No Geek Here!

DLL (Dynamic-Link Library) Search Order

2009-10-21T08:46:00.000+08:00

Are you sure that your program loads the DLLs expected? You may want to check the search order for loading the proper DLLs.

Standard Search Order (SafeDllSearchMode is enabled)
1. The directory from which the application loaded.
2. The system directory. Use the GetSystemDirectory function to get the path of this directory.
3. The 16-bit system directory. There is no function that obtains the path of this directory, but it is searched.
4. The Windows directory. Use the GetWindowsDirectory function to get the path of this directory.
5. The current directory.
6. The directories that are listed in the PATH environment variable. Note that this does not include the per-application path specified by the App Paths registry key. The App Paths key is not used when computing the DLL search path.

More Detail Information
Dynamic-Link Library Search Order

Mp4 Explorer

2009-09-12T10:56:00.001+08:00

Brief Introdution
This software is a very helpful tool to inspect and see in details a mp4 file and it is open source. In my case, I was trying to write a program to convert certain video to be compatible with iPhone, but I had no idea about it. Then, I found this useful utility and used it to inspect the video structure of some compatible mp4 files.

You can download the program and its source code in the following web site:

Official Website - Mp4 Explorer
http://mp4explorer.codeplex.com/

How To: Get the Content of Certain Environment Variable, ie: %ProgramFiles%

2009-08-26T08:55:00.000+08:00

Code Snippet

#include <windows.h>
#include <string>

using namespace std;

wstring GetContentFromEnvironmentVariable(const wstring& wstrVariable)
{
  // Get the content of %ProgramFiles%

  wstring wstrRtn;
  DWORD dwSize = ::GetEnvironmentVariableW(wstrVariable.c_str(), NULL, NULL);
  if(dwSize > 0)
  {
    wchar_t* wszContent = new wchar_t [dwSize];
    dwSize = ::GetEnvironmentVariableW(wstrVariable.c_str(), wszContent, dwSize);

    wstrRtn = wszContent;

    delete [] wszContent;
    wszContent = NULL;
}

return wstrRtn;
}

Reference on MSDN
GetEnvironmentVariable Function

How To: Get the Installation Directory of Windows Media Player

2009-07-30T18:28:00.004+08:00

Code Snippet

bool GetWMPInstallDirectory(wstring& wstrDirectory)
{
  bool bOK = false;
  HKEY hkResult = NULL;

  LONG lRet = ::RegOpenKeyExW(HKEY_LOCAL_MACHINE,
    L"SOFTWARE\\Microsoft\\MediaPlayer", NULL, NULL, &hkResult);

  if(lRet == ERROR_SUCCESS)
  {
    wchar_t wszRet[_MAX_PATH] = {0};
    DWORD type = REG_SZ;
    DWORD cbData = sizeof(wszRet);

    lRet = ::RegQueryValueExW(hkResult, L"Installation Directory",
      NULL, &type, (LPBYTE)wszRet, &cbData);

    if(lRet == ERROR_SUCCESS)
    {
      // We've got the installation directory of WMP
      wstrDirectory = wszRet;
      bOK = true;
    }

    ::RegCloseKey(hkResult);
    hkResult = NULL;
  }

  return bOK;
}

How To: Disable General Protection Fault Dialog for Your Program

2009-06-12T09:20:00.003+08:00

Abstraction

Are you using any 3rd-party componet or ActiveX, which is not stable enough, in your program? You will get a GPF dialog if the componet in your program goes abnormal. That is not your problem totally, but actually your program crashed. There's a Windows API to prevent showing GPF dialog, you may adapt this solution if the crash can be ignored.

Code Snippet

UINT uPrevErrMode = SetErrorMode(SEM_NOGPFAULTERRORBOX);

Do you not know what GPF is?

General Protection Fault

Reference on MSDN

SetErrorMode Function

Read/Write Windows Registry on Windows 64-Bits Platforms (C# Version)

2009-06-06T09:03:00.004+08:00

Abstraction

How does a 32-bits(x64) program running on Windows 64-bits(x64) access the 64-bits registry? In C#, you can use P/Invoke to call RegOpenKeyEx function with KEY_WOW64_KEY to access the 64-bits registry.

Code Snippet

//
// This is a C# example to get the version of Windows Media Center on Windows 7 64-bits.
//
class RegQueryValueDemo
{
  [DllImport("advapi32.dll", CharSet = CharSet.Unicode, EntryPoint = "RegOpenKeyExW", SetLastError = true)]
  public static extern int RegOpenKeyEx(UIntPtr hKey, string subKey, uint options, int sam, out UIntPtr phkResult);
  public static UIntPtr HKEY_CURRENT_USER = (UIntPtr)0x80000001;
  public static UIntPtr HKEY_LOCAL_MACHINE = (UIntPtr)0x80000002;
  public static int KEY_QUERY_VALUE = 0x0001;
  public static int KEY_SET_VALUE = 0x0002;
  public static int KEY_CREATE_SUB_KEY = 0x0004;
  public static int KEY_ENUMERATE_SUB_KEYS = 0x0008;
  public static int KEY_WOW64_64KEY = 0x0100;
  public static int KEY_WOW64_32KEY = 0x0200;

