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  • How do you return a string from a function correctly in Dynamic C?

    - by aquanar
    I have a program I am trying to debug, but Dynamic C apparently treats strings differently than normal C does (well, character arrays, anyway). I have a function that I made to make an 8 character long (well, 10 to include the \0 ) string of 0s and 1s to show me the contents of an 8-bit char variable. (IE, I give it the number 13, it returns the string "0001101\0" ) When I use the code below, it prints out !{happy face] 6 times (well, the second one is the happy face alone for some reason), each return comes back as 0xDEAE or "!\x02. I thought it would dereference it and return the appropriate string, but it appears to just be sending the pointer and attempting to parse it. This may seem silly, but my experience was actually in C++ and Java, so going back to C brings up a few issues that were dealt with in later programming languages that I'm not entirely sure how to deal with (like the lack of string variables). How could I fix this code, or how would be a better way to do what I am trying to do (I thought maybe sending in a pointer to a character array and working on it from the function might work, but I thought I should ask to see if maybe I'm just trying to reinvent the wheel). Currently I have it set up like this: this is an excerpt from the main() display[0] = '\0'; for(i=0;i<6;i++) { sprintf(s, "%s ", *char_to_bits(buffer[i])); strcat(display, s); } DispStr(8,5, display); and this is the offending function: char *char_to_bits(char x) { char bits[16]; strcpy(bits,"00000000\0"); if (x & 0x01) bits[7]='1'; if (x & 0x02) bits[6]='1'; if (x & 0x04) bits[5]='1'; if (x & 0x08) bits[4]='1'; if (x & 0x10) bits[3]='1'; if (x & 0x20) bits[2]='1'; if (x & 0x40) bits[1]='1'; if (x & 0x80) bits[0]='1'; return bits; } and just for the sake of completion, the other function is used to output to the stdio window at a specific location: void DispStr(int x, int y, char *s) { x += 0x20; y += 0x20; printf ("\x1B=%c%c%s", x, y, s); }

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  • How do I access the enumerated item with an indexer and assign array string to it for display?

    - by g00p3k
    EDITED: Updated 3/23/09. See rest of post at bottom. I'm still having trouble with the indexer. Anymore help or examples would really help me out. Write a class, MyCourses, that contains an enumeration of all the courses that you are currently taking. This enum should be nested inside of your class MyCourses. Your class should also have an array field that provides a short description (as a String) of each of your courses. Write an indexer that takes one of your enumerated courses as an index and returns the String description of the course. Write a class MyFriends that contains an indexer that provides access to the names of your friends. namespace IT274_Unit4Project { public class MyCourses { // enumeration that contains an enumeration of all the courses that // student is currently enrolled in public enum CourseName {IT274= 0,CS210 = 1} // array field that provides short description for each of classes, // returns string description of the course private String[] courseDescription = {"Intermediate C#: Teaches intermediate elements of C# programming and software design", "Career Development Strategies: Teaches principles for career progression, resume preparation, and overall self anaylsis"}; // indexer that takes one of the enumerated courses as an index // and returns the String description of the course public String this[CourseName index] { get { if (index == 1) return courseDescription[0]; else return courseDescription[1]; } set { if (index == 1) courseDescription[0] = value; else courseDescription[1] = value; } } } }//end public class MyCourses I'm working on this homework project and having trouble understanding the text explaining how to correctly take the accessed value of the enumeration and then apply the string array value to it. Can you please help me understand this? The text we are using is very difficult and poorly written for a beginner to understand, so I'm kind of on my own here. I've got the first parts written, but need some help on the accessing of the enumeration value and assigning, i think i'm close, but don't understand how to properly get and set the values on this. Please do not provide me with direct code answers, unless a MSDN style explanation that is generalized and not specific to my project. ie: public class MyClass { string field1; string field2; //properties public string Value1 get etc... Thanks!

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  • How can I obtain the IP address of my server program?

