modal/src/modal.c

#include <stdio.h>

/* dict */

static char dict[0x8000], *next = dict;

static char *
save(char *s, char c)
{
	char *o = next;
	while((*next++ = *s++) && *s)
		;
	*next++ = c;
	return o;
}

static char *
push(char *s, char c)
{
	char *d = dict;
	for(d = dict; d < next; d++) {
		char *ss = s, *dd = d, a, b;
		while((a = *dd++) == (b = *ss++))
			if(!a && !b) return d;
	}
	return save(s, c);
}

/* rule */

typedef struct {
	char *a;
	char *b;
} Rule;

static int rules_len;
static Rule rules[0x100];

static void
addrule(FILE *f)
{
	int depth = 0;
	char c, *left, *right;
	left = next;
	while(f && fread(&c, 1, 1, f) && c && c != 0xa) {
		if(c == '(') depth++;
		if(c == ')') --depth;
		if(c == ' ' && !depth)
			break;
		else
			*next++ = c;
	}
	*next++ = 0;

	right = next;
	while(f && fread(&c, 1, 1, f) && c && c != 0xa) {
		if(c == '(') depth++;
		if(c == ')') --depth;
		if(c == ' ' && !depth)
			break;
		else
			*next++ = c;
	}
	*next++ = 0;

	printf("rule: %s -> %s\n", left, right);
}

/* program */

static char program[0x1000], *prog_ = program;

static void
addprogram(FILE *f)
{
	char c;
	while(f && fread(&c, 1, 1, f) && c && c != 0xa)
		*prog_++ = c;
	*prog_++ = 0x20;
}

static void
tokenize(char *t, FILE *f)
{
	if(t[0] == '<' && t[1] == '>') {
		addrule(f);
		return;
	}
	addprogram(f);
}

static int
walk(FILE *f)
{
	char c, token[0x40], *tokptr;
	tokptr = token;
	while(f && fread(&c, 1, 1, f)) {
		if(c < 0x21)
			*tokptr++ = 0x00, tokenize(token, f), tokptr = token;
		else if(tokptr - token < 0x3f)
			*tokptr++ = c;
		else
			return printf("Token too long: %s\n", token);
	}
	*tokptr++ = 0x00, tokenize(token, f), tokptr = token;
	return 1;
}

static void
display(Rule *r, char *p)
{
	printf("Program: %s\n", p);
}

static int
eval(char *path)
{
	FILE *f;
	if(!(f = fopen(path, "r")))
		return !printf("Invalid file: %s\n", path);
	walk(f);
	display(rules, program);
	fclose(f);
	return 1;
}

int
main(int argc, char **argv)
{
	if(argc < 2)
		return !printf("usage: modal [-v] source.modal\n");
	if(argc < 3 && argv[1][0] == '-' && argv[1][1] == 'v')
		return !printf("Modal - Modal Interpreter, 3 Apr 2024.\n");
	return !eval(argv[1]);
}