Class: FFI::StructGenerator

Inherits:
Object
  • Object
show all
Defined in:
lib/ffi/tools/struct_generator.rb

Overview

Generates an FFI Struct layout.

Given the @@@ portion in:

module 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.

Defined Under Namespace

Classes: Field

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, options = {}) ⇒ StructGenerator

Returns a new instance of StructGenerator



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# 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

Instance Attribute Details

#fieldsObject (readonly)

Returns the value of attribute fields



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

def fields
  @fields
end

#sizeObject

Returns the value of attribute size



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

def size
  @size
end

Class Method Details

.optionsObject



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

def self.options
  @options
end

.options=(options) ⇒ Object



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

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

Instance Method Details

#calculate(options = {}) ⇒ Object



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# 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

    output = `gcc #{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) ⇒ Object



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# File 'lib/ffi/tools/struct_generator.rb', line 124

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) ⇒ Object



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# File 'lib/ffi/tools/struct_generator.rb', line 114

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

#found?Boolean

Returns:

  • (Boolean)


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# File 'lib/ffi/tools/struct_generator.rb', line 120

def found?
  @found
end

#generate_layoutObject



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# File 'lib/ffi/tools/struct_generator.rb', line 130

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) ⇒ Object



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# File 'lib/ffi/tools/struct_generator.rb', line 148

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

#include(i) ⇒ Object



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# File 'lib/ffi/tools/struct_generator.rb', line 152

def include(i)
  @includes << i
end

#name(n) ⇒ Object



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# File 'lib/ffi/tools/struct_generator.rb', line 156

def name(n)
  @struct_name = n
end