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C2PH(1)		Perl Programmers Reference Guide	  C2PH(1)

NAME
     c2ph, pstruct - Dump C structures as generated from "cc -g
     -S" stabs

SYNOPSIS
	 c2ph [-dpnP] [var=val] [files ...]

     OPTIONS

	 Options:

	 -w  wide; short for: type_width=45 member_width=35 offset_width=8
	 -x  hex; short for:  offset_fmt=x offset_width=08 size_fmt=x size_width=04

	 -n  do not generate perl code	(default when invoked as pstruct)
	 -p  generate perl code		(default when invoked as c2ph)
	 -v  generate perl code, with C decls as comments

	 -i  do NOT recompute sizes for intrinsic datatypes
	 -a  dump information on intrinsics also

	 -t  trace execution
	 -d  spew reams of debugging output

	 -slist	 give comma-separated list a structures to dump

DESCRIPTION
     The following is the old c2ph.doc documentation by Tom
     Christiansen <tchrist@perl.com> Date: 25 Jul 91 08:10:21 GMT

     Once upon a time, I wrote a program called pstruct.  It was
     a perl program that tried to parse out C structures and
     display their member offsets for you.  This was especially
     useful for people looking at binary dumps or poking around
     the kernel.

     Pstruct was not a pretty program.	Neither was it particu-
     larly robust. The problem, you see, was that the C compiler
     was much better at parsing C than I could ever hope to be.

     So I got smart:  I decided to be lazy and let the C compiler
     parse the C, which would spit out debugger stabs for me to
     read.  These were much easier to parse.  It's still not a
     pretty program, but at least it's more robust.

     Pstruct takes any .c or .h files, or preferably .s ones,
     since that's the format it is going to massage them into
     anyway, and spits out listings like this:

perl v5.8.8		   2006-06-30				1

C2PH(1)		Perl Programmers Reference Guide	  C2PH(1)

      struct tty {
	int			     tty.t_locker			  000	   4
	int			     tty.t_mutex_index			  004	   4
	struct tty *		     tty.t_tp_virt			  008	   4
	struct clist		     tty.t_rawq				  00c	  20
	  int			     tty.t_rawq.c_cc			  00c	   4
	  int			     tty.t_rawq.c_cmax			  010	   4
	  int			     tty.t_rawq.c_cfx			  014	   4
	  int			     tty.t_rawq.c_clx			  018	   4
	  struct tty *		     tty.t_rawq.c_tp_cpu		  01c	   4
	  struct tty *		     tty.t_rawq.c_tp_iop		  020	   4
	  unsigned char *	     tty.t_rawq.c_buf_cpu		  024	   4
	  unsigned char *	     tty.t_rawq.c_buf_iop		  028	   4
	struct clist		     tty.t_canq				  02c	  20
	  int			     tty.t_canq.c_cc			  02c	   4
	  int			     tty.t_canq.c_cmax			  030	   4
	  int			     tty.t_canq.c_cfx			  034	   4
	  int			     tty.t_canq.c_clx			  038	   4
	  struct tty *		     tty.t_canq.c_tp_cpu		  03c	   4
	  struct tty *		     tty.t_canq.c_tp_iop		  040	   4
	  unsigned char *	     tty.t_canq.c_buf_cpu		  044	   4
	  unsigned char *	     tty.t_canq.c_buf_iop		  048	   4
	struct clist		     tty.t_outq				  04c	  20
	  int			     tty.t_outq.c_cc			  04c	   4
	  int			     tty.t_outq.c_cmax			  050	   4
	  int			     tty.t_outq.c_cfx			  054	   4
	  int			     tty.t_outq.c_clx			  058	   4
	  struct tty *		     tty.t_outq.c_tp_cpu		  05c	   4
	  struct tty *		     tty.t_outq.c_tp_iop		  060	   4
	  unsigned char *	     tty.t_outq.c_buf_cpu		  064	   4
	  unsigned char *	     tty.t_outq.c_buf_iop		  068	   4
	(*int)()		     tty.t_oproc_cpu			  06c	   4
	(*int)()		     tty.t_oproc_iop			  070	   4
	(*int)()		     tty.t_stopproc_cpu			  074	   4
	(*int)()		     tty.t_stopproc_iop			  078	   4
	struct thread *		     tty.t_rsel				  07c	   4

     etc.

     Actually, this was generated by a particular set of options.
     You can control the formatting of each column, whether you
     prefer wide or fat, hex or decimal, leading zeroes or what-
     ever.

     All you need to be able to use this is a C compiler than
     generates BSD/GCC-style stabs.  The -g option on native BSD
     compilers and GCC should get this for you.

