sleq(t, ws.BytesWritten(), wpex)
	rf(t, ws, []byte{})

	// seeks and reads.
	sk(t, ws, 1, io.SeekStart)
	rf(t, ws, []byte{2, 7})
	sk(t, ws, -2, io.SeekCurrent)
	rf(t, ws, []byte{2, 7})
	sk(t, ws, -4, io.SeekEnd)
	rf(t, ws, []byte{2, 7})
	off := sk(t, ws, 0, io.SeekEnd)
	sk(t, ws, off, io.SeekStart)

	// seek back and overwrite
	sk(t, ws, 1, io.SeekStart)
	wf(t, ws, []byte{9, 11})
	wpex = []byte{1, 9, 11, 8, 9}

	{0x1bb2, "Nd"},
	{0x10147, "Nl"},
	{0x2478, "No"},
	{0xfe33, "Pc"},
	{0x2011, "Pd"},
	{0x301e, "Pe"},
	{0x2e03, "Pf"},
	{0x2e02, "Pi"},
	{0x0022, "Po"},
	{0x2770, "Ps"},
	{0x00a4, "Sc"},
	{0xa711, "Sk"},
	{0x25f9, "Sm"},
	{0x2108, "So"},
	{0x2028, "Zl"},
	{0x2029, "Zp"},
	{0x202f, "Zs"},
	// Unifieds.
	{0x04aa, "L"},
	{0x0009, "C"},
	{0x1712, "M"},
	{0x0031, "N"},
	{0x00bb, "P"},
	{0x00a2, "S"},

since those use the underlying algorithm. This list is sent to the client if
it supports the server-sig-algs extension. Order is irrelevant.

Valid values
```
ssh-ed25519
sk******@****.***
sk******@****.***
ecdsa-sha2-nistp256
ecdsa-sha2-nistp384
ecdsa-sha2-nistp521
rsa-sha2-256
rsa-sha2-512
ssh-rsa
ssh-dss
```

//    Rule: Never break between consecutive runes of this category.
//
// 2) Mid:
//    MidLetter, MidNumLet, Single_Quote.
//    (Cf. case-ignorable: MidLetter, MidNumLet, Single_Quote or cat is Mn,
//    Me, Cf, Lm or Sk).
//    Rule: Don't break between Letter and Mid, but break between two Mids.
//
// 3) Break:
//    Any other category: NewLine, MidNum, CR, LF, Double_Quote, Katakana, and
//    Other.

qu: Runa Simi
rm: rumantsch grischun
rn: Ikirundi
ro: Română
ru: русский язык
rw: Ikinyarwanda
sa: संस्कृतम्
sc: sardu
sd: सिन्धी
se: Davvisámegiella
sg: yângâ tî sängö
si: සිංහල
sk: slovenčina
sl: slovenščina
sn: chiShona
so: Soomaaliga
sq: shqip
sr: српски језик
ss: SiSwati
st: Sesotho
su: Basa Sunda
sv: svenska
sw: Kiswahili
ta: தமிழ்
te: తెలుగు
tg: тоҷикӣ

04F02F02F12F03U03"],["NL",18,"U04F10"],["NO",15,"F04F06F01"],["PK",24,"U04A16"],["PL",28,"F08F16"],["PS",29,"U04A21"],["PT",25,"F04F04F11F02"],["RO",24,"U04A16"],["RS",22,"F03F13F02"],["SA",24,"F02A18"],["SE",24,"F03F16F01"],["SI",19,"F05F08F02"],["SK",24,"F04F06F10"],["SM",27,"U01F05F05A12"],["ST",25,"F08F11F02"],["TL",23,"F03F14F02"],["TN",24,"F02F03F13F02"],["TR",26,"F05F01A16"],["VG",24,"U04F16"],["XK",20,"F04F10F02"],["AO",25,"F21"],["BF",27,"F23"],["BI",16,"F12"],["BJ",28,"F24"],["CI",28,"...

000002e0  69 4b a8 51 ee de b3 b0  f7 1a 57 a3 28 72 d2 13  |iK.Q......W.(r..|
000002f0  a6 d3 17 0b c4 45 34 7f  10 3b 81 cb 0c 8d 51 b6  |.....E4..;....Q.|
00000300  0b 86 21 d0 ee 1d 7e 73  6b ea 77 8c 66 dc 65 16  |..!...~sk.w.f.e.|
00000310  03 03 00 04 0e 00 00 00                           |........|
>>> Flow 3 (client to server)
00000000  16 03 03 00 25 10 00 00  21 20 ed 3e ba a7 43 53  |....%...! .>..CS|

00000110  a9 54 af 0b 55 e2 d3 35  73 56 9b 9a 19 fd 93 9a  |.T..U..5sV......|
00000120  21 c3 5f f8 cf fe e0 a1  63 62 b8 58 bf 35 29 1d  |!._.....cb.X.5).|
00000130  69 58 f6 d3 e8 60 66 1b  db 53 4b 26 0b 78 d9 5e  |iX...`f..SK&.x.^|
00000140  73 d5 34 5a 11 57 98 8d  0c 9f 85 28 80 a4 ee 47  |s.4Z.W.....(...G|
00000150  f8 23 ca 31 7a 24 d5 dd  9b 49 7b 62 ab e5 69 fa  |.#.1z$...I{b..i.|

var Sentence_Terminal <type 1>;
var Sharada <type 1>;
var Shavian <type 1>;
var Siddham <type 1>;
var SignWriting <type 1>;
func SimpleFold (r <type -21>) <type -21>;
var Sinhala <type 1>;
var Sk <type 1>;
var Sm <type 1>;
var So <type 1>;
var Soft_Dotted <type 1>;
var Sora_Sompeng <type 1>;
var Space <type 1>;
type <type 10>;
var Sundanese <type 1>;
var Syloti_Nagri <type 1>;