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MODULE D1

WIN32 AND C PROGRAMMING 4

 

 

 

 

What are in this Module?

1. Obtaining and Setting File Information

2. Searching for One or More Files

3. Members

4. Retrieving and Changing File Attributes

5. Retrieving File Type Information

6. Determining a File Size

 

My Training Period: zz hours. Before you begin, read some instruction here.   The Win32 C programming skills: Be familiar and play around with the Win32 programming. Able to understand the Windows file system (NTFS), directory and file. Able to find and collect information about file management functions. Able to understand and use the collected information about the functions in programs. Obtaining and Setting File Information: Searching for One or More Files An application can search the current directory for all file names that match a given pattern by using the FindFirstFile(), FindFirstFileEx(), FindNextFile(), and FindClose() functions.  The pattern must be a valid file name and can include wildcard characters. The FindFirstFile() and FindFirstFileEx() functions create handles thatFindFirstFileEx() uses to search for other files with the same pattern. All functions return information about the file that was found.  This information includes the file name, size, attributes, and time. The FindFirstFileEx() function also allows an application to search for files based on additional search criteria.  The function can limit searches to device names or directory names. The FindClose() function destroys handles created byFindFirstFile() and FindFirstFileEx(). An application can search for a single file on a specific path by using the SearchPath() function. The following Table lists the needed information in order to use the FindFirstFile() function. Information Description The function FindFirstFile(). The use Searches a directory for a file or subdirectory whose name matches the specified name.  To specify additional attributes to be used in the search, use theFindFirstFileEx() function. The prototype HANDLE FindFirstFile(LPCTSTR lpFileName, LPWIN32_FIND_DATA lpFindFileData); Example WIN32_FIND_DATA FileData;   FindFirstFile("*.txt", &FileData); The parameters lpFileName - [in] Pointer to a null-terminated string that specifies a valid directory or path and file name, which can contain wildcard characters (* and ?).  If the string ends with a wildcard, a period, or a directory name, the user must have access to the root and all subdirectories on the path. In the ANSI version of this function, the name is limited toMAX_PATH characters.  To extend this limit to 32,767 wide characters, call the Unicode version of the function and prepend "\\?\" to the path.   lpFindFileData - [out] Pointer to theWIN32_FIND_DATA structure that receives information about the found file or subdirectory. The return value If the function succeeds, the return value is a search handle used in a subsequent call toFindNextFile() or FindClose().  If the function fails, the return value isINVALID_HANDLE_VALUE.  To get extended error information, callGetLastError(). The header file <windows.h>   Table 8:  FindFirstFile() information.

 

 

 

 

 

 

 

• The following Table lists the needed information in order to use the FindNextFile() function.

• The following Table lists the needed information in order to use the FindClose() function.

• The WIN32_FIND_DATA structure describes a file found by theFindFirstFile(), FindFirstFileEx(), or FindNextFile() function.

• The following is the information for the WIN32_FIND_DATA structure.  Its usage is same as you have learnt before and an example how to access structure’s element will be presented in another Module.

typedef struct _WIN32_FIND_DATA {

    DWORD dwFileAttributes;

    FILETIME ftCreationTime;

    FILETIME ftLastAccessTime;

    FILETIME ftLastWriteTime;

    DWORD nFileSizeHigh;

    DWORD nFileSizeLow;

    DWORD dwReserved0;

    DWORD dwReserved1;

    TCHAR cFileName[MAX_PATH];

    TCHAR cAlternateFileName[14];

} WIN32_FIND_DATA, *PWIN32_FIND_DATA;

• For this structure, using the typedef, we can use WIN32_FIND_DATA or *WIN32_FIND_DATA (pointer type) as a shorter (synonym) name for the data type instead of struct _WIN32_FIND_DATA whenever we want to access the structure’s member.

• It looks like a normal variable when used in programs but it is a structure.  This is a normal construct in Win32 programming.

Members

dwFileAttributes - File attributes of the file found.  This member can be one or more of the following values.

ftCreationTime - AFILETIME structure that specifies when the file or directory was created.  If the underlying file system does not support creation time, this member is zero.

ftLastAccessTime - AFILETIME structure.  For a file, the structure specifies when the file was last read from or written to. For a directory, the structure specifies when the directory was created. If the underlying file system does not support last access time, this member is zero.

