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• LIBPCAP and WIRESHARK Capture on PPP

  - by user655629

  Hi, I have written a small bridge program using LIBPCAP API. I have installed Winpcap 3.1 Beta for support in order to capture from a PPP interface. What i do is, I capture from the PPP interface through my LIBPCAP program and send the traffic to another Ethernet interface in my computer. Then i connect this Ethernet Interface to another Ethernet Interface at another computer where i monitor it through Wireshark. So in short my PPP-Ethernet Bridge is on computer 1. And Another computer2 directly connected to computer1 on Ethernet monitors the incoming traffic from the bridge through wireshark. The problem i face is that when i capture PPP traffic through wireshark in computer1, i see reasonable delay between the packets. But when i use my LIBPCAP program to capture and relay traffic and check the traffic on computer 2 using Wireshark it gives jumps of 0.5seconds delay after some packets. This is quite unexplainable to me. I dont understand how wireshark PPP direct capture on computer 1 does not give delay and LIBPCAP program is giving delay. I have checked my bridge for Ethernet to Ethernet relaying and there is no delay like the one i am experiencing in case of PPP-Ethernet. a higher delay between packets is acceptable but such a BIG delay after a couple of packets is unacceptable. Please help if you can. Best Regards FIKA

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• drop/truncate and rollback segment

  - by trojanwarrior3000

  I know that drop removes the data as well as the table structure whereas truncate retains table structure. Does drop/truncate write to roll back segment ?

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• g++ problem with -l option and PostgreSQL

  - by difek

  Hi I've written simple program. Here a code: #include <iostream> #include <stdio.h> #include <D:\Program Files\PostgreSQL\8.4\include\libpq-fe.h> #include <string> using namespace std; int main() { PGconn *conn; PGresult *res; int rec_count; int row; int col; cout << "ble ble: " << 8 << endl; conn = PQconnectdb("dbname=db_pm host=localhost user=postgres password=postgres"); if (PQstatus(conn) == CONNECTION_BAD) { puts("We were unable to connect to the database"); exit(0); } } I'm trying to connect with PostgreSQL. I compile this code with following command: gcc -I/"d:\Program Files\PostgreSQL\" -L/"d:\Program Files\PostgreSQL\8.4\lib\" -lpq -o firstcpp.o firstcpp.cpp This command is from following site: http://www.mkyong.com/database/how-to-building-postgresql-libpq-programs/ And when I compile it I get following error: /cygnus/cygwin-b20/H-i586-cygwin32/i586-cygwin32/bin/ld: cannot open -lpq: No such file or directory collect2: ld returned 1 exit status Does anyone help me? Difek

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• Fatal error when using FILE* in Windows from DLL

  - by AlannY

  Hi there. Recently, I found a problem with Visual C++ 2008 compiler, but using minor hack avoid it. Currently, I cannot use the same hack, but problem exists as in 2008 as in 2010 (Express). So, I've prepared for you 2 simple C file: one for DLL, one for program: DLL (file-dll.c): #include <stdio.h> __declspec(dllexport) void print_to_stream (FILE *stream) { fprintf (stream, "OK!\n"); } And for program, which links this DLL via file-dll.lib: Program: #include <stdio.h> __declspec(dllimport) void print_to_stream (FILE *stream); int main (void) { print_to_stream (stdout); return 0; } To compile and link DLL: cl /LD file-dll.c To compile and link program: cl file-test.c file-dll.lib When invoking file-test.exe, I got the fatal error (similar to segmentation fault in UNIX). As I said early, I had that the same problem before: about transferring FILE* pointer to DLL. I thought, that it may be because of compiler mismatch, but now I'm using one compiler for everything and it's not the problem. ;-( What can I do now? UPD: I've found solution: cl /LD /MD file-dll.c cl /MD file-test.c file-dll.lib The key is to link to dynamic library, but (I did not know it) by default it links staticaly and (hencefore) error occurs (I see why). P.S. Thanks for patience.

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• How can I find the last value in a multidimensional array in php?