    - by Dr Dork
    Hello! This question is related to another question I just posted. I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code and client side code setup to communicate. Currently, my client code successfully connects to the server code and the server code sends it a test message, then both quit out. Perfect! That's exactly what I wanted to accomplish. Now I'm playing around with the functions used to obtain info about the two environments (server and client). I'd like to obtain my server program's IP address. Here's the code I currently have to do this, but it's not working... int sockfd; unsigned int len; socklen_t sin_size; char msg[]="test message"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char s[INET6_ADDRSTRLEN]; char ip[INET6_ADDRSTRLEN]; //zero struct memset(&hints,0,sizeof(hints)); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; //get the server info if((rv = getaddrinfo(NULL, SERVERPORT, &hints, &serverinfo ) != 0)){ perror("getaddrinfo"); exit(-1); } // loop through all the results and bind to the first we can for( p = serverinfo; p != NULL; p = p->ai_next) { //Setup the socket if( (sockfd = socket( p->ai_family, p->ai_socktype, p->ai_protocol )) == -1 ) { perror("socket"); continue; } //Associate a socket id with an address to which other processes can connect if(bind(sockfd, p->ai_addr, p->ai_addrlen) == -1){ close(sockfd); perror("bind"); continue; } break; } if( p == NULL ){ perror("Fail to bind"); } inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr), s, sizeof(s)); printf("Server has TCP Port %s and IP Address %s\n", SERVERPORT, s); and the output for the IP is always empty... server has TCP Port 21412 and IP Address :: any ideas for what I'm missing? thanks in advance for your help! this stuff is really complicated at first.

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  • What's the fastest lookup algorithm for a key, pair data structure (i.e, a map)?

    - by truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 – 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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  • [C#] How to do a search from a list with non-prefix keywords

    - by aNui
    First of all, sorry if my english or my post got any mistakes. I am programming a program to search the name from the list and I need to find them if the keyword is not in front of the names (that's what I mean non-prefix) e.g. if I my list is the music instruments and I type "guit" to the search textbox. It should find the names "Guitar, Guitarrón, Acoustic Guitar, Bass Guitar, ..." or something like this Longdo Dictionary's search suggestion. here is my simple and stupid algorithm (that's all I can do) const int SEARCHROWLIMIT = 30; private string[] DoSearch(string Input, string[] ListToSearch) { List<string> FoundNames = new List<string>(); int max = 0; bool over = false; for (int k = 0; !over; k++) { foreach (string item in ListToSearch) { max = (max > item.Length) ? max : item.Length; if (k > item.Length) continue; if (k >= max) { over = true; break; } if (!Input.Equals("Search") && item.Substring(k, item.Length - k).StartsWith(Input, StringComparison.OrdinalIgnoreCase)) { bool exist = false; int i = 0; while (!exist && i < FoundNames.Count) { if (item.Equals(FoundNames[i])) { exist = true; break; } i++; } if (!exist && FoundNames.Count < SEARCHROWLIMIT) FoundNames.Add(item); else if (FoundNames.Count >= SEARCHROWLIMIT) over = true; } } } return FoundNames.ToArray(); } I think this algorithm is too slow for a large number of names and after several trial-and-error, I decided to add SEARCHROWLIMIT to breaks the operation And I also think there're some readymade methods that can do that. And another problem is I need to search music instruments by a category like strings, percussions, ... and by the country of origins. So I need to search them with filter by type and country. please help me. P.S. Me and my friends are just student from Thailand and developing the project to compete in Microsoft Imagine Cup 2010 and please become fan on our facebook page [KRATIB][3]. And we're so sorry we don't have much information in English but you can talk to us in English.

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  • Advice needed: stay with Java team or move to C++ team?

    - by user68759
    Some background - I have been programming in Java as a professional for the last few years. This is mainly using Java SE. I have also touched bits and pieces of other various Java technologies and have some basic knowledge about them. I consider my self as an intermediate Java programmer. I like Java very much. I think it is only going to get bigger. Recently, my manager asked my opinion on whether I would like to be transferred to another team within the company that is developing a product in C++. This is mainly because my current Java team simply didn't make enough money due to poor sales and the economic downturn. Now, I have never had any experience with C++ nor have I ever coded a single line of code in C++. I have always wanted to learn it and now is my chance. But I really want to make sure I get benefit out of it in the future, in the sense that I will have the skills that will still be on-demand in the future. So, what do you experts think? Is C++ still the language to learn these days to secure yourself for the future? What will I learn more in C++ but not in Java? And are they worthy to learn considering the current and possible future demands in IT industry? (Apart from the obvious more control over memory management and something along that line.) What is a good excuse to refuse the offer in order to stay with the Java team? I don't want to blatantly refuse it because you can never predict the future and I could possibly come back to my manager in the future and ask him to transfer me to the C++ team. How do I say it nicely that I am taking the offer but I would like to still be involved with Java one way or another, such as when there is a new Java project I would like to be considered. I have to admit that I am kind of 50-50 at the moment. I want to learn C++ for the sake of improving my skills and also helping my company to reduce the fund required for the Java team. But it is also hard for me to leave Java because I know Java is going to get bigger, so I am afraid of getting behind when I start concentrating on C++. I could, of course, decide to just join the C++ team, and then spend my free time reading about Java to keep in touch with it, but I thought I would ask anyway in case some people can point out the strong points of either over the other given the current and possibly future circumstances.