  [DllImport("advapi32.dll", CharSet = CharSet.Unicode, EntryPoint = "RegQueryValueExW", SetLastError = true)]
  public static extern int RegQueryValueEx(UIntPtr hKey, string lpValueName, int lpReserved, out uint lpType,
    StringBuilder lpData, ref int lpcbData);

  public string GetMCEIdent()
  {
    UIntPtr regKeyHandle;
    if (RegOpenKeyEx(
    HKEY_LOCAL_MACHINE,
    "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Media Center",
    0, KEY_QUERY_VALUE | KEY_WOW64_64KEY, out regKeyHandle) == 0)
    {
      uint type;

      StringBuilder stringBuilder = new StringBuilder(2048);
      int cbData = stringBuilder.Capacity;
      if (RegQueryValueEx(regKeyHandle, "Ident", 0, out type, stringBuilder, ref cbData) == 0)
      {
        return stringBuilder.ToString();
      }
    }

    return string.Empty;
  }
}

Find a C++ version?
Read/Write Windows Registry on Windows 64-Bits Platforms

Reference on MSDN:
RegOpenKeyEx Function
32-bit and 64-bit Application Data in the Registry

How To: A Web Page Interacts with a Embedded Web Browser Control

2009-05-24T23:22:00.001+08:00

If your application contains a web browser control to show certain web page, can the web page interact with your application by script language? Yes, it can.

There's a sample on MSDN, it's very short but clear, please refer to the following link:

Reference on MSDN

WebBrowser.ObjectForScripting Property

Windows Media ASF Viewer

2009-05-20T19:06:00.001+08:00

Windows Media® ASF Viewer 9 Series is a tool for inspecting the contents of files (such as .asf. .wma, and .wmv file) to make sure they meet the requirements of the Advanced Systems Format (ASF) specification. -- Microsoft

Brief Introduction

This tool is very helpful for analyzing the contents of ASF files, it helps us to know the media structure and content easily. I was trying to encode WMV using Windows Media Format SDK, and this tool really helped me to verify the output content.

Download from Microsoft

Windows Media ASF Viewer 9 Series

How To: Extracting the embedded album art from a MP3 / WMA

2009-05-14T23:15:00.003+08:00

I'm using Windows Media Sync Reader in Windows Media Format SDK to get the album art from id3 tag of a MP3, it can also get from a WMA.

Code Snippet:

#include <windows.h>
#include <wmsdk.h>
#include <atlbase.h>

#pragma comment(lib, "wmvcore.lib")

bool ExtractEmbeddedAlbumArt(LPCWSTR wszAudioFile)
{
  bool bOK = false;

  WM_PICTURE* pPicture = NULL;;

  do {

    CComPtr<IWMSyncReader> pIWMSyncReader;
    if(FAILED(WMCreateSyncReader(NULL, 0, &pIWMSyncReader))) break;

    if(FAILED(pIWMSyncReader->Open(wszAudioFile))) break;

    CComPtr<IWMHeaderInfo3> pIWMHeaderInfo3;
    if(FAILED(pIWMSyncReader->QueryInterface(&pIWMHeaderInfo3))) break;

    WMT_ATTR_DATATYPE wmtDataType = WMT_TYPE_BINARY;
    WORD wStreamNum = 0;
    WORD wLength = 0;
    if(FAILED(pIWMHeaderInfo3->GetAttributeByName(
      &wStreamNum, g_wszWMPicture, &wmtDataType, NULL, &wLength))) break;

    pPicture = (WM_PICTURE*)new BYTE[wLength];

    if(FAILED(pIWMHeaderInfo3->GetAttributeByName(
      &wStreamNum, g_wszWMPicture, &wmtDataType, (BYTE*)pPicture, &wLength))) break;

    bOK = true;

  } while(false);

  if(pPicture)
  {
    //
    // TODO: Save the picture or do something with it
    //

    delete [] (BYTE*)pPicture;
    pPicture = NULL;
  }

  return bOK;
}

How To: Handle dynamic format change in ReceiveConnection function on a renderer filter.

2009-04-28T21:27:00.002+08:00

I was trying to correctly handle dynamic format change on my video null renderer and had fought against it for several days.

The following code snippet is my final work for handling dynamic format change, it seems to work fine, I hope so :p

STDMETHODIMP CNullRendererInputPin::ReceiveConnection(IPin * pConnector, const AM_MEDIA_TYPE *pmt)
{
  CAutoLock lock(m_pLock);

  CMediaType newMediaType(*pmt);

  HRESULT hr = E_FAIL;

  if(m_Connected && m_Connected == pConnector && newMediaType != m_mt)
  {
    do {

      hr = CheckMediaType(&newMediaType);
      if(FAILED(hr)) break;

      BITMAPINFO bmpinfo = {0};
      if(FORMAT_VideoInfo == pmt->formattype && 1 == pmt->bFixedSizeSamples)
      {
        VIDEOINFOHEADER* t = (VIDEOINFOHEADER*)(pmt->pbFormat);
        bmpinfo.bmiHeader = t->bmiHeader;
      }
      else if(FORMAT_VideoInfo2 == pmt->formattype && 1 == pmt->bFixedSizeSamples)
      {
        VIDEOINFOHEADER2* t = (VIDEOINFOHEADER2*)(pmt->pbFormat);
        bmpinfo.bmiHeader = t->bmiHeader;
      }
      else
      {
        hr = E_UNEXPECTED;
        break;
      }

