How to get Unicode text from known Tj operators


`i have some Tj operators read from my PDF, like (\000\003) Tj or [<d7a1b7bfb3c7cfe7bda8c9e8ccfcd0c5cfa2b9abbfaae4afc0c0d7a8d3c3>] TJ`

i can get the actual unicode text by itextsharp , 

But I don't know how to get these actual unicode texts by pdfiumcore api (cmap to unicode)

core/fpdfapi/font/cpdf_cmap.cpp
core/fpdfapi/cmaps/fpdf_cmaps.cpp

do you have any idea ?