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• Writing a VM - well formed bytecode?

  - by David Titarenco

  Hi, I'm writing a virtual machine in C just for fun. Lame, I know, but luckily I'm on SO so hopefully no one will make fun :) I wrote a really quick'n'dirty VM that reads lines of (my own) ASM and does stuff. Right now, I only have 3 instructions: add, jmp, end. All is well and it's actually pretty cool being able to feed lines (doing it something like write_line(&prog[1], "jmp", regA, regB, 0); and then running the program: while (machine.code_pointer <= BOUNDS && DONE != true) { run_line(&prog[machine.cp]); } I'm using an opcode lookup table (which may not be efficient but it's elegant) in C and everything seems to be working OK. My question is more of a "best practices" question but I do think there's a correct answer to it. I'm making the VM able to read binary files (storing bytes in unsigned char[]) and execute bytecode. My question is: is it the VM's job to make sure the bytecode is well formed or is it just the compiler's job to make sure the binary file it spits out is well formed? I only ask this because what would happen if someone would edit a binary file and screw stuff up (delete arbitrary parts of it, etc). Clearly, the program would be buggy and probably not functional. Is this even the VM's problem? I'm sure that people much smarter than me have figured out solutions to these problems, I'm just curious what they are!

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• Conversion failed when converting the varchar value to int

  - by onedaywhen

  Microsoft SQL Server 2008 (SP1), getting an unexpected 'Conversion failed' error. Not quite sure how to describe this problem, so below is a simple example. The CTE extracts the numeric portion of certain IDs using a search condition to ensure a numeric portion actually exists. The CTE is then used to find the lowest unused sequence number (kind of): CREATE TABLE IDs (ID CHAR(3) NOT NULL UNIQUE); INSERT INTO IDs (ID) VALUES ('A01'), ('A02'), ('A04'), ('ERR'); WITH ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 ); The error is, 'Conversion failed when converting the varchar value 'RR' to data type int.' I can't understand why the value ID = 'ERR' should be being considered for conversion because the predicate ID LIKE 'A[0-9][0-9]' should have removed the invalid row from the resultset. When the base table is substituted with an equivalent CTE the problem goes away i.e. WITH IDs (ID) AS ( SELECT 'A01' UNION ALL SELECT 'A02' UNION ALL SELECT 'A04' UNION ALL SELECT 'ERR' ), ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 ); Why would a base table cause this error? Is this a known issue? UPDATE @sgmoore: no, doing the filtering in one CTE and the casting in another CTE still results in the same error e.g. WITH FilteredIDs (ID) AS ( SELECT ID FROM IDs WHERE ID LIKE 'A[0-9][0-9]' ), ValidIDs (ID, seq) AS ( SELECT ID, CAST(RIGHT(ID, 2) AS INTEGER) FROM FilteredIDs ) SELECT MIN(V1.seq) + 1 AS next_seq FROM ValidIDs AS V1 WHERE NOT EXISTS ( SELECT * FROM ValidIDs AS V2 WHERE V2.seq = V1.seq + 1 );

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• C system calls open / read / write / close problem.

  - by Andrei Ciobanu

  Hello, given the following code (it's supposed to write "hellowolrd" in a "helloworld" file, and then read the text): #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define FNAME "helloworld" int main(){ int filedes, nbytes; char buf[128]; /* Creates a file */ if((filedes=open(FNAME, O_CREAT | O_EXCL | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR)) == -1){ write(2, "Error1\n", 7); } /* Writes hellow world to file */ if(write(filedes, FNAME, 10) != 10) write(2, "Error2\n", 7); /* Close file */ close(filedes); if((filedes = open(FNAME, O_RDONLY))==-1) write(2, "Error3\n", 7); /* Prints file contents on screen */ if((nbytes=read(filedes, buf, 128)) == -1) write(2, "Error4\n", 7); if(write(1, buf, nbytes) != nbytes) write(2, "Error5\n", 7); /* Close rile afte read */ close(filedes); return (0); } The first time i run the program, the output is: helloworld After that every time I to run the program, the output is: Error1 Error2 helloworld I don't understand why the text isn't appended, as I've specified the O_APPEND file. Is it because I've included O_CREAT ? It the file is already created, shouldn't O_CREAT be ignored ?

