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  • Lightweight spinlocks built from GCC atomic operations?

    - by Thomas
    I'd like to minimize synchronization and write lock-free code when possible in a project of mine. When absolutely necessary I'd love to substitute light-weight spinlocks built from atomic operations for pthread and win32 mutex locks. My understanding is that these are system calls underneath and could cause a context switch (which may be unnecessary for very quick critical sections where simply spinning a few times would be preferable). The atomic operations I'm referring to are well documented here: http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Atomic-Builtins.html Here is an example to illustrate what I'm talking about. Imagine a RB-tree with multiple readers and writers possible. RBTree::exists() is read-only and thread safe, RBTree::insert() would require exclusive access by a single writer (and no readers) to be safe. Some code: class IntSetTest { private: unsigned short lock; RBTree<int>* myset; public: // ... void add_number(int n) { // Aquire once locked==false (atomic) while (__sync_bool_compare_and_swap(&lock, 0, 0xffff) == false); // Perform a thread-unsafe operation on the set myset->insert(n); // Unlock (atomic) __sync_bool_compare_and_swap(&lock, 0xffff, 0); } bool check_number(int n) { // Increment once the lock is below 0xffff u16 savedlock = lock; while (savedlock == 0xffff || __sync_bool_compare_and_swap(&lock, savedlock, savedlock+1) == false) savedlock = lock; // Perform read-only operation bool exists = tree->exists(n); // Decrement savedlock = lock; while (__sync_bool_compare_and_swap(&lock, savedlock, savedlock-1) == false) savedlock = lock; return exists; } }; (lets assume it need not be exception-safe) Is this code indeed thread-safe? Are there any pros/cons to this idea? Any advice? Is the use of spinlocks like this a bad idea if the threads are not truly concurrent? Thanks in advance. ;)

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  • Get a tableview insertRowsAtIndexPaths to accept indexOfObject?

    - by Emil
    Hey. I have a code snippet that looks like this: [tableView beginUpdates]; [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationLeft]; [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:[array indexOfObject:[array objectAtIndex:indexPath.row]]] withRowAnimation:UITableViewRowAnimationLeft]; [tableView endUpdates]; [tableView reloadData]; It gets executed when a user clicks on an accessory. The first part is only there to provide a smooth animation, and does not really matter, as the tableView is reloaded milliseconds later, but as I said, it's there to provide an animation. It is supposed to move a selected object from its current indexPath to the value from an array at the same indexPath. Obviously, this code does not work, so I just want to know what can be done to fix it? PS: I get a warning when compiling, too. The usual "passing argument 1 of 'arrayWithObject:' makes pointer from integer without a cast..." (line 3)

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  • Printing double variable contents

    - by Adil
    I tried following code snippet and output is surprising me: #include <stdio.h> #include <math.h> int main() { double num; unsigned char ch; ch = 19; num = 1.0E+20 ; num += ch * 1.0E+18; printf("E18 = %lf \n",num); printf("E18 = %e \n",num); num = 11.0E+21 ; num += ch * 1.0E+19; printf("E19 = %lf <------\n",num); printf("E19 = %e <------\n",num); num = 11.0E+22 ; num += ch * 1.0E+20; printf("E20 = %lf\n",num); printf("E20 = %e\n",num); num = 11.0E+23 ; num += ch * 1.0E+21; printf("E21 = %lf\n",num); printf("E21 = %e\n",num); num = 11.0E+24 ; num += ch * 1.0E+22; printf("E22 = %lf <------\n",num); printf("E22 = %e <------\n",num); return 0; } The output of the program: E18 = 119000000000000000000.000000 E18 = 1.190000e+20 E19 = 11190000000000000524288.000000 <------ E19 = 1.119000e+22 <------ E20 = 111900000000000001048576.000000 E20 = 1.119000e+23 E21 = 1119000000000000044040192.000000 E21 = 1.119000e+24 E22 = 11189999999999999366660096.000000 <------ E22 = 1.119000e+25 <------ Why the data corrupted when printed while in exponent form its OK

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  • How to obtain an scroll_insensitive resultSet from a callableStatement in Java JDBC?

