I have very long collection - GList (huge amount of samples). For validation of every sample I am using g_list_foreach. The processing of the whole list lasts long. Sometimes it would be very useful to interrupt processing (via system signal SIGINT). Is there any way to interrupt foreach function?
It's trivial to implement something like g_list_foreach which would check a flag on each iteration, then you just need to install a signal handler to set the flag.
Here is the entire implementation of g_list_foreach:
void
g_list_foreach (GList *list,
GFunc func,
gpointer user_data)
{
while (list)
{
GList *next = list->next;
(*func) (list->data, user_data);
list = next;
}
}
How to install the handler will depend on how you want to structure your application, but if nothing else you could use a GOnce to install the handler, so something like:
static volatile gboolean my_flag = FALSE;
static void
handle_sigint(int id) {
my_flag = TRUE;
}
static gpointer
install_handler(gpointer data)
{
signal(SIGINT, handle_sigint);
return NULL;
}
/* Returns FALSE if interrupted, TRUE otherwise. */
gboolean
my_g_list_foreach (GList *list,
GFunc func,
gpointer user_data)
{
static GOnce handler_once = G_ONCE_INIT;
g_once(&handler_once, install_handler, NULL);
my_flag = FALSE;
while (list)
{
if (flag)
return FALSE;
GList *next = list->next;
(*func) (list->data, user_data);
list = next;
}
return TRUE;
}
Related
Consider:
namespace WindowsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
//int[] val = { 0, 0};
int val;
if (textBox1.Text == "")
{
MessageBox.Show("Input any no");
}
else
{
val = Convert.ToInt32(textBox1.Text);
Thread ot1 = new Thread(new ParameterizedThreadStart(SumData));
ot1.Start(val);
}
}
private static void ReadData(object state)
{
System.Windows.Forms.Application.Run();
}
void setTextboxText(int result)
{
if (this.InvokeRequired)
{
this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });
}
else
{
SetTextboxTextSafe(result);
}
}
void SetTextboxTextSafe(int result)
{
label1.Text = result.ToString();
}
private static void SumData(object state)
{
int result;
//int[] icount = (int[])state;
int icount = (int)state;
for (int i = icount; i > 0; i--)
{
result += i;
System.Threading.Thread.Sleep(1000);
}
setTextboxText(result);
}
delegate void IntDelegate(int result);
private void button2_Click(object sender, EventArgs e)
{
Application.Exit();
}
}
}
Why is this error occurring?
An object reference is required for the nonstatic field, method, or property 'WindowsApplication1.Form1.setTextboxText(int)
It looks like you are calling a non static member (a property or method, specifically setTextboxText) from a static method (specifically SumData). You will need to either:
Make the called member static also:
static void setTextboxText(int result)
{
// Write static logic for setTextboxText.
// This may require a static singleton instance of Form1.
}
Create an instance of Form1 within the calling method:
private static void SumData(object state)
{
int result = 0;
//int[] icount = (int[])state;
int icount = (int)state;
for (int i = icount; i > 0; i--)
{
result += i;
System.Threading.Thread.Sleep(1000);
}
Form1 frm1 = new Form1();
frm1.setTextboxText(result);
}
Passing in an instance of Form1 would be an option also.
Make the calling method a non-static instance method (of Form1):
private void SumData(object state)
{
int result = 0;
//int[] icount = (int[])state;
int icount = (int)state;
for (int i = icount; i > 0; i--)
{
result += i;
System.Threading.Thread.Sleep(1000);
}
setTextboxText(result);
}
More info about this error can be found on MSDN.
For this case, where you want to get a Control of a Form and are receiving this error, then I have a little bypass for you.
Go to your Program.cs and change
Application.Run(new Form1());
to
public static Form1 form1 = new Form1(); // Place this var out of the constructor
Application.Run(form1);
Now you can access a control with
Program.form1.<Your control>
Also: Don't forget to set your Control-Access-Level to Public.
And yes I know, this answer does not fit to the question caller, but it fits to googlers who have this specific issue with controls.
You start a thread which runs the static method SumData. However, SumData calls SetTextboxText which isn't static. Thus you need an instance of your form to call SetTextboxText.
Your method must be static
static void setTextboxText(int result)
{
if (this.InvokeRequired)
{
this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });
}
else
{
SetTextboxTextSafe(result);
}
}
Credit to #COOLGAMETUBE for tipping me off to what ended up working for me. His idea was good but I had a problem when Application.SetCompatibleTextRenderingDefault was called after the form was already created. So with a little change, this is working for me:
static class Program
{
public static Form1 form1; // = new Form1(); // Place this var out of the constructor
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(form1 = new Form1());
}
}
I actually got this error because I was checking InnerHtml for some content that was generated dynamically - i.e. a control that is runat=server.