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• Windows Service doesn't start process with different credentials

  - by Marcus

  I have a Windows Service, running as a user, that should start several processes under different user credentials. I'm using the following code to start a process: Dim winProcess As New System.Diagnostics.Process With winProcess .StartInfo.Arguments = "some_args" .StartInfo.CreateNoWindow = True .StartInfo.ErrorDialog = False .StartInfo.FileName = "C:\TEMP\ProcessFromService\ProcessFromService\bin\Debug\ProcessFromService.exe" .StartInfo.UseShellExecute = False .StartInfo.WindowStyle = ProcessWindowStyle.Hidden 'Opgave WorkingDirectory kan soms tot problemen leiden, indien betreffende directory 'niet bereikbaar (rechten) is voor opgegeven gebruiker. 'Beter dus om deze niet op te geven. '.StartInfo.WorkingDirectory = My.Computer.FileSystem.SpecialDirectories.Temp .StartInfo.Domain = "" .StartInfo.UserName = "MyUserId" Dim strPassword As String = "MyPassword" Dim ssPassword As New Security.SecureString For Each chrPassword As Char In strPassword.ToCharArray ssPassword.AppendChar(chrPassword) Next .StartInfo.Password = ssPassword .Start() End With The process is correctly started when I use the same credentials as of which the Windows Service is running under. The process is not started, without any error, when I use different credentials. In other words: If the Windows Service is running as UserA then I can start a process running as UserA. If the Windows Service is running as UserB then I can not start a process running as UserA. I have created a test project in which I can reproduce this problem. If you put this project in C:\Temp then the used paths will be correct. You can download this test project here: https://dl.dropboxusercontent.com/u/5391091/ProcessFromService.zip NB: I hope this info is enough to explain it. If you need more info, please let me know and I will add it.

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• SQL Server 2008 - Keyword search using table Join

  - by Aaron Wagner

  Ok, I created a Stored Procedure that, among other things, is searching 5 columns for a particular keyword. To accomplish this, I have the keywords parameter being split out by a function and returned as a table. Then I do a Left Join on that table, using a LIKE constraint. So, I had this working beautifully, and then all of the sudden it stops working. Now it is returning every row, instead of just the rows it needs. The other caveat, is that if the keyword parameter is empty, it should ignore it. Given what's below, is there A) a glaring mistake, or B) a more efficient way to approach this? Here is what I have currently: ALTER PROCEDURE [dbo].[usp_getOppsPaged] @startRowIndex int, @maximumRows int, @city varchar(100) = NULL, @state char(2) = NULL, @zip varchar(10) = NULL, @classification varchar(15) = NULL, @startDateMin date = NULL, @startDateMax date = NULL, @endDateMin date = NULL, @endDateMax date = NULL, @keywords varchar(400) = NULL AS BEGIN SET NOCOUNT ON; ;WITH Results_CTE AS ( SELECT opportunities.*, organizations.*, departments.dept_name, departments.dept_address, departments.dept_building_name, departments.dept_suite_num, departments.dept_city, departments.dept_state, departments.dept_zip, departments.dept_international_address, departments.dept_phone, departments.dept_website, departments.dept_gen_list, ROW_NUMBER() OVER (ORDER BY opp_id) AS RowNum FROM opportunities JOIN departments ON opportunities.dept_id = departments.dept_id JOIN organizations ON departments.org_id=organizations.org_id LEFT JOIN Split(',',@keywords) AS kw ON (title LIKE '%'+kw.s+'%' OR [description] LIKE '%'+kw.s+'%' OR tasks LIKE '%'+kw.s+'%' OR requirements LIKE '%'+kw.s+'%' OR comments LIKE '%'+kw.s+'%') WHERE ( (@city IS NOT NULL AND (city LIKE '%'+@city+'%' OR dept_city LIKE '%'+@city+'%' OR org_city LIKE '%'+@city+'%')) OR (@state IS NOT NULL AND ([state] = @state OR dept_state = @state OR org_state = @state)) OR (@zip IS NOT NULL AND (zip = @zip OR dept_zip = @zip OR org_zip = @zip)) OR (@classification IS NOT NULL AND (classification LIKE '%'+@classification+'%')) OR ((@startDateMin IS NOT NULL AND @startDateMax IS NOT NULL) AND ([start_date] BETWEEN @startDateMin AND @startDateMax)) OR ((@endDateMin IS NOT NULL AND @endDateMax IS NOT NULL) AND ([end_date] BETWEEN @endDateMin AND @endDateMax)) OR ( (@city IS NULL AND @state IS NULL AND @zip IS NULL AND @classification IS NULL AND @startDateMin IS NULL AND @startDateMax IS NULL AND @endDateMin IS NULL AND @endDateMin IS NULL) ) ) ) SELECT * FROM Results_CTE WHERE RowNum >= @startRowIndex AND RowNum < @startRowIndex + @maximumRows; END

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• IE8 claims my page has an error, firefox doesn't, and I can't find any error. Help!

