// errors — error type (a string) and a few sentinels. Plan 9 model:
// the empty string means OK, a non-empty string is the message.

type error = str;

def eEOF:        error = "eof";
def eShortRead:  error = "short read";
def eShortWrite: error = "short write";
def eClosed:     error = "closed";
def eInvalid:    error = "invalid argument";
def ePerm:       error = "permission denied";
def eNotFound:   error = "not found";
def eExists:     error = "already exists";

export fn isnil(e: error) bool = {
	return e.len == 0;
};

// is — compare an error against a sentinel (or any other error). Pure
// byte equality; same shape as strings.equal but kept here so callers
// don't have to pull in strings just to compare.
export fn is(e: error, want: error) bool = {
	if (e.len != want.len) { return false; };
	let i: i32 = 0;
	for (i < e.len) {
		if (e[i] != want[i]) { return false; };
		i += 1;
	};
	return true;
};