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  • Reduce function calls

    - by Curious2learn
    Hello, I profiled my python program and found that the following function was taking too long to run. Perhaps, I can use a different algorithm and make it run faster. However, I have read that I can also possibly increase the speed by reducing function calls, especially when it gets called repeatedly within a loop. I am a python newbie and would like to learn how to do this and see how much faster it can get. Currently, the function is: def potentialActualBuyers(setOfPeople,theCar,price): count=0 for person in setOfPeople: if person.getUtility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count where setOfPeople is a list of person objects. I tried the following: def potentialActualBuyers(setOfPeople,theCar,price): count=0 Utility=person.getUtility for person in setOfPeople: if Utility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count This, however, gives me an error saying local variable 'person' referenced before assignment Any suggestions, how I can reduce function calls or any other changes that can make the code faster. Again, I am a python newbie and even though I may possibly be able to use a better algorithm, it is still worthwhile learning the answer to the above question. Thanks very much.

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  • Optimizing a bin-placement algorithm

    - by user258651
    Alright, I've got two collections, and I need to place elements from collection1 into the bins (elements) of collection2, based on whether their value falls within a given bin's range. For a concrete example, assume I have a sorted collection objects (bins) which have an int range ([1...4], [5..10], etc). I need to determine the range an int falls in, and place it in the appropriate bin. foreach(element n in collection1) { foreach(bin m in collection2) { if (m.inRange(n)) { m.add(n); break; } } } So the obvious NxM complexity algorithm is there, but I really would like to see Nxlog(M). To do this I'd like to use BinarySearch in place of the inner foreach loop. To use BinarySearch, I need to implement an IComparer class to do the searching for me. The problem I'm running into is this approach would require me to make an IComparer.Compare function that compares two different types of objects (an element to its bin), and that doesn't seem possible or correct. So I'm asking, how should I write this algorithm?

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  • Sending files using Winsock - optimal send() data length?

    - by Meta
    I am using Winsock with non-blocking sockets to send a file to a client. The way I'm doing it right now is that I read a chunk of 8192 bytes from the file, and then loop until all of it successfully goes through send() (obviously handling WSAEWOULDBLOCK as it occurs). I then move on and read the next 8192 bytes, and so on... Although I can use any other number than 8192 when I test the transfer on my local machine, once I try it over a network, it seems like 8191 is the largest number I can use. When I try to use any number higher than 8191 (starting with 8192), the file transfer becomes extremely slow (about 5 times slower). Is there any reason why 8191 is so special? I've done some more testing and it turns out that using 8000 is slightly faster (by 0.5%). If you understand why 8191 is so special, can you tell me if there is a number better than the others (better than 8000)? I have a feeling that it has something to do with the fact that the default send buffer allocated to the socket by Winsock is 8KB, but I don't understand why. It might also have something to do with the Nagle algorithm, but again, I'm not sure how. Note that I have not modified the SO_SNDBUF option nor the TCP_NODELAY option. Or am I doing this all wrong? What's the best way of sending a file over a non-blocking socket?

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  • Nerd Dinner tutorial question (can't pull data off Model)

    - by Alexander
    I am just following the tutorial about NerdDinner and was stuck because when I am implementing the "Index" View Template I got no data from it. It seems that when I loop around in the code below: <asp:Content ID="Title" ContentPlaceHolderID="TitleContent" runat="server"> Upcoming Dinners </asp:Content> <asp:Content ID="Main" ContentPlaceHolderID="MainContent" runat="server"> <h2>Upcoming Dinners</h2> <ul> <% foreach (var dinner in Model) { %> <li> <%=Html.ActionLink(dinner.Title, "Details", new { id=dinner.DinnerID }) %> on <%=Html.Encode(dinner.EventDate.ToShortDateString())%> @ <%=Html.Encode(dinner.EventDate.ToShortTimeString())%> </li> <% } %> </ul> </asp:Content> There seems to be nothing in the Model... why is this? I am pretty sure there's data in the database because the details view template worked. FYI I am following the tutorial up to this page

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  • How to sum up a fetched result's number property based on the object's category?

