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• ACL architechture for a Software As a service in Spring 3.0

  - by geoaxis

  I am making a software as a service using Spring 3.0 (Spring MVC, Spring Security, Spring Roo, Hibernate) I have to come up with a flexible access control list mechanism.I have three different kinds of users System (who can do any thing to the system, includes admin and internal daemons) Operations (who can add and delete users, organizations, and do maintenance work on behalf of users and organizations) End Users (they belong to one or more organization, for each organization, the user can have one or more roles, like being organization admin, or organization read-only member) (role like orgadmin can also add users for that organization) Now my question is, how should i model the entity of User? If I just take the End User, it can belong to one or more organizations, so each user can contain a set of references to its organizations. But how do we model the users role for each organization, So for example User UX belongs to organizations og1, og2 and og3, and for og1 he is both orgadmin, and org-read-only-user, where as for og2 he is only orgadmin and for og3 he is only org-read-only-user I have the possibility of making each user belong to one organization alone, but that's making the system bounded and I don't like that idea (although i would still satisfy the requirement) If you have a better extensible ACL architecture, please suggest it. Since its a software as a service, one would expect that alot of different organizations would be part if the same system. I had one concern that it is not a good idea to keep og1 and og2 data on the same DB (if og1 decides to spawn a 100 reports on the system, og2 should not suffer) But that is some thing advanced for now and is not directly related to ACL but to the physical distribution of data and setup of services based on those ACLs This is a community Wiki question, please correct any thing which you wish to do so. Thanks

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• New to Linux Kernel/Driver development...

  - by CVS-2600Hertz-wordpress-com

  Recently, i began developing a driver of an embedded device running linux. Until now i have only read about linux internals. Having no prior experience in driver devlopment, i am finding it a tad difficult to land my first step. I have downloaded the kernel source-code (v2.6.32). I have read (skimped) Linux Device Drivers (3e) I read a few related posts here on StackOverflow. I understand that linux has a "monolithic" approach. I have built kernel (included existing driver in menuconfig etc.) I know the basics of kconfig and makefile files so that should not be a problem. Can someone describe the structure (i.e. the inter-links) of the various folders in the kernel-source code. In other words given a source-code file, which other files would it refer to for related code (The "#include"-s provide a partial idea) Could someone please help me in getting a better idea? Any help will be greatly appreciated Thank You.

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• How to replace openSSL calls with C# code?

  - by fonix232

  Hey there again! Today I ran into a problem when I was making a new theme creator for chrome. As you may know, Chrome uses a "new" file format, called CRX, to manage it's plugins and themes. It is a basic zip file, but a bit modified: "Cr24" + derkey + signature + zipFile And here comes the problem. There are only two CRX creators, written in Ruby or Python. I don't know neither language too much (had some basic experience in Python though, but mostly with PyS60), so I would like to ask you to help me convert this python app to a C# code that doesn't depend on external programs. Also, here is the source of crxmake.py: #!/usr/bin/python # Cribbed from http://github.com/Constellation/crxmake/blob/master/lib/crxmake.rb # and http://src.chromium.org/viewvc/chrome/trunk/src/chrome/tools/extensions/chromium_extension.py?revision=14872&content-type=text/plain&pathrev=14872 # from: http://grack.com/blog/2009/11/09/packing-chrome-extensions-in-python/ import sys from array import * from subprocess import * import os import tempfile def main(argv): arg0,dir,key,output = argv # zip up the directory input = dir + ".zip" if not os.path.exists(input): os.system("cd %(dir)s; zip -r ../%(input)s . -x '.svn/*'" % locals()) else: print "'%s' already exists using it" % input # Sign the zip file with the private key in PEM format signature = Popen(["openssl", "sha1", "-sign", key, input], stdout=PIPE).stdout.read(); # Convert the PEM key to DER (and extract the public form) for inclusion in the CRX header derkey = Popen(["openssl", "rsa", "-pubout", "-inform", "PEM", "-outform", "DER", "-in", key], stdout=PIPE).stdout.read(); out=open(output, "wb"); out.write("Cr24") # Extension file magic number header = array("l"); header.append(2); # Version 2 header.append(len(derkey)); header.append(len(signature)); header.tofile(out); out.write(derkey) out.write(signature) out.write(open(input).read()) os.unlink(input) print "Done." if __name__ == '__main__': main(sys.argv) Please could you help me?

