    SYMBOLS_END
#endif
};

const size_t total_symbols = SYMBOLS_END;

int symbol_is_terminal(symbol s)    { return s < EP; }
int symbol_is_input_end(symbol s)   { return s == END_INPUT; }

#define PROD(LHS, _, ...) {LHS, (symbol[]){__VA_ARGS__}, sizeof((symbol[]){__VA_ARGS__})/sizeof(symbol)}
struct production grammar[] = {
#if (CHOOSE_GRAMMAR == 0)
    PROD(EP, ->, E, END_INPUT),
    PROD(E, -->, L, EQUAL, R),
    PROD(E, -->, R),
    PROD(L, -->, STAR, R),
    PROD(L, -->, ID),
    PROD(R, -->, L),
#else
    PROD(EP, ->, E, END_INPUT),
    PROD(E, -->, C, C),
    PROD(C, -->, SC, C),
    PROD(C, -->, SD),
#endif
};

const size_t total_productions = sizeof(grammar)/sizeof(*grammar);

int main(void)
{
    util_tables_fill();
    table_allocate();
    
    itemset_handle((struct item[]){{0, 0, END_INPUT}}, 1);
    table_print();

    seen_sets_free();
    table_free();
    util_tables_free();
}

#endif