container/std: syscall JSON adapter

This provides cross-platform JSON adapter for syscall number.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/std/seccomp_test.go

@@ -0,0 +1,63 @@
+package std_test
+
+import (
+	"encoding/json"
+	"errors"
+	"math"
+	"reflect"
+	"syscall"
+	"testing"
+
+	"hakurei.app/container/std"
+)
+
+func TestScmpSyscall(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name string
+		data string
+		want std.ScmpSyscall
+		err  error
+	}{
+		{"select", `"select"`, syscall.SYS_SELECT, nil},
+		{"clone3", `"clone3"`, std.SYS_CLONE3, nil},
+
+		{"oob", `-2147483647`, -math.MaxInt32,
+			&json.UnmarshalTypeError{Value: "number", Type: reflect.TypeFor[string](), Offset: 11}},
+		{"name", `"nonexistent_syscall"`, -math.MaxInt32,
+			std.SyscallNameError("nonexistent_syscall")},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			t.Run("decode", func(t *testing.T) {
+				var got std.ScmpSyscall
+				if err := json.Unmarshal([]byte(tc.data), &got); !reflect.DeepEqual(err, tc.err) {
+					t.Fatalf("Unmarshal: error = %#v, want %#v", err, tc.err)
+				} else if err == nil && got != tc.want {
+					t.Errorf("Unmarshal: %v, want %v", got, tc.want)
+				}
+			})
+			if errors.As(tc.err, new(std.SyscallNameError)) {
+				return
+			}
+
+			t.Run("encode", func(t *testing.T) {
+				if got, err := json.Marshal(&tc.want); err != nil {
+					t.Fatalf("Marshal: error = %v", err)
+				} else if string(got) != tc.data {
+					t.Errorf("Marshal: %s, want %s", string(got), tc.data)
+				}
+			})
+		})
+	}
+
+	t.Run("error", func(t *testing.T) {
+		const want = `invalid syscall name "\x00"`
+		if got := std.SyscallNameError("\x00").Error(); got != want {
+			t.Fatalf("Error: %q, want %q", got, want)
+		}
+	})
+}