      ALLOCATOR_PROPERTIES allocProperties = {0};
      {
        hr = m_pAllocator->GetProperties(&allocProperties);
        if(FAILED(hr)) break;

        allocProperties.cbBuffer = bmpinfo.bmiHeader.biSizeImage;
      }

      hr = SetMediaType(&newMediaType);
      if(FAILED(hr)) break;

      hr = m_pAllocator->Decommit();
      if(FAILED(hr)) break;

      {
        ALLOCATOR_PROPERTIES newAllocProperties = {0};
        hr = m_pAllocator->SetProperties(&allocProperties, &newAllocProperties);
        if(FAILED(hr)) break;
      }

      hr = m_pAllocator->Commit();
      if(FAILED(hr)) break;

      hr = S_OK;

    } while(false);
  }
  else
  {
    hr = CBasePin::ReceiveConnection(pConnector, pmt);
  }

  return hr;
}

Why will WCF client be disconnected after the connection idles for a long time?

2009-04-15T22:25:00.003+08:00

The default receive timeout is 10 minutes, so WCF client will be disconnected after the idle time exceeded that limitation. What can I do if the connection needs to be kept alive?

Solution #1 - Server provides a dummy operation for client calls it regularly to let it not idle.

Solution #2 - Enable reliableSession and set receiveTimeout and inactivityTimeout to "infinite" in both the client and server.

The configuration snippet may like the following:

<system.serviceModel>
  <bindings>
    <wsHttpBinding>
      <binding name="WSHttpBinding" receiveTimeout="infinite">
        <reliableSession inactivityTimeout="infinite" enabled="true" />
      </binding>
    </wsHttpBinding>
  </bindings>
  <services>
  ...
  </services>
  ...
</system.serviceModel>

You can get more detail explanation in the following reference link.

Reference in MSDN:
Binding.ReceiveTimeout Property

Reference in Paulo Reichert's Blog
WCF Reliable Sessions Puzzle

How To: Detect Windows Media Center Version

2009-04-10T08:34:00.007+08:00

If your program is depending on a specified version of Windows Media Center, just try the following code to identify Windows Media Center versions.

Sample Code:

//
// Get Windows Media Center version from registry
// Function return false if no media center is installed on your windows
//
// Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Media Center
// Registry value name: Ident
// Registry value data type: REG_SZ
//
bool GetMediaCenterIdent(wstring& wstrIdent)
{
  bool bRtn = false;

  HKEY hkResult = NULL;
  LONG lRetOpen = ::RegOpenKeyExW(
    HKEY_LOCAL_MACHINE,
    L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Media Center",
    NULL, KEY_READ, &hkResult);

  if(lRetOpen == ERROR_SUCCESS)
  {
    WCHAR wszRet[2048] = {0};
    DWORD type_1 = REG_SZ;
    DWORD cbData = sizeof(wszRet);

    LONG lRetQuery = ::RegQueryValueExW(hkResult, L"Ident", NULL,
      &type_1, (unsigned char *)wszRet, &cbData);
    if(lRetQuery == ERROR_SUCCESS)
    {
      wstrIdent = wszRet;
      bRtn = true;
    }
  }

  if(hkResult)
  {
    ::RegCloseKey(hkResult);
    hkResult = NULL;
  }

  return bRtn;
}

Ident value v.s Windows Media Center version

< 2.7 = Windows XP Media Center Edition 2002
2.7 or 2.8 = Windows XP Media Center Edition 2004
3.0 = Windows XP Media Center Edition 2005
3.1 = Windows XP Media Center Edition 2005 with Update Rollup 1
4.0 = Windows XP Media Center Edition 2005 with Update Rollup 2
5.0 = Windows Vista
5.1 = Windows Vista with Media Center TV Pack 2008
6.0 = Windows 7

Reference on MSDN:
Identifying Windows Media Center Versions

How To: Determine whether a 32-bits application is running on Windows 64-bits platform

2009-04-06T19:04:00.008+08:00

WOW64 is the x86 emulator that allows 32-bit Windows-based applications to run seamlessly on 64-bit Windows.

Sample Code:

bool IsRunningOnWow64()
{
  BOOL bIsWow64 = FALSE;

  BOOL (WINAPI *fnIsWow64Process)(HANDLE, PBOOL);
  fnIsWow64Process = (BOOL(WINAPI*)(HANDLE, PBOOL))::GetProcAddress(
    ::GetModuleHandleW(L"kernel32"), "IsWow64Process");

  if(NULL != fnIsWow64Process)
    fnIsWow64Process(GetCurrentProcess(), &bIsWow64);

  return bIsWow64 ? true : false;
}

Reference on MSDN:
IsWow64Process Function

Read/Write Windows Registry on Windows 64-Bits Platforms

2009-04-02T19:18:00.004+08:00

On Windows Vista 64-bits, there's a 32-bits emulator called WOW64 for 32-bits applications. A 32-bits application running on WOW64 uses the registry redirector, because the 64-bit version of an application may use different registry keys and values than the 32-bit version.

For 32-bits application:
On 64-bit platforms, it runs on WOW64 and accesses 32-bit registry (inside Wow6432Node).

For 64-bits application:
On 64-bit platforms, it runs natively and accesses 64-bit registry (not inside Wow6432Node).

Whatever, you can explicitly indicate which version of registry you want to access, just use RegOpenKeyEx function with KEY_WOW64_32KEY or KEY_WOW64_64KEY in the desired access rights parameter.

