My working life..

Certificates

2013-02-18T21:32:00.000-05:00

Introduction
Certificates is a new way to prove identity. Unfortunately this topic sometimes is hidden from publicity and still is a mystery for average Internet user. I would like to share some knowledge about certificates, their structure and the way how I understand them. This article covers very basic questions about certificates that users may have.

Certificate structure (simplified)
What is certificates for? The main purpose is to verify identity (prove that information written in certificate belongs to certificate owner).

Certificate consists of three main parts:

Information - everything that you can see when open certificate in MMC console or other certificate viewer;

Public key - a unique sequence that belong to certificate owner;
Signature Algorithm - methods that was used to create certificate signature (usually it is built from encryption algorithm and digest algorithm. For example SHA1 with RSA)

Signature - another unique sequence that represent result of applying encryption and digest.

Lets take a closer look to every part

Information:
Here we can add any information we would like to present and prove.
According to Internet standard RFC2459 there are mandatory fields
- issuer - id who created signature
- subject (owner) - owners name or other owners unique information
- serial number - issuer certificate serial number. A pair serial/issuer creates an unique certificate id
- not before, not after - expiration date and effective date.
- constrains - main purpose for the certificate. For example if constrains is main exchange - it should not be used for SSL, ets.

Public key:
This section contains a public key of any asymmetric cryptographic system. The most popular asymmetric system are RSA and Diffie–Hellman

Information + public key also called TBSCertificate. Every
TBSCertificate contains the names of the subject and issuer, a public
key associated with the subject, a validity period, a version number,
and a serial number; some may contain optional unique identifier fields. (from RFC)

Signature algorithm and Signature:
In order to verify certificate, a verifier should know how to verify certificate signature. For example, if algorithm is SHA1 with RSA then this means that in order to verify certificate signature we need to get SHA1 from certificate and then it should match with data we have got by decrypting signature with issuers public key. The most popular message digest algorithms are SHA1, MD5, MD4, MD6.

How to create signature?
Issuer is an authority who sign certificates.
In order to create issuer signature. Issuer gets a digest of certificate data (for example it can use SHA1 algorithm for this) then using private key encrypts digest. As result you will have an encrypted certificate digest.

How to verify signature?
Anyone could verify certificate signature in order to confirm that certificate content belongs to owner.
In order to verify certificate signature we should:
- Decrypt signature it using issuers public key;
- Get digest of certificate;
- Compare results. on one hand you have decrypted signature, on other hand digest. They should be the same because issuer created signature in the same way.

This verification is based on assumption that no one, except issuer, doesn't have issuers private key.

Lets have some example:
Root or self signed certificate

Private key : 44 33 22 11
(Private key stored separately from certificate and it is confidential)

Certificate Root
Issuer : Government
Subject : Government
PublicKey : 11 22 33 44
Signature Algorithm: RSA with SHA1
Signature : 55 44

This is a simplified version of root or self-signed certificate. Issuer and Subject here are the same. Signature in this case is a digest encrypted with issuers private key. Because issuer and owner are the same, there is no way to prove that private/public key belongs to owner.

It could be compromised by replacing public key and signature. That is why we have many trusted authorities that could prove each other identities. This is partially solved by distributing root certificates together with firmware or operating system.

Another example:

Private key : DD CC BB AA
(Private key stored separately from certificate and it is confidential)

Certificate Library
Issuer : Government
Subject : Computer
Public Key : AA BB CC DD
Signature Algorithm: RSA with SHA1
Signature : EE FF

In case if we trust Certificate Root. We can verify and confirm that information in certificate is not compromised and belongs to Library.

Why we can trust "Certificate Library"?

Because Root we trust has been verified and proved by its signature that "Certificate Library" belongs to Library, and because we trust "Certificate Root" we can say that we trust "Certificate Library ".

Lets find out what is Library certificate signature in this case:
Signature : EE FF

This is suppose to be an encrypted digest. Digest we get from "Certificate Library" body and encrypted with issuer (Certificate Root) private key.
In our example signature EE FF is the result of
RSA([issuers private key], SHA1( Certificate Library's TBSCertificate))

[EE FF] = RSA([ 44 33 22 11], SHA1( "TBSCertificate Library" ))

Using similar approach we can build a certificate trusted chain. For example you don't trust issuer and don't trust issuer's issuer but you do trust issuer's issuer's issuer.

Why it works?
Signature verification works because we made some assumptions.

First (the most important) is that for asymmetric encryption systems for key pair (public/private keys) there is no easy way (mathematicians didn't find one yet) to calculate private key based on public key.

The nature of asymmetric systems allows to encrypt message with private key and decrypt message using public key. That is true in opposite direction.

Second assumption is related to one way hash functions that are used to create certificate digest. for long enough input data it is possible to generate unique digest and there is no easy way to find out what is input data from digest.

.