  - by Bears will eat you

  This is something of a follow-up question to my question here. You can find the HTML source in a text file here. When I load that page in IE8, I get the "Done, but with errors on page." message in my status bar. The detail view shows Expected identifier sms Line: 147 Code: 0 Char: 67 and I see absolutely no problems anywhere near there. In IE8, the page is still behaving erratically w/r/t the randomly losing focus as mentioned in my other question. When I load the same exact page in Firefox (using Firebug) the console shows no errors and the page works perfectly. Any thoughts on what's going on here? This is driving me nuts and making me want to give up on even trying to write an IE friendly page. Edit: Thanks for all the comments! This page is written as a JSP, so I edit in Eclipse. I found an Eclipse warning about the onblur event for the username field. I switched it from onblur="alert(document.activeElement + ' class:' + document.activeElement.class)" to onblur="alert(document.activeElement)" and that made the bizarre IE page error vanish. I had been trying to give more info (namely, its CSS class) about specifically which element is stealing focus - to my own detriment, apparently, since Javascript was interpreting the '.class' part in the Java(script) sense. And, no, the page doesn't validate. But the errors were mostly/all ones that just didn't make sense, such as Line 14, Column 41: Attribute "LANGUAGE" is not a valid attribute. Did you mean "language"? to which I say, WTF?! But I'm still stuck trying to figure out why, as I enter text in the username & password fields, focus randomly switches to a div (working on figuring out which div currently). Edit 2: It's the div between the two "global nav" comments, at the very top of the body. Still no idea why it's happening, though.

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• Boost binding a function taking a reference

  - by Jamie Cook

  Hi all, I am having problems compiling the following snippet int temp; vector<int> origins; vector<string> originTokens = OTUtils::tokenize(buffer, ","); // buffer is a char[] array // original loop BOOST_FOREACH(string s, originTokens) { from_string(temp, s); origins.push_back(temp); } // I'd like to use this to replace the above loop std::transform(originTokens.begin(), originTokens.end(), origins.begin(), boost::bind<int>(&FromString<int>, boost::ref(temp), _1)); where the function in question is // the third parameter should be one of std::hex, std::dec or std::oct template <class T> bool FromString(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec) { std::istringstream iss(s); return !(iss >> f >> t).fail(); } the error I get is 1>Compiling with Intel(R) C++ 11.0.074 [IA-32]... (Intel C++ Environment) 1>C:\projects\svn\bdk\Source\deps\boost_1_42_0\boost/bind/bind.hpp(303): internal error: assertion failed: copy_default_arg_expr: rout NULL, no error (shared/edgcpfe/il.c, line 13919) 1> 1> return unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]); 1> ^ 1> 1>icl: error #10298: problem during post processing of parallel object compilation Google is being unusually unhelpful so I hope that some one here can provide some insights.

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• Incompatible types when assigning to type 'struct compartido'

  - by user1660559

  I have one problem with this code. I should create one structure and share it across 5 new process created from the father: #include <stdio.h> #include <stdlib.h> #include <sys/wait.h> #include <unistd.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/sem.h> #include <time.h> struct compartido { int pid1, pid2, pid3, pid4, pid5; int propietario; int contador; int pidpadre; }; struct compartido var; int main(int argc, char *argv[]) { key_t llave1,llavesem; int idmem,idsem; llave1=ftok("/tmp",'a'); idmem=shmget(llave1,sizeof(int),IPC_CREAT|0600); if (idmem==-1) { perror ("shmget"); return 1; } var=shmat(idmem,0,0); /*This line is giving the error*/ /*rest of the code*/ } The exact error is giving is: error: incompatible types when assigning to type 'struct compartido' from type 'void *' I need to put this structure in the shared variable to be able to see and modify all those data from the 6 process (5 children and the father). What I'm doing bad? Thanks in advance and best regards,

