+string
+TextDecoder::remove_invalid_characters_for_xml(string text)
+{
+ string output;
+
+ /* https://www.w3.org/TR/REC-xml/#charsets says that XML may only contain 0x9, 0xa, 0xd below 0x32.
+ * Not sure if we should be doing direct UTF-8 manipulation here.
+ */
+ for (size_t i = 0; i < text.length(); ++i) {
+ auto const c = text[i];
+ if ((c & 0xe0) == 0xc0) {
+ // start of 2-byte code point
+ output += c;
+ output += text[i + 1];
+ ++i;
+ } else if ((c & 0xf0) == 0xe0) {
+ // start of 3-byte code point
+ output += c;
+ output += text[i + 1];
+ output += text[i + 2];
+ i += 2;
+ } else if ((c & 0xf8) == 0xf0) {
+ // start of 4-byte code point
+ output += c;
+ output += text[i + 1];
+ output += text[i + 2];
+ output += text[i + 3];
+ i += 3;
+ } else {
+ if (c >= 0x20 || c == 0x9 || c == 0xa || c == 0xd) {
+ output += c;
+ }
+ }
+ }
+
+ return output;
+}
+
+