Undersranding android gestures

2011-06-13T23:59:00.003-04:00

Android gestures is another dark horse because it is wrapped into an Android library and it becomes a part of SDK.

From Android SDK it is clear that gesture library should be put in a raw folder in resources or it could be just a separate file in private or public folder, but what is the gesture library format?. You can browse Android SDK here that describes only high level design.

I still cannot find gesture library format but I saw on the market there are many applications that uses gestures.

My first clue was to use Gesture Builder from Android example SDK.
It is located under \samples\android-8\GestureBuilder

Lets take a close look:

GestureLibrary lib;
// create lib instanse from file name pass empty file
lib = GestureLibraries.fromFile(new File("gestures")));
..
lib.addGesture("gesture's name", gestureProcessor); // adding
lib.save();

// We could build gesture object from overlay
private class GestureProcessor implements GestureOverlayView.OnGestureListener {
public void onGestureStarted(GestureOverlayView overlay, MotionEvent event) {
}

public void onGesture(GestureOverlayView overlay, MotionEvent event) {
}

public void onGestureEnded(GestureOverlayView overlay, MotionEvent event) {
mGesture = overlay.getGesture();
if (mGesture.getLength() < LENGTH_THRESHOLD) {
overlay.clear(false);
}
}

Multilayout ListView

2011-01-29T19:18:00.058-05:00

This is a multi Layout view sample. You can use it when you need to display the same amount of data (in sample text and images but it should be located differently

You need to build a special ListView adaptor

Source code for MultiLayout Adapter is bellow

Beginning Android 2

Code Highlighting

2011-01-29T18:30:00.075-05:00

Highlighted code in my samples

I found excellent javascript project. It was written by Alex Gorbatchev, and it is free (Thanks Alex!). I will use it to highlight code samples. There is no need to host JS and CSS inside your blog system, you can just reference files instead.
The most popular programming languages are supported here

You can download project and use it in your web sites or you can use hosted version of highlighter. Unfortunately, Google blog system doesn't allow you to insert link tag, but I have used loadjscssfile function to load script and css files.
Lets test hosted version: (javascript example) Here is a function that loads scripts and css.

function loadjscssfile(filename, filetype)
{
   if (filetype=="js"){
       var fileref=document.createElement('script')
       fileref.setAttribute("type","text/javascript")
       fileref.setAttribute("src", filename)
   } 
   else if (filetype=="css"){
       var fileref=document.createElement("link")
             fileref.setAttribute("rel", "stylesheet")
             fileref.setAttribute("type", "text/css") 
             fileref.setAttribute("href", filename)
   } 
   if (typeof fileref!="undefined"){
      document.getElementsByTagName("head")[0].appendChild(fileref)
   }
} 

var pathToScript = "http://alexgorbatchev.com/pub/sh/current/"; 
loadjscssfile(pathToScript + "styles/shCore.css", "css"); 
loadjscssfile(pathToScript + "styles/shThemeDefault.css", "css"); 
loadjscssfile(pathToScript + "scripts/shCore.js", "js"); 
loadjscssfile(pathToScript + "scripts/shBrushJava.js", "js"); 
loadjscssfile(pathToScript + "scripts/shBrushJScript.js","js");

Android Java example:

import android.widget.TextView;
public class TestClass {
    private static final int[] LAYOUTS = new int[] {
        R.layout.center,
        R.layout.left, 
        R.layout.right 
    private final Context _context;
    private final ArrayList _data = new ArrayList();
    public TestClass(Context context, ArrayList data){ 
        _context = context;
        _data.addAll( data );
  
    }
}

Java pre-processor

2011-01-11T01:42:00.002-05:00

How Eclipse works to compile project?

If we are looking for android project compilation process, it contains from many builders
- before resource generator builder;
- resource builder;
- Java compiler;
- package builder;

Next builder will be started after previous one was finished successfully.

Sometimes you may want to use one source for different incompatible platforms (like JavaME MIPS2.0 or Java SE or some other Java specific platform like Android).

The best approach here to have you project separated from Java SDK by creating wrappers on SDK layer and then refer only wrapped classes in your project. Then when in and script for package builder build your project together with Java specific library wrapper.(recommended)

Another way to dial with this problem is to have a preprocessor like C preprocessor and wrap platform specific code. This approach is less clear and it feels like some comments you cannot remove. (not recommended)

If you need Java cross platform but it is difficult to separate api in your project - you have to redesign you project.

Custom Java preprocessor (also could be done using ant script as well as using external preprocessor tool (like C preprocessor). To understand how it works I have created my own custom preprocessor using ant

Eclipse defines 4 targets

before clean

manual build

auto build

during clean

I have created a simple xml file with 4 targets that is shown below:
<project name="new builder" >
<target name="before_clean"/>
<target name="manual_build"/>
<target name="auto_build"/>
<target name="during_clean">
</project>

Do you have other solution how to build the same app on different Java platforms?