    - by mr_kurrupt
    I have a NSFetchRequest that is returning all my saved objects (call them Items) and storing them in an NSMutableArray. Each of these Items have a category, an amount, and some other properties. My goal is to check the category of each Item and store the sum of the amounts for objects of the same category. So if I had these Items: Red; 10.00 Blue; 20.00 Green; 5.00 Red; 5.00 Green; 15.00 then I would have an array or other type of container than has: Red; 15.00 Blue; 20.00 Green; 20.00 What would be the best way to organize the data in such a manner? I was going to create a object class (call it Totals) that just has the category and amount. As I traverse through the fetch results in a for-loop, add Items with the same category in a Totals object an store them in a NSMutableArray. The problem I ran into with that is that I'm not sure how to check if an array contains a Totals object with a specific property. Specifically, a category that already exists. So if 'Red' exists, add the amount to it, otherwise create a new Totals object with category 'Red' and a the first Item's amount. Thanks.

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  • Recursion in prepared statements

    - by Rob
    I've been using PDO and preparing all my statements primarily for security reasons. However, I have a part of my code that does execute the same statement many times with different parameters, and I thought this would be where the prepared statements really shine. But they actually break the code... The basic logic of the code is this. function someFunction($something) { global $pdo; $array = array(); static $handle = null; if (!$handle) { $handle = $pdo->prepare("A STATEMENT WITH :a_param"); } $handle->bindValue(":a_param", $something); if ($handle->execute()) { while ($row = $handle->fetch()) { $array[] = someFunction($row['blah']); } } return $array; } It looked fine to me, but it was missing out a lot of rows. Eventually I realised that the statement handle was being changed (executed with different param), which means the call to fetch in the while loop will only ever work once, then the function calls itself again, and the result set is changed. So I am wondering what's the best way of using PDO prepared statements in a recursive way. One way could be to use fetchAll(), but it says in the manual that has a substantial overhead. The whole point of this is to make it more efficient. The other thing I could do is not reuse a static handle, and instead make a new one every time. I believe that since the query string is the same, internally the MySQL driver will be using a prepared statement anyway, so there is just the small overhead of creating a new handle on each recursive call. Personally I think that defeats the point. Or is there some way of rewriting this?

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  • Will this class cause memory leaks, and does it need a dispose method? (asp.net vb)

    - by Phil
    Here is the class to export a gridview to an excel sheet: Imports System Imports System.Data Imports System.Configuration Imports System.IO Imports System.Web Imports System.Web.Security Imports System.Web.UI Imports System.Web.UI.WebControls Imports System.Web.UI.WebControls.WebParts Imports System.Web.UI.HtmlControls Namespace ExcelExport Public NotInheritable Class GVExportUtil Private Sub New() End Sub Public Shared Sub Export(ByVal fileName As String, ByVal gv As GridView) HttpContext.Current.Response.Clear() HttpContext.Current.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", fileName)) HttpContext.Current.Response.ContentType = "application/ms-excel" Dim sw As StringWriter = New StringWriter Dim htw As HtmlTextWriter = New HtmlTextWriter(sw) Dim table As Table = New Table table.GridLines = GridLines.Vertical If (Not (gv.HeaderRow) Is Nothing) Then GVExportUtil.PrepareControlForExport(gv.HeaderRow) table.Rows.Add(gv.HeaderRow) End If For Each row As GridViewRow In gv.Rows GVExportUtil.PrepareControlForExport(row) table.Rows.Add(row) Next If (Not (gv.FooterRow) Is Nothing) Then GVExportUtil.PrepareControlForExport(gv.FooterRow) table.Rows.Add(gv.FooterRow) End If table.RenderControl(htw) HttpContext.Current.Response.Write(sw.ToString) HttpContext.Current.Response.End() End Sub Private Shared Sub PrepareControlForExport(ByVal control As Control) Dim i As Integer = 0 Do While (i < control.Controls.Count) Dim current As Control = control.Controls(i) If (TypeOf current Is LinkButton) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, LinkButton).Text)) ElseIf (TypeOf current Is ImageButton) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, ImageButton).AlternateText)) ElseIf (TypeOf current Is HyperLink) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, HyperLink).Text)) ElseIf (TypeOf current Is DropDownList) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, DropDownList).SelectedItem.Text)) ElseIf (TypeOf current Is CheckBox) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, CheckBox).Checked)) End If If current.HasControls Then GVExportUtil.PrepareControlForExport(current) End If i = (i + 1) Loop End Sub End Class End Namespace Will this class cause memory leaks? And does anything here need to be disposed of? The code is working but I am getting frequent crashes of the app pool when it is in use. Thanks.