To solve this I had to remove the "static" keyword on my method, and it ran fine.
From my looking you give a null value to a textbox and return in a ToString() as it is a static method. You can replace it with Convert.ToString() that can enable null value.
Make the function static. This must solve your problem.
The essence, and solution, to your problem is this:
using System;
namespace myNameSpace
{
class Program
{
private void method()
{
Console.WriteLine("Hello World!");
}
static void Main(string[] args)
{
method();//<-- Compile Time error because an instantiation of the Program class doesnt exist
Program p = new Program();
p.method();//Now it works. (You could also make method() static to get it to work)
}
}
}
While testing programs it would be nice to be able to pump strings into stdin for processing (libvala-0.36 on VSCode 1.15.0-insider/Linux Mint 18.2). Below is just for illustration, but stdin.puts/stdin.flush doesn't seem to work. How can I pump keystrokes/strings into stdin?
private void test_func(){
...do stuff
stdin.puts("""{"event":"server.connected","params":{"version":"0.0.1","pid":0}}""");
...do stuff
stdin.puts("exit\r\n");
}
public static int main (string[] args) {
string line;
...do stuff
#if DEBUG
test_func();
#endif
while ((line = stdin.read_line ()) != null) {
line = line.strip ();
if (line.length > 0) {
if (line == "exit") break;
gJsonRPC.handle_request (line);
}
}
...do stuff
}
Update:
Have not found functionality similar to .Net "SendKeys" class in GLib, so temporarily settled on this method....
public static void SendKeys(string sKeys) {
//--------------------------------------------------------------
//OSS:Hack:SendKeys
//--------------------------------------------------------------
char[] _keys = sKeys.to_utf8();
for (int i = _keys.length; i >= 0; i--)
stdin.ungetc (_keys[i]);
//--------------------------------------------------------------
}
#Lasall suggested FileStream.open(¨/dev/stdin¨, ¨w¨), so I try that next.
GLib.stdin really is just a GLib.FileStream.
You can encapsulate your processing code in a function that takes a FileStream like this:
public void my_processing_func (FileStream stream) {
while ((line = stream.read_line ()) != null) {
line = line.strip ();
if (line.length > 0) {
if (line == "exit") break;
gJsonRPC.handle_request (line);
}
}
}
}
Then in your main you can conditionally use either your test data or stdin:
#ifdef DEBUG
var stream = test_func ();
#else
var stream = stdin;
#endif
my_processing_func (stream);
I probably wouldn't use DEBUG, but some more descriptive name like TEST_DATA, also it might be better to use proper unit testing and write a test program instead of #ifdefing your main program.
I would like to parse binary file (from some old game) as on desktop as in browser.
So, I should use abstract class, which can read binary data from array of bytes:
abstract class BinData {
int readByte();
String readNullString(){
var buffer = new StringBuffer();
int char;
do {
char = readByte();
if (char == 0){
break;
}
buffer.writeCharCode(char);
} while(true);
return buffer.toString();
}
}
Now I can implement my parser. For example:
class Parser {
BinData _data;
void load(BinData data){
...
}
}
For desktop console application I use dart:io RandomAccessFile:
class FileBinData extends BinData {
RandomAccessFile _file;
FileBinData.from(RandomAccessFile file){
this._file = file;
}
int readByte(){
return this._file.readByteSync();
}
}
For web application I have to use dart:html FileReader. However, this class has only Future-based API, which isn't compatible with my interface:
class WebFileBinData extends BinData {
File _file;
int _position = 0;
WebFileBinData.from(File file){
this._file = file;
}
int readByte(){
Blob blob = _file.slice(_position, _position + 1);
FileReader reader = new FileReader();
var future = reader.onLoad.map((e)=>reader.result).first
.then((e) { ... });
reader.readAsArrayBuffer(blob);
...
}
}
How can I solve it?
Your readByte() should return Future<int> instead of int. You can return a Future from a function/method even when it doesn't do any async operation (return new Future.value(5);) but you can not return int (or any non-Future value) from a function which executes async operations, at least not when the value should be returned as result of the async operation.
You also need to ensure to connect all async calls.
Future<int> readByte(){
return reader.onLoad.map((e)=>reader.result).first
.then((e) {
...
return reader.readAsArrayBuffer(blob);
});
** readNullString
Future<String> readNullString() {
var buffer = new StringBuffer();
int char;
return Future.doWhile(() {
return readByte().then((char) {
if (char == 0) {
return false; // end doWhile
}
buffer.writeCharCode(char);
return true; // continue doWhile
});
}).then((_) => buffer.toString()); // return function result
}
I'm trying to create a server-side Dart class that performs various data-related tasks. All of these tasks rely on the database having been first initialized. The problem is that the init of the database happens asynchronously (returns a Future). I first tried to put the init code into the constructor, but have given up on this approach as it seems to not be viable.