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• Mac OS X and static boost libs -> std::string fail

  - by Ionic

  Hi all, I'm experiencing some very weird problems with static boost libraries under Mac OS X 10.6.6. The error message is main(78485) malloc: *** error for object 0x1000e0b20: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug [1] 78485 abort (core dumped) and a tiny bit of example code which will trigger this problem: #define BOOST_FILESYSTEM_VERSION 3 #include <boost/filesystem.hpp> #include <iostream> int main (int argc, char **argv) { std::cout << boost::filesystem::current_path ().string () << '\n'; } This problem always occurs when linking the static boost libraries into the binary. Linking dynamically will work fine, though. I've seen various reports for quite a similar OS X bug with GCC 4.2 and the _GLIBCXX_DEBUG macro set, but this one seems even more generic, as I'm neither using XCode, nor setting the macro (even undefining it does not help. I tried it just to make sure it's really not related to this problem.) Does anybody have any pointers to why this is happening or even maybe a solution (rather than using the dynamic library workaround)? Best regards, Mihai

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• How can I get contentWindow for an Object element in IE7

  - by Scott Leis

  I have a HTML object element like this: <object title="Search results as XML" standby="Loading XML document..." type="text/xml" data="/__CA25761100195585.nsf/WebPrintListingXML?OpenAgent&date1=01/06/2009" width="100%" height="100%" border="0" name="resultIFrame" id="resultIFrame" Error: could not embed search results. </object I also have this javascript function (alert() calls added for debugging): function getFrameByName(fParent,fName) { var fArray=fParent.frames; if (!fName) return; if (fArray) { if (fArray.length) { for (var i=0; i<fArray.length; i++) { alert('loop '+i); if (fArray[i]) { if (fArray[i].name==fName) return fArray[i]; } } } } var tmp=document.getElementsByName(fName); if (tmp[0]) { alert('returning '+tmp[0]); if (!(tmp[0].contentWindow)) alert('contentWindow is null'); return tmp[0].contentWindow; } } And finally, this button is meant to print the content of the Object element: <input type="button" value="Print" name="printBtn" onclick="getFrameByName(window,'resultIFrame').print();" The button works perfectly in Firefox. Opera is good enough, though it prints the main document instead of just the object. IE7 gives the following error details: Line: 57 Char: 1 Error: 'undefined' is null or not an object Line 57 is where the button's "input" tag starts in the HTML source. Thanks to the alert('contentWindow is null') call in the JS function, I know that the object I'm getting in IE has no contentWindow property. I have tried changing the object tag to an iframe tag. This changes the JS behaviour, but causes other issues such as the height attribute being ignored and the content not displaying. Sticking with an object tag, how can I get this Object's window in IE7?

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• Remove and Replace multiple chars ( spaces, hyphen, brackets, period) from string in sql

  - by Muhammad Kashif Nadeem

  +39 235 6595750 19874624611 +44 (0)181 446 5697 +431 6078115-2730 +1 617 358 5128 +48.40.23755432 +44 1691 872 410 07825 893217 0138 988 1649 (415) 706 2001 00 44 (0) 20 7660 4650 (765) 959-1504 07731 508 486 please reply by email dont have one +447769146971 Please see the above given phone numbers. I need to replace all spaces, hyphen, period, brackets and leading 0 etc from these numbers. I need this format +447469186974 If number has leading plus sign then don't replace it otherwise I have to concatenate + sign with it. E.G +39 235 6595750 in this number I just need to remove spaces. +44 (0)181 446 5697 in this i need to removes spaces and brackets and 0 in between brackets i.e (0) 07825 893217 in this I need to replace leading 0 with + sign and remove spaces (415) 706 2001 in this replace '(' with + sign and remove ')' and spaces. 'please reply by email' This is the entry in phone number field and I just need to ignore this. +48.40.23755432 Remove period in phone number (765) 959-1504 Remove brackets and spaces and hyphen and add + sign in front of number. 7798724250 just need to add + sign in front of number 00 44 (0) 20 7660-4650 Need to remove leading 0 I.E '00' remove spaces and brackets and 0 in between brackets and hyphen and add + sign in front of number Only leading '0' will be replaced not anyother occourence of '0' The desired result is +447769146971 Should I use nested REPLACE, CHARINDES, PATINDES for each char I want to replace? Thanks.

