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• Android USB Host Communication

  - by Kip Russell

  I'm working on a project that utilizes the USB Host capabilities in Android 3.2. I'm suffering from a deplorable lack of knowledge and talent regarding USB/Serial communication in general. I'm also unable to find any good example code for what I need to do. I need to read from a USB Communication Device. Ex: When I connect via Putty (on my PC) I enter: >GO And the device starts spewing out data for me. Pitch/Roll/Temp/Checksum. Ex: $R1.217P-0.986T26.3*60 $R1.217P-0.986T26.3*60 $R1.217P-0.987T26.3*61 $R1.217P-0.986T26.3*60 $R1.217P-0.985T26.3*63 I can send the initial 'GO' command from the Android device at which time I receive an echo of 'GO'. Then nothing else on any subsequent reads. How can I: 1) Send the 'go' command. 2) Read in the stream of data that results. The USB device I'm working with has the following interfaces (endpoints). Device Class: Communication Device (0x2) Interfaces: Interface #0 Class: Communication Device (0x2) Endpoint #0 Direction: Inbound (0x80) Type: Intrrupt (0x3) Poll Interval: 255 Max Packet Size: 32 Attributes: 000000011 Interface #1 Class: Communication Device Class (CDC) (0xa) Endpoint #0 Address: 129 Number: 1 Direction: Inbound (0x80) Type: Bulk (0x2) Poll Interval (0) Max Packet Size: 32 Attributes: 000000010 Endpoint #1 Address: 2 Number: 2 Direction: Outbound (0x0) Type: Bulk (0x2) Poll Interval (0) Max Packet Size: 32 Attributes: 000000010 I'm able to deal with permission, connect to the device, find the correct interface and assign the endpoints. I'm just having trouble figuring out which technique to use to send the initial command read the ensuing data. I'm tried different combinations of bulkTransfer and controlTransfer with no luck. Thanks. I'm using interface#1 as seen below: public AcmDevice(UsbDeviceConnection usbDeviceConnection, UsbInterface usbInterface) { Preconditions.checkState(usbDeviceConnection.claimInterface(usbInterface, true)); this.usbDeviceConnection = usbDeviceConnection; UsbEndpoint epOut = null; UsbEndpoint epIn = null; // look for our bulk endpoints for (int i = 0; i < usbInterface.getEndpointCount(); i++) { UsbEndpoint ep = usbInterface.getEndpoint(i); Log.d(TAG, "EP " + i + ": " + ep.getType()); if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) { if (ep.getDirection() == UsbConstants.USB_DIR_OUT) { epOut = ep; } else if (ep.getDirection() == UsbConstants.USB_DIR_IN) { epIn = ep; } } } if (epOut == null || epIn == null) { throw new IllegalArgumentException("Not all endpoints found."); } AcmReader acmReader = new AcmReader(usbDeviceConnection, epIn); AcmWriter acmWriter = new AcmWriter(usbDeviceConnection, epOut); reader = new BufferedReader(acmReader); writer = new BufferedWriter(acmWriter); }

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• Pthread-ed filetransfer application crash

  - by N.R.S.Sowrabh

  I am developing a file transfer application and am using pthreads on the receiver side for receiving multiple files. The function which is passed to pthreads calls the following function and at the end of this function I get a SIGABRT error and stack-smashing error appears on the terminal. Please help me find the bugs. If you need anymore code I'd be able to post the same. Thanks in advance. void recv_mesg(int new_sockid, char *fname) { cout<<"New Thread created with "<<new_sockid<<" and "<<fname<<endl; char buf[MAXLINE]; int fd; fd = open(fname, O_WRONLY ); int len =0; while (len<1024) { int curr = recv(new_sockid, buf, 1024-len, 0); //fprintf(stdout,"Message from Client:\n"); len += curr; //write (fd, buf, curr); fputs(buf, stderr); } int file_size = 0; sscanf(buf,"%d",&file_size); if(file_size<=0) perror("File Size < 0"); sprintf(buf,"Yes"); send(new_sockid,buf,strlen(buf),0); len = 0; while (len<file_size) { int curr = recv(new_sockid, buf, min(file_size-len,MAXLINE), 0); len += curr; write (fd, buf, curr); //fputs(buf, stdout); //fflush(stdout); } len = 0; close(fd); close(new_sockid); }

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• How to create closed areas (convex polygons) from set of line segments ?