Example: A 32-bit application running on WOW64 accesses the 64-bit registry

HKEY hkResult = NULL;
REGSAM samDesired = KEY_READ | KEY_WOW64_64KEY;
LONG lRetOpen = ::RegOpenKeyExW(
  HKEY_LOCAL_MACHINE,
  L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Media Center",
  NULL, samDesired, &hkResult);

Reference on MSDN:
32-bit and 64-bit Application Data in the Registry

Where can I find the list of installed ACM codecs on Vista?

2009-03-10T22:15:00.002+08:00

It has moved to a strange place on Vista. Do the following steps to see the list:

1. Click on Windows Media Player 11 -> Help -> About -> Technical Support Information

2. It will generate "Support Information for Windows Media Player" and look under "Audio Codecs".

You can also see the information about windows media player binaries and the list of video codecs.

Reference:

Moving to Vista-- Part D'oh

error C3861: 'CoInitializeEx': identifier not found, even with argument-dependent lookup

2009-03-04T22:31:00.002+08:00

You may get the following errors when trying to call CoInitializeEx(NULL, COINIT_MULTITHREADED).

error C2065: 'COINIT_MULTITHREADED' : undeclared identifier

error C3861: 'CoInitializeEx': identifier not found, even with argument-dependent lookup

The article in MSDN says "You must include the #define _WIN32_DCOM preprocessor directive at the beginning of your code to be able to use CoInitializeEx."

Look at the code snap in ObjBase.h:

#if (_WIN32_WINNT >= 0x0400 ) || defined(_WIN32_DCOM) // DCOM

WINOLEAPI CoInitializeEx(IN LPVOID pvReserved, IN DWORD dwCoInit);

WINOLEAPI CoGetCallerTID( LPDWORD lpdwTID );

#endif // DCOM

So, you need to follow the above rule if you want to call CoInitializeEx, of course you also need to include <objbase.h>.

Reference in MSDN:

CoInitializeEx

Why is the media sample upside down after convert its buffer data from YUV to RGB?

2009-03-01T14:08:00.002+08:00

Question

I converted the buffer of a media sample from YUY2 to RGB24 pixel by pixel, and then I got a upside-down image. What's wrong with it?

Answer

The definition of the biHeight field of BITMAPINFOHEADER depends the the biCompression field of BITMAPINFOHEADER.

If the bitmap is uncompressed RGB format, the positive biHeight value means the image is bottom-up image; if the bitmap is one of YUV formats such as YUY2, UYVY, and YV12, the image is top-down oriented and the sign of biHeight value must be ignored.

So, I need to do a vertical flip to get a correct image after convert buffer data from YUY2 to RGB24.

You can get more detail information in FOURCC.org: Bitmap Orientation and biHeight

FORMAT_VideoInfo v.s. FORMAT_VideoInfo2

2009-02-21T00:05:00.004+08:00

If the media type is FORMAT_VideoInfo, it means the format buffer is a VIDEOINFOHEADER struct; if the media type is FORMAT_VideoInfo2, it means the format buffer is a VIDEOINFOHEADER2 struct. So, what's different between VIDEOINFOHEADER and VIDEOINFOHEADER2?

VIDEOINFOHEADER and VIDEOINFOHEADER2 are very different, VIDEOINFOHEADER2 is not just an entended struct of VIDEOINFOHEADER. This means you cannot cast a pointer of VIDEOINFOHEADER2 to a pointer of VIDEOINFOHEADER.

INCORRECT:

if(pmt->formattype == FORMAT_VideoInfo || pmt->formattype == FORMAT_VideoInfo2)

{

VIDEOINFOHEADER *pVIH = (VIDEOINFOHEADER*)pmt->pbFormat;

// *** Wrong! ***

}

CORRECT:

if(pmt->formattype == FORMAT_VideoInfo)

{

VIDEOINFOHEADER *pVIH = (VIDEOINFOHEADER*)pmt->pbFormat;

// Now you can use pVIH.

}

else if(pmt->formattype == FORMAT_VideoInfo2)

{

VIDEOINFOHEADER2 *pVIH = (VIDEOINFOHEADER2*)pmt->pbFormat;

// Now you can use pVIH.

}

Reference in MSDN:

VIDEOINFOHEADER Structure

VIDEOINFOHEADER2 Structure

How To: Toggle / Next Bookmark in Visual C++

2009-02-17T23:12:00.004+08:00

Bookmarking is a very useful feature of Visual C++ when you are coding, but the keyboard short cuts of this function is hard to remember. In the menu, you can find the short cuts of toggle and next bookmark are "Ctrl + K Ctrl +K" and "Ctrl + K Ctrl + N" respectively, but why do I need to press so many keys just for toggle or next bookmark?

You can do it more easily, just use the following short cuts:

Toggle Bookmark - Ctrl + F2

Next Bookmark - F2

Wow! It is very easy to use, isn't it? Enjoy bookmarking feature during your coding time.

I have tried it on Visual C++ 6 / 2003 / 2005 / 2008, it works fine.

(Note: The key mapping of Visual Studio is set to default "Visual C++".)

Reference in This Site:

The easiest way to toggle / next bookmark in Visual Studio

How To: STL String Case-insensitive Compare

2009-02-12T08:49:00.015+08:00

This article is talking about how to do a case-insensitive compare for STL string and wstring, there're 2 ways to reach the goal.

