Parsing RTF non-breaking space - parsing

Question

I am making a simple parser from RTF to HTML.
I have the following raw RTF:
who\\~nursed\\~and
According to the RTF specification \~ is the keyword for a non-breaking space.
The end of a keyword is marked by a Delimiter which is defined as follows:
A space. This serves only to delimit a control word and is ignored in subsequent processing.
A numeric digit or an ASCII minus sign (-), which indicates that a numeric parameter is associated with the control word. The subsequent digital sequence is then delimited by any character other than an ASCII digit (commonly another control word that begins with a backslash). The parameter can be a positive or negative decimal number. The range of the values for the number is nominally –32768 through 32767, i.e., a signed 16-bit integer. A small number of control words take values in the range −2,147,483,648 to 2,147,483,647 (32-bit signed integer). These control words include \binN, \revdttmN, \rsidN related control words and some picture properties like \bliptagN. Here N stands for the numeric parameter. An RTF parser must allow for up to 10 digits optionally preceded by a minus sign. If the delimiter is a space, it is discarded, that is, it’s not included in subsequent processing.
Any character other than a letter or a digit. In this case, the delimiting character terminates the control word and is not part of the control word. Such as a backslash “\”, which means a new control word or a control symbol follows.
As i understand it, the highlighted part above, is the rule used in this particular instance. But if that is the case, then my parser would read until the ~ sign, and conclude that since this is not a letter or a digit, it is not part of the keyword.
This currently results in the following output:
who~nursed~and
I have the following code for reading a keyword:
public GetKeyword(index: number): KeywordSet {
var keywordarray: string[] = [];
var valuearray: string[] = [];
index++;
while (index < this.m_input.length) {
var remainint = this.m_input.substr(index);
//Keep going until we hit a delimiter
if (this.m_input[index] == " ") {
index++;
break;
} else if (this.IsNumber(this.m_input[index])) {
valuearray.push(this.m_input[index]);
} else if (this.IsDelimiter(this.m_input[index])) {
break;
} else keywordarray.push(this.m_input[index]);
index++;
}
var value: number = null;
if (valuearray.length > 0) value = parseInt(valuearray.join(""));
var keywordset = new KeywordSet(keywordarray.join(""), index, value);
return keywordset;
}
private IsDelimiter(char: string): boolean {
if (char == "*" || char == "'") return false;
return !this.IsLetterOrDigit(char);
}
When GetKeyword() reaches "~" it recognises it as a delimiter, and stops reading, resulting in an empty keyword as return value.
I do not have an AST constructed for this. Don't think it is necessary for this?

Answer 1

The quote in your question describes the syntax of an entity called control word but the \~ is actually a different entity called control symbol. Control symbols have a different syntax:
Control Symbol
A control symbol consists of a backslash followed by a single, non-alphabetical character. For example, \~ (backslash tilde) represents a non-breaking space. Control symbols do not have delimiters, i.e., a space following a control symbol is treated as text, not a delimiter.
See page 9 of Rich Text Format (RTF) Specification, version 1.9.1.