  - by Marten

  The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop through that data (which is still line segments but doesn't comply with Voronoi anymore) and generate "neigbourhoods" that are bordered with the "roads". I looked at some graph diagrams and shortest path theories, but I could not figure it out. Logically it could be done by starting at left edge from one point, finding the way back to that point using the shortest path with available lines (using only clockwise directions). Then mark this line set down and remove from the data. Then you can repeat the same process and get all the areas like that. I tried to implement that but it did not get me anywhere as I could not figure out a way to write a C++ code that could do that. Problem was with choosing the most counterclockwise line from available lines from a specific point. All angle based math I did gave wrong answers because the way sin/cos are implemented in c++. So to summarize - if you can help me with a totally new approach to the problem its good, if not could you help me find a way to write the part of the code that finds the shortest clockwise path back to the beginning point using the line segment set as paths back. Thank you for your help!

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• Problem writing HTML content to Word document in ASP.NET

  - by saran

  I am trying to export the HTML page contents to Word. My Html display page is: What is your favourite color? NA List the top three school ? one National two Devs three PS And a button for click event. The button click event will open MS word and paste the page contents in word. The word page contains the table property of html design page. It occurs only in Word 2003. But in word 2007 the word document contains the text with out table property. How can I remove this table property in word 2003. I am not able to add the snapshots. Else i will make you clear. I am designing the web page by aspx. I am exporting the web page content by the following code. protected void Button1_Click(object sender, EventArgs e) { Response.ContentEncoding = System.Text.Encoding.UTF7; System.Text.StringBuilder SB = new System.Text.StringBuilder(); System.IO.StringWriter SW = new System.IO.StringWriter(); System.Web.UI.HtmlTextWriter htmlTW = new System.Web.UI.HtmlTextWriter(SW); tbl.RenderControl(htmlTW); string strBody = "<html>" + "<body>" + "<div><b>" + htmlTW.InnerWriter.ToString() + "</b></div>" + "</body>" + "</html>"; Response.AppendHeader("Content-Type", "application/msword"); Response.AppendHeader("Content-disposition", "attachment; filename=" + fileName); Response.ContentEncoding = System.Text.Encoding.UTF7; string fileName1 = "C://Temp/Excel" + DateTime.Now.Millisecond.ToString(); BinaryWriter writer = new BinaryWriter(File.Open(fileName1, FileMode.Create)); writer.Write(strBody); writer.Close(); FileStream fs = new FileStream(fileName1, FileMode.Open, FileAccess.Read); byte[] renderedBytes; // Create a byte array of file stream length renderedBytes = new byte[fs.Length]; //Read block of bytes from stream into the byte array fs.Read(renderedBytes, 0, System.Convert.ToInt32(fs.Length)); //Close the File Stream fs.Close(); FileInfo TheFile = new FileInfo(fileName1); if (TheFile.Exists) { File.Delete(fileName1); } Response.BinaryWrite(renderedBytes); Response.Flush(); Response.End(); }

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• PHP upload with progress bar

  - by Mitchan Adams

  Hi all I want to create an upload form to upload large files. Thats pretty much easy, however, the upload process itself taks long and basically looks like nothing is happening for a few minutes. So now I'd like to insert a progress bar to show the user that something is happening and they should just sit tight. I've read of numerous methods like APC and certian flash plugins, but my site is hosted on a shared server and I cant install any new applications on it. I'm thinking, maybe if it is possible to read the size of the temp file it creates via an ajax page. By polling the size every few seconds I should be able to get the progress of the upload. Now the question I pose is...where is the temp file situated?

