Once a package has been created, an application may need to obtain information about each of the files in that package. To do this, the functions GetFirstPackageFile and GetNextPackageFile may be used. Here is an example that lists each of the files in a package and writes their names to the console:

// Write each of the files in the package to standard output

HPACKAGE hPackage; 
PACKAGE_FILE_INFORMATION fileInfo; 
LPCTSTR lpszPackageFile = _T("update.pkg");    // package file 
LPCTSTR lpszPassword = _T("secret");           // package password 
BOOL bResult;

// Open the package for read-only access

hPackage = OpenPackage(lpszPackageFile,          // package file 
                       lpszPassword,             // package password 
                       PACKAGE_OPEN_READONLY,    // read-only access 
                       NULL, 0);                 // callback function

if (hPackage == INVALID_PACKAGE_HANDLE) 
{ 
    // The package could not be opened; use the GetLastError 
    // function to determine the reason 
    return; 
}

// Initialize the fileInfo structure with the size of the 
// structure, and call the GetFirstPackageFile function

fileInfo.cbStructure = sizeof(PACKAGE_FILE_INFORMATION); 
bResult = GetFirstPackageFile(hPackage, &fileInfo);

while (bResult) 
{ 
      // Write the file name to standard output 
      printf("%s\n", fileInfo.szFileName);

      bResult = GetNextPackageFile(hPackage, &fileInfo); 
}

ClosePackage(hPackage);

The first step in this example is to open the package, since we need a valid package handle in order to list the files. The package is opened in read-only mode using the OpenPackage function, and the return value is checked to make sure that it was successful.

The next step is to initialize the fileInfo structure by setting the cbStructure member to the size of the structure. This is used internally by the function to make sure that a pointer to the correct structure is being passed, and to ensure backwards compatibility in future versions.

Next, the GetFirstPackageFile function is called. The first parameter is the handle to the package that was opened and the second parameter is a pointer to the structure that will contain information about the file. If the function is successful, it returns a non-zero value, which results in the file name being written to standard output, and then the GetNextPackageFile function is called repeatedly, until the last file in the package is reached. At this point, the function will return a value of zero, and the loop exits. The package is then closed, releasing the handle.