How to map from cid to unicode

Question

Hello.
I'm now trying to convert cid to unicode by using the toUnicode cmap.
The toUnicode cmap I extracted is as follows:
/CIDInit /ProcSet findresource begin
12 dict begin
begincmap
/CIDSystemInfo
<< /Registry (Adobe)
/Ordering (UCS) /Supplement 0 >> def
/CMapName /Adobe-Identity-UCS def
/CMapType 2 def
1 begincodespacerange
<0000> <FFFF>
endcodespacerange
35 beginbfchar
<0F3B> <7528>
<0CA1> <8AAD>
<0F62> <5229>
<034B> <3042>
<034D> <3044>
<0358> <304F>
<027B> <3002>
<027C> <FF0C>
<035D> <3054>
<035E> <3055>
<0360> <3057>
<0369> <3060>
<0370> <3067>
<0372> <3069>
<0373> <306A>
<0294> <30FC>
<0374> <306B>
<0378> <306F>
<0388> <307F>
<0394> <308B>
<03A5> <30A9>
<02CE> <FF0A>
<03AF> <30B3>
<03B5> <30B9>
<03B9> <30BD>
<03BB> <30BF>
<03BF> <30C3>
<03C4> <30C8>
<03CD> <30D1>
<03D1> <30D5>
<03D2> <30D6>
<03DA> <30DE>
<03E8> <30EC>
<03EF> <30F3>
<08BC> <8A66>
endbfchar
endcmap CMapName currentdict /CMap defineresource pop end end
I think that the mapping process needs "beginbfrange" and "endbfrange."
But, the above cmap does not include them.
There should be a way to map from cid to unicode, because the Preview(Mac application) can search the same text.
Please let me know my lack of understanding on toUnicode cmap.

Answer 1

You might want to lookup ToUnicode maps in the standard. ISO 32000-1:2008 says in section 9.10.3 "ToUnicode CMaps":
The CMap defined in the ToUnicode entry of the font dictionary shall follow the syntax for CMaps introduced in 9.7.5, "CMaps" and fully documented in Adobe Technical Note #5014, Adobe CMap and CIDFont Files Specification. Additional guidance regarding the CMap defined in this entry is provided in Adobe Technical Note #5411, ToUnicode Mapping File Tutorial. This CMap differs from an ordinary one in these ways:
The only pertinent entry in the CMap stream dictionary (see Table 120) is UseCMap, which may be used if the CMap is based on another ToUnicode CMap.
The CMap file shall contain begincodespacerange and endcodespacerange operators that are consistent with the encoding that the font uses. In particular, for a simple font, the codespace shall be one byte long.
It shall use the beginbfchar, endbfchar, beginbfrange, and endbfrange operators to define the mapping from character codes to Unicode character sequences expressed in UTF-16BE encoding.