d.scratch.addRune(r)
		goto scan_esc
	}

	r2 := d.u4()
	if r2 < 0 {
		return "", d.mkError(ErrSyntax, "in unicode escape sequence")
	}

	// write surrogate pair
	d.scratch.addRune(utf16.DecodeRune(r, r2))
	c = d.next()
	goto scan
}

// u4 reads four bytes following a \u escape
func (d *Decoder) u4() rune {
	// logic taken from:
	// github.com/buger/jsonparser/blob/master/escape.go#L20