Adds values to the list, in every form an output can write them.
Secret values, such as a bank's credentials.
How many forms the list now holds.
Finds every known value in a text, and any mask already there.
Any text an output is about to write.
A span for each, which writes the mask. Spans can overlap, and
writeSpans joins those that do.
Replaces every known value in a text with the mask.
Any text an output is about to write.
The text with each known value masked.
A growing list of secret values, and the text masker they make.