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  • PHP curl timing mismatch

    - by JonoB
    I am running a php script that: queries a local database to retrieve an amount executes a curl statement to update an external database with the above amount + x queries the local database again to insert a new row reflecting that the curl statement has been executed. One of the problems that I am having is that the curl statement takes 2-4 seconds to execute, so I have two different users from the same company running the same script at the same time, the execution time of the curl command can cause a mismatch in what should be updated in the external database. This is the because the curl statement has not yet returned from the first user...so the second user is working off incorrect figures. I am not sure of the best options here, but basically I need to prevent two or more curl statements being run at the same time. I thought of storing a value in the database that indicates that the curl statement is being executed at that time, and prevent any other curl statements being run until its completed. Once the first curl statement has been executed, then the database flag is updated and the next one can run. If this field is 'locked', then I could loop through the code and sleep for (5) seconds, and then check again if the flag has been reset. If after (3) loops, then reset the flag automatically (i've never seen the curl take longer than 5 seconds) and continue processing. Are there any other (more elegant) ways of approaching this?

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  • Function in JS returns undefined

    - by megapool020
    Hello there, I have the following problem. The alert allways returns undefined, but I know it has a value. What am I doing wrong. I'm out of solutions... I'm using JQUERY jquery-1.4.2.min.js Tnx in advance $(document).ready(function(){ $('#generateButton').click(createIBAN); }); function createIBAN(){ //---- First check if a bank has been selected, //---- if not, then show error if($('#selectBank').val()==''){ alert('Selecte a bank!'); }else{ var bankAccount = generateBankAccount(); alert(bankAccount); } return false; } function generateBankAccount(){ //---- Create "elfproef" bankaccount var bankAccount = ''; //---- Set the amount of digits in a bankaccount digitAmount = 9; //---- Make random digitstring for (var i = 0; i < digitAmount; i++) { bankAccount += Math.floor(Math.random() * digitAmount); } //---- validate the string, if not "elf-proef" if (elfProef(bankAccount)==false) { //---- regenerate the string generateBankAccount(); }else{ return bankAccount; } } function elfProef(bankAccount) { //---- set sum to 0 and start the for-loop for counting var sum = 0; for (var i = 0; i < digitAmount; i++) { //---- for every digit multiply it times 9 - number //---- of the digit and count it to the sum var sum += bankAccount.charAt(i) * (digitAmount - i); } //---- Check if sum can be devided by 11 without having ##,## if(sum % 11==0){ //---- return true means string is "elf-proef" return true; }else { //---- String is not "elf-proef", try again return false; } }

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  • Using django and django-voting app, how can I order a queryset according to the votes of each item?

    - by snz3
    (I'm new to python and django so please bear with me for a second. I apologise if this has been answered elsewhere and couldn't find it) Let's say I have a Link model and through the django-voting application users can vote on link instances. How can I order those link instances according to their score, eg. display those with the higher score first. I assume I could use the get_top manager of django-voting, but that would only give me the top scoring link instances and wouldn't take into consideration other parameters I would like to add (for example, those links that belong to a specific user or paging or whatever). My guess would be to write a custom manager for my Link model where by I can filter a queryset according to each item's score. If I understand correctly that will require me to loop through each item, check its score, and then place it a list (or dictionary) which will then be sorted according to the score of each item. That wouldn't return a queryset but a dictionary with each item. Am I missing something here?