I am now attempting to figure out how to force the DB initialization as a first step in any method call that accesses data. So in other words, when attemptLogin() is called below, I'd like to first check if the DB has been initialized and initialize it if necessary.
However, there are two obstacles. If the database hasn't been initialized, the code is straightforward - initialize the db, then use the then() method of the returned future to do the rest of the function. If the db is not yet initialized, what do I attach my then() method to?
Second related question is what happens when a database is currently being initialized but this process is not yet complete? How can I pull in and return this "in-progress" Future?
This is the basic gist of the code I'm trying to wrangle:
class DataManager {
bool DbIsReady = false;
bool InitializingDb = false;
Db _db;
Future InitMongoDB() {
print("Initializing MongoDB");
InitializingDb = true;
_db = new Db("mongodb://127.0.0.1/test");
return _db.open().then((_) {
DbIsReady = true;
InitializingDb = false;
});
}
Future<List> attemptLogin(String username, String password) {
Future firstStep;
if ((!DbIsReady) && (!InitializingDb) {
Future firstStep = InitMongoDB()
}
else if (InitializingDb) {
// Need to return the InitMongoDB() Future that's currently running, but how?
}
else {
// How do I create a blank firstStep here?
}
return firstStep.then((_) {
users = _db.collection("users");
return // ... rest of code cut out for clarity
});
}
}
Thanks in advance for your help,
Greg
Just return
return new Future<bool>.value(true);
// or any other value instead of `true` you want to return.
// or none
// return new Future.value();
Just keep the future alive:
class DataManager {
Future _initializedDb;
Future initMongoDb() { ... }
Future<List> attemptLogin(String username, String password) {
if (_initializedDb == null) {
_initializedDb = initMongoDB();
}
return _initializedDb.then((db) {
users = db.collection("users");
return // ... rest of code cut out for clarity
});
}
}
You might need to pay attention for the error-case. It's up to you if you want to deal with errors in the initMongoDB or after it.
One of the possible solutions:
import "dart:async";
void main() {
var dm = new DataManager();
var selectOne = dm.execute("SELECT 1");
var selectUsers = dm.execute("SELECT * FROM users");
var users = selectOne.then((result) {
print(result);
return selectUsers.then((result) {
print(result);
});
});
users.then((result) {
print("Goodbye");
});
}
class Event {
List<Function> _actions = new List<Function>();
bool _raised = false;
void add(Function action) {
if (_raised) {
action();
} else {
_actions.add(action);
}
}
void raise() {
_raised = true;
_notify();
}
void _notify() {
if (_actions.isEmpty) {
return;
}
var actions = _actions.toList();
_actions.clear();
for (var action in actions) {
action();
}
}
}
class DataManager {
static const int _STATE_NOT_INITIALIZED = 1;
static const int _STATE_INITIALIZING = 2;
static const int _STATE_READY = 3;
Event _initEvent = new Event();
int _state = _STATE_NOT_INITIALIZED;
Future _init() {
if (_state == _STATE_NOT_INITIALIZED) {
_state = _STATE_INITIALIZING;
print("Initializing...");
return new Future(() {
print("Initialized");
_state = _STATE_READY;
_initEvent.raise();
});
} else if (_state == _STATE_INITIALIZING) {
print("Waiting until initialized");
var completer = new Completer();
_initEvent.add(() => completer.complete());
return completer.future;
}
return new Future.value();
}
Future execute(String query, [Map arguments]) {
return _init().then((result) {
return _execute(query, arguments);
});
}
Future _execute(String query, Map arguments) {
return new Future.value("query: $query");
}
}
Output:
Initializing...
Waiting until initialized
Initialized
query: SELECT 1
query: SELECT * FROM users
Goodbye
I think that exist better solution but this just an attempt to answer on your question (if I correctly understand you).