Google Translation

2011-01-09T22:36:00.048-05:00

I would like to share a Google Translate JavaScript plug-in.
To add a translation to your web pages you can use JavaScript and Google translate services.

Here is a sample that add a translate combo box to your page:
// define div tag where translation combobox will be placed
<div id="google_translate_element">
</div>

// define "new" translate element function
<script>
function googleTranslateElementInit() {
new google.translate.TranslateElement({
pageLanguage: 'uk',
includedLanguages: 'et,tl',
}, 'google_translate_element');
}</script>

// add all necessary sources to do the translation
<script src="//translate.google.com/translate_a/element.js?cb=googleTranslateElementInit"></script>

pros:
- easy to use
- using it you can create a copy of your blog/site to other languages

cons:
- not all languages supported
- engine itself is quite new and translation is not perfect

if you need translation to any language remove includedLanguages parameter

There are some useful links that may help you with building your copy:

Simple and vary helpful generator of Google JavaScript code
Google Translate API JavaScript Reference
Translator Toolket you are able to translate html pages and correct translations. Interface is similar to Google Docs

Android and Ant builder. Part 2

2011-01-04T08:29:00.010-05:00

About ant commands :
You can create your own command processor with ant (you are able to create elements and ant is able to process commands in ants way (using xml to join parts )

For example for search and replace there is a command that is mapped to java or to implemented in other language application

<replaceregexp file="file" match="pattern" replace="pattern"
flags="options"
byline="true|false" /> ;

it is actually a prepared a java class(s) that do the job

Is Ant depends on Java JRE or it is a separate native application? I think it is...
Probably that's why Java and Ant is so close...

I also would like to understand how preprocessor works in Eclipse. It may helps me with my tasks

Android Ant builder

2010-12-22T01:31:00.003-05:00

Android build process is quite complicated
First of all it is based on ant script together with sdk tools and java apps aligned to ant.

Lets take a closer look to it
to create ant script manually just type:

cmd <enter>
if you don't have Android SDK folder in system PATH environmental variable - add it
set path=%path%;X:\android\android-sdk-windows-1.5_r3\tools

now you can create new or update existent eclipse project
(I assume that you like me create project in eclipse first and then, for some reason, you need to build your fancy application from command line

set current dir to your android project dir

cd c:\apps\myapp <enter>
android update project <enter>

now you have build.xml in your projects root folder

for now you can open them in eclipse but you cannot build (execute) ant script from eclipse
The problem is in java component that connect you build.xml ant script with platform dependent android ant script that located in SDK

for example for API level 8 it will be android_rules_r3.xml.

File contains a lot of comments about every section
but I'll explain some of them just for those who who know nothing about ant engine :)

Ant stuff
I will explain only things that I need to build android project manually

every project contains
<project name="myapps" default="<default target>" basedir=<path to your android project>
...
project>
nice to see basedir here because you are able to move you Ant script

main concept of ant is targets (like "release", "debug", "release-signed", ets.)
every target could have dependency on other targets
and targets could be public and private (hidden)

for example simple target:
<target name="help">
<echo>This project has extended helpecho>
target>

complex target
<target name="release" depends="resources, java_compiler, zip, sign, renameing">

target>

you can specify properties ( they are playing the same function as variables in other languages )
<property name="app.file.name" value="${build.prop.name}" />
let me explain this
you can read/ write app.file.name using ${app.file.name} sintax
in sample you define property and set value for it equal to value of build.prop.name property

you could override this prop value in build.properties file
lets call it first level of customization

you also able to define properties in build.properties and then load to project
<property file="build.properties"/>

Combination of both <property name.../> and <property file=.../> creates a list of properties that could be redefined in a separate settings file
Example:

<property name="one" value="ha-ha"/>
<property file="build.properties"/>

now we can move to targets and other xml elements

<taskdef name="setup" classname="com.android.ant.SetupTask"
classpathref="android.antlibs"/>

Defines a java class with a starting "main" point in com.android.ant.SetupTask.
reference android.antlibs - a link to path(s) where SetupTask could be found.
All android elements (tags) could use (execute) this application
using <setup>setup> tag

few more samples
<taskdef name="apkbuilder"
classname="com.android.ant.ApkBuilderTask"
classpathref="android.antlibs" />

<taskdef name="xpath"
classname="com.android.ant.XPathTask"
classpathref="android.antlibs" />
usage:

<xpath input="AndroidManifest.xml" expression="/manifest/@package"
output="manifest.package" />

<aaptexec executable="${aapt}"
command="package"
verbose="${verbose}"
manifest="AndroidManifest.xml"
androidjar="${android.jar}"
rfolder="${gen.absolute.dir}">
aaptexec>
if you command sequence that you have to use in different targets you could write a macro
definition:

<macrodef name="dex-helper">
<element name="external-libs" optional="yes" />
<element name="extra-parameters" optional="yes" />
<sequential>
<echo>Converting compiled files and external libraries into ${intermediate.dex.file}...echo>
sequential>
macrodef>usage:
<dex-helper />
or
<dex-helper>
<extra-parameters>
<arg value="--no-locals" />
extra-parameters>
<external-libs>
<fileset file="${emma.dir}/emma_device.jar" />
external-libs>
dex-helper/>

I hope you've got the idea.

