Base64Encoder example

        /* RFC 2045, 6.8 The encoding process represents 24-bit groups of input bits as output strings of 4 encoded characters. Proceeding from left to right, a 24-bit input group is formed by concatenating 3 8bit input groups. These 24 bits are then treated as 4 concatenated 6-bit groups, each of which is translated into a single digit in the base64 alphabet. */

        $encoder = new Base64Encoder();
        $this->assertEquals('MTIz', $encoder->encodeString('123'), '3 bytes of input should yield 4 bytes of output');
        $this->assertEquals('MTIzNDU2', $encoder->encodeString('123456'), '6 bytes in input should yield 8 bytes of output');
        $this->assertEquals('MTIzNDU2Nzg5', $encoder->encodeString('123456789'), '%s: 9 bytes in input should yield 12 bytes of output');
    }

    public function testPadLength()
    {
        /* RFC 2045, 6.8 Special processing is performed if fewer than 24 bits are available at the end of the data being encoded. A full encoding quantum is always completed at the end of a body. When fewer than 24 input bits are available in an input group, zero bits are added (on the right) to form an integral number of 6-bit groups. Padding at the end of the data is performed using the "=" character. Since all base64 input is an integral number of octets, only the following cases can arise: (1) the final quantum of encoding input is an integral multiple of 24 bits; here, the final unit of encoded output will be an integral multiple of 4 characters with no "=" padding, (2) the final quantum of encoding input is exactly 8 bits; here, the final unit of encoded output will be two characters followed by two "=" padding characters, or (3) the final quantum of encoding input is exactly 16 bits; here, the final unit of encoded output will be three characters followed by one "=" padding character. */