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grammar.c
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grammar.c
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#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <err.h>
#include "tokens.h"
#include "grammar.h"
// #define VERBOSE_GRAMMAR_DEBUG
int
get_id_for_rule(grammar *g, char *rule) {
int i;
for(i = 0; g->lastrule >= i; i++) {
if(strcmp(rule, g->rules[i].name) == 0) {
return i;
}
}
g->lastrule++;
assert(g->lastrule < sizeof(g->rules) / sizeof(struct rule));
memset(&g->rules[g->lastrule], 0, sizeof(struct rule));
g->rules[g->lastrule].id = g->lastrule;
g->rules[g->lastrule].name = strdup(rule);
#ifdef VERBOSE_GRAMMAR_DEBUG
printf("Creating rule %d for %s\n", g->lastrule, rule);
#endif
return g->lastrule;
}
struct rulepart *
parse_branch(grammar *g, char *str) {
char *part, *tokenizer;
struct rulepart *head;
struct rulepart **tail = &head;
assert(strchr(str, '|') == NULL);
part = strtok_r(str, " ", &tokenizer);
do {
// Handle part
*tail = malloc(sizeof(struct rulepart));
if(part[0] == '\'' && part[2] == '\'' && part[3] == 0) {
(*tail)->is_literal = 1;
(*tail)->token = part[1];
} else if(((*tail)->token = string_to_token(part)) != 0) {
(*tail)->is_literal = 1;
} else {
(*tail)->is_literal = 0;
(*tail)->rule = get_id_for_rule(g, part);
}
tail = &(*tail)->next;
} while((part = strtok_r(NULL, " ", &tokenizer)) != NULL);
*tail = NULL;
return head;
}
grammar *
parse_grammar(char *file) {
FILE *fh = fopen(file, "r");
if(fh == NULL) {
perror("Could not load grammar");
abort();
}
char buf[1024];
grammar *g = malloc(sizeof(grammar));
g->lastrule = -1;
while(!feof(fh)) {
char *def;
if(fgets(buf, sizeof(buf), fh) == NULL) {
if(feof(fh)) {
break;
}
err(1, "fgets");
}
if(buf[0] == '#') {
continue;
}
def = strstr(buf, " := ");
assert(def != NULL);
*def = 0;
def += 4;
def[strlen(def) - 1] = 0;
#ifdef VERBOSE_GRAMMAR_DEBUG
printf("'%s': '%s'\n", buf, def);
#endif
struct rule *rule = &g->rules[get_id_for_rule(g, buf)];
int branchno = 0;
char *nextbranch = def;
do {
char *branch = nextbranch;
nextbranch = strstr(branch, " | ");
if(nextbranch != NULL) {
*nextbranch = 0;
nextbranch += 3;
}
rule->branches[branchno++] = parse_branch(g, branch);
assert(branchno < (sizeof(rule->branches) / sizeof(struct rulepart *)));
} while(nextbranch != NULL);
#ifdef VERBOSE_GRAMMAR_DEBUG
printf("Found %d branches for rule %s\n", branchno, rule->name);
#endif
}
fclose(fh);
return g;
}
void
show_grammar(grammar *g) {
int i;
for(i = 0; g->lastrule >= i; i++) {
if(g->rules[i].branches[0] == NULL) {
fprintf(stderr, "Rule %s (#%d) not defined\n", g->rules[i].name, i);
continue;
}
#ifdef VERBOSE_GRAMMAR_DEBUG
printf("Rule %s :=\n", g->rules[i].name);
#endif
int b;
for(b = 0; g->rules[i].branches[b] != NULL; b++) {
struct rulepart *p = g->rules[i].branches[b];
printf("\t");
do {
if(p->is_literal) {
printf("%s ", token_to_string(p->token));
} else {
printf("%s ", g->rules[p->rule].name);
}
} while((p = p->next) != NULL);
printf("\n");
}
}
}