Now about problem I met

for android platform 2.2 (API level 8)
if you open build script that contains external targets (targets that were defined in android_rules_r3.xml or other external files)
in eclipse. you've get ant compilation errors (unknown target)

if you run the same script (build.xml) from command promt - it works fine

for example in case with auto-generated build.xml

this one return error unknown help target if you open it in eclipse
after that you are not able to compile you app!!!
As a not very good solution is moving build.xml file outside project root dir in this case eclipce will not see it and you can add to get it working from command line

Java final String optimisation

2010-11-30T00:56:00.011-05:00

Some times I need a sub string of a string and I noticed that if you add final keyword, Java compiler makes a small optimization, isn't it?

For example :

String name = "this is a simple string";
String simple = name.substring(0,4);

Here Java creates two strings
but if you write this code in different way you get rid of one extra allocation

final String name = "this is a simple string";
final String simple = name.substring(0,4);

Both objects points to the same memory block and String object itself has a constant context
Am I right?

I am not sure about this conclusions, so, I will check it again when I have time.

If you know something how to use final for Strings and what exactly java compiler does,

I'll be pleased if someone share his knowledges in this area

Bugs aligned to CString

2010-11-30T00:37:00.004-05:00

Today I noticed a funny thing. Class CString C++ sometimes works like class String in Java
For example :

class Example

{

  CString mName;



public: 

  void setName(const CString & name)

  {

     mName = name; 

  }

  void modify()

  {

     memset((VPVOID)(LPTSTR) mName,65,mName.GetLength()*sizeof(TCHAR));

  }

}



class Other

{

// we set up this name somewere in code 

public: 

  CString getName() const

  {

     return mName; 

  } 

}





void main()

{

   std::autoptr o1 =

std::autoptr(

new  Other(_T("simple string")));

   Example ex1;

   ex.setName( o1->getName() );

   ex.modyfy();

   // here you will have empty string for o1 and for ex classes 

   // because it refers to the same string data in memory

// so both classes will contain modified data

Conclusion : don't mix API because you never know about class implementation.
Fix is simple, just use mText.Empty() or mText[n] to modify string and never (LPTSTR)(mText)[n]

Windows messaging system

2010-07-24T21:51:00.009-04:00

How I understand windows messaging system

I have taken a look to MFC, WTL frameworks and desided to explain some moments aligned to window creation and user interaction on Windows API level

Creating a Window

To create window in Windows OS you call CreateWindow(className,...)
There is a enum of predefined classes
COMBOBOX, BUTTON, STATIC, LISTBOX and other default classes

As far as thay are already pressent in the system they asosiated with WindowProc. Actually every window class is asociated with windowProc inside OS.
What is window proc? it is just a function like below

INT_PTR CALLBACK MyDialog_DialogProc( HWND hwnd,
UINT messageId,
WPARAM wParam,
LPARAM lParam )

WindowProc is responsible for the window message processing. Thats why BUTTON for example looks like button :) , so to create a dialog not from window resources you need. To understand how OS GUI works lets create a dialog manually and not using resource file for that.

Creating Dialog window not from recources

1. register class

WNDCLASS wndClass = {0};
wndClass.lpfnWndProc = (WNDPROC)MyDialog_DialogProc;
wndClass.lpszClassName = L"DIALOG";
ATOM atom = RegisterClass(&wndClass);
HWND dialogHwnd = CreateWindow(L"DIALOG", L"MyDlg", ~WS_DLGFRAME & ~WS_CLIPSIBLINGS, 10,10, 200,200, NULL, (HMENU)0, instance, 0);

2. write a WindowProc

INT_PTR CALLBACK MyDialog_DialogProc( HWND hwnd,

UINT messageId,

WPARAM wParam,

LPARAM lParam )

{

if (messageId == WM_CREATE)

{

// create button

HINSTANCE hInstance = GetModuleHandle(NULL);

   HWND myButton = CreateWindow(L"BUTTON", L"ClickMe"
   , WS_CHILD, 10,10, 100,20, hwnd
   ,(HMENU)1, hInstance,0);

if (!myButton)

{

// log error

}

ShowWindow(myButton, SW_SHOWNORMAL);

// create othe controls if there is a need!

return TRUE;

}

return DefWindowProc( hwnd, messageId, wParam, lParam);

}

You can change this default WindowProc and this process is so calling subclassing
There is a lot of windows messages so if you don't need (or you don't want) to process all of them you need to call oldWindowProc to process messages that your new WindowProc doesn't process