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• Using SQL dB column as a lock for concurrent operations in Entity Framework

  - by Sid

  We have a long running user operation that is handled by a pool of worker processes. Data input and output is from Azure SQL. The master Azure SQL table structure columns are approximated to [UserId, col1, col2, ... , col N, beingProcessed, lastTimeProcessed ] beingProcessed is boolean and lastTimeProcessed is DateTime. The logic in every worker role is: public void WorkerRoleMain() { while(true) { try { dbContext db = new dbContext(); // Read foreach (UserProfile user in db.UserProfile .Where(u => DateTime.UtcNow.Subtract(u.lastTimeProcessed) > TimeSpan.FromHours(24) & u.beingProcessed == false)) { user.beingProcessed = true; // Modify db.SaveChanges(); // Write // Do some long drawn processing here ... ... ... user.lastTimeProcessed = DateTime.UtcNow; user.beingProcessed = false; db.SaveChanges(); } } catch(Exception ex) { LogException(ex); Sleep(TimeSpan.FromMinutes(5)); } } // while () } With multiple workers processing as above (each with their own Entity Framework layer), in essence beingProcessed is being used a lock for MutEx purposes Question: How can I deal with concurrency issues on the beingProcessed "lock" itself based on the above load? I think read-modify-write operation on the beingProcessed needs to be atomic but I'm open to other strategies. Open to other code refinements too.

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• Android Apps: What is the recommended targetSdk for broadest appeal?

  - by johnrock

  I have an Android app that only needs internet access and would like to target API level 3 (1.5) to reach the broadest handset base. However, it appears that targeting API level 3 implicitly requires two additional permissions that are visible to users: modify sd card, and read phone state. See: http://stackoverflow.com/questions/1747178/android-permissions-phone-calls-read-phone-state-and-identity) So the connundrum, do I target API level 4 and turn away users running 1.5, or do I target API level 3 and turn away users who are upset that my app is requesting so many permissions that it shouldn't need? What is the smartest thing to do here? Are there really a lot of users still limited to API level 3? I appreciate any wisdom offered! Thanks!

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• Union on ValuesQuerySet in django

  - by Wuxab

  I've been searching for a way to take the union of querysets in django. From what I read you can use query1 | query2 to take the union... This doesn't seem to work when using values() though. I'd skip using values until after taking the union but I need to use annotate to take the sum of a field and filter on it and since there's no way to do "group by" I have to use values(). The other suggestions I read were to use Q objects but I can't think of a way that would work. Do I pretty much need to just use straight SQL or is there a django way of doing this? What I want is: q1 = mymodel.objects.filter(date__lt = '2010-06-11').values('field1','field2').annotate(volsum=Sum('volume')).exclude(volsum=0) q2 = mymodel.objects.values('field1','field2').annotate(volsum=Sum('volume')).exclude(volsum=0) query = q1|q2 But this doesn't work and as far as I know I need the "values" part because there's no other way for Sum to know how to act since it's a 15 column table.

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• 50 sequences in one line

  - by user343934

  I have Muttiple sequence alignment (clustal) file and i want to read this file and arrange sequences in a such a way that in looks more clear and precise in order. I am doing this from biopython using AlignIO object. My codes like this alignment = AlignIO.read("opuntia.aln", "clustal") print "Number of rows: %i" % len(align) for record in alignment: print "%s - %s" % (record.id, record.seq) My Output-- http://i48.tinypic.com/ae48ew.jpg , it looks messy and long scrolling. What i want to do is print only 50 sequences in each line and continue till the end of alignment file. I wish to have output like this---http://i45.tinypic.com/4vh5rc.jpg from --http://www.ebi.ac.uk/Tools/clustalw2/, sorry two links are just a text due to my reputation. Any suggestions, algorithm and sample code is appreciated Thanks in advance Br,

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• asp.net mvc Ajax.BeginForm clone.

