C99 Mode – Whatever that is…

So, I’ve never dabbled in C until now while using it with AVR microcontrollers – and while trying to complie a simple for loop:

  for (uint8_t bit = 0x80; bit; bit >>= 1) {
    ...
  }

I got this error:

error: 'for' loop initial declaration used outside C99 mode

and to fix it I would move my decloration of the varabile outside of the loop. This seemed stupid to me so a quick Google search turned up this

Back in the old days, when dinosaurs roamed the earth and programmers used punch cards, you were not allowed to declare variables anywhere except at the very beginning of a block.

Solution was to add -std=c99 to the Makefile. My new AVR Makefile now looks like this..

8-Bit Sine Wave Table

This was what I needed for a rainbow RGB LED cycle…

ATtiny software PWM to drive RGB LED

Based on Atmel’s AVR136: Low-Jitter Multi-Channel Software PWM Application note, here’s a 3 channel software-based pulse width modulator to drive a RGB LED. This is a proof of concept and currently there is some in-efficient color cycling code in there, but the goal is to drive these cheap chips using an I2C (two wire serial) bus. Disco dance floor anyone?…

AVR ATTiny85 Makefile

This is what I’m using as a Makefile – based on what was included in a downloaded XCode template project – Can’t remember where I downloaded the starting point, but thanks…

Backing up your DB on a Capistrano deployment

Yeah, it’s simple but useful. Since I’m using sqlite at the moment, it’s just a copy but you could run any command in a similar way. I’m also tagging the backup name with a date. Here’s a snip from my Capistrano deploy file….

# ...snip...
namespace :deploy do
  task :restart do
    t=Time.now
    run "cp /path/to/db.sqlite3 /path/to/backup/#{t.year}-#{t.month}-#{t.day}_#{t.hour}:#{t.min}:#{t.sec}_db.sqlite3"
    run "touch #{current_path}/tmp/restart.txt" 
  end
end

Facebook OAuth with Sinatra

This MOSTLY is working, so, here’s what I found when trying to connect to Facebook with OAuth. It needs some serious refactoring because a lot of this was done in an “investigative” trial and error way. It also looks like Facebook have improved their docs on this since I was first looking at them…

First, you need to initiate a connection:

    get '/:blog_name/facebook/oauth/create' do
      redirect "https://graph.facebook.com/oauth/authorize?client_id=##FACEBOOK API KEY##&redirect_uri=##CALLBACK URL##&scope=publish_stream,user_status,user_photos,user_about_me"
    end

where ##FACEBOOK API KEY## = your applications API key (mine is a 32 digit hex value) and ##CALLBACK URL## = the URL that will be processing the next step. Also, the scope value let’s you get more access to the user’s account. Check their extended permissions doc for more info.

Next, you need to process what comes back from Facebook. I am stashing what comes back in the DB (the FacebookOauthToken model). Also using the Mechanize gem which is pretty silly. Some of the code below is specific to my app, so ignore those bits…

    get '/:blog_name/facebook/oauth/callback' do
      if !params['code'].blank?
        url="https://graph.facebook.com/oauth/access_token"
        client_id="client_id=##CLIENT ID##"
        client_secret="client_secret=## CLIENT SECRET ##"
        code="code=#{URI.escape(params['code'])}"
        redirect_uri="redirect_uri=http://example.org/#{@blog.url_name}/facebook/oauth/callback"
 
        url="#{url}?#{client_id}&#{client_secret}&#{code}&#{redirect_uri}"
        begin
          res=open(url)
        rescue
          flash[:error]="There was a problem connecting to Facebook"
          redirect "/#{@blog.url_name}/"
        end
        read=res.read
        access_token=CGI.parse(read)['access_token']
        if !access_token.blank?
          @blog.facebook_oauth_token = FacebookOauthToken.new(:access_token=>access_token,:blog_name=>params[:blog_name])
          if @blog.save
            begin
              a=Mechanize.new
              res=a.get("https://graph.facebook.com/me/?access_token=#{access_token}")
              @blog.facebook_oauth_token.facebook_id=JSON(res.body)['id']
              @blog.save!
            rescue
              flash[:error]="There was a problem getting information from Facebook"
              redirect "/#{@blog.url_name}/"
            end
            flash[:notice]="Facebook connection created!"
            redirect "/#{@blog.url_name}/"
          else
            flash[:error]="There was a problem saving Facebook connection"
            redirect "/#{@blog.url_name}/"
          end
        else
          flash[:error]="There was a problem making Facebook connection"
          redirect "/#{@blog.url_name}/"
        end
      else
        flash[:error]="There was a problem connecting to Facebook"
        redirect "/#{@blog.url_name}/"
      end
    end

Where ##CLIENT ID## = your Application ID (mine is a 12 digit numeric value) and ## CLIENT SECRET ## = your Application Secret (mine is a 32 digit hex value).

Once you have an access_token you should be able to make calls to URLs like this:
"https://graph.facebook.com/me/?access_token=#{access_token}". The /me path is the connected user’s data and I’m grabbing their Facebook ID from the returned JSON for use elsewhere.

