Might be interesting to you since you are subscribed to the FFI mailing list. The article is here: http://www.elabs.se/blog/61-advanced-topics-in-ruby-ffi

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Hello,

I have an issue using FFI::AutoPointer on an array of structs.

This is the C function declaration:

glibtop_map_entry * glibtop_get_proc_map (glibtop_proc_map *buf, pid_t pid);

The returned value is an array of glibtop_map_entry structs should be freed using g_free .

If I declare the pointer to the array of structs entries using FFI::Pointer, everything works fine, and the output of the structs is correct:


s = GTop::ProcessMemoryMaps.new
addr = GTop.process_memory_maps(s, Process.pid)
ss_pointer = FFI::Pointer.new(GTop::MemoryMapEntry, addr)
s[:number].times do |i|
  ssi = GTop::MemoryMapEntry.new(ss_pointer[i])
  p Hash[ ssi.members.map { |m| [ m, ssi[m].is_a?(FFI::StructLayout::CharArray) ? ssi[m].to_s.force_encoding('UTF-8') : ssi[m] ] } ]
end
GTop::GLib.g_free ss_pointer


This is a part the ouput:


{:flags=>8191, :start=>140496509870080, :end=>140496510115840, :offset=>0, :perm=>21, :inode=>2494196, :device=>2054, :size=>245760, :rss=>8192, :shared_clean=>8192, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>"/lib/x86_64-linux-gnu/libpcre.so.3.13.1"}
{:flags=>8191, :start=>140496510115840, :end=>140496512208896, :offset=>245760, :perm=>16, :inode=>2494196, :device=>2054, :size=>2093056, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>"/lib/x86_64-linux-gnu/libpcre.so.3.13.1"}
{:flags=>8191, :start=>140496512208896, :end=>140496512212992, :offset=>241664, :perm=>17, :inode=>2494196, :device=>2054, :size=>4096, :rss=>4096, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>4096, :filename=>"/lib/x86_64-linux-gnu/libpcre.so.3.13.1"}
[...]
{:flags=>8191, :start=>140496599904256, :end=>140496620888064, :offset=>0, :perm=>19, :inode=>0, :device=>0, :size=>20983808, :rss=>20844544, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>20844544, :filename=>"[heap]"}
{:flags=>8191, :start=>140737331818496, :end=>140737331953664, :offset=>0, :perm=>19, :inode=>0, :device=>0, :size=>139264, :rss=>49152, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>49152, :filename=>"[stack]"}
{:flags=>8191, :start=>140737332150272, :end=>140737332154368, :offset=>0, :perm=>21, :inode=>0, :device=>0, :size=>4096, :rss=>4096, :shared_clean=>4096, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>"[vdso]"}
{:flags=>8191, :start=>18446744073699065856, :end=>18446744073699069952, :offset=>0, :perm=>21, :inode=>0, :device=>0, :size=>4096, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>"[vsyscall]"}


However, when I use FFI::AutoPointer:


s = GTop::ProcessMemoryMaps.new
addr = GTop.process_memory_maps(s, Process.pid)
pre_ss_pointer = FFI::Pointer.new(GTop::MemoryMapEntry, addr)
ss_pointer = FFI::AutoPointer.new pre_ss_pointer, GTop::GLib.method(:g_free)
s[:number].times do |i|
  ssi = GTop::MemoryMapEntry.new(ss_pointer[i])
  p Hash[ ssi.members.map { |m| [ m, ssi[m].is_a?(FFI::StructLayout::CharArray) ? ssi[m].to_s.force_encoding('UTF-8') : ssi[m] ] } ]
end


the output is corrupted:


{:flags=>8191, :start=>140185021132800, :end=>140185021378560, :offset=>0, :perm=>21, :inode=>2494196, :device=>2054, :size=>245760, :rss=>8192, :shared_clean=>8192, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>"/lib/x86_64-linux-gnu/libpcre.so.3.13.1"}
{:flags=>31, :start=>547597738800, :end=>547597739760, :offset=>1513209474796486656, :perm=>17582052945254416384, :inode=>432345564227577358, :device=>8, :size=>960, :rss=>32, :shared_clean=>32, :shared_dirty=>0, :private_clean=>0, :private_dirty=>3386706919782612992, :filename=>"lib/x86_64-linux-gnu/libpcre.so.3.13.1"}
[...]
{:flags=>0, :start=>1376256, :end=>163459629056, :offset=>134610944, :perm=>16106127360, :inode=>536870912, :device=>536870912, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>8660248813382860800, :private_clean=>7596496373740942904, :private_dirty=>3419760881481315694, :filename=>"libpcre.so.3.13.1"}
{:flags=>0, :start=>5376, :end=>638514176, :offset=>525824, :perm=>62914560, :inode=>2097152, :device=>2097152, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>4069054363051241216, :private_clean=>7956009158131998518, :private_dirty=>7795578597039503477, :filename=>"ibpcre.so.3.13.1"}
{:flags=>0, :start=>21, :end=>2494196, :offset=>2054, :perm=>245760, :inode=>8192, :device=>8192, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>3907004821653777455, :private_clean=>8461816663211521631, :private_dirty=>7596498852877118840, :filename=>"bpcre.so.3.13.1"}
[...]
{:flags=>3543826231318490725, :start=>3223091, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>3688780367150412590, :start=>12590, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>3329058624053866355, :start=>49, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>3543826243108679279, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>13843071262143278, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>54074497117747, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>211228504366, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>825111345, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>3223091, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}
{:flags=>12590, :start=>0, :end=>0, :offset=>0, :perm=>0, :inode=>0, :device=>0, :size=>0, :rss=>0, :shared_clean=>0, :shared_dirty=>0, :private_clean=>0, :private_dirty=>0, :filename=>""}

As you can see, the struct values "get chewed" from entry to entry.

Is it a known issue?

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See here: https://github.com/ffi/ffi/wiki/Projects-Using-FFI

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I am writing a libgtop2 wrapper using ffi in order to learn how to use ffi; I am new to ffi, so I have a lot of doubts.

libgtop2 lets get system and processes informations (cpu usage, memory usage, ...).

Here some informations about glibtop_get_cpu:

Library function `glibtop_get_cpu':

     void glibtop_get_cpu (glibtop_cpu *buf);
     void glibtop_get_cpu_l (glibtop *server, glibtop_cpu *buf);

   Declaration of `glibtop_cpu' in `<glibtop/cpu.h>':

     typedef struct _glibtop_cpu     glibtop_cpu;

     struct _glibtop_cpu
     {
         guint64   flags,
             total,
             user,
             nice,
             sys,
             idle,
             iowait,
             irq,
             softirq,
             frequency,
             xcpu_total [GLIBTOP_NCPU],
             xcpu_user [GLIBTOP_NCPU],
             xcpu_nice [GLIBTOP_NCPU],
             xcpu_sys  [GLIBTOP_NCPU],
             xcpu_idle [GLIBTOP_NCPU],
             xcpu_iowait [GLIBTOP_NCPU],
             xcpu_irq [GLIBTOP_NCPU],
             xcpu_softirq [GLIBTOP_NCPU],
             xcpu_flags;
     };

...


Here is what I wrote:

require 'ffi'

class GlibtopCpu < FFI::Struct
  layout :flags,        :guint64,
         :total,        :guint64,
         :user,         :guint64,
         :nice,         :guint64,
         :sys,          :guint64,
         :idle,         :guint64,
         :iowait,       :guint64,
         :irq,          :guint64,
         :softirq,      :guint64,
         :frequency,    :guint64,
         :xcpu_total,   :guint64,
         :xcpu_user,    :guint64,
         :xcpu_nice,    :guint64,
         :xcpu_sys,     :guint64,
         :xcpu_idle,    :guint64,
         :xcpu_iowait,  :guint64,
         :xcpu_irq,     :guint64,
         :xcpu_softirq, :guint64,
         :xcpu_flags,   :guint64
end

module LibGtop
 
  extend FFI::Library
  ffi_lib 'libgtop-2.0'
  attach_function :glibtop_get_cpu, [:pointer], :void

end

# taken from https://github.com/ffi/ffi/wiki/Structs
pointer = FFI::MemoryPointer.new :byte, GlibtopCpu.size, false
a = GlibtopCpu.new pointer
p LibGtop.glibtop_get_cpu(a)

Executing this gives (unsurprisingly) an error:

$ ruby lib/lib_gtop.rb
/home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/types.rb:57:in `find_type': unable to resolve type 'guint64' (TypeError)
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:316:in `find_type'
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:309:in `find_field_type'
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:351:in `array_layout'
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:261:in `layout'
    from lib/lib_gtop.rb:4:in `<class:GlibtopCpu>'
    from lib/lib_gtop.rb:3:in `<main>'

It doesn't find the guint64 type; how should I declare it?

Also: xcpu_total, xcpu_user are arrays... how should I declare them?

Finally... if someone could give me an explanation and an example of how to implement the bind to glibtop_get_cpu, I would appreciate it very much :)

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Hola!

I am writing a libgtop2 wrapper using ffi in order to learn how to use ffi; I am new to ffi, so I have a lot of doubts :)

libgtop2 lets get system and processes informations (cpu usage, memory usage, ...).