On FAT, the specified date for both files and directories will be correct, but the time of day will always be set to midnight.

ftLastWriteTime - AFILETIME structure. For a file, the structure specifies when the file was last written to. For a directory, the structure specifies when the directory was created. If the underlying file system does not support last write time, this member is zero.

nFileSizeHigh - High-order DWORD value of the file size, in bytes.  This value is zero unless the file size is greater than MAXDWORD.  The size of the file is equal to (nFileSizeHigh * (MAXDWORD+1)) + nFileSizeLow.

nFileSizeLow - Low-order DWORD value of the file size, in bytes.

dwReserved0 - If the dwFileAttributes member includes the FILE_ATTRIBUTE_REPARSE_POINT attribute, this member specifies the reparse tag.  Otherwise, this value is undefined and should not be used.

dwReserved1 - Reserved for future use.

cFileName - A null-terminated string that specifies the name of the file.

cAlternateFileName - A null-terminated string that specifies an alternative name for the file.  This name is in the classic 8.3 (filename.ext) file name format.

Retrieving and Changing File Attributes

• An application can retrieve the file attributes by using the GetFileAttributes() or GetFileAttributesEx() function.

• The following Table lists the needed information in order to use the GetFileAttributes() function.

• The CreateFile() and SetFileAttributes() functions can set many of the attributes. However, applications cannot set all attributes.

• The GetFileInformationByHandle() function retrieves information about a file and stores it in aBY_HANDLE_FILE_INFORMATION structure.  This information includes creation time, file size, and the file attributes.

• The following program example copies all text files in the current working directory to a new directory of read-only files named newdir.  Files in the new directory are changed to read only, if necessary.

• The application creates the newdir directory using the CreateDirectory() function.

• The application searches the current working directory for all .txt files by using the FindFirstFile() and FindNextFile() functions.  In this case we have several text files under the current directory.

• Each .txt file is copied to the newdir directory.  After a file is copied, theGetFileAttributes() function determines whether the file is read only.  If the file is not read only, the application changes directories tonewdir and converts the copied file to read only by using theSetFileAttributes() function.

• After all the .txt files in the current directory have been copied, the application closes the search handle by using the FindClose() function.

• The following program example uses the CreateDirectory(), FindFirstFile(), CopyFile(), GetFileAttributes(),SetFileAttributes(), FindNextFile(), lstrcpy() (string copy), lstrcat() (string cat) and FindClose() functions.

• WIN32_FIND_DATA structure also used here.

#include <windows.h>

#include <stdio.h>

 

int main()

{

WIN32_FIND_DATA FileData;

HANDLE hSearch;

DWORD dwAttrs;

char szDirPath[] = "G:\\newdir\\";

char szNewPath[MAX_PATH];

BOOL fFinished = FALSE;

 

// create a new directory. If something wrong

if(!CreateDirectory(szDirPath, NULL))

{

printf("Could not create %s directory.\n", szDirPath);

 // just exit

exit (0);

}

else

printf("%s directory successfully created.\n", szDirPath);

 

// start searching for .txt files in the current directory.

// failed when tested with a path...need to change the current working directory???

hSearch = FindFirstFile("*.txt", &FileData);

if(hSearch == INVALID_HANDLE_VALUE)

{

    printf("No .txt files found lol.\n");

    //just exit

    exit (0);

}

 

// copy each .txt file to the new directory and change it to read only, if not already.

while(!fFinished)

{ // copies a string in szDirPath to szNewPath buffer...

   lstrcpy(szNewPath, szDirPath);

   // appends the filename to the path...

   lstrcat(szNewPath, FileData.cFileName);

 

   // in the buffer, do the file copy...

    if(CopyFile(FileData.cFileName, szNewPath, FALSE))

   {

      printf("%s file successfully copied.\n", FileData.cFileName);

      // and gets the file attribute...

      dwAttrs = GetFileAttributes(FileData.cFileName);

      // change to read only where applicable...

      if(!(dwAttrs & FILE_ATTRIBUTE_READONLY))

        SetFileAttributes(szNewPath, dwAttrs | FILE_ATTRIBUTE_READONLY);

   }

   else

       printf("Could not copy %s file.\n", FileData.cFileName);

    if(!FindNextFile(hSearch, &FileData))

    {

        if(GetLastError() == ERROR_NO_MORE_FILES)

        {

            printf("No more file lol!\n");

            fFinished = TRUE;

        }

        else

           printf("Could not find next file.\n");

     }

}

// close the search handle.