Method #1: C Run-time Library - _stricmp() and _wcsicmp()

#include <string>

using namespace std;

string strUpperCase = "ABC";
string strLowerCase = "abc";
if(_stricmp(strUpperCase.c_str(), strLowerCase.c_str()) == 0)
// For wstring, use _wcsicmp() instead.
{
  // Do something you need
}

Method #2: STL Algorithm - transform()

#include <cctype>
#include <string>
#include <algorithm>

using namespace std;

// I make a helper function to compare string
bool CompareCaseInsensitive(string strFirst, string strSecond)
{
  // Convert both strings to upper case by transfrom() before compare.
  transform(strFirst.begin(), strFirst.end(), strFirst.begin(), toupper);
  transform(strSecond.begin(), strSecond.end(), strSecond.begin(), toupper);
  if(strFirst == strSecond) return true; else return false;
}

string strUpperCase = "ABC";
string strLowerCase = "abc";
if(CompareCaseInsensitive(strUpperCase, strLowerCase))
{
  // Do something you need
}

Reference in This Site:
How to convert STL string / wstring to upper / lower case?

Reference in MSDN:
_stricmp, _wcsicmp, _mbsicmp, _stricmp_l, _wcsicmp_l, _mbsicmp_l

More explanation of CoInitialize() and CoUninitialize()

2009-01-19T19:53:00.002+08:00

In this article, I'll not talk about how it works about the COM's apartment model, but the coding practice.

CoInitializeEx() provides the same functionality as CoInitialize() except it provides a parameter to specify the thread's apartment model. So, MSDN recommands us to call CoInitializeEx() instead of CoInitialize().

For using CoInitializeEx(), we also need to follow the same rules as CoInitialize(), I mentioned in the previous article.

The following examples explain how to use CoInitializeEx() and CoUninitialize():

Example #1: CoInitializeEx() will return S_FALSE if the COM library was loaded.

void main()

{

HRESULT hr = E_FAIL;

// The first call

hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED); // hr = S_OK

// The second call

hr = CoInitialize(NULL); // hr = S_FALSE, CoInitialize(NULL) = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED)

// ... skip ...

// For the second call

CoUninitialize();

// For the first call

CoUninitialize(); // COM library will be unloaded

}

Example #2: CoInitializeEx() will return RPC_E_CHANGED_MODE if a previous call to CoInitializeEx() specified a different apartment model

void main()

{

HRESULT hr = E_FAIL;

// The first call

hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED); // hr = S_OK

// The second call

hr = CoInitializeEx(NULL, COINIT_MULTITHREADED); // hr = RPC_E_CHANGED_MODE, the thread's apartment model is still the single thread apartment.

// ... skip ...

// NOTE: We do not need to call CoUninitialize() if the corresponding call made by CoInitializeEx() returns error.

// For the first call

CoUninitialize(); // COM library will be unloaded

}

A clear explanation of CoInitialize() and CoUninitialize()

2009-01-18T22:25:00.003+08:00

As you know, when you are using DirectShow or the other COM-based components, the first thing you have to do is calling CoInitialize() to initialize the COM library.

Furthermore, there are several rules you should follow. Now, I will give you a clear explanation here.

Rule #1: For each thread, you have to call CoInitialize() before you call any of the COM library funtions except CoGetMalloc() and the memory allocation functions.

Rule #2: For each successful call made by CoInitialize(), you have to call CoUninitialize() to free the COM library.

Rule #3: Do not call CoInitialize() or CoUninitialize() from the DllMain() function.

Rule #4: The first thread in the application that calls CoInitialize() must be the last thread to call CoUninitialize().

Reference in MSDN:
CoInitialize

fatal error RC1015: cannot open include file 'activex.ver'.

2009-01-15T08:46:00.002+08:00

Error Message:

fatal error RC1015: cannot open include file 'activex.ver'.

When compile the DirectShow filter sample in DXSDK, you may get the above error message.

Root Cause:

The resource file(.rc) includes <activex.ver> and <activex.rcv>, but compiler cannot find them.

Solution:

activex.ver and activex.rcv are in %DXSDK%\Samples\C++\DirectShow\BaseClasses

(%DXSDK% is your dx sdk installed directory.)

Add the above path to "VC++ Directories" of your VC++ setting,

or add it to "Additional Include Directories" of your project setting.

How to correctly call HttpOpenRequest() with specified accept types?

2009-01-10T20:41:00.012+08:00

Windows API: (Wininet)

HINTERNET HttpOpenRequest(

__in HINTERNET hConnect,

__in LPCTSTR lpszVerb,

__in LPCTSTR lpszObjectName,

__in LPCTSTR lpszVersion,

__in LPCTSTR lpszReferer,

__in LPCTSTR *lplpszAcceptTypes,

__in DWORD dwFlags,

__in DWORD_PTR dwContext

);

Tips:

lplpszAcceptTypes is not a pointer to a null-terminated string, it is a pointer to a null-terminated array of strings.

Sample Code:

// A null-terminated array of null-terminated strings

const char* lplpszAcceptTypes[] = {"text/*", NULL}; // Accept only text documents

HINTERNET hHttpFile = HttpOpenRequestA(

hConnect,

"GET",

"/TextDocument",

HTTP_VERSION,

NULL,

lplpszAcceptTypes,

INTERNET_FLAG_DONT_CACHE, 1);

Reference in MSDN:

HttpOpenRequest Function

How to get the last modified date of a file in C++?

