Write Your C Extension for Ruby (Jian Weihang) @tonytonyjan - - PowerPoint PPT Presentation

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Write Your C Extension for Ruby (Jian Weihang) @tonytonyjan - - PowerPoint PPT Presentation

Mar 01, 2024 50 likes •1.07k views

Write Your C Extension for Ruby (Jian Weihang) @tonytonyjan Bonjour Jian, Weihang tonytonyjan.net tonytonyjan tonytonyjan tonytonyjan tonytonyjan tonytonyjan tonytonyjan Double Keyboard Player Ruby Postgraduate

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Write Your C Extension for Ruby

簡煒航 (Jian Weihang) @tonytonyjan

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Bonjour

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簡煒航 Jian, Weihang

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tonytonyjan.net

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tonytonyjan

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tonytonyjan

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tonytonyjan

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tonytonyjan

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tonytonyjan

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tonytonyjan

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Double Keyboard Player

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Ruby

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Postgraduate

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Freelancer

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Book Writer

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Coach of Rails Girls Taipei

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Startup

brainana.com 5xruby.tw

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Taiwan

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臺灣（Taiwan）

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臺灣（Taiwan）

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2015-02-18

Montreal Taipei

  • 18°C 19°C
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Happy Chinese New Year

It’s Year of the RAM Ram

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Write Your C Extension for Ruby

簡煒航 (Jian Weihang) @tonytonyjan

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Overview

  • Compilation
  • File Structure
  • Basic MRI API
  • Pointer Wrapper
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Why C Extension?

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Beast from “Kung Fu Hustle”

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“What a fast code!”

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“You code fast!”

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Code Performance vs Development Efficiency

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Performance Development C Ruby Python Perl C++ ASM C Extension

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First step?

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Profiling Tool

gem install ruby-prof

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Jaro-winkler Distance Pure Ruby Implementation

1.6918 ms

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Replace with C Extension

0.5103 ms

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Ruby EXIF Readers

  • mini_exiftool - CLI wrapper of Exiftool
  • exifr - Pure Ruby
  • exif - C Extension of libexif
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tonytonyjan/jaro_winkler tonytonyjan/exif

GitHub

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Make C Extension

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Solutions

  • C API of Ruby
  • rubyinline - mixing C code into Ruby
  • SWIG - Simplified Wrapper and Interface Generator
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rubyinline

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SWIG

$ swig -ruby libfoo.i libfoo_wrap.c foo.c foo.h libfoo.i foo.c foo.h libfoo.so

2k lines

clang/gcc

1 function 1 declaration 3x bigger than MRI C API implementation
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SWIG is similar to C, but not C

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MRI API is just Fine

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What happen in “require”

RbConfig::CONFIG['DLEXT']

foo.so, foo.o and foo.bundle It will load “foo.rb”

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To write a loadable Ruby module is easy.

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What about write a native loadable module?

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Entry of a C Program

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Entry of C Extension

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Compilation

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How to compile?

  • Compile in-line
  • autoconf/pkg-config
  • MakeMakefile (recommended)
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Compile in-line

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pkg-config

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mkmf (Make Makefile)

$ ruby extconf.rb $ make

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installation path

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custom source path

$ ruby extconf.rb $ make

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Conditional Processing

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Conditional Processing

AutoConfig - Generic Header Checks

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Conditional Processing

mkmf methods Compilor Optoins have_header(“foo”)

  • DHAVE_FOO_H

have_library(“foo”)

  • lexif

have_type(“foo”)

  • DHAVE_TYPE_FOO

have_var(“foo”)

  • DHAVE_FOO

have_struct_member('struct foo', 'bar')

  • DHAVE_STRUCT_FOO_BAR

have_func(“foo”)

  • DHAVE_FOO
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It’s just DSL

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Configurable Target Path

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dir_config

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Setup Gemspec

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That’s it

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Yon’t need autotools, mkmf gives you the best.

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File Structure

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Typical File Structure

mysql2, nokogiri, sqlite3

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It’s ambiguous!

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Better File Structure

pg, bcrypt, eventmachine

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Development Workflow

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`gem install` will generate Makefile & build automatically.

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While developing…

$ cd ext/ $ ruby extconf.rb $ make $ cd .. $ ruby -I ext -r foo_ext -e ‘…’

It’s too tedious.

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Life can be easier.

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gem install rake-compiler

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$ rake -D

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Using rake-compiler

$ rake compile test

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rake-compiler is for development.

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It’s nothing to do with gem installation.

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Basic C API

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Key Knowledge

  • Ruby is OO, C is not.
  • C variables have types but data don’t.
  • Ruby variables have no types but data do.
  • Data in Ruby are represented by C type “VALUE”,

and “VALUE” data has its own data-type.

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Define Module/Class

Ruby C

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Nested Class/Module

Ruby C

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Define Method

Ruby C

argc function pointer

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Singleton Instance of rb_cNilClass (there are also Qfalse, Qtrue) Convert Ruby String to C String self self

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Ruby data <-> C data

Fixnum Numeric String int FIX2INT(value) INT2FIX(i) NUM2INT(value) INT2NUM(l) long FIX2LONG(value) LONG2FIX(l) NUM2LONG(value) LONG2NUM(l) double NUM2DBL(value) rb_float_new(f) char* StringValueCStr(value) rb_str_new_cstr(s)

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Steps of implementation

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Type Checking

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Ruby C

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internal VALUE Types

T_NIL T_STRING T_STRUCT T_FILE T_OBJECT T_REGEXP T_BIGNUM T_TRUE T_CLASS T_ARRAY T_FIXNUM T_FALSE T_MODULE T_HASH T_COMPLEX T_DATA T_FLOAT T_SYMBOL T_RATIONAL

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Pointer Wrapper

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C is not OOP

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However, there is structure in C.

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SLIDE 94 char name[20] char desc[20] Wrapped C Struct User instance hello() new() char name[20] char desc[20] Wrapped C Struct User instance hello() new()

u1 = User.new(…) u2 = User.new(…)

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User#new(name, desc)

Ruby class C struct mark function pointer free function pointer ActiveRecord::Persistence#destroy return

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User#hello

C struct Ruby instance return

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What about C++?

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That’s it!

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Leaning Resources

  • Official Guide
  • http://guides.rubygems.org/gems-with-extensions/
  • README.EXT in ruby source code
  • @tenderlove
  • http://tenderlovemaking.com/2009/12/18/writing-ruby-c-extensions-
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  • http://tenderlovemaking.com/2010/12/11/writing-ruby-c-extensions-
part-2.html
  • Source code of pg, sqlite2, mysql2, nokogiri, kgio, bcrypt, etc
  • MRI source code
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Thanks for your listening