Click here to Skip to main content

C / C++ / MFC

Re: Synchronization and volatile

CPallini1-Jan-08 21:03

1-Jan-08 21:03

Hey George, let me understand what's your issue against the volatile keyword: Did your lineage be victim of a strange anathema? Laugh | :laugh:

Laugh | :laugh:

By the way, you missed to mention (if I remember well was David Crow to point it out) that main usage of volatile is not synchronization.

Smile | :)

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Re: Synchronization and volatile

George_George1-Jan-08 21:19

1-Jan-08 21:19

Hi CPallini,

1. I have no real issue of volatile in my work, my personal interest to learn it in depth.

2. I understand volatile has nothing directly with synchronization (compared with mutex, critical section, etc.), but it has relationship with sychronization, as mention in the article. If you read it, I think you should have some comments (whether my understanding is correct and whether you are agree with this article's points).

regards,
George

Re: Synchronization and volatile

Florin Crişan2-Jan-08 0:05

2-Jan-08 0:05

I'm not sure if you got the point, so I'm going to ramble on:

The whole idea of volatile is to tell the compiler not to cache the value. On every access, the value should be checked to see if it has been modified by another thread. The old value should not be presumed correct just because the current thread hasn't modified it.

Synchronization, on the other hand, is supposed to ensure that no thread is modifying a value while another thread is using it. You wouldn't want the state of an object to change while you are reading it.

Hope this helps.

Florin Crisan

How to use GetTimeZoneInformation

CodingLover1-Jan-08 18:54

1-Jan-08 18:54

Hi all,

I'm working on a dialog base application, dealing with the time zone details.

In the dialog box there is a text box to enter the time offset. Then user click the display button, on the next text box display the timezone name. If the given time offset have more than one timezone name, very first timezone name should be display.

That's my question.

I'm going to use Windows API for this. So that I want to read the timezone list. How can I do that using API with GetTimeZoneInformation()

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

CodingLover1-Jan-08 22:42

1-Jan-08 22:42

I this way is much prefer. I have a time offset and want to find the time zone name. That mean I have to read the registry. How can I do that. I'm confusing how to search whole registry of time zone in following path.

SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones

Under the 'Time Zones' I can see whole registered time zones. I want to get the required one. How can I do that. How can I search the whole Time Zones with given time offset.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

CodingLover2-Jan-08 0:05

2-Jan-08 0:05

One step more done. Read the registry as follows.

HKEY hKey;// Handle to the registry
DWORD dwType = REG_SZ;// Data type

char buf[255];// Data
DWORD dwBufSize = sizeof(buf);

// Sub handle to the registry
const char* subKey = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones\\Afghanistan Standard Time";

// Open the handler
if(RegOpenKey(HKEY_LOCAL_MACHINE, subKey, &hKey) == ERROR_SUCCESS)
{
    // Do the processing, find the name
    if(RegQueryValueEx(hKey, "Display", 0, &dwType, (BYTE*)buf, &dwBufSize) == ERROR_SUCCESS)
    {
        AfxMessageBox(buf);
    }
    else
    {
        AfxMessageBox("Error in reading values.", MB_OK);
    }
    // Close the handler
    RegCloseKey(hKey);
}
else
{
    AfxMessageBox("Error in reading registry.", MB_OK);
}

As you can see, this code gives the values related to the Afghanistan Standard Time. I want to iterate through the list of Time Zones.

In this way each time zone I can compare the user time offset with register values.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

David Crow2-Jan-08 2:52

2-Jan-08 2:52

Eranga Thennakoon wrote:
I want to iterate through the list of Time Zones.

So why not use RegEnumValue()?

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: How to use GetTimeZoneInformation

CodingLover2-Jan-08 18:38

2-Jan-08 18:38

I do the enumerating as follows. How can I avoid the multiple findings. I mean, say there is more than one time zone for same time offset. In that case I want to display the very first time zone name. Used a break statement as follows. For some offsets it doesn't work.

for (i=0; i < cSubKeys; i++)
       {
           cbName = MAX_KEY_LENGTH;
           // Enumerate subkeys of Time Zones
           retCode = RegEnumKeyEx(hKey, i, achKey, &cbName, NULL, NULL, NULL, &ftLastWriteTime);

       // Make the new path for the registry
           char newPath[255];
           sprintf(newPath, "%s\\%s", path, achKey);
           printf("\n%s", newPath);