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  • jquery.append() - only the last element of my list is appended, previous ones are erased

    - by jaes
    Hi, I have a page like this : <div id="daysTable"> <div id="day0" class="day"></div> <div id="day1" class="day"></div> <div id="day2" class="day"></div> <div id="day3" class="day"></div> <div id="day4" class="day"></div> <div id="day5" class="day"></div> <div id="day6" class="day"></div> </div> and some javascript to fill my calendar like this function getWeek(){ $.getJSON("/getWeek",function(events){ var eventHeight = $("#hoursTable > div").height(); var eventWidth = $("#daysTable > div").width(); var startWeek = events[0]// timestamp of the start of the week for(var i = 1; i < events.length; i ++){ $(".day").empty(); var startHour = (events[i].startDate - startWeek)/3600 var duration = (events[i].stopDate - startWeek)/3600 - startHour var dayStart = Math.floor(startHour/24); var startHour = startHour - dayStart * 24 divEvent = $('<div id="event'+events[i].idEvent+'"/>') .width(eventWidth-2) .height(duration*eventHeight) .css("border","1px solid black") .css("margin-top",startHour*eventHeight) .html(events[i].name); divEvent.appendTo("#day"+dayStart); console.log(divEvent); } }); } my problem being : events contain 3 element I'd like to display but only the last is displayed. If I stop my "for" at the first iteration I can see the first div appended, but it seems that if my loop goes for three iteration the two previous are deleted. The console.log() display some "not-anymore" existing element. Any idea ?

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  • When and why can sprintf fail?

    - by Srekel
    I'm using swprintf to build a string into a buffer (using a loop among other things). const int MaxStringLengthPerCharacter = 10 + 1; wchar_t* pTmp = pBuffer; for ( size_t i = 0; i < nNumPlayers ; ++i) { const int nPlayerId = GetPlayer(i); const int nWritten = swprintf(pTmp, MaxStringLengthPerCharacter, TEXT("%d,"), nPlayerId); assert(nWritten >= 0 ); pTmp += nWritten; } *pTaskPlayers = '\0'; If during testing the assert never hits, can I be sure that it will never hit in live code? That is, do I need to check if nWritten < 0 and handle that, or can I safely assume that there won't be a problem? Under which circumstances can it return -1? The documentation more or less just states "If the function fails". In one place I've read that it will fail if it can't match the arguments (i.e. the formatting string to the varargs) but that doesn't worry me. I'm also not worried about buffer overrun in this case - I know the buffer is big enough.

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  • PIC C - Sending 200 values over USB, but it only sends 25 or so of them...

    - by Adam
    I have a PIC18F4455 microcontroller which I am trying to use to send 200 values over USB. Basically I am using a for loop and a printf statement to print the values to the usb output stream. However, when the code executes I see in my serial port monitor that it is only sending the first 25 or so values, then stopping. My PIC C code is below. It will send out the 25th or so value (and the comma), but not send anything after and not send a newline character. I'm trying to get it to send all the values, then a newline character at the end. I am sending them all as characters because I can convert them on the PC end of it. //print #3 for (i = 0; i <= 199; i++){if (data[i]=='\0' || data[i]=='\n'){data[i]++;}} for (i = 0; i < 199; i++){printf(usb_cdc_putc, "%c,", data[i]);} printf(usb_cdc_putc, "%c\n", data[199]);

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  • most efficient method of turning multiple 1D arrays into columns of a 2D array

    - by Ty W
    As I was writing a for loop earlier today, I thought that there must be a neater way of doing this... so I figured I'd ask. I looked briefly for a duplicate question but didn't see anything obvious. The Problem: Given N arrays of length M, turn them into a M-row by N-column 2D array Example: $id = [1,5,2,8,6] $name = [a,b,c,d,e] $result = [[1,a], [5,b], [2,c], [8,d], [6,e]] My Solution: Pretty straight forward and probably not optimal, but it does work: <?php // $row is returned from a DB query // $row['<var>'] is a comma separated string of values $categories = array(); $ids = explode(",", $row['ids']); $names = explode(",", $row['names']); $titles = explode(",", $row['titles']); for($i = 0; $i < count($ids); $i++) { $categories[] = array("id" => $ids[$i], "name" => $names[$i], "title" => $titles[$i]); } ?> note: I didn't put the name = value bit in the spec, but it'd be awesome if there was some way to keep that as well.

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  • ASP Dot Net : How to repeat HTML parts with minor differences on a page?

    - by tinky05
    It's a really simple problem. I've got HTML code like this : <div> <img src="image1.jpg" alt="test1" /> </div> <div> <img src="image2.jpg" alt="test2" /> </div> <div> <img src="image3.jpg" alt="test3" /> </div> etc... The data is comming from a DB (image name, alt text). In JAVA, I would do something like : save the info in array in the back end. For the presentation I would loop through it with JSTL : <c:foeach items="${data}" var="${item}> <div> <img src="${item.image}" alt="${item.alt}" /> </div> </c:foreach> What's the best practice in ASP.net I just don't want to create a string with HTML code in it in the "code behind", it's ugly IMO.

