In essence, they are `[]byte` -> `[]byte, error` functions.

It is not possible to return *both* an error and a response.

Handlers are registered on the manager using `(*Manager).RegisterSingleHandler(id HandlerID, h SingleHandlerFn, subroute ...string)`.

The server handler function has this signature: `type SingleHandlerFn func(payload []byte) ([]byte, *RemoteErr)`.

Sample handler:
```go

		t.Fatalf("Unable to create a file \"as-directory/as-file\", %s", err)
	}
	if err = xlStorage.AppendFile(t.Context(), "exists", "as-file", []byte("Hello, World")); err != nil {
		t.Fatalf("Unable to create a file \"as-file\", %s", err)
	}
	if err = xlStorage.AppendFile(t.Context(), "exists", "as-file-parent", []byte("Hello, World")); err != nil {

}

// Split functions

// ScanBytes is a split function for a [Scanner] that returns each byte as a token.
func ScanBytes(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) == 0 {
		return 0, nil, nil
	}
	return 1, data[0:1], nil
}

var errorRune = []byte(string(utf8.RuneError))

// ScanRunes is a split function for a [Scanner] that returns each

	fieldValue := reflect.New(field.FieldType)

	if dbValue != nil {
		var bytes []byte
		switch v := dbValue.(type) {
		case []byte:
			bytes = v
		case string:
			bytes = []byte(v)
		default:
			bytes, err = json.Marshal(v)
			if err != nil {
				return err
			}
		}

		if len(bytes) > 0 {

		for range SplitSeq(benchInputHard, nil) {
		}
	}
}

func BenchmarkSplitSeqSingleByteSeparator(b *testing.B) {
	sep := []byte("/")
	for range b.N {
		for range SplitSeq(benchInputHard, sep) {
		}
	}
}

func BenchmarkSplitSeqMultiByteSeparator(b *testing.B) {
	sep := []byte("hello")
	for range b.N {
		for range SplitSeq(benchInputHard, sep) {
		}
	}
}

// MarshalMsg implements msgp.Marshaler
func (z BatchJobPrefix) MarshalMsg(b []byte) (o []byte, err error) {
	o = msgp.Require(b, z.Msgsize())
	o = msgp.AppendArrayHeader(o, uint32(len(z)))
	for zb0003 := range z {
		o = msgp.AppendString(o, z[zb0003])
	}
	return
}

// UnmarshalMsg implements msgp.Unmarshaler
func (z *BatchJobPrefix) UnmarshalMsg(bts []byte) (o []byte, err error) {
	var zb0002 uint32

			}
		})
	}
}

func TestCSVQueries2(t *testing.T) {
	testInput := []byte(`id,time,num,num2,text
1,2010-01-01T,7867786,4565.908123,"a text, with comma"
2,2017-01-02T03:04Z,-5, 0.765111,
`)
	testTable := []struct {
		name       string
		query      string
		input      []byte
		requestXML []byte // override request XML
		wantResult string
	}{
		{
			name:       "select-all",

    int bits = iterator.next().bits();
    byte[] resultBytes = new byte[bits / 8];
    for (HashCode hashCode : hashCodes) {
      byte[] nextBytes = hashCode.asBytes();
      checkArgument(
          nextBytes.length == resultBytes.length, "All hashcodes must have the same bit length.");
      for (int i = 0; i < nextBytes.length; i++) {
        resultBytes[i] = (byte) (resultBytes[i] * 37 ^ nextBytes[i]);
      }
    }

	}
	return true, ""
}

func TestCmpReaders(t *testing.T) {
	{
		r1 := bytes.NewReader([]byte("abc"))
		r2 := bytes.NewReader([]byte("abc"))
		ok, msg := cmpReaders(r1, r2)
		if !ok || msg != "" {
			t.Fatalf("unexpected")
		}
	}

	{
		r1 := bytes.NewReader([]byte("abc"))
		r2 := bytes.NewReader([]byte("abcd"))
		ok, _ := cmpReaders(r1, r2)
		if ok {
			t.Fatalf("unexpected")
		}
	}

			sw.sp = sw.sp[1:] // Ensure last fragment always remains
		}
	}

	// If the last fragment is a hole, then seek to 1-byte before EOF, and
	// read a single byte to ensure the file is the right size.
	if readLastByte && err == nil {
		_, err = mustReadFull(rs, []byte{0})
		sw.pos++
	}

	n = sw.pos - pos0
	switch {
	case err == io.EOF:
		return n, io.ErrUnexpectedEOF