ident: implement system identifier

Signed-off-by: Yonah <contrib@gensokyo.uk>

ident/system_test.go

@@ -0,0 +1,55 @@
+package ident_test
+
+import (
+	"encoding/base64"
+	"strings"
+	"testing"
+	"time"
+
+	"git.gensokyo.uk/cofront/cof-spec/ident"
+)
+
+func TestS(t *testing.T) {
+	t.Parallel()
+
+	rTestCases[ident.S, *ident.S]{
+		{"short", ident.S{}, nil, &ident.UnexpectedSizeError{
+			Data: nil,
+			Want: ident.EncodedSizeSystem,
+		}},
+
+		{"malformed", ident.S{}, []byte{
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+			0xfe, 0xe1, 0xde, 0xad,
+		}, base64.CorruptInputError(0)},
+
+		{"newline", ident.S{}, []byte(
+			"AAAA" + strings.Repeat("\n", ident.EncodedSizeSystem-4),
+		), ident.ErrNewline},
+
+		{"valid", ident.S{
+			Site: ident.TrivialSite,
+			Host: ident.TrivialHost,
+
+			Time: uint64(time.Date(
+				0xfd, 7, 15,
+				23, 59, 59, 0xcafe,
+				time.UTC,
+			).UnixNano()),
+
+			ID: 0xfee1dead0badf00d,
+		}, base64.URLEncoding.AppendEncode(nil, []byte{
+			/* site: */ 0xfe, 0xca, 0xed, 0xfe,
+			/* host: */ 0xbe, 0xba, 0xfe, 0xca,
+
+			/* time: */ 0xfe, 0, 0x43, 0xce, 0xf1, 0x92, 0x4a, 0x10,
+			/* id:   */ 0xd, 0xf0, 0xad, 0xb, 0xad, 0xde, 0xe1, 0xfe,
+		}), nil},
+	}.run(t)
+}