Apply Base85 on Euphony

[nodobi]

AS-IS

There are various bases in Euphony, but the most effective among them is Base 64.
Base64 encodes each set of 3 bytes into 4 bytes, it causes an overhead of 33%

TO-BE

I think encoding with less overhead improves communication speed.
Base85 encodes each set of 4 bytes into 5 bytes, it causes an overhead of 25%.
It means Base85 is one of the more efficient Bases than the Base64
I know Base64 is more common and compatible than Base85, but I think it is also worth a try.

When encoding abcdefghijklmnopqrst with each base,
using Base64 is YWJjZGVmZ2hpamtsbW5vcHFyc3Q= (28 character),
and using Base85 is vpA.SwObN*x>?B1zeKohADlbx (25 character)

How

I will implement based on these test cases (using Z85)

::testing::Values(
        TestParamType(std::vector<u_int8_t>{ 0x05 }, "1P"),
        TestParamType(std::vector<u_int8_t>{ 0x60 }, "u&"),
        TestParamType(std::vector<u_int8_t>{ 0x63 }, "v/"),
        TestParamType(std::vector<u_int8_t>{ 0x99 }, "Ne"),
        TestParamType(std::vector<u_int8_t>{ 0x98 }, "M&"),
        TestParamType(std::vector<u_int8_t>{ 0xa8, 0xe9 }, "SoB"),
        TestParamType(std::vector<u_int8_t>{ 0xab, 0xcd }, "Tiy"),
        TestParamType(std::vector<u_int8_t>{ 0x3d, 0x2e }, "jUu"),
        TestParamType(std::vector<u_int8_t>{ 0x4d, 0x5b }, "o<m"),
        TestParamType(std::vector<u_int8_t>{ 0x9a, 0xc7 }, "N-t"),
        TestParamType(std::vector<u_int8_t>{ 0xaa, 0xbb }, "S>e"),
        TestParamType(std::vector<u_int8_t>{ 0x61, 0x62, 0x63 }, ""),
        TestParamType(std::vector<u_int8_t>{ 0x6c, 0x6d, 0x6e, 0x6f }, "vpAZ"),
        TestParamType(std::vector<u_int8_t>{ 0x12, 0x34, 0x5a, 0x9f }, "5&r^:"),
        TestParamType(std::vector<u_int8_t>{ 0x67, 0x6f, 0x6f, 0x64 }, "xk.Z0"),
        TestParamType(std::vector<u_int8_t>{ 0xff, 0xff, 0xff, 0xff }, "%nSc0"),
        TestParamType(std::vector<u_int8_t>{ 0x10, 0x0, 0x0, 0x0, 0x0, 0x0 }, "5c8Xg000"),
        TestParamType(std::vector<u_int8_t>{ 0xc0, 0xde, 0xba, 0x5e, 0xba, 0x11 }, "Z$#UeX!a"),
        TestParamType(std::vector<u_int8_t>{
            0x6f, 0x3c, 0x4e, 0x5a,
            0x6b, 0x2d, 0x1c, 0xaa
            }, "z-*=#yB{Ka"),
        TestParamType(std::vector<u_int8_t>{
            0xa1, 0x29, 0x9b, 0x71,
            0x33, 0x09, 0x8e, 0x1f
            }, "P^=EJgyo6-"),
        TestParamType(std::vector<u_int8_t>{
            0x9f, 0x1b, 0x3c, 0x44,
            0x55, 0x1d, 0x99, 0x80,
            0x72, 0x17, 0x22, 0xcf
            }, "PbP)XrumGTAU/}C")
));