  - by Chris

  I am using a multidimensional array and I am trying to use php to find the last value of one of the arrays and based on that last number(value), add one more to it. Here is my multidimensional array structure: $_SESSION['cart']['add_complete'][1]['deck_id'] I am trying to create this structure, but instead of where it says 1 now, I want to find out what the last number in the add_complete array is and then add one more to it and put that in the place of the 1. How can I do that?

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• Information Extraction Toolkits

  - by MathGladiator

  I'm looking for information extraction libraries where I can have semi structured information that may have either hidden or incomplete data. I want to train some classifiers to pull out content based on the structure. I'm working on building a tool where I can select text in the browser, and it will generate (via some web service call) a classifier that can be used on other documents to pull out text. I'm primarily looking at how the structure of the document can be used to indicate what the content is.

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• Recursion Question : Revision

  - by stan

  My slides say that: A recursive call should always be on a smaller data structure than the current one There must be a non recursive option if the data structure is too small You need a wrapper method to make the recursive method accessible Just reading this from the slides makes no sense, especially seeing as it was a topic from before christmas! Could anyone try and clear up what it means please? Thank you

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• General JDBC Setup

  - by AeroDroid

  So I have a MySQL database set up on a Debian server and it works fine from a phpMyAdmin client. I'm currently working on a project to write a Java server that would be able to use the MySQL database that is already on this server through a JDBC connection. I've looked at many tutorials and documentations but all of them seem to just explain how to do client-side code, but I have yet to figure out how to even successfully open a JDBC connection to the server. As far as I am concerned, I believe that program has the drivers properly set up because it's not crashing anymore (I simply direct the Java Build Path of my program to the Connector/J provided by MySQL). As far as my program goes, this is what it looks like... import java.sql.*; public class JDBCTest { public static void main(String[] args) { System.out.println("Started!"); try { DriverManager.registerDriver(new com.mysql.jdbc.Driver()); System.out.println("Driver registered. Connecting..."); Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/", "root", "password"); System.out.println("Connected!"); conn.close(); } catch (SQLException e) { System.out.println("Error!"); e.printStackTrace(); } } } This is what's printed... Started! Driver registered. Connecting... It's as if the DriverManager.getConnection(String) just freezes there. I'm sure this is a problem with the server because when I intentionally misspell localhost, or an IP address, the program crashes within 20 seconds. This just hangs there forever. Sorry about this wall of text, but my final question is if anyone has any information what I should do or install on the server to get this to work? Thank you so much!

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• Having trouble with confusing behaviour of error between debug and release modes in Xcode

  - by Cocorico

  Hi guys, I am confused over something (what is new!). I have an iPhone program I am writing and using some sqlite in a certain method, and there is some error which is giving me a message that says "Program received signal: “EXC_BAD_ACCESS” Okay, so I am trying to hunt down why this is doing this, and I notice something: When I run the program in debug mode, it gives me this error every single time I access this method (I test on the device). However when I run the program in release mode, I can access this method 2 times, and then it will give me this error the third time. So I mean, can someone just give me an explanation of what might cause this, I think that maybe deep-down I am not that smart on the difference in XCode of debug and release modes. I think that release mode does optimizing, and I guess the actual assembly machine code comes out different, yes? I AM A BIG NEWBIE USER UNFORTUNATELY! I am not clear on a lot of things like this, or whether it needs for I to remove nslog commands in the release build and such. Maybe I should just post the actual code in separate Stack OVerflow post, and see if people can see the error, then maybe this all become clear to me.

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• C programming doubt!!!

  - by aks

  Hi, I am having a programming doubt? Please have a look at the below mentioned code snippet and tell me the difference? int main() { struct sockaddr_in serv_addr, cli_addr; /* Initialize socket structure */ bzero((char *) &serv_addr, sizeof(serv_addr)); } Now, what if i do something similar without typecasting (char *), then also i feel it will do the same thing? Can someone clarify? /* Initialize socket structure */ bzero( &serv_addr, sizeof(serv_addr));

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• Planning a database app

  - by ChrisC

  I am in the planning stages of a database app for personal use. I have a good bit of the database structure planned, but as I think about how I'm going to write the program, it made me wonder if I'm doing this in the right order. Which should I be planning first, the db structure or the classes?