  - by denis_n

  Hello, I'm using asp.net mvc ajax. The partial view is using Ajax.BeginForm (just an example): <div id="divPlaceholder"> <% using (Ajax.BeginForm(new AjaxOptions { UpdateTargetId = "divPlaceholder" })) { %> ... asp.net mvc controls and validation messages <input type="submit" value="Save" /> <% } %> </div> After update, if validation fails, the html is: <div id="divPlaceholder"> <div id="divPlaceholder"> ...form </div> </div> I don't like that the returned html is inserted, instead it should replace original div. Probably on POST I should not render <div> around form in partial view or render the div without id. What else can I do in this situation? I was thinking that maybe I should write a helper, something like Ajax.DivBeginForm, which will render form inside div on GET and hide the div on POST. Can somebody provide a good advice how to write such helper (Ajax.DivBeginForm)? I'd like it to work with using keyword: <% using (Ajax.DivBeginForm(new AjaxOptions { UpdateTargetId = "myId" })) { ... }%>

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• How do I correctly decode unicode parameters passed to a servlet

  - by Grant Wagner

  Suppose I have: <a href="http://www.yahoo.com/" target="_yahoo" title="Yahoo!&#8482;" onclick="return gateway(this);">Yahoo!</a> <script type="text/javascript"> function gateway(lnk) { window.open(SERVLET + '?external_link=' + encodeURIComponent(lnk.href) + '&external_target=' + encodeURIComponent(lnk.target) + '&external_title=' + encodeURIComponent(lnk.title)); return false; } </script> I have confirmed external_title gets encoded as Yahoo!%E2%84%A2 and passed to SERVLET. If in SERVLET I do: Writer writer = response.getWriter(); writer.write(request.getParameter("external_title")); I get Yahoo!â„¢ in the browser. If I manually switch the browser character encoding to UTF-8, it changes to Yahoo!TM (which is what I want). So I figured the encoding I was sending to the browser was wrong (it was Content-type: text/html; charset=ISO-8859-1). I changed SERVLET to: response.setContentType("text/html; charset=utf-8"); Writer writer = response.getWriter(); writer.write(request.getParameter("external_title")); Now the browser character encoding is UTF-8, but it outputs Yahoo!â?¢ and I can't get the browser to render the correct character at all. My question is: is there some combination of Content-type and/or new String(request.getParameter("external_title").getBytes(), "UTF-8"); and/or something else that will result in Yahoo!TM appearing in the SERVLET output?

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• How to use SMS content provider? Where are the docs?

  - by Mark

  Hi, I'd like to be able to read the system's SMS content provider. Basically I wanted to make an SMS messaging app, but it would only be useful if I could see past threads etc. It seems like there's a content provider for this, but I can't find documentation for it - anyone know where that is? Thanks -------- edit ----------- Ok I found a way to get the sms inbox provider, and I just dumped all the column names in that provider, looks like this: Uri uriSms = Uri.parse("content://sms/inbox"); Cursor c = context.getContentResolver().query(uriSms, null,null,null,null); // column names for above provider: 0: _id 1: thread_id 2: address 3: person 4: date 5: protocol 6: read 7: status 8: type 9: reply_path_present 10: subject 11: body 12: service_center 13: locked I'm just piecing this together from random threads I find around the net, I'm really wondering where this is all documented (if at all)? Thanks again

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• Flash AS3 - Scroll dynamic textfield to a specific part just like HTML anchor

  - by Aamir Mahmood

  Hi, We are building a flash website with cms at the back end, and we are allowing admin to put anchors inside a content. Later we created a smaller version of the whole content to display just a small part and then [read more] button. Which add a new layer on top of every thing acting like a popup and it is populated with complete content. Now we would like to scroll that text inside popup to that portion which [read more] button was clicked. The most common example inside HTMl is go to top link in footer on most of the sites which move the whole document to top. Happy codding.

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• How does jQuery store data with .data()?

  - by TK

  I am a little confused how jQuery stores data with .data() functions. Is this something called expando? Or is this using HTML5 Web Storage although I think this is very unlikely? The documentation says: The .data() method allows us to attach data of any type to DOM elements in a way that is safe from circular references and therefore from memory leaks. As I read about expando, it seems to have a rick of memory leak. Unfortunately my skills are not enough to read and understand jQuery code itself, but I want to know how jQuery stores such data by using data(). http://api.jquery.com/data/

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• Reading CSV files in c#

  - by JJ

  How do I read large CSV files using C# & display it on the browser?

