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Class: FFI::StructGenerator

Relationships & Source Files
Namespace Children
Classes:
Field
Inherits: Object
Defined in: lib/ffi/tools/struct_generator.rb

Overview

Generates an ::FFI Struct layout.

Given the @@@ portion in:

class Zlib::ZStream < FFI::Struct
  @@@
  name "struct z_stream_s"
  include "zlib.h"

  field :next_in,   :pointer
  field :avail_in,  :uint
  field :total_in,  :ulong

  # ...
  @@@
end

StructGenerator will create the layout:

layout :next_in, :pointer, 0,
       :avail_in, :uint, 4,
       :total_in, :ulong, 8,
       # ...

StructGenerator does its best to pad the layout it produces to preserve line numbers. Place the struct definition as close to the top of the file for best results.

Class Attribute Summary

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(name, options = {}) ⇒ StructGenerator

[ GitHub ] 

  


# File 'lib/ffi/tools/struct_generator.rb', line 39



def initialize(name, options = {})
  @name = name
  @struct_name = nil
  @includes = []
  @fields = []
  @found = false
  @size = nil

  if block_given? then
    yield self
    calculate self.class.options.merge(options)
  end
end


  







Class Attribute Details



  

    .options   (rw)
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 55



def self.options
  @options
end


  








  

    .options=(options)   (rw)
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 52



def self.options=(options)
  @options = options
end


  







Instance Attribute Details



  

    #fields   (readonly)
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 37



attr_reader   :fields


  








  

    #found?  ⇒ Boolean  (readonly)
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 121



def found?
  @found
end


  








  

    #size   (rw)
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 36



attr_accessor :size


  







Instance Method Details



  

    #calculate(options = {})  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 58



def calculate(options = {})
  binary = File.join Dir.tmpdir, "rb_struct_gen_bin_#{Process.pid}"

  raise "struct name not set" if @struct_name.nil?

  Tempfile.open("#{@name}.struct_generator") do |f|
    f.puts "#include <stdio.h>"

    @includes.each do |inc|
      f.puts "#include <#{inc}>"
    end

    f.puts "#include <stddef.h>\n\n"
    f.puts "int main(int argc, char **argv)\n{"
    f.puts "  #{@struct_name} s;"
    f.puts %[  printf("sizeof(#{@struct_name}) %u\\n", (unsigned int) sizeof(#{@struct_name}));]

    @fields.each do |field|
      f.puts <<-EOF
printf("#{field.name} %u %u\\n", (unsigned int) offsetof(#{@struct_name}, #{field.name}),
       (unsigned int) sizeof(s.#{field.name}));
  EOF
    end

    f.puts "\n  return 0;\n}"
    f.flush

    cc = ENV['CC'] || 'gcc'
    output = `#{cc} #{options[:cppflags]} #{options[:cflags]} -D_DARWIN_USE_64_BIT_INODE -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -x c -Wall -Werror #{f.path} -o #{binary} 2>&1`

    unless $?.success? then
      @found = false
      output = output.split("\n").map { |l| "\t#{l}" }.join "\n"
      raise "Compilation error generating struct #{@name} (#{@struct_name}):\n#{output}"
    end
  end

  output = `#{binary}`.split "\n"
  File.unlink(binary + (FFI::Platform.windows? ? ".exe" : ""))
  sizeof = output.shift
  unless @size
    m = /\s*sizeof\([^)]+\) (\d+)/.match sizeof
    @size = m[1]
  end

  line_no = 0
  output.each do |line|
    md = line.match(/.+ (\d+) (\d+)/)
    @fields[line_no].offset = md[1].to_i
    @fields[line_no].size   = md[2].to_i

    line_no += 1
  end

  @found = true
end


  








  

    #dump_config(io)  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 125



def dump_config(io)
  io.puts "rbx.platform.#{@name}.sizeof = #{@size}"

  @fields.each { |field| io.puts field.to_config(@name) }
end


  








  

    #field(name, type = nil)  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 115



def field(name, type=nil)
  field = Field.new(name, type)
  @fields << field
  return field
end


  








  

    #generate_layout  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 131



def generate_layout
  buf = ""

  @fields.each_with_index do |field, i|
    if buf.empty?
      buf << "layout :#{field.name}, :#{field.type}, #{field.offset}"
    else
      buf << "       :#{field.name}, :#{field.type}, #{field.offset}"
    end

    if i < @fields.length - 1
      buf << ",\n"
    end
  end

  buf
end


  








  

    #get_field(name)  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 149



def get_field(name)
  @fields.find { |f| name == f.name }
end


  








  

    #include(i)  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 153



def include(i)
  @includes << i
end


  








  

    #name(n)  
  

  [ GitHub ]


  

  


# File 'lib/ffi/tools/struct_generator.rb', line 157



def name(n)
  @struct_name = n
end