Here some informations about glibtop_get_cpu:

Library function `glibtop_get_cpu':

     void glibtop_get_cpu (glibtop_cpu *buf);
     void glibtop_get_cpu_l (glibtop *server, glibtop_cpu *buf);

   Declaration of `glibtop_cpu' in `<glibtop/cpu.h>':

     typedef struct _glibtop_cpu     glibtop_cpu;

     struct _glibtop_cpu
     {
         guint64   flags,
             total,
             user,
             nice,
             sys,
             idle,
             iowait,
             irq,
             softirq,
             frequency,
             xcpu_total [GLIBTOP_NCPU],
             xcpu_user [GLIBTOP_NCPU],
             xcpu_nice [GLIBTOP_NCPU],
             xcpu_sys  [GLIBTOP_NCPU],
             xcpu_idle [GLIBTOP_NCPU],
             xcpu_iowait [GLIBTOP_NCPU],
             xcpu_irq [GLIBTOP_NCPU],
             xcpu_softirq [GLIBTOP_NCPU],
             xcpu_flags;
     };

...


Here is what I wrote:

require 'ffi'

class GlibtopCpu < FFI::Struct
  layout :flags,        :guint64,
         :total,        :guint64,
         :user,         :guint64,
         :nice,         :guint64,
         :sys,          :guint64,
         :idle,         :guint64,
         :iowait,       :guint64,
         :irq,          :guint64,
         :softirq,      :guint64,
         :frequency,    :guint64,
         :xcpu_total,   :guint64,
         :xcpu_user,    :guint64,
         :xcpu_nice,    :guint64,
         :xcpu_sys,     :guint64,
         :xcpu_idle,    :guint64,
         :xcpu_iowait,  :guint64,
         :xcpu_irq,     :guint64,
         :xcpu_softirq, :guint64,
         :xcpu_flags,   :guint64
end

module LibGtop
 
  extend FFI::Library
  ffi_lib 'libgtop-2.0'
  attach_function :glibtop_get_cpu, [:pointer], :void

end

# taken from https://github.com/ffi/ffi/wiki/Structs
pointer = FFI::MemoryPointer.new :byte, GlibtopCpu.size, false
a = GlibtopCpu.new pointer
p LibGtop.glibtop_get_cpu(a)

Executing this gives (unsurprisingly) an error:

$ ruby lib/lib_gtop.rb
/home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/types.rb:57:in `find_type': unable to resolve type 'byte' (TypeError)
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/types.rb:160:in `type_size'
    from lib/lib_gtop.rb:33:in `initialize'
    from lib/lib_gtop.rb:33:in `new'
    from lib/lib_gtop.rb:33:in `<main>'
izietto <at> shino:~/sys-proc-info$ ruby lib/lib_gtop.rb
/home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/types.rb:57:in `find_type': unable to resolve type 'guint64' (TypeError)
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:316:in `find_type'
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:309:in `find_field_type'
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:351:in `array_layout'
    from /home/izietto/.rbenv/versions/2.0.0-p0/lib/ruby/gems/2.0.0/gems/ffi-1.4.0/lib/ffi/struct.rb:261:in `layout'
    from lib/lib_gtop.rb:4:in `<class:GlibtopCpu>'
    from lib/lib_gtop.rb:3:in `<main>'

It doesn't find the guint64 type; how should I declare it?

Also: xcpu_total, xcpu_user are arrays... how should I declare them?

Finally... if someone could give me an explanation and an example of how to implement the bind to glibtop_get_cpu, I would appreciate it very much :)

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I'm a bit out of my depth here. Any insight would be appreciated.

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For anyone interested, I've recently been working on c2ffi (https://github.com/rpav/c2ffi), which uses Clang to parse C into JSON, and I have just posted c2ffi-ruby, which transforms the JSON into a file for ruby-ffi:

    https://github.com/rpav/c2ffi-ruby

This should produce more accurate input than SWIG.

Apologies for ugly code; this was done as a bit of a test for c2ffi, and I haven't written much ruby in awhile.  Nor has it been extensively tested, but it does parse the included Cairo bindings.

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I’ve been having some issues running one of my gems (http://rubygems.org/gems/spotify) successfully on Raspberry PI, using the soft float debian “weezy” OS, downloadable from http://www.raspberrypi.org/downloads on cruby 1.9.3 (ruby 1.9.3p385 (2013-02-06 revision 39114) [armv6l-linux-eabi]).

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Hi,

I have to use a callback function with varargs (I already red issue #161).
I cannot avoid this because I cannot change the interface of the C Library.

Do you have any idea, how to solve this problem ?

Maybe define va_list as an parameter and split the elements in the implementation of the callback ?

Thanks for help.

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