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• Text piped to PowerShell.exe isn't recieved when using [Console]::ReadLine()

  - by crtracy

  I'm getting itermittent data loss when calling .NET [Console]::ReadLine() to read piped input to PowerShell.exe: >ping localhost | powershell -NonInteractive -NoProfile -C "do {$line = [Console]::ReadLine(); ('' + (Get-Date -f 'HH:mm :ss') + $line) | Write-Host; } while ($line -ne $null)" 23:56:45time<1ms 23:56:45 23:56:46time<1ms 23:56:46 23:56:47time<1ms 23:56:47 23:56:47 Normally 'ping localhost' from Vista64 looks like this, so there is a lot of data missing from the output above: Pinging WORLNTEC02.bnysecurities.corp.local [::1] from ::1 with 32 bytes of data: Reply from ::1: time<1ms Reply from ::1: time<1ms Reply from ::1: time<1ms Reply from ::1: time<1ms Ping statistics for ::1: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms But using the same API from C# recieves all the data sent to the process (excluding some newline differences). Code: namespace ConOutTime { class Program { static void Main (string[] args) { string s; while ((s = Console.ReadLine ()) != null) { if (s.Length > 0) // don't write time for empty lines Console.WriteLine("{0:HH:mm:ss} {1}", DateTime.Now, s); } } } } Output: 00:44:30 Pinging WORLNTEC02.bnysecurities.corp.local [::1] from ::1 with 32 bytes of data: 00:44:30 Reply from ::1: time<1ms 00:44:31 Reply from ::1: time<1ms 00:44:32 Reply from ::1: time<1ms 00:44:33 Reply from ::1: time<1ms 00:44:33 Ping statistics for ::1: 00:44:33 Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), 00:44:33 Approximate round trip times in milli-seconds: 00:44:33 Minimum = 0ms, Maximum = 0ms, Average = 0ms So, if calling the same API from PowerShell instead of C# many parts of StdIn get 'eaten'. Is the PowerShell host reading string from StdIn even though I didn't use 'PowerShell.exe -Command -'?

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• How do I retrieve an automated report and save it to a database?

  - by Mason Wheeler

  I've got a web server that will take scripts in Python, PHP or Perl. I don't know much about any of those languages, but of the three, Python seems the least scary. It has a MySql database set up, and I know enough SQL to manage it and write queries for it. I also have a program that I want to add automated error reporting to. Something goes wrong, it sends a bug report to my server. What I don't know how to do is write a Python script that will sit on the web server and, when my program sends in a bug report, do the following: Receive the bug report. Parse it out into sections. Insert it into the database. Have the server send me an email. From what little I understand, this seems like it shouldn't be too difficult if I only knew what I was doing. Could someone point me to a site that explains the basic principles I'd need to create a script like this?

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• Why does DataInputStream not support integers?

  - by Jason

  I need to read in a list of numbers from a file, none of which are larger than 32767. Originally I was going to use the Scanner class to pull in the data, then I read about DataInputStream. This would work well for me, except that according to the API, it supports all primitive variables EXCEPT ints! Listed are longs, shorts, bytes, chars, booleans, ect, but no ints. I have no need for double precision from the incoming data. Is this a deliberate or unintentional oversight?

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• Convert Stream to IEnumerable. If possible when "keeping laziness"

  - by Binary255

  Hi, I recieve a Stream and need to pass in a IEnumerable to another method. public static void streamPairSwitchCipher(Stream someStream) { ... someStreamAsIEnumerable = ... IEnumerable returned = anotherMethodWhichWantsAnIEnumerable(someStreamAsIEnumerable); ... } One way is to read the entire Stream, convert it to an Array of bytes and pass it in, as Array implements IEnumerable. But it would be much nicer if I could pass in it in such a way that I don't have to read the entire Stream before passing it in. public static IEnumerable<T> anotherMethodWhichWantsAnIEnumerable<T>(IEnumerable<T> p) { ... // Something uninteresting }