       // Work with the second handler
           if(RegOpenKey(HKEY_LOCAL_MACHINE, newPath, &hSubKey) == ERROR_SUCCESS)
           {
               if(RegQueryValueEx(hSubKey, "Display", 0, &dwType, (BYTE*)buf, &dwBufSize) == ERROR_SUCCESS)
               {
                   string strDisplay(buf);// Display name
                   string strSub = strDisplay.substr(4, 6);

               // String comparing
                   int result;
                   result = strcmp(strSub.c_str(), str.c_str());
                   if(result == 0)
                   {
                       printf("\n%s", strDisplay.c_str());// Time offset
                       break;
                   }

               }
               RegCloseKey(hSubKey);
           }
           else
           {
               printf("\nNo ");
           }
       }

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

dan o3-Jan-08 5:59

3-Jan-08 5:59

you wrote: For some offsets it doesn't work

which registry keys does it not work ?

Re: How to use GetTimeZoneInformation

CodingLover3-Jan-08 14:23

3-Jan-08 14:23

for -09:00 it wont work. i'm expecting it for Alaskan Standard Time time zone. That is the second subkey of the Time Zones key of the registry. My code don't recognized it at all.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

dan o3-Jan-08 21:36

3-Jan-08 21:36

i will use something like this:

i will store all zones into m_pszTimeZones
and after that it is easy to get information you want

.h
CStringArray m_pszTimeZones;

.cpp
void <myclassname>::TestTM
{
HKEY hKey, Key;
DWORD dwType = REG_SZ;
int iRet = 0;
CString strName, strValue, strPath, strKey;

strPath = _T("SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones");

iRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE, strPath, 0, KEY_READ, &hKey);

if (iRet != ERROR_SUCCESS)
return;

TCHAR achKey[MAX_PATH];
TCHAR achClass[MAX_PATH] = _T("");
DWORD cchClassName = MAX_PATH;
DWORD cSubKeys;
DWORD cbMaxSubKey;
DWORD cchMaxClass;
DWORD cValues;
DWORD cchMaxValue;
DWORD cbMaxValueData;
DWORD cbSecurityDescriptor;
FILETIME ftLastWriteTime;

DWORD i;
DWORD retCode;

TCHAR buffer[MAX_PATH];
DWORD dwSize = sizeof(buffer);

// Get the class name and the value count.
RegQueryInfoKey(hKey, // key handle
achClass, // buffer for class name
&cchClassName, // length of class string
NULL, // reserved
&cSubKeys, // number of subkeys
&cbMaxSubKey, // longest subkey size
&cchMaxClass, // longest class string
&cValues, // number of values for this key
&cchMaxValue, // longest value name
&cbMaxValueData, // longest value data
&cbSecurityDescriptor, // security descriptor
&ftLastWriteTime); // last write time

// Enumerate the child keys, until RegEnumKeyEx fails. Then
// get the name of each child key and copy it into the list box.

for (i = 0, retCode = ERROR_SUCCESS;retCode == ERROR_SUCCESS; i++)
{
ZeroMemory(&achKey, sizeof(achKey));
cbMaxSubKey = sizeof(achKey);
retCode = RegEnumKeyEx(hKey, i, achKey, &cbMaxSubKey, NULL, NULL, NULL, &ftLastWriteTime);
if (retCode == (DWORD)ERROR_SUCCESS)
{
strName.Format( _T("%s"), achKey);

strKey = strPath + "\\" + strName;
iRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE, strKey, 0, KEY_READ, &Key);

if (iRet == ERROR_SUCCESS)
{
ZeroMemory(&buffer, sizeof(buffer));
dwSize = sizeof(buffer); //again
iRet = RegQueryValueEx(Key, _T("Display"), NULL, &dwType, (BYTE *)buffer, &dwSize);

if (iRet == ERROR_SUCCESS)
{
strValue.Format(_T("%s"), buffer);
m_pszTimeZones.Add( strValue );
}

RegCloseKey(Key);
}
}
}
RegCloseKey( hKey );
}

Re: How to use GetTimeZoneInformation

CodingLover3-Jan-08 21:47

3-Jan-08 21:47

Then do the comparing with user inputs?

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

dan o3-Jan-08 22:06

3-Jan-08 22:06

yes...

like where strInput = "-09:00"

CString strTest;
int i;
for(i=0;i<=m_pszTimeZones.GetUpperBound();i++)
{
strTest = m_pszTimeZones.GetAt(i);
strTest = strTest.Mid(4,6);
if ( strTest == strInput)
break;
}

Re: How to use GetTimeZoneInformation

CodingLover3-Jan-08 22:10

3-Jan-08 22:10

Ok, thanks. I'll check it and let you know.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

CodingLover6-Jan-08 19:49

6-Jan-08 19:49

Hey dan o, your code works fine. Where I'm going wrong is the use of my buffer. I'm not sure what exactly happened, but the changing of the buffer size for different time zones gives an error.