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• What's the best way to resolve this scope problem?

  - by Peter Stewart

  I'm writing a program in python that uses genetic techniques to optimize expressions. Constructing and evaluating the expression tree is the time consumer as it can happen billions of times per run. So I thought I'd learn enough c++ to write it and then incorporate it in python using cython or ctypes. I've done some searching on stackoverflow and learned a lot. This code compiles, but leaves the pointers dangling. I tried 'this_node = new Node(...' . It didn't seem to work. And I'm not at all sure how I'd delete all the references as there would be hundreds. I'd like to use variables that stay in scope, but maybe that's not the c++ way. What is the c++ way? class Node { public: char *cargo; int depth; Node *left; Node *right; } Node make_tree(int depth) { depth--; if(depth <= 0) { Node tthis_node("value",depth,NULL,NULL); return tthis_node; } else { Node this_node("operator" depth, &make_tree(depth), &make_tree(depth)); return this_node; } };

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• Why do I get empty request from the Jakarta Commons HttpClient?

  - by polyurethan

  I have a problem with the Jakarta Commons HttpClient. Before my self-written HttpServer gets the real request there is one request which is completely empty. That's the first problem. The second problem is, sometimes the request data ends after the third or fourth line of the http request: POST / HTTP/1.1 User-Agent: Jakarta Commons-HttpClient/3.1 Host: 127.0.0.1:4232 For debugging I am using the Axis TCPMonitor. There every things is fine but the empty request. How I process the stream: StringBuffer requestBuffer = new StringBuffer(); InputStreamReader is = new InputStreamReader(socket.getInputStream(), "UTF-8"); int byteIn = -1; do { byteIn = is.read(); if (byteIn > 0) { requestBuffer.append((char) byteIn); } } while (byteIn != -1 && is.ready()); String requestData = requestBuffer.toString(); How I send the request: client.getParams().setSoTimeout(30000); method = new PostMethod(url.getPath()); method.getParams().setContentCharset("utf-8"); method.setRequestHeader("Content-Type", "application/xml; charset=utf-8"); method.addRequestHeader("Connection", "close"); method.setFollowRedirects(false); byte[] requestXml = getRequestXml(); method.setRequestEntity(new InputStreamRequestEntity(new ByteArrayInputStream(requestXml))); client.executeMethod(method); int statusCode = method.getStatusCode(); Have anyone of you an idea how to solve these problems? Alex

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• Other test cases for this openFile function?

  - by igor

  I am trying to figure out why my function to open a file is failing this autograder I submit my homework into. What type of input would fail here, I can't think of anything else? Code: bool openFile(ifstream& ins) { char fileName[256]; cout << "Enter board filename: "; cin.getline(fileName,256); cout << endl << fileName << endl; ins.open(fileName); if(!ins) { ins.clear(); cout<<"Error opening file"<<endl; return false; } return true; } Here is output from the 'Autograder' of what my program's output is, and what the correct output is supposed to be (and I do not know what is in the file they use for the input) Autograder output: ******************************************* ***** ***** ***** Your output is: ***** ***** ***** ******************************************* Testing function openFile Enter board filename: test.txt 1 Enter board filename: not a fileName Error opening file 0 ******************************************* ***** ***** ***** Correct Output ***** ***** ***** ******************************************* Testing function openFile Enter board filename: 1 Enter board filename: Error opening file 0

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• Qt 101: Why can't I use this class?

  - by Airjoe

  I have experience with C++ but I've never really used Qt before. I'm trying to connect to a SQLite database, so I found a tutorial here and am going with that. In the QtCreator IDE, I went to Add New -- C++ Class and in the header file pasted in the header the header from that link and in the .cpp file I pasted the source. My main.cpp looks like this: #include <QtGui/QApplication> #include "mainwindow.h" #include "databasemanager.h" #include <qlabel.h> int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); DatabaseManager db(); QLabel hello("nothing..."); if(db.openDB()){ hello.setText("Win!"); } else{ hello.setText("Lame!"); } hello.resize(100, 30); hello.show(); return a.exec(); } And I'm getting this error: main.cpp:13: error: request for member 'openDB' in 'db', which is of non-class type 'DatabaseManager()' Can anyone point me in the right direction? I know "copypaste" code isn't good, I just wanted to see if I could get DB connectivity working and I figured something like this would be simple... thanks for the help.