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• How to change a Linux user password from python

  - by Vaulor

  I'm having problems with changing a Linux user's password from python. I've tried so many things, but I couldn't manage to solve the issue, here is the sample of things I've already tried: sudo_password is the password for sudo, sudo_command is the command I want the system to run, user is get from a List and is the user who I want to change the password for, and newpass is the pass I want to assign to 'user' user = list.get(ANCHOR) sudo_command = 'passwd' f = open("passwordusu.tmp", "w") f.write("%s\n%s" % (newpass, newpass)) f.close() A=os.system('echo -e %s|sudo -S %s < %s %s' % (sudo_password, sudo_command,'passwordusu.tmp', user)) print A windowpass.destroy() 'A' is the return value for the execution of os.system, in this case 256. I tried also A=os.system('echo %s|sudo -S %s < %s %s' % (sudo_password, sudo_command,'passwordusu.tmp', user)) but it returns the same error code. I tried several other ways with 'passwd' command, but whithout succes. With 'chpasswd' command I 've tried this: user = list.get(ANCHOR) sudo_command = 'chpasswd' f = open("passwordusu.tmp", "w") f.write("%s:%s" % (user, newpass)) f.close() A=os.system('echo %s|sudo -S %s < %s %s' % (sudo_password, sudo_command,'passwordusu.tmp', user)) print A windowpass.destroy() also with: A=os.system('echo %s|sudo -S %s:%s|%s' % (sudo_password, user, newpass, sudo_command)) @;which returns 32512 A=os.system("echo %s | sudo -S %s < \"%s\"" % (sudo_password, sudo_command, "passwordusu.tmp")) @;which returns 256 I tried 'mkpasswd' and 'usermod' too like this: user = list.get(ANCHOR) sudo_command = 'mkpasswd -m sha-512' os.system("echo %s | sudo -S %s %s > passwd.tmp" % (sudo_password,sudo_command, newpass)) sudo_command="usermod -p" f = open('passwd.tmp', 'r') for line in f.readlines(): newpassencryp=line f.close() A=os.system("echo %s | sudo -S %s %s %s" % (sudo_password, sudo_command, newpassencryp, user)) @;which returns 32512 but, if you go to https://www.mkpasswd.net , hash the 'newpass' and substitute for 'newpassencryp', it returns 0 which theoretically means it has gone right, but so far it doesn't changes the password. I've searched on internet and stackoverflow for this issue or similar and tried what solutions exposed, but again,without success. I would really apreciate any help, and of course, if you need more info i'll be glad to supply it! Thanks in advance.

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• Check if table exists in c#

  - by apoorv020

  I want to read data from a table whose name is supplied by a user. So before actually starting to read data, I want to check if the database exists or not. I have seen several pieces of code on the NET which claim to do this. However, they all seem to be work only for SQL server, or for mysql, or some other implementation. Is there not a generic way to do this? (I am already seperately checking if I can connect to the supplied database, so I'm fairly certain that a connection can be opened to the database.)

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• Duplicate partitioning key performance impact

  - by Anshul

  I've read in some posts that having duplicate partitioning key can have a performance impact. I've two tables like: CREATE TABLE "Test1" ( CREATE TABLE "Test2" ( key text, key text, column1 text, name text, value text, age text, PRIMARY KEY (key, column1) ... ) PRIMARY KEY (key, name,age) ) In Test1 column1 will contain column name and value will contain its corresponding value.The main advantage of Test1 is that I can add any number of column/value pairs to it without altering the table by just providing same partitioning key each time. Now my question is how will each of these table schema's impact the read/write performance if I've millions of rows and number of columns can be upto 50 in each row. How will it impact the compaction/repair time if I'm writing duplicate entries frequently?