I found that class "DIALOG" is not a default class in windows. This class creates when you are going to create a dialog based on recource file. When you create dialog from recource (using CreateDialog for example) this function register dialog class read resource file read styles inside dialog and raise WM_INITDIALOG and othe windows messages (WM_FONT is GWS_FONT defined) and after that call ShowWindow (if GWS_VISIBLE is defined)
all this steps is strictly synchronous because SendMessage is sync function.
How windows looks depends on window class and on windows style

Message handling

As you may know some messages are received in thread queue others processed directly in WindowProc so you will never get WM_SIZE using GetMessage() or similar function

But messages from mouse and keybord will be sent to system queue
for example for erlier created messages in the same thread we use:

MSG msg;
while (GetMessage(&msg,0,0,0))
{
TCHAR buffer[MAX_PATH] = {0};
TCHAR windowName[MAX_PATH] = {0};
GetWindowText( msg.hwnd, windowName, MAX_PATH);
swprintf(buffer,L"Handle [0x%X] WindowName [%s] Message: [0x%X] \n",msg.hwnd, windowName , msg.message);
OutputDebugString(buffer);
DispatchMessage(&msg);
}

GetMessage Log:

Handle [0x0] WindowName [] Message: [0xC0B1]
Handle [0x0] WindowName [] Message: [0xC0B1]
Handle [0x60878] WindowName [MyDlg] Message: [0xF] // WM_PAINT
Handle [0x60870] WindowName [ClickMe] Message: [0xF] // WM_PAINT
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B7]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B9]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B9]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B9]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B9]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B9]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]
Handle [0x6086E] WindowName [CicMarshalWndAJCB] Message: [0xC0B6]

from the log we can see that only WM_PAINT message we receive from GetMessage. Messages with 0 handle are messages not aligned to windows. There is also a CicMarshalWndAJCB but we didn't create window with such mane. I created only two windows "ClickMe" and "MyDlg" so what is "CicMarshalWndAJCB" for?

of cource when I move my mouse to that window I receive all mouse/keyboard input messages like WM_MOUSEMOVE WM_KEYDOWN and othe hardware messages

In the Internet I also could not find any information about that window , so if someone reading this could help, please do

To complete this article I put log in dialog window proc to better understand what messages come first

WindowProc Log

Handle [0x3B086A] Message: [0x24] //WM_GETMINMAXINFO
Handle [0x3B086A] Message: [0x81] //WM_NCCREATE
Handle [0x3B086A] Message: [0x83] //WM_NCCALCSIZE
Handle [0x3B086A] Message: [0x1] //WM_CREATE
Handle [0x3B086A] Message: [0xD] //WM_GETTEXT my call
Handle [0x3B086A] WindowName [MyDlg] Message: [0x1] //WM_CREATE we receive only one wm create but I put log just to be sure that windowname is MyDlg
Handle [0x3B086A] Message: [0x210] // WM_PARENTNOTIFY
Handle [0x3B086A] Message: [0x18] //WM_SHOWWINDOW
Handle [0x3B086A] Message: [0x46] // WM_WINDOWPOSCHANGING
Handle [0x3B086A] Message: [0x46] // WM_WINDOWPOSCHANGING // this call from thread
Handle [0x3B086A] Message: [0x1C] // WM_ACTIVATEAPP
Handle [0x3B086A] Message: [0x86] // WM_NCACTIVATE
Handle [0x3B086A] Message: [0xD] // WM_GETTEXT
Handle [0x3B086A] Message: [0x6] // WM_ACTIVATE
Handle [0x3B086A] Message: [0x7] // WM_SETFOCUS
Handle [0x3B086A] Message: [0x85] // WM_NCPAINT
Handle [0x3B086A] Message: [0xD] // WM_GETTEXT
Handle [0x3B086A] Message: [0x14] // WM_ERASEBKGND !! I have handled it
Handle [0x3B086A] Message: [0x47] // WM_WINDOWPOSCHANGED
Handle [0x3B086A] Message: [0x5] // WM_SIZE
Handle [0x3B086A] Message: [0x3] // WM_MOVE
Handle [0x3B086A] Message: [0x7F] // WM_GETICON
Handle [0x3B086A] Message: [0x7F] // WM_GETICON
Handle [0x3B086A] Message: [0x7F] // WM_GETICON
Handle [0x3B086A] Message: [0xF] // WM_PAINT
Handle [0x3B086A] Message: [0x135] // WM_CTLCOLORBTN ClickMe send this message to parent

So this mechanism works very good
all other stuff and errors and a lot of complains alligned to higher level of API in user mode. Teoretically it is possible to rewrite user mode API to have very simple and ea sy to use operating system. I think this is might be done by 3rd party vendows that works with Windows CE OS

NDK Android

2010-07-24T16:44:00.003-04:00

Working in Android in the native level is quite interesting

To start working under Windows platform you need

1. Cygwin you need version for Windows
2. Go to Android NDK framework and download NDK, SDK
3. Install Eclipce and ADT plugin

Also you need JDK 1.5 or 1.6 installed
To Edit C++ sources you could install CDT C/C++ plugin Eclipce or use Microsoft Viusal Studio or Notepad++ with c++ plugin

Also download Android cpp sources. Using sources as manual you will understand more about what android consist of and will be able to all native library or drivers to extend Android functionality

Subclassing child window using WTL

2010-06-05T11:41:00.006-04:00

To create custom control you may use WM_DRAW_ITEM but this message you will receive in DLGPROC
So you have to draw control not in his own procedure but in parent one.

