#include <shared/syscalls.h>
#include <stdint.h>

extern int tty_fd;

static int oct_parse(char *str, size_t len);
int memcmp(const void *s1, const void *s2, size_t n); // TODO move to a dedicated file


void tar_driver(void *base) {
	// iterate over all sectors, printing filenames
	while (0 == memcmp(base + 257, "ustar", 5)) {
		int size = oct_parse(base + 124, 12);

		_syscall_write(tty_fd, base, 100);
		_syscall_write(tty_fd, " ", 1);

		base += 512;                 // skip metadata sector
		base += (size + 511) & ~511; // skip file (size rounded up to 512)
		// TODO might pagefault if the last sector was at a page boundary
	}
	_syscall_write(tty_fd, "done.", 5);
}

static int oct_parse(char *str, size_t len) {
	int res = 0;
	for (size_t i = 0; i < len; i++) {
		res *= 8;
		res += str[i] - '0'; // no format checking
	}
	return res;
}

int memcmp(const void *s1, const void *s2, size_t n) {
	const unsigned char *c1 = s1, *c2 = s2;
	for (size_t i = 0; i < n; i++) {
		if (c1[i] != c2[i]) {
			if (c1[i] < c2[i])  return -1;
			else                return 1;
		}
	}
	return 0;
}