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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 particularly 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:

	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 whatever.

       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.

       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 something 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 convenience:

	   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.

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

	--tom


perl v5.10.0			  2009-03-02			       C2PH(1)
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