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• GAE Simple Request Handler only run once

  - by Hiro

  Good day! https://developers.google.com/appengine/docs/python/gettingstarted/helloworld this is the hello world that I'm trying to run. I can seeing the Hello, world! Status: 500 message. however it will be turned to a "HTTP Error 500" after I hit the refresh. and... it seems that the appengine only shows me the good result once after I re-save either app.yaml or helloworld.py This is the trace for the good result Traceback (most recent call last): File "C:\Program Files\Google\google_appengine\google\appengine\runtime\wsgi.py", line 187, in Handle handler = _config_handle.add_wsgi_middleware(self._LoadHandler()) File "C:\Program Files\Google\google_appengine\google\appengine\runtime\wsgi.py", line 239, in _LoadHandler raise ImportError('%s has no attribute %s' % (handler, name)) ImportError: <module 'helloworld' from 'D:\work\[GAE] tests\helloworld\helloworld.pyc'> has no attribute app INFO 2012-06-23 01:47:28,522 dev_appserver.py:2891] "GET /hello HTTP/1.1" 200 - ERROR 2012-06-23 01:47:30,040 wsgi.py:189] and this is the trace for the Error 500 Traceback (most recent call last): File "C:\Program Files\Google\google_appengine\google\appengine\runtime\wsgi.py", line 187, in Handle handler = _config_handle.add_wsgi_middleware(self._LoadHandler()) File "C:\Program Files\Google\google_appengine\google\appengine\runtime\wsgi.py", line 239, in _LoadHandler raise ImportError('%s has no attribute %s' % (handler, name)) ImportError: <module 'helloworld' from 'D:\work\[GAE] tests\helloworld\helloworld.pyc'> has no attribute app INFO 2012-06-23 01:47:30,127 dev_appserver.py:2891] "GET /hello HTTP/1.1" 500 - here's my helloworld.py print 'Content-Type: text/plain' print '' print 'Hello, world!' my main.py. (app is used instead of application) import webapp2 class hello(webapp2.RequestHandler): def get(self): self.response.out.write('normal hello') app = webapp2.WSGIApplication([ ('/', hello), ], debug = True) and the app.yaml application: helloworld version: 1 runtime: python27 api_version: 1 threadsafe: true handlers: - url: /favicon\.ico static_files: favicon.ico upload: favicon\.ico - url: /hello script: helloworld.app - url: /.* script: main.app libraries: - name: webapp2 version: "2.5.1" any clue what's causing this? Regards,

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• Document-oriented database - What if the document definitions change?

  - by Sebastian Hoitz

  As I understand it, you can enter any non-structured information into a document-oriented database. Let's imagine a document like this: { name: 'John Blank', yearOfBirth: 1960 } Later, in a new version, this structure is refactored to { firstname: 'John', lastname: 'Blank', yearOfBirth: 1960 } How do you do this with Document-Oriented databases? Do you have to prepare merge-scripts, that alter all your entries in the database? Or are there better ways you can handle changes in the structure?

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• Why my async call does not work?

  - by Petr

  Hi, I am trying to understand what is IAsyncresult good and therefore I wrote this code. The problem is it behaves as I called "MetodaAsync" normal way. While debugging, the program stops here until the method completed. Any help appreciated, thank you. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading; namespace ConsoleApplication1 { class Program { delegate int Delegat(); static void Main(string[] args) { Program p=new Program(); Delegat d = new Delegat(p.MetodaAsync); IAsyncResult a = d.BeginInvoke(null, null); //I have removed callback int returned=d.EndInvoke(a); Console.WriteLine("AAA"); } private int MetodaAsync() { int AC=0; for (int I = 0; I < 600000; I++) { for (int A = 0; A < 6000000; A++) { } Console.Write("B"); } return AC; } } }

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• How to update a collection based on another collection in MongoDB?

