What does (ZydisFormatterBufferAppend do ?

[440bx]

Hello,

In the example program Formatter01, in the function ZydisFormatterPrintAddressAbsolute there is the following statement (line 89 or thereabouts):

ZYAN_CHECK(ZydisFormatterBufferAppend(buffer, ZYDIS_TOKEN_SYMBOL));

after reading the documentation, I can't figure out what that statement does and why it's there. I commented it out and the program's behavior and output was unchanged.

The questions are: what's that statement for ? what does it do ? and what are the consequences of not calling the function ?

Thank you for your help.

[flobernd]

zydis/examples/Formatter01.c

Lines 88 to 91 in ffde0f4

	ZYAN_CHECK(ZydisFormatterBufferAppend(buffer, ZYDIS_TOKEN_SYMBOL));
	ZyanString* string;
	ZYAN_CHECK(ZydisFormatterBufferGetString(buffer, &string));
	return ZyanStringAppendFormat(string, "<%s>", SYMBOL_TABLE[i].name);

This basically marks the following string as a "symbol". There are different types of tokens: https://github.com/zyantific/zydis/blob/master/include/Zydis/FormatterBuffer.h#L55

When using the ZydisFormatterFormat API, this does not make a difference. If you are using ZydisFormatterTokenize instead, you receive a list of ZydisFormatterToken in which each token has a type and a value (that can be retrieved using ZydisFormatterTokenGetValue).

That functionality is e.g. used in ZydisInfo for color coding the individual parts of the instruction:
https://github.com/zyantific/zydis/blob/master/tools/ZydisToolsShared.c#L158

[440bx]

Wonderful !! Thank you Florian, now I understand what that's for. If I understood what you said correctly, it is a way of informing the formatter the type of token that is being added. Knowing the token type may be needed to take some actions, e.g, coloring as done in ZydisInfo.

Thanks again!