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on small devices

~ shashank daté ~

stdate@gmail.com

twitter: @shanko

github.com/shanko

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minimalistic Ruby (mruby.org)

lightweight Ruby
complying with part of the Ruby ISO standard
mRuby 1.2 (36 classes, 7 modules) < Ruby 2.3 (105 classes, 19 modules)
syntax is 1.9 compatible (conceived before Ruby 2.0, in ~ 2010)

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why?

embedding (ruby code in c)
linking (libmruby.a)
distribution (of compiled code)
age of “small” devices ( # IoT)

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raspberry pi (fun!)

Single Board Computer - Raspberry Pi Zero: ($5)

CPU: ARM 11, 1GHz - 32-bit single core

GPU: Broadcom VideoCore IV

RAM: 512MB LPDDR2 (900 MHz)

Networking: none Bluetooth: none

Storage: microSD

GPIO: 40-pin header, unpopulated

Ports: mini HDMI, micro USB 2.0,

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raspberry pi (fun!)

Single Board Computer - Raspberry Pi 3: ($35)

CPU: ARM Cortex A53, 1.2 GHz, 64-bit quadcore

GPU: Broadcom VideoCore IV

RAM: 1 GB SDRAM (900 MHz)

Networking: 10/100 Mbits Ethernet, 802.11n Wifi

Storage: microSD

GPIO: 40-pin header, populated

Ports: HDMI, 4 x USB 2.0,

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verifone (profit!)

Vx570 Processor

200 MHz ARM9 32-bit RISC microprocessor

Memory

6 MB (4 MB of Flash, 2 MB of SRAM)

Display

128 x 64 pixel graphical LCD with backlighting; Supports 8 lines x 21characters

Magnetic Card Reader

Triple-track (tracks 1, 2, 3), high coercivity , bi-directional

Keypad

3 x 4 numeric keypad, plus 8 soft-function keys and 4 screen addressable keys;
PCI approved

I/O Modules

14.4k modem module; Ethernet and 14.4k modem combination module

Peripheral Ports

One USB 1.1 port supports flash memory devices;
Two RS-232 ports support peripherals including PIN pads and check readers;
One telecom port and one Ethernet (with optional Ethernet/14.4 I/O module) support communications

Security

SSL v3.0, 3DES encryption, Master/Session and DUKPT key management; VeriShield file authentication)

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lightweight

size of the executable is small
has minimal dependencies on external libraries
uses less memory at runtime
is fast (enough)

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size of the executable

$ size binary-file-name
$ strip or sstrip << to reduce the size
$ mruby-strip

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minimal dependencies

$ ldd /path/to/binary
$ lsof -P -T -p Application_PID
$ objdump -p /path/to/binary | grep
... many more

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mem @ runtime

/usr/bin/time
pmap -x PID
cat /proc/PID/statm

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install

pre-requisites:

git
gcc: build essentials
bison: parser generator
ruby: > 1.9.x

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installation

git clone https://github.com/mruby/mruby.git
cd mruby
./minirake
optionally modify PATH env variable

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generates

binaries:

mruby = interpreter
mirb = interactive shell (REPL)
mrbc = compiler (byte code, symbol-table)
mrdb = debugger
mruby-strip = irep dump debug section remover (???)

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TIMTOWDI

mirb (REPL)
mruby hello.rb (Interpreted)
compile using gcc
bytecode (.mrb)
bytecode (.c)

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embedding (ruby in c)

/* hello.c */

#include "mruby.h"

#include "mruby/compile.h"�int�main(void)�{� mrb_state *mrb = mrb_open();� if (!mrb) { printf(“handle error \n”); }� mrb_load_string(mrb, "puts 'hello world'");� mrb_close(mrb);�}

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linking

$ gcc -std=c99 \ <<< compiler options

-I /path/to/include/mruby \ <<< include headers

hello.c \ <<< program file

-lm /path/to/build/host/lib/libmruby.a \ <<< linking

-o hello <<< executable

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embedding (bytecode in c)