  - by Sean Zhu

  Now I get two collections: coll01 and coll02. And the structure of coll01 is like this: { id: 01, name: "xxx", age: 30 } and the structure of coll02 is like: { id: 01, name: "XYZ" gender: "male" } The two id fields in the both collection are indices. And the numbers of documents in these two collections are same. And what I want to do in traditional SQL is : update coll01, coll02 set coll01.name = coll02.name where coll01.id = coll02.id

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• Question about compilers and how they work

  - by Marin Doric

  This is the C code that frees memory of a singly linked list. It is compiled with Visual C++ 2008 and code works as it should be. /* Program done, so free allocated memory */ current = head; struct film * temp; temp = current; while (current != NULL) { temp = current->next; free(current); current = temp; } But I also encountered ( even in a books ) same code written like this: /* Program done, so free allocated memory */ current = head; while (current != NULL) { free(current); current = current->next; } If I compile that code with my VC++ 2008, program crashes because I am first freeing current and then assigning current-next to current. But obviously if I compile this code with some other complier ( for example, compiler that book author used ) program will work. So question is, why does this code compiled with specific compiler work? Is it because that compiler put instructions in binary file that remember address of current-next although I freed current and my VC++ doesn't. I just want to understand how compilers work.

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• Impersonate SYSTEM (or equivalent) from Administrator Account

  - by KevenK

  This question is a follow up and continuation of this question about a Privilege problem I'm dealing with currently. Problem Summary: I'm running a program under a Domain Administrator account that does not have Debug programs (SeDebugPrivilege) privilege, but I need it on the local machine. Klugey Solution: The program can install itself as a service on the local machine, and start the service. Said service now runs under the SYSTEM account, which enables us to use our SeTCBPrivilege privilege to create a new access token which does have SeDebugPrivilege. We can then use the newly created token to re-launch the initial program with the elevated rights. I personally do not like this solution. I feel it should be possible to acquire the necessary privileges as an Administrator without having to make system modifications such as installing a service (even if it is only temporary). I am hoping that there is a solution that minimizes system modifications and can preferably be done on the fly (ie: Not require restarting itself). I have unsuccessfully tried to LogonUser as SYSTEM and tried to OpenProcessToken on a known SYSTEM process (such as csrss.exe) (which fails, because you cannot OpenProcess with PROCESS_TOKEN_QUERY to get a handle to the process without the privileges I'm trying to acquire). I'm just at my wit's end trying to come up with an alternative solution to this problem. I was hoping there was an easy way to grab a privileged token on the host machine and impersonate it for this program, but I haven't found a way. If anyone knows of a way around this, or even has suggestions on things that might work, please let me know. I really appreciate the help, thanks!

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• How can I share dynamic data between Applications?

  - by Ehsan

  Hi, I use CreateFileMapping, but this method does not useful,because only static structure can be shared by this method. for example this method is good for following structure: struct MySharedData { unsigned char Flag; int Buff[10]; }; but it's not good for : struct MySharedData { unsigned char Flag; int *Buff; }; would be thankful if somebody guide me on this, Thanks in advance!

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• jQuery fancybox how to call it in my own DIV?

  - by Anton

  Hi I want to display the fancybox in my own <div> because I need another position for the output. The fancy JS is creating a <div> structure in my HTML wich i cant manipulate over CSS. This structure I want only display in <div id="xyz"> for example. Please help?

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• ggplot geom_bar - to many bars