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• Automating ftp command line application redirecting I/O in .Net

  - by SoMoS

  Hello, I'm trying to automate the ftp client that Windows includes redirecting the I/O from the process. What I'm doing is starting the process from my application and trying to read what the client prints on the screen and sending my commands to it. The problem is that I can not read almost any data sent by the ftp client. Some data is present but most data is not read. That's the code I have until now. Public Sub Start() process = New Diagnostics.Process() process.StartInfo.FileName = "ftp.exe" #'' The command is on the path process.StartInfo.CreateNoWindow = True process.StartInfo.RedirectStandardInput = True process.StartInfo.RedirectStandardOutput = True process.StartInfo.UseShellExecute = False process.Start() process.StandardInput.AutoFlush = True process.BeginOutputReadLine() End Sub #'' takes data from the stdout Private Sub process_OutputDataReceived(ByVal sender As Object, ByVal e As System.Diagnostics.DataReceivedEventArgs) Handles process.OutputDataReceived #'' At this moment here there is code to show the stdout at a textbox End Sub #'' sends data to stdin Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click process.StandardInput.WriteLine(Me.TextEdit1.Text) End Sub Now when I execute this for example and send ? I just get the first line (and I should get a lot more). Or when I send the open command I should receive an A but nothing is received. Any ideas? Another question is ... when a console applications writes on the screen it always does that by writing at the stdout or the stderr isn't it?

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• Why does Cut/Paste of form components sometimes stop working in Delphi 2007 IDE?

  - by robsoft

  This is driving me crazy. I'm not going to take it anymore. I'm going to ask, even at the risk of eternal public humiliation! (If it's something really obvious or that I've done to the system myself). For reasons I've never quite had the patience to work out, every so often the form I'm working on in Delphi 2007's visual form editor goes 'pseudo-read-only'; I can add new components to the form, I can move/resize existing ones (and change any properties in the Object Inspector), and I can select a component and 'copy' it to the clipboard. But I'm completely unable to cut a component from the form, or paste a new copy down. I don't believe it's to do with the 'Lock Controls' Edit menu option as I can toggle this on or off and it has the effect it's supposed to - this disappearance of Cut & Paste happens on the right-click context menu, from the keyboard and from the main Edit menu - it's as if the form has become read only to thing to do with the clipboard. If I close the form in the IDE and then reopen it, everything starts working fine again (just as D1, D3, D5 and D7 always did for me, previously). I'm not going mad, as I'm sure I read something about why this happens on a newsgroup once and it's caught me out from time to time many many times in the last few months, but I've failed to find the newsgroup reference this evening and I've decided that, as more and more Delphi users seem to be making use of StackOverflow, it was worth asking here. Help - when I'm doing lots of form-work it drives me absolutely mad!

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• How to forward a 'saved' request stream to another Action within the same controller?

  - by Moe Howard

  We have a need to chunk-up large http requests sent by our mobile devices. These smaller chunk streams are merged to a file on the server. Once all chunks are received we need a way to submit the saved merged request to an another method(Action) within the same controller that will process this large http request. How can this be done? The code we tried below results in the service hanging. Is there a way to do this without a round-trip? //Open merged chunked file FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read); //Read steam support variables int bytesRead = 0; byte[] buffer = new byte[1024]; //Build New Web Request. The target Action is called "Upload", this method we are in is called "UploadChunk" HttpWebRequest webRequest; webRequest = (HttpWebRequest)WebRequest.Create(Request.Url.ToString().Replace("Chunk", string.Empty)); webRequest.Method = "POST"; webRequest.ContentType = "text/xml"; webRequest.KeepAlive = true; webRequest.Timeout = 600000; webRequest.ReadWriteTimeout = 600000; webRequest.Credentials = System.Net.CredentialCache.DefaultCredentials; Stream webStream = webRequest.GetRequestStream(); //Hangs here, no errors, just hangs I have looked into using RedirectToAction and RedirecctToRoute but these methods don't fit well with what we are looking to do as we cannot edit the Request.InputStream (as it is read-only) to carry out large request stream. Thanks, Moe

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• RegistryKey ValueCount/SubKeyCount wrong

