Wednesday, March 6, 2013

Amazon Web Services

Amazon Web Services (AWS) is a service Amazon provides for hosting or storing data on the Internet.  Overall, it seems like a pretty nice (and affordable system).

One of their services, Glacier, is for very long-term storage of data that doesn't need to be accessed frequently (such as backups).  Seriously, they mean infrequently - just running the command to get a directory of your files appears to have a turnaround time of a few hours.

Unfortunately, the only interface for accessing the service requires using a programming language - there is no standard tool or web interface.

Fortunately, they supply several APIs - I am using the Java version.  They supply fragments of source code, though it is scattered throughout their slightly opaque documentation.

I have gathered together all of the relevant bits and made it into a reasonable command line application.  Since I was doing this in Linux, all of these instructions are for this system, though it should adapt to any platform.

To get it to work, you will need to:

  1. Have an AWS account
  2. Have a working Java compiler
  3. Create a working folder ('aws')
  4. Download the AWS Java SDK
    1. Extract it to 'aws/sdk' - you should get an 'aws/sdk/lib' directory, among others
  5. Download my Glacier app code
    1. Extract it to the working folder ('aws')
    2. You will need to edit two lines in 'aws/src/'
      1. Replace the text "**UNIQUE ID HERE**" with unique strings
  6. Run the "" script to rebuild the code
    1. This includes several third party libraries included in the AWS Java SDK
  7. Edit the 'bin/' file
    1. Add your personal account info from
  8. Run 'glacier' to see a list of commands
The included 'glacier' script just passes your command line arguments to the Java application:
  • create_vault - create a new vault, same as you can do from the web interface
  • delete_vault - delete a vault (note that it needs to be completely empty first)
  • describe - display info about a vault
  • list - display info about all vaults
  • upload - upload a file to a vault
  • download - download a file from a vault
  • delete - delete a file from a vault
  • dir - list the files in a vault
Note that some of these operations ('download' and 'dir' in particular) can take several hours to complete.  Also note that uploads to a vault can take up to 24 hours before they are reflected in the vault info.

Referring to any file in a vault requires its ID.  This will be displayed when the upload completes - you may wish to record this ID yourself, as listing the files in a vault with 'dir' can take a very long time.

This script could certainly be improved, but this is already many times easier than what is provided by Amazon.  I hope it is of some help!

Saturday, March 2, 2013

Dreamfall Chapters: The Longest Journey

Dreamfall Chapters: The Longest Journey has reached its funding goal on Kickstarter! Actually, it has gone well past to reach several of their stretch goals - many congratulations to them!

The first game in the series, The Longest Journey, is one of my favorite pure adventure games. It is one of the main reasons I really want to try to include an element of storytelling in my games. It proved to me that you could create a game that actually has some meaning and actually has something to say. The game takes a while to get going (OK, a long while), but I think the completely absurd amount of dialog in the first part of the game really pays off by establishing a solid character.

I'm definitely looking forward to playing this one!

Friday, March 1, 2013

A Simple Attribute File

I was looking for a way to store object attribute data, and came up with this tiny class:

class cAttribFile
    typedef std::string tID;
    typedef std::string tVal;
    typedef std::map<tID, tVal> tAttrib;
    typedef std::map<tID, cAttribFile> tNode;

    std::string &operator()(const std::string &s) { return mAttrib[s]; }
    cAttribFile &operator[](const std::string &s) { return mNode[s]; }

    tAttrib mAttrib;
    tNode mNode;

With the addition of a few simple parsing functions, this has actually been pretty useful.

In basic terms, each cAttribFile node has a set of named attributes (map from ID to Value), and a set of named nodes (map from ID to another cAttribFile).

This lets me parse a file like this, where an '=' defines a new attribute, and braces define a new node:

Name = Explosion
MaxParticles = 50


    Duration = 1
    Loop = false
    InitialParticles = 5
        Type = Lerp
        V0 = 1,0.5,0,1
        V1 = 1,0.5,0,0
Then I can refer to this data like this:
duration = attr_file["Smoke"]("Duration");
color_interpolation = attr_file["Smoke"]["Color"]("Type");
where [] operations refer to nodes and () operations refer to attributes.

Adding some iterators over attributes/nodes makes this very flexible.

OK, so it's not ALL that exciting, but it's a very simple class and file format that can be used to hold all sorts of data, without the mind-numbing aesthetics of an XML file.