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• Track mass email campaigns

  - by daeliur

  Litmus released an email analytics service last month (may 2010). See here: http://litmusapp.com/email-analytics They boast a very cool "read rate" tracking: they can track normal reads, Skims, and Glanced/Deleted. How can they track skims and glanced/deleted? This to me seems impossible :) They also track forwards and prints. Prints are easy (they include a css @media print query with a bg image). But forwards? I think this might be a combo between subsequent opens and different IPs/reffering URLs. However, this means that if I open my mail and re-read it from another computer, it counts as a forward. Any ideas on this one? To summarize: Litmus Email Analytics says they can track email reads, skims, glanced/deleted, prints and forwards. How do they do it (skims, glanced/deleted and forwards)?

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• Recommendations for a C++ polymorphic, seekable, binary I/O interface

  - by Trevor Robinson

  I've been using std::istream and ostream as a polymorphic interface for random-access binary I/O in C++, but it seems suboptimal in numerous ways: 64-bit seeks are non-portable and error-prone due to streampos/streamoff limitations; currently using boost/iostreams/positioning.hpp as a workaround, but it requires vigilance Missing operations such as truncating or extending a file (ala POSIX ftruncate) Inconsistency between concrete implementations; e.g. stringstream has independent get/put positions whereas filestream does not Inconsistency between platform implementations; e.g. behavior of seeking pass the end of a file or usage of failbit/badbit on errors Don't need all the formatting facilities of stream or possibly even the buffering of streambuf streambuf error reporting (i.e. exceptions vs. returning an error indicator) is supposedly implementation-dependent in practice I like the simplified interface provided by the Boost.Iostreams Device concept, but it's provided as function templates rather than a polymorphic class. (There is a device class, but it's not polymorphic and is just an implementation helper class not necessarily used by the supplied device implementations.) I'm primarily using large disk files, but I really want polymorphism so I can easily substitute alternate implementations (e.g. use stringstream instead of fstream for unit tests) without all the complexity and compile-time coupling of deep template instantiation. Does anyone have any recommendations of a standard approach to this? It seems like a common situation, so I don't want to invent my own interfaces unnecessarily. As an example, something like java.nio.FileChannel seems ideal. My best solution so far is to put a thin polymorphic layer on top of Boost.Iostreams devices. For example: class my_istream { public: virtual std::streampos seek(stream_offset off, std::ios_base::seekdir way) = 0; virtual std::streamsize read(char* s, std::streamsize n) = 0; virtual void close() = 0; }; template <class T> class boost_istream : public my_istream { public: boost_istream(const T& device) : m_device(device) { } virtual std::streampos seek(stream_offset off, std::ios_base::seekdir way) { return boost::iostreams::seek(m_device, off, way); } virtual std::streamsize read(char* s, std::streamsize n) { return boost::iostreams::read(m_device, s, n); } virtual void close() { boost::iostreams::close(m_device); } private: T m_device; };

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• How to trigger the event together on each two deferent class.

  - by XBasic3000

  I have two object class on a single unit, is it posible to trigger the two events? let say the FIRSTCLASS event is fired, The SECONDCLASS also will fired? Assuming...... //{Class 1}------------------------------------------------------------- type TOnEventTrigger = procedure(Sender : Tobject; Value :integer); TMyFirstClass = Class(Tcomponent) private .... public .... OnEventTrigger : TOnEventTrigger read Fevent write Fevent; end; procedure TMyFirstClass.FEvnt(Sender : Tobject; Value :integer); begin // here is normaly triggers the event // if Assigned(OnEventTrigger) then OnEventTrigger(Self,FSomevalue); // POSTMessage(GetForegroundWindow,WM_USER+3,0,0); // this is what i did here to get the result of FSomevalue // but this is not ideal. It work only on focus window. end; //{Class 2}------------------------------------------------------------- type TOnEventTrigger = procedure(Sender : Tobject; Value :integer); TMySecondClass = Class(Tobject) private .... public .... OnEventTrigger : TOnEventTrigger; read Fevent write Fevent; end; procedure TMySecondClass.FEvnt(Sender : Tobject; Value :integer); begin // I wanted here to trigger, whenenver the above is fired // if Assigned(OnEventTrigger) then OnEventTrigger(Self,FSomevalue); end;

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