.NET/Java PDF, Tiff, Barcode SDK Library

All Qt applications are event-driven, so you cannot directly follow the path of execution from the main function through all the parts of the application. Instead, you initialize your application from the main function, and the main function then calls the exec method on a QApplication object. This starts the application s event loop. (An event can be anything from a new package received over a network, a certain time having passed, or the user having pressed a key or moved the mouse.) The QApplication object waits for these events and passes them to any affected QObject. For instance, when the user clicks the Clear All button in the phone book dialog shown in Figure 2-1, the click is received by the application s event loop. The QApplication object then takes the clicked event and passes it on to the affected object: in this case, the QPushButton object representing the button. This button object then reacts to the event and emits the relevant signals. By connecting signals for buttons being clicked and list items selected to slots implementing the actual functionality of the application, the user interface is set up to react to user interaction. So a good starting point when developing an application is to identify the actions that the user can take through the UI shown in Figure 2-1.

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private static Dictionary<FileContents, List<FileContents>> BuildPotentialMatches(List<FileContents> files) { // Builds a dictionary where the entries look like: // { 0, { 1, 2, 3, 4, ... N } } // { 1, { 2, 3, 4, ... N } // ... // { N - 1, { N } } // where N is one less than the number of files. var allCombinations = Enumerable.Range(0, files.Count - 1).ToDictionary( x => files[x], x => files.Skip(x + 1).ToList()); } return allCombinations;

This set of potential matches will be whittled down to the files that really are the same by CompareBytes, which we ll get to momentarily. The DisplayResults method, shown in Example 11-38, runs through the matches and displays their names and locations.

private static void DisplayResults( List<FileContents> files, Dictionary<FileContents, List<FileContents>> currentlyMatched) { if (currentlyMatched.Count == 0) { return; } var alreadyMatched = new List<FileContents>(); Console.WriteLine("Matches"); foreach (var matched in currentlyMatched) { // Don't do it if we've already matched it previously if (alreadyMatched.Contains(matched.Key)) { continue; } else { alreadyMatched.Add(matched.Key); } Console.WriteLine("-------"); Console.WriteLine(matched.Key.FilePath); foreach (var file in matched.Value) { Console.WriteLine(file.FilePath); alreadyMatched.Add(file); } } Console.WriteLine("-------");

}

The actions identified here are very much like use cases in the Unified Modeling Language (UML), Tip

This leaves the method shown in Example 11-39 that does the bulk of the work, comparing the potentially matching files, byte for byte.

private static void CompareBytes( List<FileContents> files, Dictionary<FileContents, List<FileContents>> potentiallyMatched) { // Remember, this only ever gets called with files of equal length. int fileLength = files[0].Content.Length; var sourceFilesWithNoMatches = new List<FileContents>(); for (int fileByteOffset = 0; fileByteOffset < fileLength; ++fileByteOffset) { foreach (var sourceFileEntry in potentiallyMatched) { byte[] sourceContent = sourceFileEntry.Key.Content; for (int otherIndex = 0; otherIndex < sourceFileEntry.Value.Count; ++otherIndex) { // Check the byte at i in each of the two files, if they don't // match, then we remove them from the collection byte[] otherContent = sourceFileEntry.Value[otherIndex].Content; if (sourceContent[fileByteOffset] != otherContent[fileByteOffset]) { sourceFileEntry.Value.RemoveAt(otherIndex); otherIndex -= 1; if (sourceFileEntry.Value.Count == 0) { sourceFilesWithNoMatches.Add(sourceFileEntry.Key); } } } } foreach (FileContents fileWithNoMatches in sourceFilesWithNoMatches) { potentiallyMatched.Remove(fileWithNoMatches); } // Don't bother with the rest of the file if // there are no further potential matches if (potentiallyMatched.Count == 0) { break; } sourceFilesWithNoMatches.Clear(); } }

Summary

We re going to need to add a test file that differs only in the content. In CreateTest Files add another filename that doesn t change as we go round the loop:

The first action is to start the application When this happens, the list dialog is shown From the list dialog, the user adds a new item This shows an empty editing dialog From the list dialog, the user edits the currently selected item This shows a filled-out editing dialog From the list dialog, the user removes the currently selected item From the list dialog, the user clears the list From the list dialog, the user exits the application From the editing dialog, the user approves the changes made This means that the changes will be reflected in the list dialog From the editing dialog, the user cancels the changes made Starting from the top of the list, the host operating system has to take care of starting the application Your part in the process is to show the list dialog from the main function.

string fileSameSizeInAllButDifferentContent = "SameNameAndSizeDifferentContent.txt";

Then, inside the loop (at the bottom), we ll create a test file that will be the same length, but varying by only a single byte:

// And now one that is the same length, but with different content fullPath = Path.Combine(directory, fileSameSizeInAllButDifferentContent); builder = new StringBuilder(); builder.Append("Now with "); builder.Append(directoryIndex); builder.AppendLine(" extra"); CreateFile(fullPath, builder.ToString());