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  • How can I remove rows with unique values? As in only keeping rows with duplicate values?

    - by user1456405
    Here's the conundrum, I'm a complete and utter noob when it comes to programming. I understand the basics, but am still learning javascript. I have a spreadsheet of surveys, in which I need to see how particular users have varied over time. As such, I need to disregard all rows with unique values in a particular column. The data looks like this: Response Date Response_ID Account_ID Q.1 10/20/2011 12:03:43 PM 23655956 1168161 8 10/20/2011 03:52:57 PM 23660161 1168152 0 10/21/2011 10:55:54 AM 23672903 1166121 7 10/23/2011 04:28:16 PM 23694471 1144756 9 10/25/2011 06:30:52 AM 23732674 1167449 7 10/25/2011 07:52:28 AM 23734597 1087618 5 I've found a way to do so in VBA, which sucks as I have to use excel, per below: Sub Del_Unique() Application.ScreenUpdating = False Columns("B:B").Insert Shift:=xlToRight Columns("A:A").Copy Destination:=Columns("B:B") i = Application.CountIf(Range("A:A"), "<>") + 50 If i > 65536 Then i = 65536 Do If Application.CountIf(Range("B:B"), Range("A" & i)) = 1 Then Rows(i).Delete End If i = i - 1 Loop Until i = 0 Columns("B:B").Delete Application.ScreenUpdating = True End Sub But that requires mucking about. I'd really like to do it in Google Spreadsheets with a script that won't have to be changed. Closest I can get is retrieving all duplicate user ids from the range, but can't associate that with the row. That code follows: function findDuplicatesInSelection() { var activeRange = SpreadsheetApp.getActiveRange(); var values = activeRange.getValues(); // values that appear at least once var once = {}; // values that appear at least twice var twice = {}; // values that appear at least twice, stored in a pretty fashion! var final = []; for (var i = 0; i < values.length; i++) { var inner = values[i]; for (var j = 0; j < inner.length; j++) { var cell = inner[j]; if (cell == "") continue; if (once.hasOwnProperty(cell)) { if (!twice.hasOwnProperty(cell)) { final.push(cell); } twice[cell] = 1; } else { once[cell] = 1; } } } if (final.length == 0) { Browser.msgBox("No duplicates found"); } else { Browser.msgBox("Duplicates are: " + final); } } Anyhow, sorry if this is the wrong place or format, but half of what I've found so far has been from stack, I thought it was a good place to start. Thanks!

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  • jQuery getScript function with frames

    - by user210099
    Hello.. I'm a novice at Javascript/Jquery programming, so an apology if this is a simple/silly question. I am trying to use the jQuery .getScript() function to refresh part of an existing webpage. This webpage must be run on a local file system, and a large amount of the formatting is done using frames. Right now, there’s three main frames- a sidebar which displays possible “scopes” to choose from, a main frame which displays the majority of the contents of the webpage, and a footer frame. The main entry into the page is in an index.html file, which loads a sidebar.html, main.html, and footer.html file into each of the respective frames. In turn, the main.html has a number of javascript files which it loads, the main being a main.js, which contains numerous functions to format/process the contents for this main window. After loading this javascript file, main.html loads a few javascript files, which contain the data which is going to be displayed in the main frame. These files that are loaded have a fixed data structure, and are dependent on the functions that were loaded by the main.js file. Loading the webpage works fine now, but when a user tries to switch to another “scope”, the whole webpage is reloaded to make the switch. The only difference in the webpage is the content in the main.js frame, loaded in by a different set of .js files. Enough text, let’s look at some code. When the webpage loads, I tried to add a simple call to the getScript function in a .js file at the index.html level which handles switching scopes. This file, newFile, has different data definitions than the previously loaded oldFile.js which was loaded in the main.html file. $.getScript(/js/newFile.js); However this doesn’t work, since newFile.js depends on a parseData() function which is in main.js. If I open firebug up, parseData is not located in the dom tab, which I assume is related to some scoping issue with the main.html and main.js file existing in a different frame. I tried to do some targeting to the correct “frame” but I don’t think I understand jQuery enough to know what is happening. $(window.parent.frames[0]).getScript(/js/newFile.js); Any suggestions? If I were to type into firebug console “parseData” it can not find it: “ReferenceError: parseData is not defined” However, if I type in window.parent.frames[1].parseData, it can find the function. Sorry about all the rambling and poor understanding of javascript. Hopefully someone can provide some assistance! Thanks

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  • Flickering Image in Java?

