fn charTo6Bit(c: u8) u8
fn charTo6Bit(c: u8) u8 { return switch (c) { 'a'...'z' => c - 'a', 'A'...'Z' => c - 'A' + 26, '0'...'9' => c - '0' + 52, '.' => 62, '_' => 63, else => @panic("Failed to encode byte as 6-bit char"), }; }