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• using an alternative string quotation syntax in python

  - by Cawas

  Just wondering... I find using escape characters too distracting. I'd rather do something like this: print ^'Let's begin and end with sets of unlikely 2 chars and bingo!'^ Let's begin and end with sets of unlikely 2 chars and bingo! Note the ' inside the string, and how this syntax would have no issue with it, or whatever else inside for basically all cases. Too bad markdown can't properly colorize it (yet), so I decided to <pre> it. Sure, the ^ could be any other char, I'm not sure what would look/work better. That sounds good enough to me, tho. Probably some other language already have a similar solution. And, just maybe, Python already have such a feature and I overlooked it. I hope this is the case. But if it isn't, would it be too hard to, somehow, change Python's interpreter and be able to select an arbitrary (or even standardized) syntax for notating the strings? I realize there are many ways to change statements and the whole syntax in general by using pre-compilators, but this is far more specific. And going any of those routes is what I call "too hard". I'm not really needing to do this so, again, I'm just wondering.

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• When memory is actually freeded?

  - by zhyk

  Hello all. I'm trying to understand memory management stuff in Objective-C. If I see the memory usage listed by Activity Monitor, it looks like memory is not being freed (I mean column rsize). But in "Object Allocations" everything looks fine. Here is my simple code: #import <Foundation/Foundation.h> int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSInteger i, k=10000; while (k>0) { NSMutableArray *array = [[NSMutableArray alloc]init]; for (i=0;i<1000*k; i++) { NSString *srtring = [[NSString alloc] initWithString:@"string...."]; [array addObject:srtring]; [srtring release]; srtring = nil; } [array release]; array = nil; k-=500; } [NSThread sleepForTimeInterval:5]; [pool release]; return 0; } As for retain and release it's cool, everything is balanced. But rsize decreases only after quitting from this little program. Is it possible to "clean" memory somehow before quitting?

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• What is a NULL value

  - by Adi

  I am wondering , what exactly is stored in the memory when we say a particular variable pointer to be NULL. suppose I have a structure, say typdef struct MEM_LIST MEM_INSTANCE; struct MEM_LIST { char *start_addr; int size; MEM_INSTANCE *next; }; MEM_INSTANCE *front; front = (MEM_INSTANCE*)malloc(sizeof(MEM_INSTANCE*)); -1) If I make front=NULL. What will be the value which actually gets stored in the different fields of the front, say front-size ,front-start_addr. Is it 0 or something else. I have limited knowledge in this NULL thing. -2) If I do a free(front); It frees the memory which is pointed out by front. So what exactly free means here, does it make it NULL or make it all 0. -3) What can be a good strategy to deal with initialization of pointers and freeing them . Thanks in advance

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• How to use setTimeout / .delay() to wait for typing between characters

  - by Darcy

  Hi all, I am creating a simple listbox filter that takes the user input and returns the matching results in a listbox via javascript/jquery (roughly 5000+ items in listbox). Here is the code snippet: var Listbox1 = $('#Listbox1'); var commands = document.getElementById('DatabaseCommandsHidden'); //using js for speed $('#CommandsFilter').bind('keyup', function() { Listbox1.children().remove(); for (var i = 0; i < commands.options.length; i++) { if (commands.options[i].text.toLowerCase().match($(this).val().toLowerCase())) { Listbox1.append($('<option></option>').val(i).html(commands.options[i].text)); } } }); This works pretty well, but slows down somewhat when the 1st/2nd char's are being typed since there are so many items. I thought a solution I could use would be to add a delay to the textbox that prevents the 'keyup' event from being called until the user stops typing. The problem is, I'm not sure how to do that, or if its even a good idea or not. Any suggestions/help is greatly appreciated.