  - by Mark J Miller

  I am trying to query the following registry key values: HKLM\SOFTWARE\Microsoft\MSSQLServer\Client\SharedMemoryOn HKLM\SOFTWARE\Microsoft\MSSQLServer\Client\SuperSocketNetLib\ProtocolOrder But depending on which machine I'm running the program the query returns null. When I debug on my local machine and I inspect the value for ValueCount for: HKLM\SOFTWARE\Microsoft\MSSQLServer\Client HKLM\SOFTWARE\Microsoft\MSSQLServer\Client\SuperSocketNetLib The count is 0 and OpenSubKey returns null. I am a domain admin, in the local administrators group and have added the following to my app.manifest: <requestedExecutionLevel level="requireAdministrator" uiAccess="false" /> Any idea why? private static void ValidateSqlClientSettings() { Console.WriteLine("\r\n/////////////// LOCAL SQL CLIENT PROTOCOLS ////////////////"); RegistryKey keyHKLM = Registry.LocalMachine; ///TODO: nullreferenceexception - connect to remote machine and find out why RegistryKey sqlClientKey = keyHKLM.OpenSubKey(@"SOFTWARE\Microsoft\MSSQLServer\Client"); if (sqlClientKey == null) { WriteLine2Console(@"WARNING: unable to read registry key '{0}\SOFTWARE\Microsoft\MSSQLServer\Client'", ConsoleColor.Yellow); } var cliKeyNames = from k in sqlClientKey.GetSubKeyNames() where k == "SuperSocketNetLib" select k; ///TODO: find out why these values are always missing (even if I can see them in regedit) Console.Write("Shared Memory Disabled (cliconfg): "); if (Convert.ToBoolean(sqlClientKey.GetValue("SharedMemoryOn"))) WriteLine2Console("FAILED", ConsoleColor.Red); else if(sqlClientKey.GetValue("SharedMemoryOn") == null) WriteLine2Console(String.Format("WARNING - unable to read '{0}\\SharedMemoryOn'", sqlClientKey.Name), ConsoleColor.Yellow); else WriteLine2Console("PASS", ConsoleColor.Green); Console.Write("Client Protocol Order (cliconfg - tcp first): "); foreach (string cliKey in cliKeyNames) { RegistryKey subKey = sqlClientKey.OpenSubKey(cliKey); object order = subKey.GetValue("ProtocolOrder"); if (order != null && order.ToString().StartsWith("tcp") == false) { WriteLine2Console("FAILED", ConsoleColor.Red); } else if (order == null) { WriteLine2Console(String.Format("WARNING - unable to read '{0}\\ProtocolOrder'", subKey.Name), ConsoleColor.Yellow); } else { WriteLine2Console("PASS", ConsoleColor.Green); } subKey.Close(); } sqlClientKey.Close(); keyHKLM.Close(); }

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• Extract wrong data from a frame in C?

  - by ipkiss

  I am writing a program that reads the data from the serial port on Linux. The data are sent by another device with the following frame format: |start | Command | Data | CRC | End | |0x02 | 0x41 | (0-127 octets) | | 0x03| ---------------------------------------------------- The Data field contains 127 octets as shown and octet 1,2 contains one type of data; octet 3,4 contains another data. I need to get these data. Because in C, one byte can only holds one character and in the start field of the frame, it is 0x02 which means STX which is 3 characters. So, in order to test my program, On the sender side, I construct an array as the frame formatted above like: char frame[254]; frame[0] = 0x02; // starting field frame[1] = 0x41; // command field which is character 'A' ..so on.. And, then On the receiver side, I take out the fields like: char result[254]; // read data read(result); printf("command = %c", result[1]); // get the command field of the frame // get other field's values the command field value (result[1]) is not character 'A'. I think, this because the first field value of the frame is 0x02 (STX) occupying 3 first places in the array frame and leading to the wrong results on the receiver side. How can I correct the issue or am I doing something wrong at the sender side? Thanks all. related questions: http://stackoverflow.com/questions/2500567/parse-and-read-data-frame-in-c http://stackoverflow.com/questions/2531779/clear-data-at-serial-port-in-linux-in-c

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• Convert 4 bytes to int

  - by Oscar Reyes

  I'm reading a binary file like this: InputStream in = new FileInputStream( file ); byte[] buffer = new byte[1024]; while( ( in.read(buffer ) > -1 ) { int a = // ??? } What I want to do it to read up to 4 bytes and create a int value from those but, I don't know how to do it. I kind of feel like I have to grab 4 bytes at a time, and perform one "byte" operation ( like << & FF and stuff like that ) to create the new int What's the idiom for this? EDIT Ooops this turn out to be a bit more complex ( to explain ) What I'm trying to do is, read a file ( may be ascii, binary, it doesn't matter ) and extract the integers it may have. For instance suppose the binary content ( in base 2 ) : 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010 The integer representation should be 1 , 2 right? :- / 1 for the first 32 bits, and 2 for the remaining 32 bits. 11111111 11111111 11111111 11111111 Would be -1 and 01111111 11111111 11111111 11111111 Would be Integer.MAX_VALUE ( 2147483647 )

