The magic that is with struct block and merge(), backpatch() and such...

["Auke Folkerts" <auke.folkerts () gmail com>]

Hello,


For a school project I am currently delving deep into the tcpdump (and
libpcap) source code. The goal is to create a program that uses the
same expression language as tcpdump but using a different backend.

I have examined the scanner.l and grammer.y files. The grammer rules
are clear, but I do not quite understand the abstract syntax tree that
is built in the actions of the grammar rules.

Could someone explain (or point me in the right direction on) how
those blocks contain the information that is supplied in the
command-line expression?

Especially the backpatching and merging of the block-structures and
thus forming 'and' or 'or' conditions seems like black magic so far.
Can anyone enlighten me please?

Any help is greatly appreciated!

With kind regards,
--
Auke Folkerts
Computer Science Student
Vrije Universiteit Amsterdam
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