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  • Why are compilers so stupid?

    - by martinus
    I always wonder why compilers can't figure out simple things that are obvious to the human eye. They do lots of simple optimizations, but never something even a little bit complex. For example, this code takes about 6 seconds on my computer to print the value zero (using java 1.6): int x = 0; for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) { x += x + x + x + x + x; } System.out.println(x); It is totally obvious that x is never changed so no matter how often you add 0 to itself it stays zero. So the compiler could in theory replace this with System.out.println(0). Or even better, this takes 23 seconds: public int slow() { String s = "x"; for (int i = 0; i < 100000; ++i) { s += "x"; } return 10; } First the compiler could notice that I am actually creating a string s of 100000 "x" so it could automatically use s StringBuilder instead, or even better directly replace it with the resulting string as it is always the same. Second, It does not recognize that I do not actually use the string at all, so the whole loop could be discarded! Why, after so much manpower is going into fast compilers, are they still so relatively dumb? EDIT: Of course these are stupid examples that should never be used anywhere. But whenever I have to rewrite a beautiful and very readable code into something unreadable so that the compiler is happy and produces fast code, I wonder why compilers or some other automated tool can't do this work for me.

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  • adding an uncertain number of fields using javascript

    - by user306472
    I'm new to javascript and a novice programmer, so this might be a really easy question to answer. I would like to loop over the values of x number of fields and add them up to display the sum in a final field. I can perform this function if I explicitly call each field, but I want to abstract this so I can deal with a flexible number of fields. Here's example code I've come up with (that's not working for me). Where am I going wrong? <html> <head> <script type="text/javascript"> function startAdd(){ interval = setInterval("addfields()",1); } function addfields(){ a = document.addition.total.value; b = getElementByTagName("sum").value; for (i=0; i<=b.length; i++){ a+=i; } return a; } function stopAdd(){ clearInterval(interval); } </script> </head> <body> <form name="addition"> <input type="text" name="sum" onFocus="startAdd();" onBlur="stopAdd;"> + <input type="text" name="sum" onFocus="startAdd();" onBlur="stopAdd;"> = <input type="text" name ="total"> </form> </body> </html>

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  • How to decrypt a string encrypted with HMACSHA1?

    - by Bob
    I'm an encryption novice trying to pass some values back and forth between systems. I can encrypt the value, but can't seem to figure out how to decrypt on the other end. I've created a simple Windows Forms application using VB.NET. Trying to input a value and a key, encrypt and then decrypt to get the original value. Here's my code so far. Any help greatly appreciated. Thanks. Imports System Imports System.IO Imports System.Security.Cryptography Imports System.Text Public Class Form1 Private Sub btnEncode_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncode.Click Dim hmacsha1 As New HMACSHA1(Encoding.ASCII.GetBytes(txtKey.Text)) Dim hashValue As Byte() = hmacsha1.ComputeHash(Encoding.ASCII.GetBytes(txtValue.Text)) txtResult.Text = BytesToHexString(hashValue) hmacsha1.Clear() End Sub Private Sub btnDecode_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDecode.Click '??? End Sub Private Function BytesToHexString(ByVal bytes As Byte()) As String Dim output As String = String.Empty Dim i As Integer = 0 Do While i < bytes.Length output += bytes(i).ToString("X2") i += 1 Loop Return output End Function End Class

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  • curl_multi_exec stops if one url is 404, how can I change that?