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• record output sound in python

  - by aaronstacy

  i want to programatically record sound coming out of my laptop in python. i found PyAudio and came up with the following program that accomplishes the task: import pyaudio, wave, sys chunk = 1024 FORMAT = pyaudio.paInt16 CHANNELS = 1 RATE = 44100 RECORD_SECONDS = 5 WAVE_OUTPUT_FILENAME = sys.argv[1] p = pyaudio.PyAudio() channel_map = (0, 1) stream_info = pyaudio.PaMacCoreStreamInfo( flags = pyaudio.PaMacCoreStreamInfo.paMacCorePlayNice, channel_map = channel_map) stream = p.open(format = FORMAT, rate = RATE, input = True, input_host_api_specific_stream_info = stream_info, channels = CHANNELS) all = [] for i in range(0, RATE / chunk * RECORD_SECONDS): data = stream.read(chunk) all.append(data) stream.close() p.terminate() data = ''.join(all) wf = wave.open(WAVE_OUTPUT_FILENAME, 'wb') wf.setnchannels(CHANNELS) wf.setsampwidth(p.get_sample_size(FORMAT)) wf.setframerate(RATE) wf.writeframes(data) wf.close() the problem is i have to connect the headphone jack to the microphone jack. i tried replacing these lines: input = True, input_host_api_specific_stream_info = stream_info, with these: output = True, output_host_api_specific_stream_info = stream_info, but then i get this error: Traceback (most recent call last): File "./test.py", line 25, in data = stream.read(chunk) File "/Library/Python/2.5/site-packages/pyaudio.py", line 562, in read paCanNotReadFromAnOutputOnlyStream) IOError: [Errno Not input stream] -9975 is there a way to instantiate the PyAudio stream so that it inputs from the computer's output and i don't have to connect the headphone jack to the microphone? is there a better way to go about this? i'd prefer to stick w/ a python app and avoid cocoa.

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• vsts load test datasource issues

  - by ashish.s

  Hello, I have a simple test using vsts load test that is using datasource. The connection string for the source is as follows <connectionStrings> <add name="MyExcelConn" connectionString="Driver={Microsoft Excel Driver (*.xls)};Dsn=Excel Files;dbq=loginusers.xls;defaultdir=.;driverid=790;maxbuffersize=4096;pagetimeout=20;ReadOnly=False" providerName="System.Data.Odbc" /> </connectionStrings> the datasource configuration is as follows and i am getting following error estError TestError 1,000 The unit test adapter failed to connect to the data source or to read the data. For more information on troubleshooting this error, see "Troubleshooting Data-Driven Unit Tests" (http://go.microsoft.com/fwlink/?LinkId=62412) in the MSDN Library. Error details: ERROR [42000] [Microsoft][ODBC Excel Driver] Cannot update. Database or object is read-only. ERROR [IM006] [Microsoft][ODBC Driver Manager] Driver's SQLSetConnectAttr failed ERROR [42000] [Microsoft][ODBC Excel Driver] Cannot update. Database or object is read-only. I wrote a test, just to check if i could create an odbc connection would work and that works the test is as follows [TestMethod] public void TestExcelFile() { string connString = ConfigurationManager.ConnectionStrings["MyExcelConn"].ConnectionString; using (OdbcConnection con = new OdbcConnection(connString)) { con.Open(); System.Data.Odbc.OdbcCommand objCmd = new OdbcCommand("SELECT * FROM [loginusers$]"); objCmd.Connection = con; OdbcDataAdapter adapter = new OdbcDataAdapter(objCmd); DataSet ds = new DataSet(); adapter.Fill(ds); Assert.IsTrue(ds.Tables[0].Rows.Count > 1); } } any ideas ?

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• bash - how to filter java exception info