2009-01-01T18:16:00.013+08:00

On Win32 platform, you can get the attribute information of a file easily by just calling GetFileAttributesEx().

The information you got includes creation time, last access time, and last write time (last modified date).

Windows API:

BOOL WINAPI GetFileAttributesEx(

__in LPCTSTR lpFileName,

__in GET_FILEEX_INFO_LEVELS fInfoLevelId,

__out LPVOID lpFileInformation

);

Sample Code:

WIN32_FILE_ATTRIBUTE_DATA fileAttrData = {0};

GetFileAttributesExW(L"C:\\abc.txt, GetFileExInfoStandard, &fileAttrData);

// GetFileAttributesExA for non-unicode

FILETIME ftLastModifiedDate = fileAttrData.ftLastWriteTime;

Reference in This Site:

SYSTEMTIME, FILETIME, and LARGE_INTEGER

What happened to LocalFileTimeToFileTime() / FileTimeToLocalFileTime()?

Reference in MSDN:

GetFileAttributesEx Function

How to create a file that will be deleted automatically after close its handle?

2008-12-19T15:12:00.007+08:00

Use CreateFile() API with the flag: FILE_FLAG_DELETE_ON_CLOSE

If we want to create a file when the process starts and delete it when the process exits, CreateFile() is convenient to you.

FILE_FLAG_DELETE_ON_CLOSE means the file will be deleted automatically after close hanlde. Even if the process was crashed, it would also be deleted.

Reference in MSDN:

CreateFile Function

What happened to LocalFileTimeToFileTime() / FileTimeToLocalFileTime()?

2008-11-08T14:00:00.007+08:00

When you want to convert a time between UTC and local, you may choose the API LocalFileTimeToFileTime() or FileTimeToLocalFileTime() for this job.

Do you know you may get an unexpected result if it is daylight saving time?

LocalFileTimeToFileTime() and FileTimeToLocalFileTime() use the current settings for the time zone and daylight saving time. Therefore, if it is daylight saving time, these functions will take daylight saving time into account, even if the time you are converting is in standard time.

Solution:

You can use SystemTimeToTzSpecificLocalTime() and TzSpecificLocalTimeToSystemTime() instead.

Reference in This Site:

SYSTEMTIME, FILETIME, and LARGE_INTEGER

Reference in MSDN:

SystemTimeToTzSpecificLocalTime Function

Why is INSERT / UPDATE command very bad performance on SQLite?

2008-11-03T23:27:00.007+08:00

When you do a lot of INSERT / UPDATE on a table, it is a good time to contain them within a transaction,

begin;
insert into table values (..);
insert into table values (..);
insert into table values (..);
....
commit;

This will make SQLite save all changes to the disk at once.

Reference in SQLite:
http://www.sqlite.org/cvstrac/wiki?p=PerformanceConsiderations

How to raise an user break exception (int 3) dynamically in my code?

2008-10-12T17:07:00.008+08:00

The embedded assembly code way:
_asm int 3

The Windows API way:
DebugBreak()

After raised an user break exception in your code, the program can be attached to a debugger. For some situation, this is a good way to debug your buggy problem.

Reference in MSDN:
http://msdn.microsoft.com/en-us/library/ms679297.aspx

How to convert STL string / wstring to upper / lower case?

2008-10-04T10:40:00.011+08:00

This is the STL algorithm way, I think it is better than the itoa() way.

Sample Code:

#include <cctype>

#include <string>
#include <algorithm>

using namespace std;

// Convert string to lower case
string strTest = "I am a STL string";
transform(
  strTest.begin(), strTest.end(),
  strTest.begin(),
  tolower); // toupper for upper case

// Convert wstring to upper case
wstring wstrTest = L"I am a STL wstring";

transform(
  wstrTest.begin(), wstrTest.end(),
  wstrTest.begin(),
  towupper); // towlower for lower case

Reference in MSDN:

transfom

How to mute an Audio Capture Filter of webcam in DirectShow?

2008-09-28T16:19:00.007+08:00

If you want to mute an audio capture of webcam, you have to query IAMAudioInputMixer interface on its INPUT PIN, and then use put_Enable method to disable it.

Both the audio capture filter itself and its input pin have IAMAudioInputMixer interface, but the put_Enable / get_Enable methods are implemented on input pin only.

Reference in MSDN:
http://msdn.microsoft.com/en-us/library/ms783820.aspx

How to get the string from GUID in DirectShow?

2008-09-07T14:25:00.002+08:00

There is a very useful global array that contains strings representing the GUIDs defined in Uuids.h

char* GuidNames[guid]

Example:
const char* GetMajorTypeString(CMediaType* pMediaType)
{
return GuidNames[*(pMediaType->Type())];
}

Reference:
http://msdn.microsoft.com/en-us/library/ms783758.aspx

Small, simple, cross-platform, free and fast C++ XML Parser

2008-09-06T12:59:00.004+08:00

I prefer using this one of XML Parser. It is really simple and convenience. And it contains ONLY TWO files, including "xmlparser.cpp" and "xmlparser.h"

I can compile it without error on VC++ (Visual C++) 2003 and 2005, and it works very well.

You can get more detail information on author's web site.