    - by Rob
    Currently, my cURL multi exec stops if one url it connects to doesn't work, so a few questions: 1: Why does it stop? That doesn't make sense to me. 2: How can I make it continue? EDIT: Here is my code: $SQL = mysql_query("SELECT url FROM shells") ; $mh = curl_multi_init(); $handles = array(); while($resultSet = mysql_fetch_array($SQL)){ //load the urls and send GET data $ch = curl_init($resultSet['url'] . $fullcurl); //Only load it for two seconds (Long enough to send the data) curl_setopt($ch, CURLOPT_TIMEOUT, 5); curl_multi_add_handle($mh, $ch); $handles[] = $ch; } // Create a status variable so we know when exec is done. $running = null; //execute the handles do { // Call exec. This call is non-blocking, meaning it works in the background. curl_multi_exec($mh,$running); // Sleep while it's executing. You could do other work here, if you have any. sleep(2); // Keep going until it's done. } while ($running > 0); // For loop to remove (close) the regular handles. foreach($handles as $ch) { // Remove the current array handle. curl_multi_remove_handle($mh, $ch); } // Close the multi handle curl_multi_close($mh);

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  • linux raw socket programming question

    - by user194420
    Hi all, I am trying to create a raw socket which send and receive message with ip/tcp header under linux. I can successfully binds to a port and receive tcp message(ie:syn) However, the message seems to be handled by the os, but not mine. I am just a reader of it(like wireshark). My raw socket binds to port 8888, and then i try to telnet to that port . In wireshark, it shows that the port 8888 reply a "rst ack" when it receive the "syn" request. In my program, it shows that it receive a new message and it doesnot reply with any message. Any way to actually binds to that port?(prevent os handle it) Here is part of my code, i try to cut those error checking for easy reading sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_TCP); int tmp = 1; const int *val = &tmp; setsockopt (sockfd, IPPROTO_IP, IP_HDRINCL, val, sizeof (tmp)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(8888); bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)); //call recv in loop

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  • How might I wrap the FindXFile-style APIs to the STL-style Iterator Pattern in C++?

    - by BillyONeal
    Hello everyone :) I'm working on wrapping up the ugly innards of the FindFirstFile/FindNextFile loop (though my question applies to other similar APIs, such as RegEnumKeyEx or RegEnumValue, etc.) inside iterators that work in a manner similar to the Standard Template Library's istream_iterators. I have two problems here. The first is with the termination condition of most "foreach" style loops. STL style iterators typically use operator!= inside the exit condition of the for, i.e. std::vector<int> test; for(std::vector<int>::iterator it = test.begin(); it != test.end(); it++) { //Do stuff } My problem is I'm unsure how to implement operator!= with such a directory enumeration, because I do not know when the enumeration is complete until I've actually finished with it. I have sort of a hack together solution in place now that enumerates the entire directory at once, where each iterator simply tracks a reference counted vector, but this seems like a kludge which can be done a better way. The second problem I have is that there are multiple pieces of data returned by the FindXFile APIs. For that reason, there's no obvious way to overload operator* as required for iterator semantics. When I overload that item, do I return the file name? The size? The modified date? How might I convey the multiple pieces of data to which such an iterator must refer to later in an ideomatic way? I've tried ripping off the C# style MoveNext design but I'm concerned about not following the standard idioms here. class SomeIterator { public: bool next(); //Advances the iterator and returns true if successful, false if the iterator is at the end. std::wstring fileName() const; //other kinds of data.... }; EDIT: And the caller would look like: SomeIterator x = ??; //Construct somehow while(x.next()) { //Do stuff } Thanks! Billy3

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  • Connections hanging on read()

    - by viraptor
    Hi, Short version: I've got a strange issue with a server accepting TCP connections. Even though there are normally some processes waiting, at some volume of connections it hangs. Long version: The server is written in Perl and binds a $srv socket with the reuse flag and listen == 5. Afterwards, it forks into 10 processes with a loop of $clt=$srv->accept(); do_processing($clt); $clt->shutdown(2); The client written in C is also very simple - it sends some lines, then receives all lines available and does a shutdown(sockfd, 2); There's nothing async going on and at the end both send and receive queues are empty (as reported by netstat). Connections last only ~20ms. All clients behave the same way, are the same implementation, etc. Now let's say I'm accepting X connections from client 1 and another X from client 2. Processes still report that they're idle all the time. If I add another X connections from client 3, suddenly the server processes start hanging just after accepting. The first blocking thing they do after accept(); is while (<$clt>) ... - but they don't get any data (on the first try already). Suddenly all 10 processes are in this state and do not stop waiting. On strace, the server processes seem to hang on read(), which makes sense. There are loads of connections in TIME_WAIT state belonging to that server (~100 when the problem starts to manifest), but this might be a red herring. What could be happening here?