Capistrano deploy to multiple locations

Pretty simple, but wanted to log here so I can look this up in the future…

I wanted to deploy to both a stage and a live site. Here’s how that went down:

First I installed the capistrano-ext gem. Second, I edited my Capfile to look like this:

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require 'capistrano/ext/multistage'
set :default_stage, "beta"
set :stages, %w(beta live)

Third, I created a deploy folder and added my two recipes there. beta.rb looks like this:

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load 'deploy' if respond_to?(:namespace) # cap2 differentiator
 
default_run_options[:pty] = true
 
# be sure to change these
set :user, 'username'
set :domain, 'beta.example.org'
set :application, 'fundastache'
 
# the rest should be good
set :repository,  "#{user}@#{domain}:git/#{application}.git" 
#set :repository,  "/home/#{user}/git/#{application}.git" 
set :deploy_to, "/home/#{user}/#{domain}" 
set :deploy_via, :remote_cache
set :scm, 'git'
set :branch, 'master'
set :git_shallow_clone, 1
set :scm_verbose, true
set :use_sudo, false
 
server domain, :app, :web
 
namespace :deploy do
  task :restart do
    run "touch #{current_path}/tmp/restart.txt" 
  end
end

The live recipe looks almost identical.

Now when I

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cap live deploy

the site is deployed to the live environment and when I

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cap beta deploy

or simply

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cap deploy

the site is deployed to the beta site.

Curl command to test JSON posts

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curl -i -H "Content-Type: application/json" -H "Accept: application/json" -X POST -d '{"user":{"username_or_email":"username","password":"password"}}' http://fas/test_json_post

Lost sleep over JSON and Rack::PostBodyContentTypeParser

I’ve been fighting this issue the last couple nights. I wrote earlier about how Rack::PostBodyContentTypeParser can automagically turn a posted JSON object into a Rack / Sinatra params hash. So, I wrote some tests to make sure this was the case and moved on. Well, it turns out in real life things weren’t working and I couldn’t figure out why. Everything looked cool, but the hash wasn’t getting set when I did an AJAX call in the browser – everything was empty. I looked at everything, from the server, to the JS library, to the browser, to setting different content types in prototype.js etc… UGH!

The short of it is that Rack::PostBodyContentTypeParser requires exactly application/json in order to automagically turn the posted JSON object into Rack params and prototype.js (and jquery.js were adding an encoding type of charset=UTF-8 so the entire header entry was coming across as this CONTENT_TYPE: application/json; charset=UTF-8. So, as a fix, I’m just including the Rack::PostBodyContentTypeParser in the Sinatra application with one small change. Here’s the code:

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module Rack
 
  # A Rack middleware for parsing POST/PUT body data when Content-Type is
  # not one of the standard supported types, like <tt>application/json</tt>.
  #
  # TODO: Find a better name.
  #
  class PostBodyContentTypeParser
 
    # Constants
    #
    CONTENT_TYPE = 'CONTENT_TYPE'.freeze
    POST_BODY = 'rack.input'.freeze
    FORM_INPUT = 'rack.request.form_input'.freeze
    FORM_HASH = 'rack.request.form_hash'.freeze
 
    # Supported Content-Types
    #
 
    ################## turned into regex so it matches type with encoding data...
    #APPLICATION_JSON = 'application/json'.freeze
    APPLICATION_JSON = /^application\/json/.freeze
 
    def initialize(app)
      @app = app
    end
 
    def call(env)
      case env[CONTENT_TYPE]
      when APPLICATION_JSON
        env.update(FORM_HASH => JSON.parse(env[POST_BODY].read), FORM_INPUT => env[POST_BODY])
      end
      @app.call(env)
    end
 
  end
end

I tested that this worked by writing the following:

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def test_post_as_json_converts_to_params
  # sanity check that post with normal params works...
  post '/test_params_as_json', :param1=>"param one"
  assert_equal last_response.body,"params[:param1]=param one"
  post '/test_params_as_json', {:param1=>"param one"}.to_json, "CONTENT_TYPE"=>"application/json"
  assert_equal last_response.body,"params[:param1]=param one"
  # this is the problem, adding a charset to the content type seems to breaks rack-contrib/post_body_content_type_parser.rb
  post '/test_params_as_json', {:param1=>"param one"}.to_json, "CONTENT_TYPE"=>"application/json; charset=UTF-8"
  assert_equal last_response.body,"params[:param1]=param one"    
end

Couldn’t get that last thing to work so keeping it simple (stupid)

This could undoubtedly be more elegant, but it’s late and I want it to work now. May take another stab at it later…

TODO: limit the content types and only allow rendering if they are ok.

Setting up a before filter:

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before do
  # remove and grab the file extension
  request.path_info.sub! %r{\.([^\./]+)$}, ''
  @format=$1 || 'html'
  @charset=mime_type($1) || 'text/html'
  content_type @charset, :charset => 'utf-8'
end

and using a case statement:

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get "/home" do
  case @format
  when 'html'
    @stylesheet='home.css'
    haml :home, :layout=>:layout_simple
  when 'js'
    "{'js':true}"
  else
    pass
  end
end