    - by rafa colunga
    Hi, I have a stored procedure in an Oracle 10g database, in my java code, i call it with: CallableStatement cs = bdr.prepareCall("Begin ADMBAS01.pck_basilea_reportes.cargar_reporte(?,?,?,?,?); END;", ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY); cs.setInt(1, this.reportNumber); cs.registerOutParameter(2, OracleTypes.CURSOR); cs.registerOutParameter(3, OracleTypes.INTEGER); cs.registerOutParameter(4, OracleTypes.VARCHAR); cs.setDate(5, new java.sql.Date(this.fecha1.getTime())); cs.execute(); ResultSet rs = (ResultSet)cs.getObject(2); i do obtain an ResultSet with correct records in it, but when i try an "scroll_insensitive - only" operation, (like absolute(1) ). I keep getting an SQLException stating that it doesn't work on FORWARD only resultSet. So how can i obtain this ResultSet with scroll_insensitive capabilites? Thanks in Advance.

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  • Display a boolean model field in a django form as a radio button rather than the default Checkbox.

    - by Lakshman Prasad
    This is how I went about, to display a Boolean model field in the form as Radio buttons Yes and No. choices = ( (1,'Yes'), (0,'No'), ) class EmailEditForm(forms.ModelForm): #Display radio buttons instead of checkboxes to_send_form = forms.ChoiceField(choices=choices,widget=forms.RadioSelect) class Meta: model = EmailParticipant fields = ('to_send_email','to_send_form') def clean(self): """ A workaround as the cleaned_data seems to contain u'1' and u'0'. There may be a better way. """ self.cleaned_data['to_send_form'] = int(self.cleaned_data['to_send_form']) return self.cleaned_data As you can see in the code above, I need a clean method that converts input string to an integer, which may be unnecessary. Is there a better and/or djangoic way to do this. If so, how? And no, using BooleanField seems to cause a lot more problems. Using that seemed obvious to me; but it isn't. Why is it so.

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  • bitset to dynamic bitset

    - by mr.bio
    Hi.. I have a function where i use bitset.Now i need to convert it to a dynamic bitset.. but i don't know how. Can somebody help me ? set<string> generateCandidates(set<string> ck,unsigned int k){ set<string> nk ; for (set<string>::const_iterator p = ck.begin( );p != ck.end( ); ++p){ for (set<string>::const_iterator q = ck.begin( );q != ck.end( ); ++q){ bitset<4> bs1(*p); bitset<4> bs2(*q); bs1|= bs2 ; if(bs1.count() == k){ nk.insert(bs1.to_string<char,char_traits<char>,allocator<char> >()); } } } return nk; }

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  • LINQ To Entities - Items, ItemCategories & Tags

    - by Simon
    Hi There, I have an Entity Model that has Items, which can belong to one or more categories, and which can have one or more tags. I need to write a query that finds all tags for a given ItemCategory, preferably with a single call to the database, as this is going to get called fairly often. I currently have: Dim q = (From ic In mContext.ItemCategory _ Where ic.CategoryID = forCategoryID _ Select ic).SelectMany(Function(cat) cat.Items).SelectMany(Function(i) i.Tags) _ .OrderByDescending(Function(t) t.Items.Count).ToList This is nearly there, apart from it doesn't contain the items for each tag, so I'd have to iterate through, loading the item reference to find out how many items each tag is related to (for font sizing). Ideally, I want to return a List(Of TagCount), which is just a structure, containing Tag as string, and Count as integer. I've looked at Group and Join, but I'm not getting anywhere so any help would be greatly appreciated!

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  • GAE, JDO, count() doesn't work ?