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• Problem with close socket

  - by zp26

  Hi, I have a problem with my socket program. I create the client program (my code is below) I have a problem when i close the socket with the disconnect method. Can i help me? Thanks and sorry for my English XP CFSocketRef s; -(void)CreaConnessione { CFSocketError errore; struct sockaddr_in sin; CFDataRef address; CFRunLoopSourceRef source; CFSocketContext context = { 0, self, NULL, NULL, NULL }; s = CFSocketCreate( NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketDataCallBack, AcceptDataCallback, &context); memset(&sin, 0, sizeof(sin)); int port = [fieldPorta.text intValue]; NSString *tempIp = fieldIndirizzo.text; const char *ip = [tempIp UTF8String]; sin.sin_family = AF_INET; sin.sin_port = htons(port); sin.sin_addr.s_addr = (long)inet_addr(ip); address = CFDataCreate(NULL, (UInt8 *)&sin, sizeof(sin)); errore = CFSocketConnectToAddress(s, address, 0); if(errore == 0){ buttonInvioMess.enabled = TRUE; fieldMessaggioInvio.enabled = TRUE; labelTemp.text = [NSString stringWithFormat:@"Connesso al Server"]; CFRelease(address); source = CFSocketCreateRunLoopSource(NULL, s, 0); CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopDefaultMode); CFRelease(source); CFRunLoopRun(); } else{ labelTemp.text = [NSString stringWithFormat:@"Errore di connessione. Verificare Ip e Porta"]; switchConnection.on = FALSE; } } //the socket doesn't disconnect -(void)Disconnetti{ CFSocketInvalidate(s); CFRelease(s); } -(IBAction)Connetti { if(switchConnection.on) [self CreaConnessione]; else [self Disconnetti]; }

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• Factorial in Prolog and C++

  - by Joshua Green

  I would like to work out a number's factorial. My factorial rule is in a Prolog file and I am connecting it to a C++ code. Can someone tell me what is wrong with my C++ interface please? % factorial.pl factorial( 1, 1 ):- !. factorial( X, Fac ):- X > 1, Y is X - 1, factorial( Y, New_Fac ), Fac is X * New_Fac. // factorial.cpp # headerfiles term_t t1; term_t t2; term_t goal_term; functor_t goal_functor; int main( int argc, char** argv ) { argc = 4; argv[0] = "libpl.dll"; argv[1] = "-G32m"; argv[2] = "-L32m"; argv[3] = "-T32m"; PL_initialise(argc, argv); if ( !PL_initialise(argc, argv) ) PL_halt(1); PlCall( "consult(swi('plwin.rc'))" ); PlCall( "consult('factorial.pl')" ); cout << "Enter your factorial number: "; long n; cin >> n; PL_put_integer( t1, n ); t1 = PL_new_term_ref(); t2 = PL_new_term_ref(); goal_term = PL_new_term_ref(); goal_functor = PL_new_functor( PL_new_atom("factorial"), 2 ); PL_put_atom( t1, t2 ); PL_cons_functor( goal_term, goal_functor, t1, t2 ); PL_halt( PL_toplevel() ? 0 : 1 ); }

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• pthread_exit and/or pthread_join causing Abort and SegFaults.

  - by MJewkes

  The following code is a simple thread game, that switches between threads causing the timer to decrease. It works fine for 3 threads, causes and Abort(core dumped) for 4 threads, and causes a seg fault for 5 or more threads. Anyone have any idea why this might be happening? #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <errno.h> #include <assert.h> int volatile num_of_threads; int volatile time_per_round; int volatile time_left; int volatile turn_id; int volatile thread_running; int volatile can_check; void * player (void * id_in){ int id= (int)id_in; while(1){ if(can_check){ if (time_left<=0){ break; } can_check=0; if(thread_running){ if(turn_id==id-1){ turn_id=random()%num_of_threads; time_left--; } } can_check=1; } } pthread_exit(NULL); } int main(int argc, char *args[]){ int i; int buffer; pthread_t * threads =(pthread_t *)malloc(num_of_threads*sizeof(pthread_t)); thread_running=0; num_of_threads=atoi(args[1]); can_check=0; time_per_round = atoi(args[2]); time_left=time_per_round; srandom(time(NULL)); //Create Threads for (i=0;i<num_of_threads;i++){ do{ buffer=pthread_create(&threads[i],NULL,player,(void *)(i+1)); }while(buffer == EAGAIN); } can_check=1; time_left=time_per_round; turn_id=random()%num_of_threads; thread_running=1; for (i=0;i<num_of_threads;i++){ assert(!pthread_join(threads[i], NULL)); } return 0; }

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• Counting string length in javascript and Ruby on Rails