    - by Noah Cagle
    OK so I am coding a game right now to prepair for Ludum Dare SharkJam, and I am using a new method for programming, because the last method I had crashes my PC, so this one should work. Well it does work and all, better too, but the images that I put in it flicker. Here is the whole main class (where the images are drawn) package me.NoahCagle.watermaze; import java.awt.Color; import java.awt.Graphics; import java.awt.Image; import java.awt.image.BufferedImage; import javax.swing.JFrame; import me.NoahCagle.watermaze.entity.EntityShark; import me.NoahCagle.watermaze.entity.Player; import me.NoahCagle.watermaze.input.Keys; import me.NoahCagle.watermaze.map.Map; public class Game extends JFrame { private static final long serialVersionUID = 1L; Map map = new Map(0, 0); Player player = new Player(50, 30); static EntityShark shark = new EntityShark(400, 400); public Image dbImage; public Game() { setSize(800, 600); setDefaultCloseOperation(EXIT_ON_CLOSE); setLocationRelativeTo(null); setVisible(true); setTitle("Water Maze"); setResizable(false); setBackground(Color.blue); addKeyListener(new Keys()); } public static void main(String[] args) { new Game(); Thread s = new Thread(shark); s.start(); } public void paint(Graphics g) { dbImage = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_RGB); g.drawImage(dbImage, map.x, map.y, null); g.drawImage(player.player, player.x, player.y, this); g.drawImage(shark.shark, shark.x, shark.y, this); repaint(); } } What this code does for me is makes the Images work correctly, just flickering, alot. Can anyone help me with my issue? EDIT: I think it has something to do with where I call the repaint method in the paint method, so look there.

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  • How can I find a URL called [link] inside a block of HTML containing other URLs?

    - by DrTwox
    I'm writing a script to rewrite Reddit's RSS feeds. The script needs to find a URL named [link] inside a block of HTML that contains other URLs. The HTML is contained in an XML element called <description>. Here are two examples of the <description> element from I need to parse and the [link] I would need to get. First example: <description>submitted by &lt;a href=&#34;http://www.reddit.com/user/wildlyinaccurate&#34;&gt; wildlyinaccurate &lt;/a&gt; &lt;br/&gt; &lt;a href=&#34;http://wildlyinaccurate.com/a-hackers-guide-to-git&#34;&gt;[link]&lt;/a&gt; &lt;a href="http://www.reddit.com/r/programming/comments/26jvl7/a_hackers_guide_to_git/"&gt;[66 comments]&lt;/a&gt;</description> The [link] is: http://wildlyinaccurate.com/a-hackers-guide-to-git Second example: <description>&lt;!-- SC_OFF --&gt;&lt;div class=&#34;md&#34;&gt;&lt;p&gt;I work a support role at a company where I primarily fix issues our customers our experiencing with our software, which is a browser based application written primarily in javascript. I&amp;#39;ve been doing this for 2 years, but I want to take it to the next level (with the long term goal being that I become proficient enough to call myself a developer). I&amp;#39;ve been reading &amp;quot;Javascript The Definitive Guide&amp;quot; by O&amp;#39;Reilly but I was wondering if any of you more experienced users out there had some tips on taking it to the next level. Should I start incorporating some PHP and Jquery into my learning? Side projects on my spare time? Any good online resources? Etc. &lt;/p&gt; &lt;p&gt;Thanks! &lt;/p&gt; &lt;/div&gt;&lt;!-- SC_ON --&gt; submitted by &lt;a href=&#34;http://www.reddit.com/user/56killa&#34;&gt; 56killa &lt;/a&gt; &lt;br/&gt; &lt;a href=&#34;http://www.reddit.com/r/javascript/comments/26nduc/i_want_to_become_more_experienced_with_javascript/&#34;&gt;[link]&lt;/a&gt; &lt;a href="http://www.reddit.com/r/javascript/comments/26nduc/i_want_to_become_more_experienced_with_javascript/"&gt;[4 comments]&lt;/a&gt;</description> The [link] is: http://www.reddit.com/r/javascript/comments/26nduc/i_want_to_become_more_experienced_with_javascript/

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  • jQuery image loop not displaying any images