  - by Andreas

  I am sorry for the non-informative title. exstatus <- structure(list(org = structure(c(2L, 1L, 7L, 3L, 6L, 2L, 2L, 7L, 2L, 1L, 2L, 2L, 4L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 8L, 4L, 2L, 2L, 5L, 7L, 8L, 6L, 2L, 7L, 2L, 2L, 7L, 2L, 2L, 2L, 2L, 4L, 2L, 2L, 1L, 2L, 2L, 7L, 2L, 7L, 2L, 4L, 7L, 2L, 4L, 2L, 2L, 2L, 7L, 7L, 2L, 7L, 2L, 7L, 1L, 7L, 5L, 2L, 2L, 1L, 7L, 3L, 5L, 3L, 2L, 2L, 2L, 7L, 4L, 2L, 7L, 2L, 4L, 2L, 2L, 2L, 4L, 6L, 2L, 4L, 4L, 7L, 2L, 2L, 2L, 7L, 6L, 2L, 2L, 1L, 2L, 2L, 4L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 6L, 2L, 7L, 7L, 2L, 7L, 8L, 7L, 8L, 6L, 7L, 2L, 2L, 2L, 7L, 2L, 7L, 2L, 7L, 2L, 7L, 2L, 4L, 2L, 7L, 2L, 4L, 8L, 2L, 3L, 4L, 2L, 7L, 3L, 8L, 8L, 6L, 2L, 2L, 2L, 7L, 7L, 7L, 7L, 2L, 2L, 2L, 2L, 7L, 2L, 4L, 7L, 7L, 8L, 2L, 7L, 2L, 2L, 2L, 2L, 1L, 7L, 7L, 2L, 1L, 7L, 2L, 7L, 7L, 2L, 2L, 7L, 2L, 2L, 7L, 7L, 2L, 7L, 2L, 7L, 5L, 2L), .Label = c("gl", "il", "gm", "im", "gk", "ik", "tv", "tu"), class = "factor"), art = structure(c(2L, 1L, 3L, 1L, 2L, 2L, 2L, 3L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 3L, 2L, 2L, 2L, 1L, 3L, 3L, 2L, 2L, 3L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 3L, 2L, 3L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 2L, 3L, 2L, 3L, 1L, 3L, 1L, 2L, 2L, 1L, 3L, 1L, 1L, 1L, 2L, 2L, 2L, 3L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 2L, 2L, 2L, 3L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 3L, 3L, 2L, 3L, 3L, 3L, 3L, 2L, 3L, 2L, 2L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 2L, 2L, 3L, 2L, 2L, 3L, 2L, 1L, 2L, 2L, 3L, 1L, 3L, 3L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 2L, 2L, 2L, 2L, 3L, 2L, 2L, 3L, 3L, 3L, 2L, 3L, 2L, 2L, 2L, 2L, 1L, 3L, 3L, 2L, 1L, 3L, 2L, 3L, 3L, 2L, 2L, 3L, 2L, 2L, 3L, 3L, 2L, 3L, 2L, 3L, 1L, 2L), .Label = c("Finish", "Attending", "Something"), class = "factor"), type = structure(c(2L, 2L, 5L, 3L, 1L, 2L, 2L, 5L, 2L, 2L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 4L, 3L, 2L, 2L, 1L, 5L, 4L, 1L, 2L, 5L, 2L, 2L, 5L, 2L, 2L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 5L, 2L, 5L, 2L, 3L, 5L, 2L, 3L, 2L, 2L, 2L, 5L, 5L, 2L, 5L, 2L, 5L, 2L, 5L, 1L, 2L, 2L, 2L, 5L, 3L, 1L, 3L, 2L, 2L, 2L, 5L, 3L, 2L, 5L, 2L, 3L, 2L, 2L, 2L, 3L, 1L, 2L, 3L, 3L, 5L, 2L, 2L, 2L, 5L, 1L, 2L, 2L, 2L, 2L, 2L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 5L, 5L, 2L, 5L, 4L, 5L, 4L, 1L, 5L, 2L, 2L, 2L, 5L, 2L, 5L, 2L, 5L, 2L, 5L, 2L, 3L, 2L, 5L, 2L, 3L, 4L, 2L, 3L, 3L, 2L, 5L, 3L, 4L, 4L, 1L, 2L, 2L, 2L, 5L, 5L, 5L, 5L, 2L, 2L, 2L, 2L, 5L, 2L, 3L, 5L, 5L, 4L, 2L, 5L, 2L, 2L, 2L, 2L, 2L, 5L, 5L, 2L, 2L, 5L, 2L, 5L, 5L, 2L, 2L, 5L, 2L, 2L, 5L, 5L, 2L, 5L, 2L, 5L, 1L, 2L), .Label = c("short", "long", "between", "young", "old"), class = "factor")), .Names = c("org", "art", "type"), row.names = c(NA, -192L), class = "data.frame") and then the plot ggplot(exstatus, aes(x=type, fill=art))+ geom_bar(aes(y=..count../sum(..count..)),position="dodge") The problem is that the two rightmost bars ("young", "old") are too thick - "something" takes up the whole width - whcih is not what I intended. I am sorry that I can not explain it better.

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• Java Code for calculating Leap Year, is this code correct ?