  - by Michael Mao

  Hi all: We've got a multi-agent Java environment where different agent would most likely produce all sorts of exceptions thrown to stderr. Here is a sample taken from the huge exception log **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) **java.security.AccessControlException: access denied (java.io.FilePermission ..\tournament\Driver\HotelRoomAnalyser.class read)** at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkRead(Unknown Source) at java.io.File.length(Unknown Source) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) at emarket.client.EmarketSandbox$SandboxFileLoader.loadClass(EmarketSandbox.java:199) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) at MySmarterAgent.hotelRoomBookings(MySmarterAgent.java:108) fortunately all top-tier exceptions are denoted by no leading spaces, as wrapped by ** above. My concern is to get all of the top-tier exception name (delimited by colon :), together with the first line below which contains something like at emarket.client.EmarketSandbox$SandboxFileLoader.loadClassData(EmarketSandbox.java:218) Basically, something with padded style, starts with "at" and ends with ".java:108" So this info can be forwarded to the owner of that error-prone agent and let him/her fix it. My code in ~/.bashrc is incompleted now : alias startmatch='java -jar "emarket.jar" ../tournament 100'; function geterrors() { startmatch 2>"$1"; a=0; while read line do if true; then a=$(($a+1)); echo $a; fi; done } What it does now is to redirect all stderr to a text file specified by the first argument passed in, and after that, parse that text file line by line, if certain conditions returns true, echo only that line. And I am stuck with what to do inside the loop. Any suggestion is much appreciates, any hint is welcomed.

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• Sqlite3 "chained" query

  - by Arrieta

  I need to create a configuration file from a data file that looks as follows: MAN1_TIME '01-JAN-2010 00:00:00.0000 UTC' MAN1_RX 123.45 MAN1_RY 123.45 MAN1_RZ 123.45 MAN1_NEXT 'MAN2' MAN2_TIME '01-MAR-2010 00:00:00.0000 UTC' MAN2_RX 123.45 [...] MAN2_NEXT 'MANX' [...] MANX_TIME [...] This file describes different "legs" of a trajectory. In this case, MAN1 is chained to MAN2, and MAN2 to MANX. In the original file, the chains are not as obvious (i.e., they are non-sequential). I've managed to read the file and store in an Sqlite3 database (I'm using the Python interface). The table is stored with three columns: Id, Par, and Val; for instance, Id='MAN1', Par='RX', and Val='123.45'. I'm interested in querying such database for obtaining the information related to 'n' legs. In English, that would be: "Select RX,RY,RZ for the next five legs starting on MAN1" So the query would go to MAN1, retrieve RX, RY, RZ, then read the parameter NEXT and go to that Id, retrieve RX, RY, RZ; read the parameter NEXT; go to that one ... like this five times. How can I pass such query with "dynamic parameters"? Thank you.

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• Bash Templating: How to build configuration files from templates with Bash?

  - by FractalizeR

  Hello. I'm writting a script to automate creating configuration files for Apache and PHP for my own webserver. I don't want to use any GUIs like CPanel or ISPConfig. I have some templates of Apache and PHP configuration files. Bash script needs to read templates, make variable substitution and output parsed templates into some folder. What is the best way to do that? I can think of several ways. Which one is the best or may be there are some better ways to do that? I want to do that in pure Bash (it's easy in PHP for example) 1)http://stackoverflow.com/questions/415677/how-to-repace-variables-in-a-nix-text-file template.txt: the number is ${i} the word is ${word} script.sh: #!/bin/sh #set variables i=1 word="dog" #read in template one line at the time, and replace variables #(more natural (and efficient) way, thanks to Jonathan Leffler) while read line do eval echo "$line" done < "./template.txt" BTW, how do I redirect output to external file here? Do I need to escape something if variables contain, say, quotes? 2) Using cat & sed for replacing each variable with it's value: Given template.txt: The number is ${i} The word is ${word} Command: cat template.txt | sed -e "s/\${i}/1/" | sed -e "s/\${word}/dog/" Seems bad to me because of the need to escape many different symbols and with many variables the line will be tooooo long. Can you think of some other elegant and safe solution?

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• python: nonblocking subprocess, check stdout

  - by Will Cavanagh

  Ok so the problem I'm trying to solve is this: I need to run a program with some flags set, check on its progress and report back to a server. So I need my script to avoid blocking while the program executes, but I also need to be able to read the output. Unfortunately, I don't think any of the methods available from Popen will read the output without blocking. I tried the following, which is a bit hack-y (are we allowed to read and write to the same file from two different objects?) import time import subprocess from subprocess import * with open("stdout.txt", "wb") as outf: with open("stderr.txt", "wb") as errf: command = ['Path\\To\\Program.exe', 'para', 'met', 'ers'] p = subprocess.Popen(command, stdout=outf, stderr=errf) isdone = False while not isdone : with open("stdout.txt", "rb") as readoutf: #this feels wrong for line in readoutf: print(line) print("waiting...\\r\\n") if(p.poll() != None) : done = True time.sleep(1) output = p.communicate()[0] print(output) Unfortunately, Popen doesn't seem to write to my file until after the command terminates. Does anyone know of a way to do this? I'm not dedicated to using python, but I do need to send POST requests to a server in the same script, so python seemed like an easier choice than, say, shell scripting. Thanks! Will