    - by user1871097
    I'm trying to create a very basic image gallery in jQuery. The goal is to have 3 images fade in and out in a sequential order. So image 1 is displayed, fades to image 2 etc. then the whole thing loops again. My HTML code so far is as follows: <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Slider</title> <style type="text/css"> .slider{ width: 2848px; height: 2136px; overflow: hidden; margin: 30px auto; } .slider img{ width:2848px; height:2136px; display:none; } </style> <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script> <script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.9.2/jquery-ui.min.js"></script> <script src="Slider2.js"></script> </head> <body onload="Slider2"();> <div class="slider"> <img id="1" src="31.jpg" border="0" alt="city"/> <img id="2" src="2vrtigo2.jpg" border="0" alt="roof"/> <img id="3" src="3.jpg" border="0" alt="sea"/> </div> </body> And the jQuery code looks like this: function Slider2() { var total = $(".slider img").size(); for (i=1; i<=total; i+=1) { $(".slider #"+i).fadeIn(600); $(".slider #"+i).delay(2000).hide; }} A quick syntactical note, I've also tried using i++ in the last argument of the For Loop. The result of this code is a blank, white page. I know some of the HTML is being compiled because the enormous 2848x2136 div creates scroll bars on the browser. If anyone could help me out, that would be greatly appreciated. Obviously I'm relatively new to web programming and would love some insight into why this isn't working. Thanks!

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  • how to create multiple tcp connections between server and client

    - by lowcosthighperformance
    I am new in Unix/Linux networking programming, so I have written server-client program in below.In this code there is one socket between client and server, client requests to server, then server responses from 1 to 100 numbers to client. So my question is how can we do this process with 3 socket( tcp connection) without using thread? ( e.g. First socket runs then second runs then third runs then first again .. ) Do you have any suggestion? Thank you client.c int main() { int sock; struct sockaddr_in sa; int ret; char buf[1024]; int x; sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_port = htons(SERVER_PORT); inet_pton (AF_INET, SERVER_IP, &sa.sin_addr); ret = connect (sock, (const struct sockaddr *) &sa,sizeof (sa)); if (ret != 0) { printf ("connect failed\n"); exit (0); } x = 0; while (x != -1) { read (sock, buf , sizeof(int)); x = ntohl(*((int *)buf)); if (x != -1) printf ("int rcvd = %d\n", x); } close (sock); exit (0); } server.c int main() { int list_sock; int conn_sock; struct sockaddr_in sa, ca; socklen_t ca_len; char buf[1024]; int i; char ipaddrstr[IPSTRLEN]; list_sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_addr.s_addr = htonl(INADDR_ANY); sa.sin_port = htons(SERVER_PORT); bind (list_sock,(struct sockaddr *) &sa,sizeof(sa)); listen (list_sock, 5); while (1){ bzero (&ca, sizeof(ca)); ca_len = sizeof(ca); // important to initialize conn_sock = accept (list_sock,(struct sockaddr *) &ca,&ca_len); printf ("connection from: ip=%s port=%d \n",inet_ntop(AF_INET, &(ca.sin_addr), ipaddrstr, IPSTRLEN),ntohs(ca.sin_port)); for (i=0; i<100; ++i){ *((int *)buf) = htonl(i+20); // we using converting to network byte order write (conn_sock, buf, sizeof(int)); } * ((int *)buf) = htonl(-1); write (conn_sock, buf, sizeof(int)); close (conn_sock); printf ("server closed connection to client\n"); } }

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  • Type casting int into double C++

    - by user1705380
    I am new to programming and this might be an obvious question, though i cannot for life of me figure out why my program is not returning as a double. I am suppose to write a stocks program that takes in shares of stock, whole dollar portion of price and the fraction portion. And the fraction portion is to be inputted as two int values, and include a function definition with 3 int values.The function returns the price as a double. #include <iostream> using namespace std; int price(int, int, int); int main() { int dollars, numerator, denominator, price1, shares; char ans; do { cout<<"Enter the stock price and the number of shares.\n"; cout<<"Enter the price and integers: Dollars, numerator, denominator\n"; cin>>dollars>>numerator>>denominator; cout<<"Enter the number of shares held\n"; cin>>shares; cout<<shares; price1 = price(dollars,numerator,denominator); cout<<" shares of stock with market price of "; cout<< dollars << " " << numerator<<'/'<<denominator<<endl; cout<<"have a value of " << shares * price1<<endl; cout<<"Enter either Y/y to continue"; cin>>ans; }while (ans == 'Y' || ans == 'y'); system("pause"); return 0; } int price(int dollars, int numerator, int denominator) { return dollars + numerator/static_cast<double>(denominator); }