    - by NilsBor
    On GAE with Spring/JDO after saving 2 entities (in transaction). On calling getById - entities fetched from data storage. On calling getCount() returns "0" and - on calling getAll() - returns empty collection. plz help me ! DAO: @Override public Long getCount() { return ((Integer) getJdoTemplate().execute(new JdoCallback() { @Override public Object doInJdo(PersistenceManager pm) throws JDOException { Query q = pm.newQuery(getPersistentClass()); q.setResult("count(this)"); return q.execute(); } })).longValue(); } @Override public void saveOrUpdate(T entity) { getJdoTemplate().makePersistent(entity); } @Override public List getAll() { return new ArrayList(getJdoTemplate().find(getPersistentClass())); }

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  • ReadOnly Property in Custom Column Types in Sharepoint

    - by Ray Booysen
    Hey all I'm creating a custom column in a feature for Sharepoint. It is essentially this: <Field Type="Integer" ID="<insert guid here>" ReadOnly="true" Name="xxx" DisplayName="XXX" Group="YYY" /> When the field is deployed and attached to a content type, the content type shows no instance of this field being attached. The documentation about ReadOnly is a bit vague but definitely states that the column will be available for viewing in a View. However, when I create a view it is not available. The moment I remove ReadOnly from the field, it is available on the content type without any problems. Any ideas?

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  • How to identify a selected slide is a master slide in PowerPoint 2003 Programmatically

    - by Gayan
    Recently I was working with a code to open a PowerPoint presentation (by vb.net) object and process each slide by slide. If processing slide is not null or a master slide I need to skip and go to the next one. Can anyone show me how to check whether a given slide is a master slide? Is there any way to check it by slide type? Public Sub CheckForProprtychecker(ByVal Presn As PowerPoint.Presentation) For SlideIndex As Integer = 1 To Presn.Slides.Count() If Presn.Slides(SlideIndex) Is Nothing Then Continue For End If ‘do other process Next End Sub

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  • Compare two String with MySQL

    - by Scorpi0
    Hi, I wan't to compare two strings in a SQL request so I can retrieve the best match, the aim is to propose to an operator the best zip code possible. For example, in France, we have Integer Zip code, so I made an easy request : SELECT * FROM myTable ORDER BY abs(zip_code - 75000) This request returns first the data closest of Paris. Unfortunatelly, United Kingdom have zip code like AB421RS, so my request can't do it. I see in SQL Server a function 'Difference' : http://www.java2s.com/Code/SQLServer/String-Functions/DIFFERENCEworkoutwhenonestringsoundssimilartoanotherstring.htm But I use MySQL.. Is there anyone who have a good idea to do the trick in one simple request ? PS : the Levenshtein Distance will not do it, as I really wan't to compare string like if they were number. ABCDEF have to be closer to AWXYZ than to ZBCDEF.

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  • std::vector iterator or index access speed question

    - by Simone Margaritelli
    Just a stupid question . I have a std::vector<SomeClass *> v; in my code and i need to access its elements very often in the program, looping them forward and backward . Which is the fastest access type between those two ? Iterator access std::vector<SomeClass *> v; std::vector<SomeClass *>::iterator i; std::vector<SomeClass *>::reverse_iterator j; // i loops forward, j loops backward for( i = v.begin(), j = v.rbegin(); i != v.end() && j != v.rend(); i++, j++ ){ // some operations on v items } Subscript access (by index) std::vector<SomeClass *> v; unsigned int i, j, size = v.size(); // i loops forward, j loops backward for( i = 0, j = size - 1; i < size && j >= 0; i++, j-- ){ // some operations on v items } And, does const_iterator offer a faster way to access vector elements in case i do not have to modify them? Thank you in advantage.