FindClose(hSearch);

return 0;

}

The output:   G:\newdir\ directory successfully created. module15.txt file successfully copied. module16.txt file successfully copied. module17.txt file successfully copied. module18.txt file successfully copied. module19.txt file successfully copied. module20.txt file successfully copied. module21.txt file successfully copied. No more file lol! Press any key to continue

• The following Table lists the needed information in order to use the SearchPath() function.

• The following program example uses the SearchPath() function.  This program has been run at the command prompt.

#include <windows.h>

#include <stdio.h>

 

char lpBuffer[500];

LPSTR *lpFilePart;

 

int main(int argc, char *argv[ ])

{

// if not enough arguments supplied 

if(argc != 3)

{

       printf("Usage: %s <path> <filename.ext>\n", argv[0]);

       exit (1);

}

 

  DWORD test = SearchPath(

  argv[1],

  argv[2],

  NULL,

  500,

  lpBuffer,

  lpFilePart);

 // if something wrong to the SearchPath()

  if(!test)

  {

         printf("%s file not found!\n", argv[2]);

         exit (1);

  }

 // display the result...

 else

  {

   printf("The return value is: %d, error: %d\n", test, GetLastError());

   printf("The path is %s\n", lpBuffer);

   printf("The path is %p\n", lpFilePart);

  }

return 0;

}

 

The output:

G:\vcnetprojek\win32prog\Debug>win32prog

Usage: win32prog <path> <filename.ext>

 

G:\vcnetprojek\win32prog\Debug>win32prog G:\

Usage: win32prog <path> <filename.ext>

 

G:\vcnetprojek\win32prog\Debug>win32prog G:\ testfile.txt

testfile.txt file not found!

G:\vcnetprojek\win32prog\Debug>win32prog C:\ testfile.txt

The return value is: 15, error: 0

The path is C:\testfile.txt

The path is 00000000

 

G:\vcnetprojek\win32prog\Debug>

 

Retrieving File Type Information

• The GetFileType() function retrieves the type of a file: disk, character (such as a console), pipe, or unknown.

• The following Table lists the needed information in order to use the GetFileType() function.

• The GetBinaryType() function determines whether a file is executable, and if so, the type of executable file it is.

• The following Table lists the needed information in order to use the GetBinaryType() function.

• The following example uses GetFileType(), GetBinaryType() to test the file type and whether it is executable type or not.

#include <windows.h>

#include <stdio.h>

 

int main()

{

// handle for file

HANDLE hFile;

DWORD lpBinaryType[100];

// file and path

char fname[20] = "c:\\test.doc";

char fname2[30] = "c:\\windows\\NOTEPAD.EXE";

 

hFile = CreateFile(fname,        // file to be opened

                GENERIC_READ,    // open for reading

                FILE_SHARE_READ, // share for reading

                NULL,           // default security

                OPEN_EXISTING,   // open existing file

                FILE_ATTRIBUTE_READONLY, // the file is read only

                NULL);          // no attribute template

if(hFile == INVALID_HANDLE_VALUE)

    printf("Could not open %s file, error %d\n", fname, GetLastError());

printf("File's HANDLE is OK!\n");

 

if(GetFileType(hFile) == 0)

       printf("The %s file is character type.\n", fname);

else if (GetFileType(hFile) == 1)

       printf("The %s file is disk file.\n", fname);

else if (GetFileType(hFile) == 2)

       printf("The %s file is socket or named pipe.\n", fname);

else if (GetFileType(hFile) == 4)

       printf("The %s file is UNKNOWN type or GetFileType() failed!\n", fname);

CloseHandle(hFile);

if(GetBinaryType(fname2, lpBinaryType) != 0)

       printf("The %s file is executable.\n", fname2);

else

       printf("The %s is file non-executable.\n", fname2);

return 0;

}

 

The output:

 

File's HANDLE is OK!

The c:\test.doc file is disk file.

The c:\windows\NOTEPAD.EXE file is executable.

Press any key to continue

Determining a File Size

• The GetFileSize() function retrieves the size of a file.  Because the NTFS implementation of files allows for multiple streams within a file, any application you write that accesses files must account for the possibility that the creator of the file may include multiple streams in the file.

• The following Table lists the needed information in order to use the GetFileSize() function.

• If multiple streams are not verified for in a file, the application may underestimate the total size of the file, among other errors. The following example extracts the file type and size usingGetFileType() and GetFileSize().