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• Java split xml file

  - by CC

  Hi all, I'm working on a piece of code to split files. I want to split flat file (that's ok, it is working fine) and xml file. The idea is to split based of a number of files to split: I have a file, and I want to split it in x files (x is a parameters). I'm doing the split by taking the size of the file and spliting the size by the number of files to split. Then, mysolution was to use a BufferedReader and to use it like while ((n = reader.read(buffer, 0, buffer.length)) != -1) { { The main problem is that for the xml file I cannot just split it, but I have to split it based on a block delimited by a start xml tag and end xml tag: <start tag> bla bla xml stuff </end tag> So I cannot cut a block at the middle. So if when I'm at the half of a block, is the size of my new file is greater than my max, I will have to read until the end of the tag, and then, to start a next file. The problem is that I have all sort of cases, and is a bit difficult to search the end tag. - the block reads a text until the middle of the end tag - the block reads a text until the end of the end tag, and no more other caracter after - etc and in the same time to have a loop and read the next block. Some times the end of a block concatenated with the start of the next one, I have the end xml tag. I hope you get the idea. My question is, does anyone have some algorithm that does that more accurate and who i treating all special cases ? The idea is to split the file as quickly as possible. Thanks alot.

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• Stream Reuse in C#

  - by MikeD

  I've been playing around with what I thought was a simple idea. I want to be able to read in a file from somewhere (website, filesystem, ftp), perform some operations on it (compress, encrypt, etc.) and then save it somewhere (somewhere may be a filesystem, ftp, or whatever). It's a basic pipeline design. What I would like to do is to read in the file and put it onto a MemoryStream, then perform the operations on the data in the MemoryStream, and then save that data in the MemoryStream somewhere. I was thinking I could use the same Stream to do this but run into a couple of problems: Everytime I use a StreamWriter or StreamReader I need to close it and that closes the stream so that I cannot use it anymore. That seems like there must be some way to get around that. Some of these files may be big and so I may run out of memory if I try to read the whole thing in at once. I was hoping to be able to spin up each of the steps as separate threads and have the compression step begin as soon as there is data on the stream, and then as soon as the compression has some compressed data available on the stream I could start saving it (for example). Is anything like this easily possible with the C# Streams? ANyone have thoughts as to how to accomplish this best? Thanks, Mike

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• Securely erasing a file using simple methods?

  - by Jason

  Hello, I am using C# .NET Framework 2.0. I have a question relating to file shredding. My target operating systems are Windows 7, Windows Vista, and Windows XP. Possibly Windows Server 2003 or 2008 but I'm guessing they should be the same as the first three. My goal is to securely erase a file. I don't believe using File.Delete is secure at all. I read somewhere that the operating system simply marks the raw hard-disk data for deletion when you delete a file - the data is not erased at all. That's why there exists so many working methods to recover supposedly "deleted" files. I also read, that's why it's much more useful to overwrite the file, because then the data on disk actually has to be changed. Is this true? Is this generally what's needed? If so, I believe I can simply write the file full of 1's and 0's a few times. I've read: http://www.codeproject.com/KB/files/NShred.aspx http://blogs.computerworld.com/node/5756 http://blogs.computerworld.com/node/5687 http://stackoverflow.com/questions/4147775/securely-deleting-a-file-in-c-net

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• Updating permissions on Amazon S3 files that were uploaded via JungleDisk

  - by Simon_Weaver

  I am starting to use Jungle Disk to upload files to an Amazon S3 bucket which corresponds to a Cloudfront distribution. i.e. I can access it via an http:// URL and I am using Amazon as a CDN. The problem I am facing is that Jungle Disk doesn't set 'read' permissions on the files so when I go to the corresponding URL in a browser I get an Amazon 'AccessDenied' error. If I use a tool like BucketExplorer to set the ACL then that URL now returns a 200. I really really like the simplicity of dragging files to a network drive. JungleDisk is the best program I've found to do this reliably without tripping over itself and getting confused. However it doesn't seem to have an option to make the files read-able. I really don't want to have to go to a different tool (especially if i have to buy it) to just change the permissions - and this seems really slow anyway because they generally seem to traverse the whole directory structure. JungleDisk provides some kind of 'web access' - but this is a paid feature and I'm not sure if it will work or not. S3 doesn't appear to propagate permissions down which is a real pain. I'm considering writing a manual tool to traverse my tree and set everything to 'read' but I'd rather not do this if this is a problem someone else has already solved.

