return "", "", s, ErrHeader
	}
	n -= int64(len(nStr) + 1) // convert from index in s to index in rest
	if n <= 0 {
		return "", "", s, ErrHeader
	}

	// Extract everything between the space and the final newline.
	rec, nl, rem := rest[:n-1], rest[n-1:n], rest[n:]
	if nl != "\n" {
		return "", "", s, ErrHeader
	}

	// The first equals separates the key from the value.

		if v.ok && (key != v.wantKey || val != v.wantVal) {
			t.Errorf("parsePAXRecord(%q): got (%q: %q), want (%q: %q)",
				v.in, key, val, v.wantKey, v.wantVal)
		}
		if res != v.wantRes {
			t.Errorf("parsePAXRecord(%q): got residual %q, want residual %q",
				v.in, res, v.wantRes)
		}
	}
}

func TestFormatPAXRecord(t *testing.T) {
	medName := strings.Repeat("CD", 50)
	longName := strings.Repeat("AB", 100)