To resolve this complexity you can use subclassing with the child control.
If you are using WTL - all need to do is create class dediven not from standard WTL controls with other template parameter

For example for ATL::CListBox use

class CListBoxEx;

typedef CWindowImpl< CListBoxEx, CWindow, CControlWinTraits> CMyListBox;
template <>
HWND CListBoxT::Create(HWND hWndParent, ATL::_U_RECT rect, LPCTSTR szWindowName,
DWORD dwStyle, DWORD dwExStyle,
ATL::_U_MENUorID MenuOrID, LPVOID lpCreateParam)
{
   return CMyListBox::Create( hWndParent
, rect
, szWindowName
, dwStyle
, dwExStyle
, MenuOrID
, lpCreateParam);
}

template <>
CListBoxT::CListBoxT(HWND hParentHwnd)
:CMyListBox()
{
if (::IsWindow(hParentHwnd))
{
CMyListBox::SetParent(hParentHwnd);
}
}

class CListBoxEx :
public CListBoxT
{
...
}

This code allows you create a control and using Subclass-window replace WNDPROC for that control class
Now we can create or subclass a control

class CList_boxDialog : public CAppStdDialogResizeImpl,
public CUpdateUI,
public CMessageFilter, public CIdleHandler
{
...
LRESULT OnInitDialog(UINT uMsg, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& bHandled)
{
..
CWindow wnd = GetDlgItem(IDC_LIST_ADAPTERS);
mListBox.SubclassWindow(wnd);
mListBox.SetParent(m_hWnd);

mListBox.ResetContent();
mListBox.AddString(_T("First"));
mListBox.AddString(_T("Second"));
..
}

..
CListBoxEx mListBox;
}

Code above get controls window handle and WTL replace controls window procedure

You should allow all unhandled messages to pass to old WNDPROC to do it just return 'false' from
ProcessWindowMessage()

in CListBoxEx class:

BEGIN_MSG_MAP(CListBoxEx)
MESSAGE_HANDLER(OCM_DRAWITEM, OnDrawItem)
MESSAGE_HANDLER(OCM_MESUREITEM, OnMesureItem)
END_MSG_MAP()

Next step is message reflection

One of the most difficulties is to follow code in templates ..
In your CDialog class you need to reflect all messages so they will be handled in child control class
to reflect all unhanded messages use

class CMyDialog;
BEGIN_MSG_MAP(CMyDialog)

REFLECT_NOTIFICATIONS()
CHAIN_MSG_MAP(CAppStdDialogResizeImpl<CMyDialog>)END_MSG_MAP()

Now you should be able to receive OCM_XXX and handle them in child control

This trick allow you to hold code in one place and increase portability and reduce time to create applications
As usual people don't create GUI in C++ even for Windows CE, Mobile but who knows ;)

Nano-X window system

2010-05-22T18:11:00.006-04:00

Recently I have worked in Linux environment with a great NanoX project
It is about 300k size. NanoX provide solution for timer support, windows management, user input.

To use Nano-X you need only gcc c/c++ compiler that it is included in many(most) Linux systems

Architecture:

Features:
- message based system
- small size
- simple API
- add/replace any keyboard/mouse/screen driver
- font support. It is possible to add Unicode TrueType fonts

Lets discuss how to use it:

To create nano-X window you need :

#include "nano-x.h"

int main(int argv, char[][] argv)
{
GR_WINDOW_ID wnd =
GrNewWindow( GR_ROOT_WINDOW_ID
, 0,0,100,100
, WINDOW_NO_BORDER
, FOREGROUND_COLOR
, BLACKGROUND_COLOR); // create a window

   gc = GrNewGC(); // create a graphic context

//select events. you are able to select
//only that events that you need. this will boost your application
   GrSelectEvents( wnd, GR_EVENT_MASK_ALL);

GrMapWindow( wnd ); // show window

// you may create as many windows as you wish
// there is only one message queue for all Nano-X windows

GR_EVENT anEvent;
while (true)
{
GrCheckNextEvent(&anEvent);
if (anEvent.type == GR_EVENT_TYPE_NONE )
{
sleep(1);
continue;
}
if (HandleEvent(anEvent) == NEED_TO_EXIT) break;
}
// close all handles and exit
GrUnmapWindow(wnd); // hide window
GrDestroyGC( gc ); //
GrDestroyWindow( wnd );
}

Now you might understand nano-x weak side:

Messages might not be synchronized. ( for example when you kill window but some messages that was in queue might come)
Timer messages might not work proper under some circumstances (for example when you create a timer event, then change time in your system)
Pure focus management (for example you can use GrSetFocus() then destroy window and then GrGetFocus() doesn't return you focus to a parent window like it is in MS Window OS,
Font support is available but you have to dig into sources to add it.

iPhone SDK

2010-04-10T05:26:00.003-04:00

Yesterday, I start investigating IPhone SDK
there are few links that may help to start developing

MAC OS reference library SDK and framework

Objective C /C/C++ compiler for windows platform

Yii framework

2010-03-28T19:43:00.006-04:00

Not so long time ago I have learned php5 Yii framework
It is quite simple and well documented MVC framework
I like it!

So why I think it will be popular?
because it is easy to use.. and it is free
Here is few the most important features for me

Localization
first of all I pay attention to frameworks localization
only one static function

Yii::t("section", "string")

Security
It is very important to have only one entry point for all user requests
in this case you can wrap this entry with security patterns and framework itself already did it for you

All requests have the same entry for example

http://mysite.com/index.php?r=action&...

of cause you are able to create more attractive requests like

http://mysite.com/home/livingroom
http://mysite.com/2010/09/01/school

there is a trick.. all this urls redirect your request to one php file. remove php file entry name like "index.php" is done using .htaccess or if you are able to configure apache yourself it is could be done in *.conf file

Database
You are able to request data from database even if you don't know sql and even if you are not sure what database is installed on you web server. I mean code that Yii framework produces is working with any sql database platform (MySQL, PostageSQL, SQLite or other PDO php extention.
As results of the request it returns associative array and all other low-level stuff framework hides inside.

Widgets and Components
Widgets is a way to reuse you code - very powerful thing

I am not going to describe all Yii features, there is a manual for that

Android Streaming Audio

2010-03-19T20:08:00.004-04:00

Android audio framework

I will try to explain as detailed as possible about streaming audio in android. For this purposes in SDK 1.5 has been added AudioRecord and AudioTrack classes. AudioRecord is responsible to get samples from microphone and AudioTrack is responsible for playback samples.

This classes works only with PCM encoded data (it means that they are not encoded at all :)

Examples:
Play one buffer loop

Initialzation

AudioRecord record = null;
AudioTrack track = null;

record = new AudioRecord(MediaRecorder.AudioSource.MIC, 8000,
AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT,
AudioRecord.getMinBufferSize(8000, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT) * 4
);

log.d("AudioTrack min buffer size: "
+ AudioTrack.getMinBufferSize(8000, AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT));

track = new AudioTrack(AudioManager.STREAM_VOICE_CALL, 8000, AudioFormat.CHANNEL_CONFIGURATION_MONO,
AudioFormat.ENCODING_PCM_16BIT, AUDIO_SYSTEM_BUFFER_SIZE, AudioTrack.MODE_STREAM);

Initialization is quite simple. All you have to do is to create AudioRecord and AudioTrack

Start audio player
track.play();

Start audio recorder

record.startRecording();

Main Loop
while (needMoreAudioData)
{
recorder.read(buffer, bufferSize);
player.write(buffer, bufferSize);
}

Stop audio player/recorder
track.stop();
record.stop();

Remove player
Because this objects works with system resources developer has to release them when they are not in use. Java garbage collector will not release them automatically because instances hold system handlers.

track.release();
record.release();

Hope you have got the idea ...

Now few practical tips

When you call record.startRecording(); recording is already started! and to reduce latency you have to read that data immediately.

You should realize that android is not a real-time operating system and often call backs come not exactly at certain. You will end-up with increased latency over time unless you apply a sort of throttling algorithm to adjust playback side.

Sintral IDE

2009-03-25T04:40:00.001-04:00

Hello All,
I decided to delay all my own projects and ideas to finish Sintral IDE project

this is a program for STOLL knitting machine. From the first glance it looks like very simple VB language but also it is quite specific.
I've start this project for all old STOLL machines. they are still working bug they didn't have support by vendors. Software for them was created in 80-90s. Once I was able to see STOLL program for windows 95.

My friend ask me started this project... and I agreed :)

Features that are already done:

- BMP to TXT image converter
- TXT to BMP converter
- Sintral highlighter
- export to MS Word
- Pack/Unpack big Jackards
- Line, Rectangle, Normal selection
- Renumeration lines
- Syntax check
- STOLL communication via com port (read, write, erase)
- Language pack (russian, english)
- Add/remove external tools in programs menu
- Users help

I've translated all sources to Delphi 2009 Unicode version
Also I remove 3rd party component UniHighlighter and wrote a plugin component for UniSyn to highlight a sin language. I could not compile UniHighlighter in 30 minutes so I decided to drop this component down and remove from future using.
If you are the one who needs this application, please contact me over email or send me request here

Canon A540 camera problem

2009-01-31T19:24:00.001-05:00

Hi there

I'd like to talk about files...