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  • Getting Frequency Components with FFT

    - by ruhig brauner
    so I was able to solv my last problem but i stubmled upon the next already. So I want to make a simple spectrogram but in oder to do so I want to understand how FFT-libaries work and what they actually calculate and return. (FFT and Signal Processing is the number 1 topic I will get into as soon as I have time but right now, I only have time for some programming exercises in the evening. ;) ) Here I just summarized the most important parts: int framesPerSecond; int samplesPerSecond; int samplesPerCycle; // right now i want to refresh the spectogram every DoubleFFT_1D fft; WAVReader audioIn; double audioL[], audioR[]; double fftL[], fftR[]; ..... framesPerSecond = 30; audioIn= new WAVReader("Strobe.wav"); int samplesPerSecond = (int)audioIn.GetSampleRate(); samplesPerCycle = (int)(audioIn.GetSampleRate()/framesPerSecond); audioL = new double[samplesPerCycle*2]; audioR = new double[samplesPerCycle*2]; fftL = new double[samplesPerCycle]; fftR = new double[samplesPerCycle]; for(int i = 0; i < samplesPerCycle; i++) { // don't even know why,... fftL[i] = 0; fftR[i] = 0; } fft = new DoubleFFT_1D(samplesPerCycle); ..... for(int i = 0; i < samplesPerCycle; i++) { audioIn.GetStereoSamples(temp); audioL[i]=temp[0]; audioR[i]=temp[1]; } fft.realForwardFull(audioL); //still stereo fft.realForwardFull(audioR); System.out.println("Check"); for(int i = 0; i < samplesPerCycle; i++) { //storing the magnitude in the fftL/R arrays fftL[i] = Math.sqrt(audioL[2*i]*audioL[2*i] + audioL[2*i+1]*audioL[2*i+1]); fftR[i] = Math.sqrt(audioR[2*i]*audioR[2*i] + audioR[2*i+1]*audioR[2*i+1]); } So the question is, if I want to know, what frequencys are in the sampled signal, how do I calculate them? (When I want to print the fftL / fftR arrays, I get some exponential formes at both ends of the array.) Thx :)

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  • Does this type of function or technique have a name?

    - by DHR
    HI there, I'm slightly new to programming, more of a hobby. I am wondering if a the following logic or technique has a specific name, or term. My current project has 7 check boxes, one for each day of the week. I needed an easy to save which boxes were checked. The following is the method to saved the checked boxes to a single number. Each checkbox gets a value that is double from the last check box. When I want to find out which boxes are checked, I work backwards, and see how many times I can divide the total value by the checkbox value. private int SetSelectedDays() { int selectedDays = 0; selectedDays += (dayMon.Checked) ? 1 : 0; selectedDays += (dayTue.Checked) ? 2 : 0; selectedDays += (dayWed.Checked) ? 4 : 0; selectedDays += (dayThu.Checked) ? 8 : 0; selectedDays += (dayFri.Checked) ? 16 : 0; selectedDays += (daySat.Checked) ? 32 : 0; selectedDays += (daySun.Checked) ? 64 : 0; return selectedDays; } private void SelectedDays(int n) { if ((n / 64 >= 1) & !(n / 64 >= 2)) { n -= 64; daySun.Checked = true; } if ((n / 32 >= 1) & !(n / 32 >= 2)) { n -= 32; daySat.Checked = true; } if ((n / 16 >= 1) & !(n / 16 >= 2)) { n -= 16; dayFri.Checked = true; } if ((n / 8 >= 1) & !(n / 8 >= 2)) { n -= 8; dayThu.Checked = true; } if ((n / 4 >= 1) & !(n / 4 >= 2)) { n -= 4; dayWed.Checked = true; } if ((n / 2 >= 1) & !(n / 2 >= 2)) { n -= 2; dayTue.Checked = true; } if ((n / 1 >= 1) & !(n / 1 >= 2)) { n -= 1; dayMon.Checked = true; } if (n > 0) { //log event } } The method works well for what I need it for, however, if you do see another way of doing this, or a better way to writing, I would be interested in your suggestions.

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  • Database advantages? Access, MySQL, msSQL, or any others?