  - by williamjones

  I've got a text area on a web site that should be limited in length. I'm allowing users to enter 255 characters, and am enforcing that limit with a Rails validation: validates_length_of :body, :maximum => 255 At the same time, I added a javascript char counter like you see on Twitter, to give feedback to the user on how many characters he has already used, and to disable the submit button when over length, and am getting that length in Javascript with a call like this: element.length Lastly, to enforce data integrity, in my Postgres database, I have created this field as a varchar(255) as a last line of defense. Unfortunately, these methods of counting characters do not appear to be directly compatible. Javascript counts the best, in that it counts what users consider as number of characters where everything is a single character. Once the submission hits Rails, however, all of the carriage returns have been converted to \r\n, now taking up 2 characters worth of space, which makes a close call fail Rails validations. Even if I were to handcode a different length validation in Rails, it would still fail when it hits the database I think, though I haven't confirmed this yet. What's the best way for me to make all this work the way the user would want? Best Solution: an approach that would enable me to meet user expectations, where each character of any type is only one character. If this means increasing the length of the varchar database field, a user should not be able to sneakily send a hand-crafted post that creates a row with more than 255 letters. Somewhat Acceptable Solution: a javascript change that enables the user to see the real character count, such that hitting return increments the counter 2 characters at a time, while properly handling all symbols that might have these strange behaviors.

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• Unit Testing Private Method in Resource Managing Class (C++)

  - by BillyONeal

  I previously asked this question under another name but deleted it because I didn't explain it very well. Let's say I have a class which manages a file. Let's say that this class treats the file as having a specific file format, and contains methods to perform operations on this file: class Foo { std::wstring fileName_; public: Foo(const std::wstring& fileName) : fileName_(fileName) { //Construct a Foo here. }; int getChecksum() { //Open the file and read some part of it //Long method to figure out what checksum it is. //Return the checksum. } }; Let's say I'd like to be able to unit test the part of this class that calculates the checksum. Unit testing the parts of the class that load in the file and such is impractical, because to test every part of the getChecksum() method I might need to construct 40 or 50 files! Now lets say I'd like to reuse the checksum method elsewhere in the class. I extract the method so that it now looks like this: class Foo { std::wstring fileName_; static int calculateChecksum(const std::vector<unsigned char> &fileBytes) { //Long method to figure out what checksum it is. } public: Foo(const std::wstring& fileName) : fileName_(fileName) { //Construct a Foo here. }; int getChecksum() { //Open the file and read some part of it return calculateChecksum( something ); } void modifyThisFileSomehow() { //Perform modification int newChecksum = calculateChecksum( something ); //Apply the newChecksum to the file } }; Now I'd like to unit test the calculateChecksum() method because it's easy to test and complicated, and I don't care about unit testing getChecksum() because it's simple and very difficult to test. But I can't test calculateChecksum() directly because it is private. Does anyone know of a solution to this problem?

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• Compilation errors calling find_if using a functor

  - by Jim Wong

  We are having a bit of trouble using find_if to search a vector of pairs for an entry in which the first element of the pair matches a particular value. To make this work, we have defined a trivial functor whose operator() takes a pair as input and compares the first entry against a string. Unfortunately, when we actually add a call to find_if using an instance of our functor constructed using a temporary string value, the compiler produces a raft of error messages. Oddly (to me, anyway), if we replace the temporary with a string that we've created on the stack, things seem to work. Here's what the code (including both versions) looks like: typedef std::pair<std::string, std::string> MyPair; typedef std::vector<MyPair> MyVector; struct MyFunctor: std::unary_function <const MyPair&, bool> { explicit MyFunctor(const std::string& val) : m_val(val) {} bool operator() (const MyPair& p) { return p.first == m_val; } const std::string m_val; }; bool f(const char* s) { MyFunctor f(std::string(s)); // ERROR // std::string str(s); // MyFunctor f(str); // OK MyVector vec; MyVector::const_iterator i = std::find_if(vec.begin(), vec.end(), f); return i != vec.end(); } And here's what the most interesting error message looks like: /usr/include/c++/4.2.1/bits/stl_algo.h:260: error: conversion from ‘std::pair, std::allocator , std::basic_string, std::allocator ’ to non-scalar type ‘std::string’ requested Because we have a workaround, we're mostly curious as to why the first form causes problems. I'm sure we're missing something, but we haven't been able to figure out what it is.

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