Thanks buddy,

At the same time, I'm try to do another thing. Say I want to get both display name and standard zone name. How can I do that through the above your code.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

dan o6-Jan-08 22:28

6-Jan-08 22:28

ok, anyway
just closing this item now...

just make a new stringarray
CStringArray m_pszTimeZonesNames

if (iRet == ERROR_SUCCESS)
{
ZeroMemory(&buffer, sizeof(buffer));
dwSize = sizeof(buffer); //again
iRet = RegQueryValueEx(Key, _T("Std"), NULL, &dwType, (BYTE *)buffer, &dwSize);

if (iRet == ERROR_SUCCESS)
{
strValue.Format(_T("%s"), buffer);
m_pszTimeZonesNames.Add( strValue );
}

have a nice day

Re: How to use GetTimeZoneInformation

CodingLover6-Jan-08 22:39

6-Jan-08 22:39

That's what I have tried. But when I add a CStringArray and compile its ok, but I can't run the code. When I run following exception given,

Unhandled exception at 0x00414ff3 in TimeZone.exe: 0xC0000005: Access violation writing location 0x00000020.

on following line of code.

m_pMainWnd = &dlg;

I have no idea about that. Even on CStringArray documentation there is no such explanation.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

dan o6-Jan-08 23:10

6-Jan-08 23:10

i wonder if you did exactly as below

.h

m_pszTimeZones
m_pszTimeZonesNames

.cpp
void <myclassname>::TestTZ()
{
HKEY hKey, Key;
DWORD dwType = REG_SZ;
int iRet = 0;
CString strName, strValue, strPath, strKey;

strPath = _T("SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones");

iRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE, strPath, 0, KEY_READ, &hKey);

if (iRet != ERROR_SUCCESS)
return;

TCHAR achKey[MAX_PATH];
TCHAR achClass[MAX_PATH] = _T("");
DWORD cchClassName = MAX_PATH;
DWORD cSubKeys;
DWORD cbMaxSubKey;
DWORD cchMaxClass;
DWORD cValues;
DWORD cchMaxValue;
DWORD cbMaxValueData;
DWORD cbSecurityDescriptor;
FILETIME ftLastWriteTime;

DWORD i;
DWORD retCode;

TCHAR buffer[MAX_PATH];
DWORD dwSize = sizeof(buffer);

// Get the class name and the value count.
RegQueryInfoKey(hKey, // key handle
achClass, // buffer for class name
&cchClassName, // length of class string
NULL, // reserved
&cSubKeys, // number of subkeys
&cbMaxSubKey, // longest subkey size
&cchMaxClass, // longest class string
&cValues, // number of values for this key
&cchMaxValue, // longest value name
&cbMaxValueData, // longest value data
&cbSecurityDescriptor, // security descriptor
&ftLastWriteTime); // last write time

// Enumerate the child keys, until RegEnumKeyEx fails. Then
// get the name of each child key and copy it into the list box.

for (i = 0, retCode = ERROR_SUCCESS;retCode == ERROR_SUCCESS; i++)
{
ZeroMemory(&achKey, sizeof(achKey));
cbMaxSubKey = sizeof(achKey);
retCode = RegEnumKeyEx(hKey, i, achKey, &cbMaxSubKey, NULL, NULL, NULL, &ftLastWriteTime);
if (retCode == (DWORD)ERROR_SUCCESS)
{
strName.Format( _T("%s"), achKey);

strKey = strPath + "\\" + strName;
iRet = RegOpenKeyEx(HKEY_LOCAL_MACHINE, strKey, 0, KEY_READ, &Key);

if (iRet == ERROR_SUCCESS)
{
ZeroMemory(&buffer, sizeof(buffer));
dwSize = sizeof(buffer); //again
iRet = RegQueryValueEx(Key, _T("Display"), NULL, &dwType, (BYTE *)buffer, &dwSize);

if (iRet == ERROR_SUCCESS)
{
strValue.Format(_T("%s"), buffer);
m_pszTimeZones.Add( strValue );
}

if (iRet == ERROR_SUCCESS)
{
ZeroMemory(&buffer, sizeof(buffer));
dwSize = sizeof(buffer); //again
iRet = RegQueryValueEx(Key, _T("Std"), NULL, &dwType, (BYTE *)buffer, &dwSize);

if (iRet == ERROR_SUCCESS)
{
strValue.Format(_T("%s"), buffer);
m_pszTimeZonesNames.Add( strValue );
}
}

RegCloseKey(Key);
}
}
}
RegCloseKey( hKey );
}</myclassname>

Re: How to use GetTimeZoneInformation

CodingLover6-Jan-08 23:27

6-Jan-08 23:27

Oops, it's work.