     To learn more, just type a bogus option, like -\?, and a
     long usage message will be provided.  There are a fair
     number of possibilities.

perl v5.8.8		   2006-06-30				2

C2PH(1)		Perl Programmers Reference Guide	  C2PH(1)

     If you're only a C programmer, than this is the end of the
     message for you. You can quit right now, and if you care to,
     save off the source and run it when you feel like it.  Or
     not.

     But if you're a perl programmer, then for you I have some-
     thing much more wondrous than just a structure offset
     printer.

     You see, if you call pstruct by its other incybernation,
     c2ph, you have a code generator that translates C code into
     perl code!	 Well, structure and union declarations at least,
     but that's quite a bit.

     Prior to this point, anyone programming in perl who wanted
     to interact with C programs, like the kernel, was forced to
     guess the layouts of the C structures, and then hardwire
     these into his program.  Of course, when you took your
     wonderfully crafted program to a system where the sgtty
     structure was laid out differently, your program broke.
     Which is a shame.

     We've had Larry's h2ph translator, which helped, but that
     only works on cpp symbols, not real C, which was also very
     much needed.  What I offer you is a symbolic way of getting
     at all the C structures.  I've couched them in terms of
     packages and functions.  Consider the following program:

	 #!/usr/local/bin/perl

	 require 'syscall.ph';
	 require 'sys/time.ph';
	 require 'sys/resource.ph';

	 $ru = "\0" x &rusage'sizeof();

	 syscall(&SYS_getrusage, &RUSAGE_SELF, $ru)	 && die "getrusage: $!";

	 @ru = unpack($t = &rusage'typedef(), $ru);

	 $utime =  $ru[ &rusage'ru_utime + &timeval'tv_sec  ]
		+ ($ru[ &rusage'ru_utime + &timeval'tv_usec ]) / 1e6;

	 $stime =  $ru[ &rusage'ru_stime + &timeval'tv_sec  ]
		+ ($ru[ &rusage'ru_stime + &timeval'tv_usec ]) / 1e6;

	 printf "you have used %8.3fs+%8.3fu seconds.\n", $utime, $stime;

     As you see, the name of the package is the name of the
     structure.	 Regular fields are just their own names.  Plus
     the following accessor functions are provided for your con-
     venience:

perl v5.8.8		   2006-06-30				3

C2PH(1)		Perl Programmers Reference Guide	  C2PH(1)

	 struct	     This takes no arguments, and is merely the number of first-level
		     elements in the structure.	 You would use this for indexing
		     into arrays of structures, perhaps like this

			 $usec = $u[ &user'u_utimer
				     + (&ITIMER_VIRTUAL * &itimerval'struct)
				     + &itimerval'it_value
				     + &timeval'tv_usec
				   ];

	 sizeof	     Returns the bytes in the structure, or the member if
		     you pass it an argument, such as

			     &rusage'sizeof(&rusage'ru_utime)

	 typedef     This is the perl format definition for passing to pack and
		     unpack.  If you ask for the typedef of a nothing, you get
		     the whole structure, otherwise you get that of the member
		     you ask for.  Padding is taken care of, as is the magic to
		     guarantee that a union is unpacked into all its aliases.
		     Bitfields are not quite yet supported however.

	 offsetof    This function is the byte offset into the array of that
		     member.  You may wish to use this for indexing directly
		     into the packed structure with vec() if you're too lazy
		     to unpack it.

	 typeof	     Not to be confused with the typedef accessor function, this
		     one returns the C type of that field.  This would allow
		     you to print out a nice structured pretty print of some
		     structure without knoning anything about it beforehand.
		     No args to this one is a noop.  Someday I'll post such
		     a thing to dump out your u structure for you.

     The way I see this being used is like basically this:

	     % h2ph <some_include_file.h  >  /usr/lib/perl/tmp.ph
	     % c2ph  some_include_file.h  >> /usr/lib/perl/tmp.ph
	     % install

     It's a little tricker with c2ph because you have to get the
     includes right. I can't know this for your system, but it's
     not usually too terribly difficult.

     The code isn't pretty as I mentioned  -- I never thought it
     would be a 1000- line program when I started, or I might not
     have begun. :-)  But I would have been less cavalier in how
     the parts of the program communicated with each other, etc.
     It might also have helped if I didn't have to divine the
     makeup of the stabs on the fly, and then account for micro
     differences between my compiler and gcc.

perl v5.8.8		   2006-06-30				4

C2PH(1)		Perl Programmers Reference Guide	  C2PH(1)

     Anyway, here it is.  Should run on perl v4 or greater.
     Maybe less.

      --tom


perl v5.8.8		   2006-06-30				5

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