P.S. EDITED at 11 July 2014
Slightly modified (with error handling) example.
import "dart:async";
void main() {
var dm = new DataManager();
var selectOne = dm.execute("SELECT 1");
var selectUsers = dm.execute("SELECT * FROM users");
var users = selectOne.then((result) {
print(result);
return selectUsers.then((result) {
print(result);
});
});
users.then((result) {
print("Goodbye");
});
}
class DataManager {
static const int _STATE_NOT_INITIALIZED = 1;
static const int _STATE_INITIALIZING = 2;
static const int _STATE_READY = 3;
static const int _STATE_FAILURE = 4;
Completer _initEvent = new Completer();
int _state = _STATE_NOT_INITIALIZED;
Future _ensureInitialized() {
switch (_state) {
case _STATE_NOT_INITIALIZED:
_state = _STATE_INITIALIZING;
print("Initializing...");
new Future(() {
print("Initialized");
_state = _STATE_READY;
// throw null;
_initEvent.complete();
}).catchError((e, s) {
print("Failure");
_initEvent.completeError(e, s);
});
break;
case _STATE_INITIALIZING:
print("Waiting until initialized");
break;
case _STATE_FAILURE:
print("Failure detected");
break;
default:
print("Aleady intialized");
break;
}
return _initEvent.future;
}
Future execute(String query, [Map arguments]) {
return _ensureInitialized().then((result) {
return _execute(query, arguments);
});
}
Future _execute(String query, Map arguments) {
return new Future.value("query: $query");
}
}
For those that are still wondering how to create a blank Future in Dart and later complete them, you should use the Completer class like in the next example.
class AsyncOperation {
final Completer _completer = new Completer();
Future<T> doOperation() {
_startOperation();
return _completer.future; // Send future object back to client.
}
// Something calls this when the value is ready.
void finishOperation(T result) {
_completer.complete(result);
}
// If something goes wrong, call this.
void _errorHappened(error) {
_completer.completeError(error);
}
}
Future<Type> is non nullable in Dart, meaning that you have to initialize it to a value. If you don't, Dart throws the following error:
Error: Field should be initialized because its type 'Future<Type>' doesn't allow null.
To initialize a Future<Type>, see the following example:
Future<String> myFutureString = Future(() => "Future String");
Here "Future String" is a String and so the code above returns an instance of Future<String>.
So coming to the question of how to create a blank/empty Future, I used the following code for initializing an empty Future List.
Future<List> myFutureList = Future(() => []);
I found this link to be quite useful in understanding Futures in Flutter and Dart: https://meysam-mahfouzi.medium.com/understanding-future-in-dart-3c3eea5a22fb
I've add timer to display images in my app.
is there any way to check the timer is running or not.?
after checking , the timer should be cancel using timer.cancel() method.
Pls hlp me.
Blackberry's Timer is very cheesy - it's just like a Runnable with Thread.sleep() inside. Very commonly for Blackberry, it contains lot of crap you don't actually need and doesn't contain things you do need.
I would dump the Timer and make a class specially for my needs:
abstract public class MyTimer extends Thread {
private final Object waitobj = new Object();
private volatile boolean running;
private volatile boolean canceled;
private final long due;
public MyTimer setDelay(long delay) {
long cur = System.currentTimeMillis();
due = cur + delay;
return this;
}
public MyTimer setAlarmTime(long dueTimeMillis) {
due = dueTimeMillis;
return this;
}
synchronized void setIsRunning(boolean running) {
this.running = running;
}
synchronized public boolean isRunning() {
return running;
}
synchronized public void cancel() {
synchronized (waitobj) {
canceled = true;
waitobj.notify();
}
}
public void run() {
setIsRunning(true);
long cur = System.currentTimeMillis();
long sleep = due - cur;
while (sleep > 0) {
synchronized (waitobj) {
waitobj.wait(sleep);
}
if (isCanceled()) return;
cur = System.currentTimeMillis();
sleep = due - cur;
}
alarm();
setIsRunning(false);
}
private boolean isCanceled() {
return canceled;
}
abstract void alarm();
}
Then I would invoke it like this:
timer = new MyTimer() {
void alarm() {
// do cool things
}
};
timer.setDelay(10000).start();
If I need to cancel it I would do it like this:
if (timer.isRunning()) {
timer.cancel();
}
or simply
timer.cancel();
PS: Note volatile and synchronized things in MyTimer class.
You can manage this yourself by recording the timers unique integer and use it later to cancel. I find a useful place to set/cancel this is in the onVisibilityChanged(boolean) override. I'm assuming here your timed images are for animation.
// start
if (renderLoop==-1) renderLoop = UiApplication.getUiApplication().invokeLater( this, 50, true );
// stop
if (renderLoop!=-1)
{
UiApplication.getUiApplication().cancelInvokeLater( renderLoop );
renderLoop = -1;
}
//assumes your screen implements Runnable
public void run() {
// do something cool
}
Assuming that you're programming in Java with Swing, you have a method called isRunning() within the Timer Class.
http://download.oracle.com/javase/7/docs/api/javax/swing/Timer.html#isRunning%28%29
Regards