    - by JimZ
    Dear all Stackoverflowers, I just started to learn programming and now I'm putting this question online based on a quote: no question is silly My work needs to develop a order system based on web, which wants a database system. Since using Excel for years as a general office user, I naturally turn this to Access. However, most people say Access is very limited comparing to MySQL or MSSQL, or any other more professional database system. But after developing some functions for my company's order system, I really find Access can fulfill my request. And I also tried MSSQL to develop, which I found it not quite convenient to use. I have searched in stackoverflow and find no general answer about my doubt. Now I am sincerely hoping some experienced and professional developers could clear my doubts. Now I'm listing some Access advantages, which I don't think other database system have. I hope you could help me also find these advantages in others. 1. Access is portable, I can just copy a xxx.accdb file to my company and continue with development. 2. Access is easy to generate helpful table, for example, it will automatically generate a field that can automatically count, could be used as primary key value. 3. it is more compatable with Excel, to display and filter data. 4. importantly, it nerely needs no environment to setup, just needs MS Office to be installed. ............others However, I also find some points that MSSQL is advantaged: 1. security reasons 2. easy to backup, ( just use BACKUP..... sql statement to do it) 3. can edit stored procedure to save some functions to database ...............others specifically, I wish some friends could tell me how to make other database portable? since I usually work both at home and in office. It's a headache to move MSSQL work to my office, since the version of MSSQL is not the same. Thank you all and best regards, :)

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  • Need advice about pointers and time elapsed program. How to fix invalid operands and cannot convert errors?

    - by user1781382
    I am trying to write a program that tells the difference between the two times the user inputs. I am not sure how to go about this. I get the errors : Line 27|error: invalid operands of types 'int' and 'const MyTime*' to binary 'operator-'| Line |39|error: cannot convert 'MyTime' to 'const MyTime*' for argument '1' to 'int DetermineElapsedTime(const MyTime*, const MyTime*)'| I also need a lot of help in this problem. I don't have a good curriculum, and my class textbook is like cliffnotes for programming. This will be my last class at this university. The C++ teztbook I use(my own not for class) is Sam's C++ One hour a day. #include <iostream> #include<cstdlib> #include<cstring> using namespace std; struct MyTime { int hours, minutes, seconds; }; int DetermineElapsedTime(const MyTime *t1, const MyTime *t2); long t1, t2; int DetermineElapsedTime(const MyTime *t1, const MyTime *t2) { return((int)t2-t1); } int main(void) { char delim1, delim2; MyTime tm, tm2; cout << "Input two formats for the time. Separate each with a space. Ex: hr:min:sec\n"; cin >> tm.hours >> delim1 >> tm.minutes >> delim2 >> tm.seconds; cin >> tm2.hours >> delim1 >> tm2.minutes >> delim2 >> tm2.seconds; DetermineElapsedTime(tm, tm2); return 0; } I have to fix the errors first. Anyone have any ideas??

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  • Else without if

    - by user2808951
    I'm trying to write a code for my computer programming class for a project due Monday, and I'm pretty new to Java, but I'm trying to write a program that will first determine if a number the user inputs is even or odd and then determine if the number is prime or not. I'm not sure if I did the algorithm right or not, so if anyone has any corrections on the program to my algorithm or anything else please say so, but my real issue is that the program is refusing to compile. Every time I try, it says it's having an else without if problem. Here's a link to my command box: http://s1341.photobucket.com/user/Emi_Nightshade/media/Capture_zps45f9a2ea.png.html Here's my code: import java.io.*; import java.util.*; public class Lesson9p1_ThuotteEmily { public static void main(String args[]) { Scanner kbReader0=new Scanner(System.in); System.out.print("\n\nPlease enter an integer. An integer is whole number, and it can be either negative or positive. Please enter your number: "); long num=kbReader0.nextLong(); if(num%2==0) //if and else with braces { System.out.println("Your integer " + num + " is even."); } else { System.out.println("Your integer " + num + " is odd."); } Scanner kbReader1=new Scanner(System.in); System.out.print("\n\nWould you like to know if your number is prime? Please enter yes or no: "); String yn=kbReader1.nextLine(); if(yn.equals.IgnoreCase("Yes")) { System.out.println("Okay. Give me a moment."); { if(num%2==0) { System.out.println("Your number isn't prime."); } else if(num==2) { System.out.println("Your number is 2, which is the only even prime number in existence. Cool, right?"); } for(int i=3;i*i<=n;i+=2) { if(n%1==0) { System.out.println("Your number isn't prime."); } } else { System.out.println("Your number is prime!"); } } } if(yn.equals.IgnoreCase("No")) { System.out.println("Okay."); } } } If anyone could help me out with this and also any problems I may have made elsewhere in the program, I'd be very grateful! Thanks.

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  • Boost MultiIndex - objects or pointers (and how to use them?)?