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  • Corrupted mysql table, cause crash in mysql.h (c++)

    - by Francesco
    i've created a very simple mysql class in c+, but when happen that mysql crash , indexes of tables become corrupted, and all my c++ programs crash too because seems that are unable to recognize corrupted table and allowing me to handle the issue .. Q_RES = mysql_real_query(MY_mysql, tmp_query.c_str(), (unsigned int) tmp_query.size()); if (Q_RES != 0) { if (Q_RES == CR_COMMANDS_OUT_OF_SYNC) cout << "errorquery : CR_COMMANDS_OUT_OF_SYNC " << endl; if (Q_RES == CR_SERVER_GONE_ERROR) cout << "errorquery : CR_SERVER_GONE_ERROR " << endl; if (Q_RES == CR_SERVER_LOST) cout << "errorquery : CR_SERVER_LOST " << endl; LAST_ERROR = mysql_error(MY_mysql); if (n_retrycount < n_retry_limit) { // RETRY! n_retrycount++; sleep(1); cout << "SLEEP - query retry! " << endl; ping(); return select_sql(tmp_query); } return false; } MY_result = mysql_store_result(MY_mysql); B_stored_results = true; cout << "b8" << endl; LAST_affected_rows = (mysql_num_rows(MY_result) + 1); // coult return -1 cout << "b8-1" << endl; the program terminate with a "segmentation fault" after doing the "b8" and before the "b8-1" , Q_RES have no issue even if the table is corrupted.. i would like to know if there is a way to recognize that the table have problems and so then i can run a mysql repair or mysql check .. thanks, Francesco

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  • Average performance of binary search algorithm?

    - by Passonate Learner
    http://en.wikipedia.org/wiki/Binary_search_algorithm#Average_performance BinarySearch(int A[], int value, int low, int high) { int mid; if (high < low) return -1; mid = (low + high) / 2; if (A[mid] > value) return BinarySearch(A, value, low, mid-1); else if (A[mid] < value) return BinarySearch(A, value, mid+1, high); else return mid; } If the integer I'm trying to find is always in the array, can anyone help me write a program that can calculate the average performance of binary search algorithm?

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  • Outlook VBA to BCC emails sent not working in outlook 2007

    - by Pixfizz
    Inserted code in "ItemSend" and saved the ThisOutlookSession module. It worked once and no longer works. Before anyone asks; it was saved as BVaproject.OTM and is still there when I open the module back up after restarting outlook. Private Sub Application_ItemSend(ByVal Item As Object, _ Cancel As Boolean) Dim objRecip As Recipient Dim strMsg As String Dim res As Integer Dim strBcc As String On Error Resume Next ' #### USER OPTIONS #### ' address for Bcc -- must be SMTP address or resolvable ' to a name in the address book strBcc = "[email protected]" Set objRecip = Item.Recipients.Add(strBcc) objRecip.Type = olBCC If Not objRecip.Resolve Then strMsg = "Could not resolve the Bcc recipient. " & _ "Do you want still to send the message?" res = MsgBox(strMsg, vbYesNo + vbDefaultButton1, _ "Could Not Resolve Bcc Recipient") If res = vbNo Then Cancel = True End If End If Set objRecip = Nothing End Sub

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  • LB_SETTABSTOPS does not appear to affect a CheckedListBox

    - by BP
    I am trying to set tab stops in a CheckedListBox in my WinForms application, but no matter what I do, it does not seem to have any effect. I have the following in the code for my form: <DllImport("user32.dll")> _ Public Sub SendMessage(ByVal hWnd As IntPtr, ByVal uMsg As Int32, ByVal wParam As Int32, ByRef lParam As Int32) End Sub Public Const LB_SETTABSTOPS As Int32 = &H192 And in the form's load method, I am doing the following, where theList is my CheckedListBox: Dim tabStops() As Integer = {40, 140, 240} Call SendMessage(theList.Handle, LB_SETTABSTOPS, tabStops.Length, tabStops(0)) theList.Refresh() And then later on, I use this in a loop, where col1 through col4 are all string values for the columns: theList.Items.Add(col1 & vbTab & col2 & vbTab & col3 & vbTab & col4) But no matter what I use for the values of tabStops, the list is formatted with standard width tab stops.