#include <windows.h>

#include <stdio.h>

 

int main()

{

// the files' handles

HANDLE hFile, hFile1;

// filenames, change accordingly

char fname[ ] = "c:\\test.doc";

char fname1[ ] = "c:\\txtcodes\\module11.txt";

// temporary storage for file sizes

DWORD dwFileSize;

DWORD dwFileType;

   // create the test file. Open it "Create Always" to overwrite any existing file...

  hFile = CreateFile(fname, GENERIC_READ | GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

  if(hFile == INVALID_HANDLE_VALUE)

  {

    printf("hFile is NULL\n");

    printf("Could not create %s\n", fname);

    // return error

    return 4;

  }

// get the file type...

dwFileType = GetFileType(hFile);

// verify that the correct file size was written.

dwFileSize = GetFileSize(hFile, NULL);

printf("%s size is %d bytes and file type is %d\n", fname, dwFileSize, dwFileType);

CloseHandle(hFile);   //close the file handle and the file itself

// opening the existing file

hFile1 = CreateFile(fname1,                      // file to open

                GENERIC_READ,                      // open for reading

                FILE_SHARE_READ,               // share for reading

                NULL,                                          // default security

                OPEN_EXISTING,                     // existing file only

                FILE_ATTRIBUTE_NORMAL,  // normal file

                NULL);                     // no attribute template

 

if(hFile1 == INVALID_HANDLE_VALUE)

{

    printf("Could not open %s file, error %d\n", fname1, GetLastError());

    return 1;

}

dwFileType = GetFileType(hFile1);

dwFileSize = GetFileSize(hFile1, NULL);

printf("%s size is %d bytes and file type is %d\n", fname1, dwFileSize, dwFileType);

// close the file's handle and itself

CloseHandle(hFile1);

return 0;

}

 

The output:

 

c:\test.doc size is 0 bytes and file type is 1

c:\txtcodes\module11.txt size is 10518 bytes and file type is 1

Press any key to continue

The following is the previous example compiled using VC++ Express Edition with SDK on Win XP Pro SP2.

 

#include <windows.h>

#include <stdio.h>

 

int main()

{

   // the files' handles

    HANDLE hFile, hFile1;

   // filenames, change accordingly

    char *fname = "c:\\test.doc";

    char *fname1 = "c:\\myfile.txt";

   // temporary storage for file sizes

    DWORD dwFileSize;

    DWORD dwFileType;

   // create the test file. Open it "Create Always" to overwrite any existing file...

    hFile = CreateFile((LPCWSTR)fname, GENERIC_READ | GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

    if(hFile == INVALID_HANDLE_VALUE)

    {

        printf("hFile is NULL\n");

        printf("Could not create %s\n", fname);

        // return error

        return 4;

    }

   // get the file type...

    dwFileType = GetFileType(hFile);

   // verify that the correct file size was written.

    dwFileSize = GetFileSize(hFile, NULL);

    printf("%s size is %d bytes and file type is %d\n", fname, dwFileSize, dwFileType);

    CloseHandle(hFile); //close the file handle and the file itself

   // opening the existing file

    hFile1 = CreateFile((LPCWSTR)fname1, // file to open

        GENERIC_READ, // open for reading

        FILE_SHARE_READ, // share for reading

        NULL, // default security

        OPEN_EXISTING, // existing file only

        FILE_ATTRIBUTE_NORMAL, // normal file

        NULL); // no attribute template

    if(hFile1 == INVALID_HANDLE_VALUE)

    {

        printf("Could not open %s file, error %d\n", fname1, GetLastError());

        return 1;

    }

        dwFileType = GetFileType(hFile1);

        dwFileSize = GetFileSize(hFile1, NULL);

        printf("%s size is %d bytes and file type is %d\n", fname1, dwFileSize, dwFileType);

        // close the file's handle and itself

        CloseHandle(hFile1);

        return 0;

    }

 

   A sample output:

 

 

 

 

 

 

 

Further reading and digging:

 

1. Check the best selling C, C++ and Windows books at Amazon.com.

2. Microsoft Visual C++, online MSDN.

3. ReactOS - Windows binary compatible OS - C/C++ source code repository, Doxygen.

4. For Multibytes, Unicode characters and Localization please refer to Locale, wide characters & Unicode (Story) and Windows users & groups programming tutorials (Implementation).

5. Windows data type information is inData types used in Windows programming.

6. Structure, enum, union and typedef story can be foundC/C++ struct, enum, union & typedef.

7. Notation used in MSDN is Hungarian Notation instead of CamelCase and is discussedVC++ programming notations.

 

 

 

 

 

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