Small, simple, cross-platform, free and fast C++ XML Parser
http://www.applied-mathematics.net/tools/xmlParser.html

The easiest way to toggle / next bookmark in Visual Studio

2008-09-05T21:39:00.005+08:00

Shortcuts:
Toggle Bookmark: Ctrl + K Ctrl +K
Next Bookmark: Ctrl + K Ctrl + N

Tips:
You can find the above shortcuts on the bookmark menu, but it is NOT the easiest way to do that.

The other Shortcuts:
Toggle Bookmark: Ctrl + F2
Next Bookmark: F2
(The key mapping is "Visual C++")

Why did the RegQueryValueEx() return ERROR_MORE_DATA?

2008-08-29T09:41:00.007+08:00

Q: Why does the RegQueryValueEx() always return ERROR_MORE_DATA?

A: If the lpData buffer is too small to receive the data, the function returns ERROR_MORE_DATA.

Windows API:

LONG WINAPI RegQueryValueEx(
  __in HKEY hKey,
  __in_opt LPCTSTR lpValueName,
  __reserved LPDWORD lpReserved,
  __out_opt LPDWORD lpType,
  __out_opt LPBYTE lpData,
  __inout_opt LPDWORD lpcbData
);

Tips:
When you are using RegQueryValueExW(), the parameter of lpcbData
SHOULD be the array size in BYTES, not in characters.

MSDN Reference:

RegQueryValueEx Function

How to use Application Verifier for a service on Vista?

2008-08-21T23:03:00.002+08:00

Q: After added the execution file of a service to Application Verifier(AV), I still can not find any log reported by AV.

A: You can find the logs here "c:\windows\system32\config\systemprofile\appverifierlogs". You can also copy it to the current user profile, then view logs from AV.

How to generate UUID (GUID) in C++?

2008-07-18T19:48:00.006+08:00

Sample Code:

#include <Rpc.h>
#pragma comment(lib, "Rpcrt4.lib")

UUID uuid;
::ZeroMemory(&uuid, sizeof(UUID));

// Create uuid or load from a string by UuidFromString() function

::UuidCreate(&uuid);

// If you want to convert uuid to string, use UuidToString() function

WCHAR* wszUuid = NULL;
::UuidToStringW(&uuid, &wszUuid);
if(wszUuid != NULL)
{
::RpcStringFree(&wszUuid);
wszUuid = NULL;
}

Reference in MSDN:

UuidCreate Function

UuidFromString Function

UuidToString Function

How to use named system events (global events) in C#?

2008-07-17T09:10:00.005+08:00

There are three classes relating to windows events, EventWaitHandle, AutoResetEvent, and ManualResetEvent.

EventWaitHandle
The EventWaitHandle class can represent either automatic or manual reset events and either local events or named system events.

AutoResetEvent
The AutoResetEvent class derives from EventWaitHandle and represents a local event that resets automatically.

ManualResetEvent
The ManualResetEvent class derives from EventWaitHandle and represents a local event that must be reset manually.

Tips:
According to above description, you should use EventWaitHanlde class to represent named system events, of course it can be either automatic or manual reset events.

MSDN reference:
http://msdn.microsoft.com/en-us/library/ksb7zs2x.aspx

Call Windows API in Ruby

2008-04-26T16:53:00.005+08:00

Sample Code:
# Close WMP by Window Message
require 'Win32API'

FindWindow = Win32API.new('user32', 'FindWindow', ["P", "P"], "L")
SendMessage = Win32API.new('user32', 'SendMessage', ["L", "L", "P", "P"], "L")
WM_CLOSE = 0x0010

def CloseWMP()
  hwnd = FindWindow.call(nil, "Windows Media Player")
  if hwnd != 0 then
    id = SendMessage.call(hwnd, WM_CLOSE, nil, nil)
  end
end
# End of Close WMP by Window Message

Reference:
http://www.rubycentral.com/pickaxe/lib_windows.html

0.0F vs 0.0 vs 0.0L and 0 vs 0L

2008-02-24T20:56:00.004+08:00

There are different types in C++.

0.0F is a float, 0.0 is a double, and 0.0L is a long double.

0 is a int and 0L is a long.

"ABC" is a ansi string and L"ABC" is a wide string.

General Protection Fault

2008-02-23T15:54:00.002+08:00

General Protection Fault = GP Fault = GPF

You received this kind of error when the program is attempting accessing a read-only memory.

For example:

class Object
{
public:
int nValue;
};

Object* pObject = NULL;
int nValueOfObject = pObject->nValue; // Accessing a memory which should not be accessed

Sample code for IWMMediaProps::GetMediaType()

2008-02-23T11:05:00.002+08:00

// Get the required buffer size
DWORD cbType = 0;
pWMMediaProps->GetMediaType(NULL, &cbType);

// Get media type
WM_MEDIA_TYPE* pType = (WM_MEDIA_TYPE*)new BYTE[cbType];
if(SUCCEEDED(pWMMediaProps->GetMediaType(pType, &cbType)))
{
// Use media type here
// ...
}

// Free buffer
// Should not use "delete [] pType", we have to cast it to (BYTE*) before delete it.
delete [] (BYTE*)pType;

How to initialize static member variable?

