I'm currently using FontBox 1.0.0.
I encountered a problem with the CMapEncodingEntry.
When the subtableFormat is 2, an entry of the glyphidToCharacterCode array can be used for two different CharacterCodes.
In this case, it is impossible to obtain the GlyphId using the character code.
To avoid this problem and to access easyly to the GlyphId, I have added a Map (key : CharCode, Value : GlyphId).
In attachement, you can find the patch for this feature.