Converting specical characters in XML stream

Question

I have an XML stream which contains special characters such ' stored in a CString object. Is there any method other than replacing individual characters in the stream to convert these special characters ?

Answer 1

I frankly don't see another option.

Answer 2

If you can, install a filter in the writer. This allows you to write the stream char by char and replace the special characters when you encounter them (saving you from having to allocate a second string object).

Try to output as many characters of the string at once as possible because calling write() in a loop for every single character is expensive. Instead use this pseudo code:

int start = 0;
for (int i=0; i<str.length(); i++) {
    char c = str.getChar(i);
    String emit = null;
    switch (c) {
    case '<': emit = "&lt;"; break;
    case '>': emit = "&gt;"; break;
    case '\'': emit = "&apos;"; break;
    case '"': emit = "&quot;"; break;
    }
    if (emit != null) {
        write(str,start,i);
        start = i;
        write(emit);
    }
}
if (start != str.length()) {
    write(str);
}

In the common case, the loop will traverse the string once (which is fast) and call write() once.

If you can't install a filter in the writer, you can use the same code to filter the string. In the common case, you will simply return the input string. In the if (emit != null), you can then allocate a new copy. But since this will only happen if there are special characters in the string, this is much cheaper than creating a copy for every string.

Answer 3

The only characters that need escaping are " < > &.

But I would recommend the use a standard XML library. That would not only take care of escaping, but a lot of other problems (encoding, entities, validation, etc.)