Question about CFF arithmetic operator dup
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Question about CFF arithmetic operator dup
by Ning Dong
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Hi,
I'm checking the cff_decoder_parse_charstrings function in cffgload.c of
FT239.
According to CFF technical note #5177, operator "dup" should
consume one element and put two elements to arguement stack:
dup any dup(12 27) any
any
But in cff_decoder_parse_charstrings, the codes like this:
case cff_op_dup:
FT_TRACE4(( " dup\n" ));
args[1] = args[0];
args++; //should
be args+=2?
break; Only one element put to arguement
stack.
Is this a bug?
FT2310 is the same.
2009-10-09
Ning Dong
_______________________________________________ Freetype-devel mailing list Freetype-devel@... http://lists.nongnu.org/mailman/listinfo/freetype-devel |
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Re: Question about CFF arithmetic operator dup
by Graham Asher
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The net effect of consuming one element and adding two is to add one.
The code looks correct to me. Graham Asher Ning Dong wrote: > Hi, > > I'm checking the cff_decoder_parse_charstrings function in cffgload.c > of FT239. > > According to CFF technical note #5177, operator "dup" should > consume one element and put two elements to arguement stack: > dup any dup(12 27) any any > > But in cff_decoder_parse_charstrings, the codes like this: > case cff_op_dup: > FT_TRACE4(( " dup\n" )); > args[1] = args[0]; > args++; //should be args+=2? > break; > Only one element put to arguement stack. > > Is this a bug? > FT2310 is the same. > 2009-10-09 > ------------------------------------------------------------------------ > Ning Dong > ------------------------------------------------------------------------ > > _______________________________________________ > Freetype-devel mailing list > Freetype-devel@... > http://lists.nongnu.org/mailman/listinfo/freetype-devel > _______________________________________________ Freetype-devel mailing list Freetype-devel@... http://lists.nongnu.org/mailman/listinfo/freetype-devel |
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Re: Re: Question about CFF arithmetic operator dup
by Ning Dong
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The reqiured arguement num of cff_op_dup defined in cff_argument_counts is 1. Before processing cff_op_dup, agrs minus 1 to points the first arguement of cff_op_dup. The comment said:
/* At this point, `args' points to the first argument of the */ /* operand in case `req_args' isn't zero. Otherwise, we have */ /* to adjust `args' manually. */ So, if cff_op_dup duplicates args[0], args should add 2 to keep these two elements on stack. According to codes of cff_op_abs, cff_op_and and cff_op_exch processing: case cff_op_abs: FT_TRACE4(( " abs\n" )); if ( args[0] < 0 ) args[0] = -args[0]; args++; break; case cff_op_add: FT_TRACE4(( " add\n" )); args[0] += args[1]; args++; break; case cff_op_exch: { FT_Fixed tmp; FT_TRACE4(( " exch\n" )); tmp = args[0]; args[0] = args[1]; args[1] = tmp; args += 2; } break; cff_op_abs consumes 1 and push 1, args++ is right; cff_op_add consumes 2 and push 1, args++ is right; cff_op_exch consumes 2 and push 2, args +=2 is right; cff_op_dup consumes 1 and push 2, args +=2 should be right; ------------------ Ning Dong 2009-10-10 ------------------------------------------------------------- 发件人：Graham Asher 发送日期：2009-10-09 22:48:53 收件人：flintning 抄送：freetype-devel 主题：Re: [ft-devel] Question about CFF arithmetic operator dup The net effect of consuming one element and adding two is to add one. The code looks correct to me. Graham Asher Ning Dong wrote: > Hi, > > I'm checking the cff_decoder_parse_charstrings function in cffgload.c > of FT239. > > According to CFF technical note #5177, operator "dup" should > consume one element and put two elements to arguement stack: > dup any dup(12 27) any any > > But in cff_decoder_parse_charstrings, the codes like this: > case cff_op_dup: > FT_TRACE4(( " dup\n" )); > args[1] = args[0]; > args++; //should be args+=2? > break; > Only one element put to arguement stack. > > Is this a bug? > FT2310 is the same. > 2009-10-09 > ------------------------------------------------------------------------ > Ning Dong > ------------------------------------------------------------------------ > > _______________________________________________ > Freetype-devel mailing list > Freetype-devel@... > http://lists.nongnu.org/mailman/listinfo/freetype-devel > _______________________________________________ Freetype-devel mailing list Freetype-devel@... http://lists.nongnu.org/mailman/listinfo/freetype-devel __________ Information from ESET Smart Security, version of virus signature database 4494 (20091009) __________ The message was checked by ESET Smart Security. http://www.eset.com _______________________________________________ Freetype-devel mailing list Freetype-devel@... http://lists.nongnu.org/mailman/listinfo/freetype-devel |
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Re: Question about CFF arithmetic operator dup
by Werner LEMBERG
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> cff_op_abs consumes 1 and push 1, args++ is right; > cff_op_add consumes 2 and push 1, args++ is right; > cff_op_exch consumes 2 and push 2, args +=2 is right; > cff_op_dup consumes 1 and push 2, args +=2 should be right; Yes, this looks good; I've changed the code accordingly. Unfortunately, I don't have a font which uses `put', `get', or `dup'. Has anyone such a beast for testing? Werner _______________________________________________ Freetype-devel mailing list Freetype-devel@... http://lists.nongnu.org/mailman/listinfo/freetype-devel |
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