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• Using perl to split a line that may contain whitespace

  - by Tommy Fisk

  Okay, so I'm using perl to read in a file that contains some general configuration data. This data is organized into headers based on what they mean. An example follows: [vars] # This is how we define a variable! $var = 10; $str = "Hello thar!"; # This section contains flags which can be used to modify module behavior # All modules read this file and if they understand any of the flags, use them [flags] Verbose = true; # Notice the errant whitespace! [path] WinPath = default; # Keyword which loads the standard PATH as defined by the operating system. Append with additonal values. LinuxPath = default; Goal: Using the first line as an example "$var = 10;", I'd like to use the split function in perl to create an array that contains the characters "$var" and "10" as elements. Using another line as an example: Verbose = true; # Should become [Verbose, true] aka no whitespace is present This is needed because I will be outputting these values to a new file (which a different piece of C++ code will read) to instantiate dictionary objects. Just to give you a little taste of what it might look like (just making it up as I go along): define new dictionary name: [flags] # Start defining keys => values new key name: Verbose new value val: 10 # End dictionary Oh, and here is the code I currently have along with what it is doing (incorrectly): sub makeref($) { my @line = (split (/=/)); # Produces ["Verbose", " true"]; }

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• Collaborative filtering in MySQL ?

  - by user281434

  Hi I'm trying to develop a site that recommends items(fx. books) to users based on their preferences. So far, I've read O'Reilly's "Collective Intelligence" and numerous other online articles. They all, however, seem to deal with single instances of recommendation, for example if you like book A then you might like book B. What I'm trying to do is to create a set of 'preference-nodes' for each user on my site. Let's say a user likes book A,B and C. Then, when they add book D, I don't want the system to recommend other books based solely other users experience with book D. I wan't the system to look up similar 'preference-nodes' and recommend books based on that. Here's an example of 4 nodes: User1: 'book A'->'book B'->'book C' User2: 'book A'->'book B'->'book C'->'book D' user3: 'book X'->'book Y'->'book C'->'book Z' user4: 'book W'->'book Q'->'book C'->'book Z' So a recommendation system, as described in the material I've read, would recommend book Z to User 1, because there are two people who recommends Z in conjuction with liking C (ie. Z weighs more than D), even though a user with a similar 'preference-node', User2, would be more qualified to recommend book D because he has a more similar interest-pattern. So does any of you have any experience with this sort of thing? Is there some things I should try to read or does there exist any open source systems for this? Thanks for your time! Small edit: I think last.fm's algorithm is doing exactly what I my system to do. Using the preference-trees of people to recommmend music more personally to people. Instead of just saying "you might like B because you liked A"

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• Documentation for java.util.concurrent.locks.ReentrantReadWriteLock

  - by Andrei Taptunov

  Disclaimer: I'm not very good at Java and just comparing read/writer locks between C# and Java to understand this topic better & decisions behind both implementations. There is JavaDoc about ReentrantReadWriteLock. It states the following about upgrade/downgrade for locks: Lock downgrading ... However, upgrading from a read lock to the write lock is not possible. It also has the following example that shows manual upgrade from read lock to write lock: // Here is a code sketch showing how to exploit reentrancy // to perform lock downgrading after updating a cache void processCachedData() { rwl.readLock().lock(); if (!cacheValid) { // upgrade lock manually #1: rwl.readLock().unlock(); // must unlock first to obtain writelock #2: rwl.writeLock().lock(); if (!cacheValid) { // recheck ... } ... } use(data); rwl.readLock().unlock(); Does it mean that actually the sample from above may not behave correctly in some cases - I mean there is no lock between lines #1 & #2 and underlying structure is exposed to changes from other threads. So it can not be considered as the correct way to upgrade the lock or do I miss something here?

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• SQL Server Clustered Index: (Physical) Data Page Order