I have a camera Canon A540 and when I get files to PC, they have name like img_XXXX.jpg

this is bad name for image because there is no information in the name. It doesn't contain when and where the photo was taken.

Other problem occurs when I try to remove some small defects (red ayes for example) I am losing last modification date and then I don't know when the photo was taken

If my camera is more smart I won't have this problem

So I decided to create a console application for changing file name. And the main task was to add date, time and prefix to filename. Sure I understand that if I change filename the last file modification date would be changed. So I add a file description to do reverse operation if there is a need.

Finally I have finished the program. It was not difficult to implement but I have no free time for that game.

So about program:

NameChanger - if you need one just mail me

You should use program with arguments:

-r - recursive search in sub-folders

-d -t - rename fonded file and insert date and time in file name

-pimg - insert prefix img in file name so all you files will start from this prefix. it is convinient when you just download photos from camera and wanted a prefix (for example: my_summer_holidays )

-ejpg - rename files only with jpg extension

-iimg - ignore files started with "img"

So in general you could use this command tool like bellow:

NameChanger.exe -d -t -r -pparty -ejpg

I have used it and noticed that some files have the same file modify date and time. In this case NameChanger add a letter to the resulted name. For example if you have three files with the same date and time then you will have

summer_2009_06_01_13_27_10.jpg

summer_2009_06_01_13_27_10A.jpg

summer_2009_06_01_13_27_10B.jpg

Windows Mobile API ToolBar

2008-10-31T22:55:00.001-04:00

Today I'd like to make some suggestion about CCommandBar class for Windows Mobile 5.0.
You can use MFC menu wrapper class or you can use Windows WINAPI function to get access to the ToolBar

MFC class CCommandBar class has no API to access to menu items and doesn't know how to control the menu. After a brief investigation and experiments with the menu I have got a working code:
TBBUTTON tbb;
::SendMessage(m_oCommandBar.GetSafeHwnd(), TB_GETBUTTON, 1, (LPARAM)&tbb);
HMENU hMenu=HMENU(tbb.dwData);
if(hMenu)
{
::DeleteMenu(hMenu,0,MF_BYPOSITION);
::InsertMenu(hMenu,0,MF_BYPOSITION, ID_MENU_FR_SHOWDETAILS, L"Show Details");
}

Here m_oCommandBar is an instance of CCommandBar. By using windows messages you can access to WINAPI menu and create a dynamic menus :-)

WMI database

2008-10-09T10:12:00.000-04:00

Hi there !
I'd like to tell you about WMI
It's a pretty huge database with common API to access to the hardware/software information
It contains different information about operating system and hardware. For example computer name, TCP/IP address, DNS, and DHCP information and many other keys that are necessary for normal working.
Also, I notice that it builds as a COM service and it is available from different languages C++, C, Pascal, Visual Basic and scripts such as VBScript.
According to C++ to invoke a method we need to do a lot of work. So I show you how to use:
I have created two classes: first is for reading properties, second to invoke methods.
WMI divided to several groups and each group contain classes:
For example Network group contains NetworkAdapter, NetworkAdapterConfigurator
It's not a c++ classes. Actually, it is a description of the class which you can use with not C++ languages.

small annoying bugs :-(

2008-09-23T11:55:00.002-04:00

Sometimes when you debugging a code, You don't expect a bug in project settings and you may spend hours to find it.

Here is some suggestions that may help you with it.
This is applicable to mobile development:

1. All resources line memory allocation, files, etc., you need to put in a wrapper: shared_ptr myPointer(rawPointer)

2. All unexpected behavior line "low memory" should throw an exception and exit.

class MyDataBlock
{
char* mData;
public:
MyDataBlock():mData(NULL){}
MyDataBlock():mData(int size)
{
ASSERT(size>0,"wrong size");
mData = new char[size];
ASSERT(mData,"low memory");
}

~MyDataBlock()
{
delete[] mData;
}
}

3. Logs

developer logs - you must have them if there is no way to run application in debug mode. This is more applicable to OS driver development or other specific domain development.
when exception happen try to log stack. When application crashes it is very useful to have function calls stack.

Factorial calculation

2008-07-31T15:39:00.002-04:00

Hello everyone!
Yesterday, I have implemented program that calculates 2347!.
That is the same as 1*2*...*2347
It is really big number that holds 10000 digits
I will publish it in the next posts. One thing I observed is: I like creating really compact programs...

User activity

2008-07-22T18:44:00.000-04:00

I'd like to create a user activity driver

It will have two modes:

in the first mode, it collects data from the user (mouse and keyboard) and store them to a local file
in the second mode, it reproduces data from the file so we could have a very small sized video demonstration.

Folder monitor

2008-07-17T09:41:00.000-04:00

I'd like to implement folder monitor. I think it should be easy because there is a Win32 API to do this.

Also, I could do this via driver...