I have to clear the array after certain time I think. Do this after some time of use the array.

m_pszTimeZones.RemoveAll();

Now seems it is work.

Another thing also tested by me.

On comparing of user input with array element, if the user input is not found what happened.

for(i=0;i<=m_pszTimeZones.GetUpperBound();i++)
{
    strTest = m_pszTimeZones.GetAt(i);
    strTemp = m_pszTimeZones.GetAt(i);
    stdTT = m_pszNames.GetAt(i);
    strTest = strTest.Mid(4,6);
    if ( strTest == strIn)
    {
        // Here find the correct zone name
        SetDetails(strTemp);
        SetDlgItemText(IDC_STD, stdTT);
        break;
    }
    else
    {
        AfxMessageBox("Error");
        break;
    }
}

This is what I have tried. Because of the second break it wont iterate. If removed the second break, get the error message until it is found. How should I avoid it.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: How to use GetTimeZoneInformation

dan o6-Jan-08 23:43

6-Jan-08 23:43

BOOL bFound = FALSE;
for(i=0;i<=m_pszTimeZones.GetUpperBound();i++)
{
strTest = m_pszTimeZones.GetAt(i);
strTemp = m_pszTimeZones.GetAt(i);
stdTT = m_pszNames.GetAt(i);
strTest = strTest.Mid(4,6);
if ( strTest == strIn)
{
// Here find the correct zone name
SetDetails(strTemp);
SetDlgItemText(IDC_STD, stdTT);
bFound = TRUE;
break;
}
}

if (!bFound)
{
AfxMessageBox("Error, No Found");
}

Re: How to use GetTimeZoneInformation

CodingLover6-Jan-08 23:57

6-Jan-08 23:57

Hmm, thanks it works. So, it's better to rate your advice to use of CStringArray. Smile | :)

Smile | :)

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Quite similer application

CodingLover7-Jan-08 18:33

7-Jan-08 18:33

Hi all,

After completing the time zone application now I'm going to workout a similar application.

Say I have a folder which contain large number of files. I want to read that folder and collect some information on those files. In details view of a folder we can see that lots of details are available.

eg: File Name, Size, Date Created, Date Modified and many more.

I want to read a specific folder and collect those details. So from where I should start this work.

I appreciate your help all the time...
Eranga Smile | :)

Smile | :)

Re: Quite similer application

dan o8-Jan-08 1:05

8-Jan-08 1:05

perhaps next code snippet helps you

CStringArray m_pszFileNames

void <myclass>::TestFile()
{
struct _finddata_t g_file;
long hFile, lTime;
CString strName, strPath, strCurrentPath;

m_pszFileNames.RemoveAll();

strPath = "c:\testpath";

/* Get the current working directory: */
char buffer[_MAX_PATH];
_getcwd( buffer, _MAX_PATH );

strCurrentPath.Format( _T("%s"), buffer);

_tchdir(strPath);

if( (hFile = _findfirst( "*.*", &g_file )) == -1L )
{
printf( "No files in current directory!\n" );
}
else
{
strName = g_file.name;
m_pszFileNames.Add(strName);

/* Find the rest of the *.* files */
while( _findnext( hFile, &g_file ) == 0 )
{
strName = g_file.name;

m_pszFileNames.Add(strName);
lTime = g_file.time_write;
}
_findclose( hFile );
}

_tchdir(strCurrentPath);
}

john56321-Jan-08 18:46

1-Jan-08 18:46

Hi Experts,

I want to name of some API to perfome the following tasks:

1.How to Restart the system programatically?
2.API that determines system getting shutdown.
3.API that tells system is starting.

Thanx in advance.

Naveen1-Jan-08 18:52

1-Jan-08 18:52

pther wrote:
1.How to Restart the system programatically?

ExitWindowsEx().

pther wrote:
2.API that determines system getting shutdown.

WM_QUERYENDSESSION

pther wrote:
3.API that tells system is starting.

If the system is in starting state then how can your application be running? Or you want your application to run on startup?

nave

[OpenedFileFinder]

General News Suggestion Question Bug Answer Joke Praise Rant Admin

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.