$ cat hello.rb

puts "hello world"

$ mrbc hello.rb # <<<< produces byte-coded hello.mrb

$ hexdump -c hello.mrb

0000000 R I T E 0 0 0 3 � � \0 \0 \0 e M A

0000010 T Z 0 0 0 0 I R E P \0 \0 \0 G 0 0

$ mruby -b hello.mrb

hello world

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embedding (symbol table)

$ cat hello.rb

puts "hello world"

$ mrbc -B hw_symbol hello.rb

^^^^ produces symbol table in hello.c

$ cmp hello_world

^^^^ magic shell script to compile

$ ./hello_world

hello world

/* hello_world.c */

#include "mruby.h"

#include "mruby/irep.h"

#include "hello.c"

int main(void)

{

mrb_state *mrb = mrb_open();

if (!mrb) {/* handle error */}

mrb_load_irep(mrb, hw_symbol);

mrb_close(mrb);

}

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magic shell script (cmp)

$ cat ~/bin/cmp

#!/bin/bash -x

gcc -std=c99 \

-I /$HOME/mruby/include $1.c \

$HOME/mruby/build/host/lib/libmruby.a \

-lm \

-o $1

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customize mruby

mrbgems: library manager to integrate C and Ruby extensions

###### build_config.rb

conf.gem '/path/to/your/gem/dir'

conf.gem :git => 'https://github.com/masuidrive/mrbgems-example.git', :branch => 'master'�conf.gem :github => 'masuidrive/mrbgems-example', :branch => 'master'�conf.gem :bitbucket => 'mruby/mrbgems-example', :branch => 'master'

## from mgem-list use :mgem option

conf.gem :mgem => 'mruby-yaml'�conf.gem :mgem => 'json' # 'mruby-' prefix could be omitted

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mruby vs. lua

Lua:

prototype based (like Javascript)
no classes or inheritance
simple (nil, boolean, number, string, function, thread, table)
compiles to bytecode
has stack-based C API
VM is register based
smaller / faster
came out in 1993
has luajit

mRuby:

class based
single inheritance
complex ( ~ 36 classes )
compiles to bytecode
has stack-based C API
VM is stack based
bigger / slower
came out in 2014
mruby jit (???)

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lua example

#include <stdio.h>�#include "lua.h"�#include "lualib.h"�#include "lauxlib.h"��/* the Lua interpreter */�lua_State* L;��int main ( int argc, char *argv[] )�{� /* initialize Lua */� L = lua_open();�� /* load Lua base libraries */� lua_baselibopen(L);�

� /* run the script */� lua_dofile(L, "hello.lua");�� /* cleanup Lua */� lua_close(L);�� return 0;�}

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mruby vs. crystal

Crystal:

Ruby like syntax
Static typing
Type inference
Compiles to native binary
No REPL
No VM
Smaller / faster
Came out in Sept 2012
Current version 0.20.4 (version 1.0 in 2017 ??)

mRuby:

Ruby syntax
Dynamic typing
Duck typing
Compiles to bytecode
Has REPL (mirb)
VM is stack based
Bigger / slower
Came out in 2014
Current version 1.2

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crystal example

require "http/client"

channel = Channel(String).new

spawn do

channel.send(HTTP::Client.get(

"https://crystal-lang.org/").body)

end

spawn do

channel.send(HTTP::Client.get(

"http://mruby.org").body)

end

2.times do

channel.receive

end

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resources

mruby.org / lua.org / crystal-lang.org /

presentations by matz:

presentations by masayoshi takahashi & yurie yamane:

mruby RTOS: https://www.youtube.com/watch?v=HuPOizo6pSE
mruby robots: https://www.youtube.com/watch?v=7qWZ5w5v7Eg
mruby debugger: https://www.youtube.com/watch?v=VXQYSa2jjLw

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hack my pi

$ ssh pi@.....

Password: rubyconfindia

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