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  • I need help with Widget and PendingIntents

    - by YaW
    Hi, I've asked here a question about Task Killers and widgets stop working (SO Question) but now, I have reports of user that they don't use any Task Killer and the widgets didn't work after a while. I have a Nexus One and I don't have this problem. I don't know if this is a problem of memory or something. Based on the API: A PendingIntent itself is simply a reference to a token maintained by the system describing the original data used to retrieve it. This means that, even if its owning application's process is killed, the PendingIntent itself will remain usable from other processes that have been given it. So, I don't know why widget stop working, if Android doesn't kill the PendingIntent by itself, what's the problem? This is my manifest code: <receiver android:name=".widget.InstantWidget" android:label="@string/app_name"> <intent-filter> <action android:name="android.appwidget.action.APPWIDGET_UPDATE" /> </intent-filter> <meta-data android:name="android.appwidget.provider" android:resource="@xml/widget_provider" /> </receiver> And the widget code: public class InstantWidget extends AppWidgetProvider { public static ArrayList<Integer> alWidgetsId = new ArrayList<Integer>(); private static final String PREFS_NAME = "com.cremagames.instant.InstantWidget"; private static final String PREF_PREFIX_NOM = "nom_"; private static final String PREF_PREFIX_RAW = "raw_"; /** * Esto se llama cuando se crea el widget. Metemos en las preferencias los valores de nombre y raw para tenerlos en proximos reboot. * @param context * @param appWidgetManager * @param appWidgetId * @param nombreSound * @param rawSound */ static void updateAppWidget(Context context, AppWidgetManager appWidgetManager, int appWidgetId, String nombreSound, int rawSound){ //Guardamos en las prefs los valores SharedPreferences.Editor prefs = context.getSharedPreferences(PREFS_NAME, 0).edit(); prefs.putString(PREF_PREFIX_NOM + appWidgetId, nombreSound); prefs.putInt(PREF_PREFIX_RAW + appWidgetId, rawSound); prefs.commit(); //Actualizamos la interfaz updateWidgetGrafico(context, appWidgetManager, appWidgetId, nombreSound, rawSound); } /** * Actualiza la interfaz gráfica del widget (pone el nombre y crea el intent con el raw) * @param context * @param appWidgetManager * @param appWidgetId * @param nombreSound * @param rawSound */ private static void updateWidgetGrafico(Context context, AppWidgetManager appWidgetManager, int appWidgetId, String nombreSound, int rawSound){ RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget); //Nombre del Button remoteViews.setTextViewText(R.id.tvWidget, nombreSound); //Creamos el PendingIntent para el onclik del boton Intent active = new Intent(context, InstantWidget.class); active.setAction(String.valueOf(appWidgetId)); active.putExtra("sonido", rawSound); PendingIntent actionPendingIntent = PendingIntent.getBroadcast(context, 0, active, 0); actionPendingIntent.cancel(); actionPendingIntent = PendingIntent.getBroadcast(context, 0, active, 0); remoteViews.setOnClickPendingIntent(R.id.btWidget, actionPendingIntent); appWidgetManager.updateAppWidget(appWidgetId, remoteViews); } public void onReceive(Context context, Intent intent) { final String action = intent.getAction(); //Esto se usa en la 1.5 para que se borre bien el widget if (AppWidgetManager.ACTION_APPWIDGET_DELETED.equals(action)) { final int appWidgetId = intent.getExtras().getInt( AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID); if (appWidgetId != AppWidgetManager.INVALID_APPWIDGET_ID) { this.onDeleted(context, new int[] { appWidgetId }); } } else { //Listener de los botones for(int i=0; i<alWidgetsId.size(); i++){ if (intent.getAction().equals(String.valueOf(alWidgetsId.get(i)))) { int sonidoRaw = 0; try { sonidoRaw = intent.getIntExtra("sonido", 0); } catch (NullPointerException e) { } MediaPlayer mp = MediaPlayer.create(context, sonidoRaw); mp.start(); mp.setOnCompletionListener(completionListener); } } super.onReceive(context, intent); } } /** Al borrar el widget, borramos también las preferencias **/ public void onDeleted(Context context, int[] appWidgetIds) { for(int i=0; i<appWidgetIds.length; i++){ //Recogemos las preferencias SharedPreferences.Editor prefs = context.getSharedPreferences(PREFS_NAME, 0).edit(); prefs.remove(PREF_PREFIX_NOM + appWidgetIds[i]); prefs.remove(PREF_PREFIX_RAW + appWidgetIds[i]); prefs.commit(); } super.onDeleted(context, appWidgetIds); } /**Este método se llama cada vez que se refresca un widget. En nuestro caso, al crearse y al reboot del telefono. Al crearse lo único que hace es guardar el id en el arrayList Al reboot, vienen varios ID así que los recorremos y guardamos todos y también recuperamos de las preferencias el nombre y el sonido*/ public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) { for(int i=0; i<appWidgetIds.length; i++){ //Metemos en el array los IDs de los widgets alWidgetsId.add(appWidgetIds[i]); //Recogemos las preferencias SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, 0); String nomSound = prefs.getString(PREF_PREFIX_NOM + appWidgetIds[i], null); int rawSound = prefs.getInt(PREF_PREFIX_RAW + appWidgetIds[i], 0); //Si están creadas, actualizamos la interfaz if(nomSound != null){ updateWidgetGrafico(context, appWidgetManager, appWidgetIds[i], nomSound, rawSound); } } } MediaPlayer.OnCompletionListener completionListener = new MediaPlayer.OnCompletionListener(){ public void onCompletion(MediaPlayer mp) { if(mp != null){ mp.stop(); mp.release(); mp = null; } } }; } Sorry for the comments in Spanish. I have the possibility to put differents widgets on the desktop, that's why I use the widgetId as the "unique id" for the PendingIntent. Any ideas please? The 70% of the functionality of my app is the widgets, and it isn't working for some users :( Thanks in advance and sorry for my English.

