braille.c

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

unsigned char convert(unsigned char c)
{
	return (c & 0x40) << 1
	     | (c & 0x07) << 4
	     | (c & 0x80) >> 4
	     | (c & 0x38) >> 3;
}

void execute(unsigned char *tape, size_t dp)
{
	unsigned char insn, arg;
	size_t ip = 0;

	while (++ip) {
		insn = tape[ip] & 0xf0;
		arg  = tape[ip] & 0x0f;

		switch (insn) {
			case 0x00: exit(arg); break;
			case 0x10: *tape += tape[dp + arg]; break;
			case 0x20: *tape -= tape[dp + arg]; break;
			case 0x30: tape[dp + arg] = *tape; break;
			case 0x40: *tape = tape[dp] + arg; break;
			case 0x50: dp += 1 << arg; break;
			case 0x60: dp -= 1 << arg; break;
			case 0x70: ip += arg + 1; break;
			case 0x80: ip -= arg + 2; break;
			case 0x90: if (!*tape) ip += arg + 1; break;
			case 0xa0: if (!*tape) ip -= arg + 2; break;
			case 0xb0: if (*tape) ip += arg + 1; break;
			case 0xc0: if (*tape) ip -= arg + 2; break;
			case 0xd0: tape[dp + arg] = getchar(); break;
			case 0xe0: putchar(tape[dp + arg]); break;
			case 0xf0: tape[dp + arg] = rand() >> 7; break;
		}
	}
}

int main(int argc, char **argv)
{
	int c;
	FILE *src;
	size_t cap = 1, len = 1;
	unsigned char *tape = calloc(1, 1);

	if (argc != 2)
		return fprintf(stderr, "Usage: %s FILE\n", *argv);

	if (!(src = fopen(argv[1], "r")))
		return fprintf(stderr, "Unable to open file '%s'\n", argv[1]);

	while ((c = fgetc(src)) != EOF) {
		if (c == 0xe2) {
			int c2 = fgetc(src); if(c2 == EOF) break;
			int c3 = fgetc(src); if(c3 == EOF) break;
			if(c2 >= 0xa0 && c2 <= 0xa3) { /* found Braille character */
				c = convert((c2 - 0xa0) * 0x40 + (c3 - 0x80));
				if (cap == len)
					tape = realloc(tape, cap <<= 1);
				tape[len++] = c;
			}
		}
	}

	srand((intptr_t) &c);
	execute(tape, len);

	fclose(src);
	free(tape);
	return 0;
}