  - by scherand

  I am struggling understanding what a clustered index in SQL Server 2005 is. I read the MSDN article Clustered Index Structures (among other things) but I am still unsure if I understand it correctly. The (main) question is: what happens if I insert a row (with a "low" key) into a table with a clustered index? The above mentioned MSDN article states: The pages in the data chain and the rows in them are ordered on the value of the clustered index key. And Using Clustered Indexes for example states: For example, if a record is added to the table that is close to the beginning of the sequentially ordered list, any records in the table after that record will need to shift to allow the record to be inserted. Does this mean that if I insert a row with a very "low" key into a table that already contains a gazillion rows literally all rows are physically shifted on disk? I cannot believe that. This would take ages, no? Or is it rather (as I suspect) that there are two scenarios depending on how "full" the first data page is. A) If the page has enough free space to accommodate the record it is placed into the existing data page and data might be (physically) reordered within that page. B) If the page does not have enough free space for the record a new data page would be created (anywhere on the disk!) and "linked" to the front of the leaf level of the B-Tree? This would then mean the "physical order" of the data is restricted to the "page level" (i.e. within a data page) but not to the pages residing on consecutive blocks on the physical hard drive. The data pages are then just linked together in the correct order. Or formulated in an alternative way: if SQL Server needs to read the first N rows of a table that has a clustered index it can read data pages sequentially (following the links) but these pages are not (necessarily) block wise in sequence on disk (so the disk head has to move "randomly"). How close am I? :)

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• Using .NET XmlSerializer with get properties and setter functions

  - by brone

  I'm trying to use XmlSerializer from C# to save out a class that has some values that are read by properties (the code being just a simple retrieval of field value) but set by setter functions (since there is a delegate called if the value changes). What I'm currently doing is this sort of thing. The intended use is to use the InT property to read the value, and use SetInT to set it. Setting it has side-effects, so a method is more appropriate than a property here. XmlSerializationOnly_InT exists solely for the benefit of the XmlSerializer (hence the name), and shouldn't be used by normal code. class X { public double InT { get { return _inT; } } public void SetInT(double newInT) { if (newInT != _inT) { _inT = newInT; Changed();//includes delegate call; potentially expensive } } private double _inT; // not called by normal code, as the property set is not just a simple // field set or two. [XmlElement(ElementName = "InT")] public double XmlSerializationOnly_InT { get { return InT; } set { SetInT(value); } } } This works, it's easy enough to do, and the XML file looks like you'd expect. It's manual labour though, and a bit ugly, so I'm only somewhat satisfied. What I'd really like is to be able to tell the XML serialization to read the value using the property, and set it using the setter function. Then I wouldn't need XmlSerializationOnly_InT at all. I seem to be following standard practise by distinguishing between property sets and setter functions in this way, so I'm sure I'm not the only person to have encountered this (though google suggests I might be). What have others done in this situation? Is there some easy way to persuade the XmlSerializer to handle this sort of thing better? If not, is there perhaps some other easy way to do it?

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• Backwards compatibility when using Core Data

  - by Alex

  Could anybody shed some light as to why is my app crashing with the following error on iPhone OS 2.2.1 dyld: Symbol not found: _OBJC_CLASS_$_NSPredicate Referenced from: /var/mobile/Applications/456F243F-468A-4969-9BB7-A4DF993AE89C/AppName.app/AppName Expected in: /System/Library/Frameworks/Foundation.framework/Foundation I have weak linked CoreData.framework, and have the Base SDK set to 3.0 and Deployment Target set to SDK 2.2 The app already uses other 3.0 features when available and I did not have any problems with those. But apparently the backward-compatibility methods used for other features do not work with Core Data. The app crashes before app delegate's applicationDidFinishLaunching gets called. Here's the debugger log: [Session started at 2010-05-25 20:17:03 -0400.] GNU gdb 6.3.50-20050815 (Apple version gdb-1119) (Thu May 14 05:35:37 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "--host=i386-apple-darwin --target=arm-apple-darwin".tty /dev/ttys001 Loading program into debugger… sharedlibrary apply-load-rules all warning: Unable to read symbols from "MessageUI" (not yet mapped into memory). warning: Unable to read symbols from "CoreData" (not yet mapped into memory). Program loaded. target remote-mobile /tmp/.XcodeGDBRemote-12038-42 Switching to remote-macosx protocol mem 0x1000 0x3fffffff cache mem 0x40000000 0xffffffff none mem 0x00000000 0x0fff none run Running… [Switching to thread 10755] [Switching to thread 10755] Re-enabling shared library breakpoint 1 Re-enabling shared library breakpoint 2 Re-enabling shared library breakpoint 3 Re-enabling shared library breakpoint 4 Re-enabling shared library breakpoint 5 (gdb) continue warning: Unable to read symbols for ""/Users/alex/iPhone Projects/AppName/build/Debug-iphoneos"/AppName.app/AppName" (file not found). dyld: Symbol not found: _OBJC_CLASS_$_NSPredicate Referenced from: /var/mobile/Applications/456F243F-468A-4969-9BB7-A4DF993AE89C/AppName.app/AppName Expected in: /System/Library/Frameworks/Foundation.framework/Foundation (gdb)

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