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  • Mongomapper query collection problem

    - by kylemac
    When I define the User has_many meetings, it automatically creates a "user_id" key/value pair to relate to the User collections. Except I can't run any mongo_mapper finds using this value, without it returning nil or []. Meeting.first(:user_id = "1234") Meeting.all(:user_id = "1234") Meeting.find(:user_id = "1234") All return nil. Is there another syntax? Basically I can't run a query on the automatically generated associative ObjectId. # Methods class User include MongoMapper::Document key :user_name, String, :required = true key :password, String many :meetings end class Meeting include MongoMapper::Document key :name, String, :required = true key :count, Integer, :default = 1 end # Sinatra get '/add' do user = User.new user.meetings "foobar") #should read: Meeting.new(:name = "foobar") user.save end get '/find' do test = Meeting.first(:user_id = "4b4f9d6d348f82370b000001") #this is the _id of the newly create user p test # WTF! returns [] end

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  • print matrix in dialog box

    - by Edan
    Hello, I'm having a little difficulty to print a matrix array on dialog box. The matrix is integer and as far as i understood i need to change it into string? anyway, here's the code: public void print_Matrix(int row, int column) { for (int i = 0; i <= row; i++) { for (int j = 0; j <= column; j++) { JOptionPane.showMessageDialog(null, matrix_Of_Life); } } what I need to do in order to print array into dialog box? thanks.