  - by Ibn Saeed

  Hello I am following "The Art and Science of Java" book and it shows how to calculate a leap year. The book uses ACM Java Task Force's library. Here is the code the books uses: import acm.program.*; public class LeapYear extends ConsoleProgram { public void run() { println("This program calculates leap year."); int year = readInt("Enter the year: "); boolean isLeapYear = ((year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0)); if (isLeapYear) { println(year + " is a leap year."); } else println(year + " is not a leap year."); } } Now, this is how I calculated the leap year. import acm.program.*; public class LeapYear extends ConsoleProgram { public void run() { println("This program calculates leap year."); int year = readInt("Enter the year: "); if ((year % 4 == 0) && year % 100 != 0) { println(year + " is a leap year."); } else if ((year % 4 == 0) && (year % 100 == 0) && (year % 400 == 0)) { println(year + " is a leap year."); } else { println(year + " is not a leap year."); } } } Is there anything wrong with my code or should i use the one provided by the book ? EDIT :: Both of the above code works fine, What i want to ask is which code is the best way to calculate the leap year.

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• JSON documentation standard?

  - by Tina

  Is there a recognized, recommended, or standard form for representing the structure of JSON? E.g., my service returns a structure, effectively, represented as JSON. How do I describe what my service returns, such that another service can consume that JSON and program to its interface?

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• Parse multiple named command line parameters

  - by scholzr

  I need to add the ability to a program to accept multiple named parameters when opening the program via the command line. i.e. program.exe /param1=value /param2=value and then be able to utilize these parameters as variables in the program. I have found a couple of ways to accomplish pieces of this, but can't seem to figure out how to put it all together. I have been able to pass one named parameter and recover it using the code below, and while I could duplicate it for every possible named parameter, I know that can't be the preffered way to do this. Dim inputArgument As String = "/input=" Dim inputName As String = "" For Each s As String In My.Application.CommandLineArgs If s.ToLower.StartsWith(inputArgument) Then inputName = s.Remove(0, inputArgument.Length) End If Next Alternatively, I can get multiple unnamed parameters from the command line using My.Application.CommandLineArgs But this requires that the parameters all be passed in the same order/format each time. I need to be able to pass a random subset of parameters each time. Ultimately, what I would like to be able to do, is separate each argument and value, and load it into a multidimentional array for later use. I know that I could find a way to do this by separating the string at the "=" and stripping the "/", but as I am somewhat new to this, I wanted to see if there was a "preffered" way for dealing with multiple named parameters?

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• Persistent (purely functional) Red-Black trees on disk performance

  - by Waneck

  I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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• Android - Two different programs at the same time in an emulator

  - by Léa Massiot

  I'm new to Android development. My OS is WinXP. I'm trying to install two different applications on an Android Device Emulator in command line. I have two Android projects "ap1" and "ap2". In the "ap1" project directory, I ran "ant debug". I got an "ap1.apk" executable. In the "ap2" project directory, I ran "ant debug". I got an "ap2.apk" executable. I created an Android Virtual Device: cmd_line android create avd -n avd1 -t 1 --abi x86 I launched the emulator: cmd_line emulator -avd avd1 -verbose The "adb devices" command returns: List of devices attached emulator-5554 device I installed the first program on the emulator: cmd_line adb -s emulator-5554 install "ap1.apk" I ran the program: cmd_line adb shell am start -a android.intent.action.MAIN -n my.pkg.android/.Activity1 = It worked. I installed the second program on the emulator: cmd_line adb -s emulator-5554 install "ap2.apk" I ran the program: cmd_line adb shell am start -a android.intent.action.MAIN -n my.pkg2.android/.AnotherActivity1 = It worked. All this works except that the second executable "replaced" of the first one. If I try to run the first executable, I get an error: cmd_line adb shell am start -a android.intent.action.MAIN -n my.pkg.android/.Activity1 Starting: Intent { act=android.intent.action.MAIN cmp=my.pkg.android/.Activity1 } Error type 3 Error: Activity class {my.pkg.android/my.pkg.android.Activity1} does not exist. It looks like I can't have the two apps at the same time in the emulator. What do you think? What do I have to do to have the two apps available (at the same time) in the emulator? Thank you for helping. Best regards.

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