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  • Update on: How to model random non-overlapping spheres of non-uniform size in a cube using Matlab?

    - by user3838079
    I am trying to use MATLAB for generating random locations for non-uniform size spheres (non-overlapping) in a cube. The for loop in the code below never seems to end. I don't know what am missing in the code. I have ran the code for no. of spheres (n) = 10; dims = [ 10 10 10 ] function [ c r ] = randomSphere( dims ) % creating one sphere at random inside [0..dims(1)]x[0..dims(2)]x... % radius and center coordinates are sampled from a uniform distribution % over the relevant domain. % output: c - center of sphere (vector cx, cy,... ) % r - radius of sphere (scalar) r = rand(1); % you might want to scale this w.r.t dims or other consideration c = r + rand( size(dims) )./( dims - 2*r ); % make sure sphere does not exceed boundaries function ovlp = nonOverlapping( centers, rads ) % check if several spheres with centers and rads overlap or not ovlp = false; if numel( rads ) == 1 return; % nothing to check for a single sphere end dst = sqrt( sum( bsxfun( @minus, permute( centers, [1 3 2] ),... permute( centers, [3 1 2] ) ).^2, 3) ); ovlp = dst >= bsxfun( @plus, rads, rads.' ); %' all distances must be smaller than r1+r2 ovlp = any( ovlp(:) ); % all must not overlap function [centers rads] = sampleSpheres( dims, n ) % dims is assumed to be a row vector of size 1-by-ndim % preallocate ndim = numel(dims); centers = zeros( n, ndim ); rads = zeros( n, 1 ); ii = 1; while ii <= n [centers(ii,:), rads(ii) ] = randomSphere( dims ); if nonOverlapping( centers(1:ii,:), rads(1:ii) ) ii = ii + 1; % accept and move on end end

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  • A potentially dangerous Request.Form value was detected: Dealing with these errors proactively, or a

    - by Albert
    I'm noticing this error more and more in my error logs. I've read through the questions here talking about this error, but they don't address what I would like to do (see below). I'm considering three options, in the order of preference: 1) When submitting a form (I use formviews almost exclusively, if that helps), if potentially dangerous characters are detected, automatically strip them out and submit. 2) When submitting a form, if potentially dangerous characters are detected, alert the user and let them fix it before trying again. 3) After the exception is generated, deal with it and alert the user. I'm hoping one of the first two options might be able to do somewhat globally...I know for the 3rd I'd have to alter a TON of Try-Catch blocks I already have in place. Doable, but labor intensive. I'd rather be proactive about it if at all possible and avoid the exception all together. Perhaps one approach to #1 would be to write a block of code that could loop through all text entry fields in a formview, during the insert/update event, and strip the characters out. I'm ok with that, but I'd rather not have to heavily alter all my Insert/Update events to accomplish this. Or maybe I just create a different class to do the text checking/deleting, and only insert 1 line of code in each Insert/Update event. If anyone can come up with some example code of any of these approaches that would be a help. Thanks for any ideas or information. I'm definitely open to other solutions too; these are only the 3 that came to mind. I can say that I don't want to turn request validation off though.

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  • Tool to detect use/abuse of String.Concat (where StringBuilder should be used)

    - by Mark Rushakoff
    It's common knowledge that you shouldn't use a StringBuilder in place of a small number of concatenations: string s = "Hello"; if (greetingWorld) { s += " World"; } s += "!"; However, in loops of a significant size, StringBuilder is the obvious choice: string s = ""; foreach (var i in Enumerable.Range(1,5000)) { s += i.ToString(); } Console.WriteLine(s); Is there a tool that I can run on either raw C# source or a compiled assembly to identify where in the source code that String.Concat is being called? (If you're not familiar, s += "foo" is mapped to String.Concat in the IL output.) Obviously, I can't realistically search through an entire project and evaluate every += to identify whether the lvalue is a string. Ideally, it would only point out calls inside a for/foreach loop, but I would even put up with all the false positives of noting every String.Concat. Also, I'm aware that there are some refactoring tools that will automatically refactor my code to use StringBuilder, but I am only interested in identifying the Concat usage at this point. I routinely run Gendarme and FxCop on my code, and neither of those tools identify what I've described.

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