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  • Is there a PHP library that performs MySQL Data Validation and Sanitization According to Column Type

    - by JW
    Do you know of any open source library or framework that can perform some basic validation and escaping functionality for a MySQL Db. i envisage something along the lines of: //give it something to perform the quote() quoteInto() methods $lib->setSanitizor($MyZend_DBAdaptor); //tell it structure of the table - colnames/coltypes/ etc $lib->setTableDescription($tableDescArray); //use it to validate and escape according to coltype foreach ($prospectiveData as $colName => $rawValue) if ( $lib->isValid($colName, $rawValue)) { //add it to the set clause $setValuesArray[$lib->escapeIdentifier($colName);] = $lib->getEscapedValue($colName,$rawValue); } else { throw new Exception($colName->getErrorMessage()); } etc... I have looked into - Zend_Db_Table (which knows about a table's description), and - Zend_Db_Adaptor (which knows how to escape/sanitize values depending on TYPE) but they do not automatically do any clever stuff during updates/inserts Anyone know of a good PHP library to preform this kind of validation that I could use rather than writing my own? i envisage alot of this kind of stuff: ... elseif (eregi('^INT|^INTEGER',$dataset_element_arr[col_type])) { $datatype='int'; if (eregi('unsigned',$dataset_element_arr[col_type])) { $int_max_val=4294967296; $int_min_val=0; } else { $int_max_val=2147483647; $int_min_val=-2147483648; } } (p.s I know eregi is deprecated - its just an example of laborious code)

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  • Storing date and time as epoch vs native datetime format in the database

    - by zakovyrya
    For most of my tasks I find it much easier to work with date and time in the epoch format: it's trivial to calculate timespan or determine if some event happened before or after another, I don't have to deal with time-zone issues if the data comes from different geographical sources, in case of scripting languages what I usually get from database when I request a datetime-typed column is a string that I need to parse in order to work with it. This list can go on, but for me in order to keep my code portable that's enough to ditch database's native datetime format and store date and time as integer. What do you guys think?

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  • Extracting text from a file where date -time is the index

    - by Soham
    I have got around 800 files of maximum 55KB-100KB each where the data is in this format Date/Time/Float1/Float2/Float3/Float4/Integer Date is in DD/MM/YYYY format and Time is in the format of HH:MM Here the date ranges from say 1st May to 1June and each day, the Time varies from 09:00 to 15:30. I want to run a program so that, for each file, it extracts the data pertaining to a particular given date and writes to a file. I will not face any problem in writing into directory operations. I am trying to get around, to form a to do a search and extract operation. I dont know, how to do it, would like to have some idea. Thanks Soham

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  • How to manage a large dataset using Spring MySQL and RowCallbackHandler

    - by rmarimon
    I'm trying to go over each row of a table in MySQL using Spring and a JdbcTemplate. If I'm not mistaken this should be as simple as: JdbcTemplate template = new JdbcTemplate(datasource); template.setFetchSize(1); // template.setFetchSize(Integer.MIN_VALUE) does not work either template.query("SELECT * FROM cdr", new RowCallbackHandler() { public void processRow(ResultSet rs) throws SQLException { System.out.println(rs.getString("src")); } }); I get an OutOfMemoryError because it is trying to read the whole thing. Any ideas?

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  • Java printf using variable field size?

    - by paxdiablo
    I'm just trying to convert some C code over to Java and I'm having a little trouble with String.printf. In C, to get a specific width based on a variable, I can use: printf("Current index = %*d\n", sz, index); and it will format the integer to be a specific size based on sz. Trying: System.out.println(String.format("Current index = %*d\n", sz, index)); results in an error since it doesn't like the *. I currently have the following kludge: System.out.println(String.format("Current index = %" + sz + "d\n", index)); but I'm hoping there's a slightly better way, yes?

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  • IEnumerable.Cast<>

    - by Renato Person
    If I can implicitly cast an integer value to a double (and vice versa), like: int a = 4; double b = a; // now b holds 4.0 Why can I not do this: int[] intNumbers = {10, 6, 1, 9}; double[] doubleNumbers2 = intNumbers.Cast<double>().ToArray<double>(); I get an "Specified cast is not valid" error message. Doing the opposite (casting from double to int) results in the same error. What am I doing wrong?

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