2008-01-25T23:31:00.000+08:00

class X
{
public:
static int i;
};
int X::i = 0; // definition outside class declaration

Notes for QueryFilterInfo()

2008-01-24T23:35:00.000+08:00

FILTER_INFO Info = {0};
pFilter->QueryFilterInfo(&Info);
if(Info.pGraph != NULL)
Info.pGraph->Release(); // You MUST release here

Microsoft Win32 to Microsoft .NET Framework API Map

2008-01-19T22:55:00.000+08:00

Microsoft Win32 to Microsoft .NET Framework API Map
http://msdn2.microsoft.com/en-us/library/aa302340.aspx

This is a very useful article for C# programmer.

Notes for writing DLL in which use STL objects

2008-01-17T23:04:00.001+08:00

You may experience an access violation when you access an STL object through a pointer or reference in a different DLL or EXE.

Root Cause:

Since the static data members in the executable images are not in sync, this action could result in an access violation or data may appear to be lost or corrupted.

Suggestion:
Avoid using STL object as the parameter or the return value of an exported DLL function.

MSDN Reference:

http://support.microsoft.com/kb/172396/en-us

Notes for HttpWebResponse class

2008-01-10T22:33:00.000+08:00

You MUST call Close method to close the response and release the connection.

HttpWebRequest HttpWReq = (HttpWebRequest)WebRequest.Create("http://www.google.com");

HttpWebResponse HttpWResp = (HttpWebResponse)HttpWReq.GetResponse();
// Insert code that uses the response object.
HttpWResp.Close();

http://msdn2.microsoft.com/en-us/library/system.net.httpwebresponse.aspx

Notes for to remove certain filter from a graph

2008-01-01T21:12:00.000+08:00

You should check that the graph is stopped or it will fail to remove any filter.

How to get the maximum length of full path in windows?

2007-12-26T22:46:00.000+08:00

_MAX_DIR = Maximum length of directory component
_MAX_DRIVE = Maximum length of drive component
_MAX_EXT = Maximum length of extension component
_MAX_FNAME = Maximum length of filename component
_MAX_PATH = Maximum length of full path.

The sum of the fields should not exceed _MAX_PATH.
(The sizes include space for 0-terminator.)

How to get the special folders of windows?

2007-12-25T23:14:00.000+08:00

(For Windows XP)
SHGetFolderPath Function
http://msdn2.microsoft.com/en-us/library/bb762181.aspx

(For Windows Vista and later)
SHGetKnownFolderPath Function
http://msdn2.microsoft.com/en-us/library/bb762188.aspx

How to use critical section?

2007-12-09T18:23:00.000+08:00

// Declaration
CRITICAL_SECTION CriticalSection;

// Initialize
::InitializeCriticalSection(&CriticalSection);

// Implementation
::EnterCriticalSection(&CriticalSection);
/* Code block */
::LeaveCriticalSection(&CriticalSection);

// Uninitialize
::DeleteCriticalSection(&CriticalSection);

Convert Any Value Type to STL String by Stringstream

2007-12-06T23:59:00.000+08:00

#include <sstream>

using namespace std;

int a = 1;
double b = 2.0;
float c = 3.0;
unsigned int d = 4;
long long f = 5;
__int64 g = 6;

wstringstream stream; (use stringstream for string)
wstring str;
stream << g; (this can be replaced by any value type)
stream >> str;

Read/Write INI Files in C#

2007-12-06T08:19:00.000+08:00

A Complete Win32 INI File Utility Class
http://www.codeproject.com/KB/files/win32fileutilityclass.aspx

C# wrap for calling windows api. Easy to use!

SYSTEMTIME, FILETIME, and LARGE_INTEGER

2007-12-05T00:02:00.000+08:00

SYSTEMTIME to FILETIME
SystemTimeToFileTime Function
http://msdn2.microsoft.com/en-us/library/ms724948.aspx

FILETIME to SYSTEMTIME
FileTimeToSystemTime Function
http://msdn2.microsoft.com/en-us/library/ms724277.aspx

Copy FILETIME to LARGE_INTEGER
LARGE_INTEGER.LowPart = FILETIME.dwLowDateTime
LARGE_INTEGER.HighPart = FILETIME.dwHighDateTime

Copy LARGE_INTEGER to FILETIME
FILETIME.dwLowDateTime = LARGE_INTEGER.LowPart
FILETIME.dwHighDateTime = LARGE_INTEGER.HighPart

LARGE_INTEGER
Perform 64-bit arthimetic on LARGE_INTEGER.QuardPart member

How to change the tab order in a MFC dialog?

2007-12-01T22:52:00.001+08:00

Step 1.

In resource view of the dialog, select menu [Format] -> [Tab Order] or just press Ctrl +D.

Step 2.
Then you can select item in specified order.

Fatal error C1010: unexpected end of file while looking for precompiled header directive

2007-11-29T23:43:00.001+08:00

Root Cause:
Cpp files in a MFC project have to include "stdafx.h" for creating precompiled headers.

Solution:
#include "stdafx.h" or turn off using precompiled headers.

Visual Studio 2003 .NET
[Properties] of that *.cpp file -> [C/C++] -> [Precompiled Headers]
Set [Create/Use Precompiled Header] to "Not Using Precompiled Headers"

Read/Write INI Files

2007-11-27T23:33:00.000+08:00

Windows API

GetPrivateProfileString
http://msdn2.microsoft.com/en-us/library/ms724353.aspx

WritePrivateProfileString
http://msdn2.microsoft.com/en-us/library/ms725501.aspx