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  • This code appears to achieve the return of a null reference in C++

    - by Chuck
    Hi folks, My C++ knowledge is somewhat piecemeal. I was reworking some code at work. I changed a function to return a reference to a type. Inside, I look up an object based on an identifier passed in, then return a reference to the object if found. Of course I ran into the issue of what to return if I don't find the object, and in looking around the web, many people claim that returning a "null reference" in C++ is impossible. Based on this advice, I tried the trick of returning a success/fail boolean, and making the object reference an out parameter. However, I ran into the roadblock of needing to initialize the references I would pass as actual parameters, and of course there is no way to do this. I retreated to the usual approach of just returning a pointer. I asked a colleague about it. He uses the following trick quite often, which is accepted by both a recent version of the Sun compiler and by gcc: MyType& someFunc(int id) { // successful case here: // ... // fail case: return *static_cast<MyType*>(0); } // Use: ... MyType& mt = somefunc(myIdNum); if (&mt) // test for "null reference" { // whatever } ... I have been maintaining this code base for a while, but I find that I don't have as much time to look up the small details about the language as I would like. I've been digging through my reference book but the answer to this one eludes me. Now, I had a C++ course a few years ago, and therein we emphasized that in C++ everything is types, so I try to keep that in mind when thinking things through. Deconstructing the expression: "*static_cast(0);", it indeed seems to me that we take a literal zero, cast it to a pointer to MyType (which makes it a null pointer), and then apply the dereferencing operator in the context of assigning to a reference type (the return type), which should give me a reference to the same object pointed to by the pointer. This sure looks like returning a null reference to me. Any advice in explaining why this works (or why it shouldn't) would be greatly appreciated. Thanks, Chuck

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  • fastest engine to convert PDF into PNG

    - by skyde
    I would like to know which of the opensource PDF engine can convert a pdf into a image the fastest. I don't care about the quality of the result (antialiasing ...) For my project it need to be very very fast. I would probably need to build my own but i dont wan't to start from scratch.

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  • Oracle Cursor and JDBC ODBC

    - by BeginnerAmongBeginners
    I have some procedures to execute in the database that has an OUT REFCURSOR parameter. When I am connecting with the JDBC thin client, everything works fine. However, if I were to change the connection string to refer to the ODBC data source pointing to the same database, those procedures will fail. The procedures that do not use an OUT REFCURSOR will still work fine though. Is this situation the result of an error on my part or expected?

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  • Is there a way to efficiently yield every file in a directory containing millions of files?

    - by Josh Smeaton
    I'm aware of os.listdir, but as far as I can gather, that gets all the filenames in a directory into memory, and then returns the list. What I want, is a way to yield a filename, work on it, and then yield the next one, without reading them all into memory. Is there any way to do this? I worry about the case where filenames change, new files are added, and files are deleted using such a method. Some iterators prevent you from modifying the collection during iteration, essentially by taking a snapshot of the state of the collection at the beginning, and comparing that state on each move operation. If there is an iterator capable of yielding filenames from a path, does it raise an error if there are filesystem changes (add, remove, rename files within the iterated directory) which modify the collection? There could potentially be a few cases that could cause the iterator to fail, and it all depends on how the iterator maintains state. Using S.Lotts example: filea.txt fileb.txt filec.txt Iterator yields filea.txt. During processing, filea.txt is renamed to filey.txt and fileb.txt is renamed to filez.txt. When the iterator attempts to get the next file, if it were to use the filename filea.txt to find it's current position in order to find the next file and filea.txt is not there, what would happen? It may not be able to recover it's position in the collection. Similarly, if the iterator were to fetch fileb.txt when yielding filea.txt, it could look up the position of fileb.txt, fail, and produce an error. If the iterator instead was able to somehow maintain an index dir.get_file(0), then maintaining positional state would not be affected, but some files could be missed, as their indexes could be moved to an index 'behind' the iterator. This is all theoretical of course, since there appears to be no built-in (python) way of iterating over the files in a directory. There are some great answers below, however, that solve the problem by using queues and notifications. Edit: The OS of concern is Redhat. My use case is this: Process A is continuously writing files to a storage location. Process B (the one I'm writing), will be iterating over these files, doing some processing based on the filename, and moving the files to another location. Edit: Definition of valid: Adjective 1. Well grounded or justifiable, pertinent. (Sorry S.Lott, I couldn't resist). I've edited the paragraph in question above.

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  • How to close all, or only some, tabs in Safari using AppleScript?

    - by Form
    I have made a very simple AppleScript to close all tabs in Safari. The problem is, it works, but not completely. The problem is that only a couple of tabs are closed. Here's the code: tell application "Safari" repeat with aWindow in windows repeat with aTab in tabs of aWindow if [some condition is encountered] then aTab close end if end repeat end repeat end tell I've also tried this script: tell application "Safari" repeat with i from 0 to the number of items in windows set aWindow to item i of windows repeat with j from 0 to the number of tabs in aWindow set aTab to item j of tabs of aWindow if [some condition is encountered] then aTab close end if end repeat end repeat end tell ... but it does not work either (same behavior). I tried that on my system (MacBook Pro jan 2008), as well as on a Mac Pro G5 under Tiger and the script fails on both, albeit with a much less descriptive error on Tiger. Running the script a few times closes a few tab each time until none is left, but always fails with the same error after closing a few tabs. Under Leopard I get an out of bounds error. Since I am using fast enumeration (not using "repeat from 0 to number of items in windows") I don't see how I can get an out of bounds error with this... My goal is to use the Cocoa Scripting Bridge to close tabs in Safari from my Objective-C Cocoa application but the Scripting Bridge fails in the same manner. The non-deletable tabs show as NULL in the Xcode debugger, while the other tabs are valid objects from which I can get values back (such as their title). In fact I tried with the Scripting Bridge first then told myself why not try this directly in AppleScript and I was surprised to see the same results. I must have a glaring omission or something in there... (seems like a bug in Safari AppleScript support to me... :S) I've used repeat loops and Obj-C 2.0 fast enumeration to iterate through collections before with zero problems, so I really don't see what's wrong here. Anyone can help? Thanks in advance!

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  • How to get a list of the latest revision number for each file in a Mercurial repository?

    - by Kimble
    I have made a build system for my web application that's rewriting all resource url's to include the file's revision number (to improve client caching). As of today I'm running this command for each file to get the revision number: hg log --template '{rev}\n' path-to-file Executing hg for each file is really time consuming. Is there a fast way to list all files in a repository with the latest revision number?

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  • Fastest way to find the largest power of 10 smaller than x

    - by peoro
    Is there any fast way to find the largest power of 10 smaller than a given number? I'm using this algorithm, at the moment, but something inside myself dies anytime I see it: 10**( int( math.log10(x) ) ) # python pow( 10, (int) log10(x) ) // C I could implement simple log10 and pow functions for my problems with one loop each, but still I'm wondering if there is some bit magic for decimal numbers.

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  • Creating new folders if they don't exist for fopen

    - by Gbps
    I have a C++ program that takes user input for fopen in order to initiate a file write. Could someone help me find a function which will return a FILE* and use the Windows specific version of mkdir in order to create the folder structure for fopen to never fail to open a new file in the specified location because one of the folders does not exist. Thanks a bunch!

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  • oracle using index even though there is no filter criteeria specified

    - by Kaushik
    In this query: SELECT WTTEMPLATE.TEMPLATEuID, MAX (WTTRX.VALUEDATE) AS template_last_use_date FROM wttemplate, wttrx WHERE WTTEMPLATE.TEMPLATEID = WTTRX.TEMPLATEID(+) AND WTTEMPLATE.CUSTID = WTTRX.CUSTID GROUP BY WTTEMPLATE.TEMPLATEuID The explain plan shows:index fast full scan using indexes on WTTEMPLATE.TEMPLATEID and (WTTRX.TEMPLATEID,WTTRX.CUSTID). My question is this: I have not specified any filter criteria , so how can it use indexes? It should do full scan...right?

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  • Faster way to dump mysql

    - by japancheese
    This may be a dumb question, but I was just watching a screencast on MySQL replication, and I learned that a master database doesn't send SQL over to a slave for replication, it actually sends data over in binary, which makes importing extremely fast. I started wondering, "if a database can export and import binary, why do mysqldumps / imports take so long?" Is there a way to get mysql to dump a database in binary in a similar fashion to speed up that process as well?

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  • SocketTimeout: Read timed out

    - by Lieven Cardoen
    I'm using Flex - IIS - ASP.NET to do remote calls. When I stresstest, all remote calls that take longer than 30 seconds fail. In Charles I get a message saying 'SocketTimeout: Read timed out'. Is this something that can be configured in IIS? Or could it be a problem with a setting in Charles?

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  • How to pass parameters dynamically in PHP?

    - by user198729
    I need to pass the $route to its inner function,but failed: function compilePath( $route ) { preg_replace( '$:([a-z]+)$i', 'pathOption' , $route['path'] ); function pathOption($matches) { global $route;//fail to get the $route } } I'm using php5.3,is there some feature that can help?

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  • Trying to write junit test missing some basisc

    - by Gandalf StormCrow
    When I try to use assertNotLesser or assertNotGreater I get compile error .. and eclipse suggest me to create a new method called like this .. http://junit-addons.sourceforge.net/junitx/framework/ComparableAssert.html I found it here I never used these options before but I need to write this test, I can do it jmock as well but I don't know how .. I need to compare my expected results let say 0, if the real result is greater that the test should fail.

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  • Inconsistent email formatting with inline css created using Javamail

    - by user1816183
    Okay, so I have a program that sends an email when it is finished running. I use inline css to format the email. This was working up until yesterday however now I am seeing different formats depending on which email account I view the email in. It coincides with an upgrade from Selenium 2.35.0 to 2.37.0 however I don't think this is my issue since I rolled back to 2.35.0 and it still happens. package tests; import java.util.Properties; import javax.mail.Message; import javax.mail.Session; import javax.mail.Transport; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; public class TESTTEST { public static void main(String[] args) throws Exception { Properties props = new Properties(); props.put("mail.smtp.host","xxx.xxx.xxx.xxx"); Session session = Session.getInstance(props); String emailFrom="[email protected]"; String emailTo1="[email protected]"; MimeMessage message = new MimeMessage(session); message.setSubject("Testing HTML Email"); message.setFrom(new InternetAddress(emailFrom)); String htmlBody = "<STYLE>body {font-family:sans-serif,arial,helvetica,sans-serif;font-size:9pt;}" +"TABLE {border-collapse:collapse;border:1px solid black;}" +"TH {background-color:grey;color:white;padding:5px;border:1px solid black;font-size:9pt;}" +"TD {padding:5px;border:1px solid black;font-size:9pt;}" +"H3 {font-size:12pt;}" +".PASSED {background-color:#00FF00}" +".FAILED {background-color:#FF0000}" +".SKIPPED {background-color:#DEDEDE}" +".ITALIC {font-style:italic}" +"</STYLE>" + "<TABLE><TR><TD CLASS=PASSED>FAIL</TD><TD STYLE=background-color:#FF0000>FAIL</TD></TR></TABLE>"; message.setContent(htmlBody, "text/html; charset=ISO-8859-1"); message.addRecipient(Message.RecipientType.TO,new InternetAddress(emailTo1)); Transport.send(message,message.getRecipients(Message.RecipientType.TO)); System.out.println(htmlBody); System.out.println("Email Sent"); } } When I view the email in Hotmail/Outlook.com, it looks fine In Gmail In Lotus Notes Anybody able to help?

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  • Java- screen capture behind the application.

    - by Auxiliary
    Is there a way to capture the screen but without the app itself getting shown. I know how to minimize or make a frame invisible but this has to be done real fast cos it's going to happen alot in each second (at least once every second). I want it to look something like the magnifier in Windows Vista/7. (The app can see behind itself.) Thanks in advance.

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  • regex unicode charater in vim

    - by aidan
    I'm being an idiot. Someone cut and pasted some text from microsoft word into my lovely html files. I now have these unicode characters instead of regular quote symbols, (i.e. quotes appear as <92 in the text) I want to do a regex replace but I'm having trouble selecting them. :%s/\u92/'/g :%s/\u5C/'/g :%s/\x92/'/g :%s/\x5C/'/g ...all fail. My google-fu has failed me.

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