    - by Sarah
    I'm programming an agent-based simulation and have decided that Boost's MultiIndex is probably the most efficient container for my agents. I'm not a professional programmer, and my background is very spotty. I've two questions: Is it better to have the container contain the agents (of class Host) themselves, or is it more efficient for the container to hold Host *? Hosts will sometimes be deleted from memory (that's my plan, anyway... need to read up on new and delete). Hosts' private variables will get updated occasionally, which I hope to do through the modify function in MultiIndex. There will be no other copies of Hosts in the simulation, i.e., they will not be used in any other containers. If I use pointers to Hosts, how do I set up the key extraction properly? My code below doesn't compile. // main.cpp - ATTEMPTED POINTER VERSION ... #include <boost/multi_index_container.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/mem_fun.hpp> #include <boost/tokenizer.hpp> typedef multi_index_container< Host *, indexed_by< // hash by Host::id hashed_unique< BOOST_MULTI_INDEX_MEM_FUN(Host,int,Host::getID) > // arg errors here > // end indexed_by > HostContainer; ... int main() { ... HostContainer testHosts; Host * newHostPtr; newHostPtr = new Host( t, DOB, idCtr, 0, currentEvents ); testHosts.insert( newHostPtr ); ... } I can't find a precisely analogous example in the Boost documentation, and my knowledge of C++ syntax is still very weak. The code does appear to work when I replace all the pointer references with the class objects themselves. As best I can read it, the Boost documentation (see summary table at bottom) implies I should be able to use member functions with pointer elements.

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  • How can I scale movement physics functions to frames per second (in a game engine)?

    - by Richard
    I am working on a game in Javascript (HTML5 Canvas). I implemented a simple algorithm that allows an object to follow another object with basic physics mixed in (a force vector to drive the object in the right direction, and the velocity stacks momentum, but is slowed by a constant drag force). At the moment, I set it up as a rectangle following the mouse (x, y) coordinates. Here's the code: // rectangle x, y position var x = 400; // starting x position var y = 250; // starting y position var FPS = 60; // frames per second of the screen // physics variables: var velX = 0; // initial velocity at 0 (not moving) var velY = 0; // not moving var drag = 0.92; // drag force reduces velocity by 8% per frame var force = 0.35; // overall force applied to move the rectangle var angle = 0; // angle in which to move // called every frame (at 60 frames per second): function update(){ // calculate distance between mouse and rectangle var dx = mouseX - x; var dy = mouseY - y; // calculate angle between mouse and rectangle var angle = Math.atan(dy/dx); if(dx < 0) angle += Math.PI; else if(dy < 0) angle += 2*Math.PI; // calculate the force (on or off, depending on user input) var curForce; if(keys[32]) // SPACE bar curForce = force; // if pressed, use 0.35 as force else curForce = 0; // otherwise, force is 0 // increment velocty by the force, and scaled by drag for x and y velX += curForce * Math.cos(angle); velX *= drag; velY += curForce * Math.sin(angle); velY *= drag; // update x and y by their velocities x += velX; y += velY; And that works fine at 60 frames per second. Now, the tricky part: my question is, if I change this to a different framerate (say, 30 FPS), how can I modify the force and drag values to keep the movement constant? That is, right now my rectangle (whose position is dictated by the x and y variables) moves at a maximum speed of about 4 pixels per second, and accelerates to its max speed in about 1 second. BUT, if I change the framerate, it moves slower (e.g. 30 FPS accelerates to only 2 pixels per frame). So, how can I create an equation that takes FPS (frames per second) as input, and spits out correct "drag" and "force" values that will behave the same way in real time? I know it's a heavy question, but perhaps somebody with game design experience, or knowledge of programming physics can help. Thank you for your efforts. jsFiddle: http://jsfiddle.net/BadDB

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  • How to use Bonjour?

    - by Roman
    First, what exactly Bonjour does (pleas read my guesses written bellow)? Here I found out that Bonjour enables automatic discovery of computers, devices, and services on IP networks. But I thought that it not only "discovers devices on IP network" it also creates an IP network by assigning IP addresses to devices where Bonjour is running. Am I right? And I still miss the essence. Does it work in the following way? First I connect devices (for example laptops) physically so that they potentially can communicate with each other. Then, let say, on some laptops I have Bonjour running and then, as a consequence, these laptops assign IP addresses to them self in automatic way. So, laptops (where Bonjour is running) build an IP network. Does it work in this way? Or may be a computer running Bonjour is not considered as a service and it does not broadcast itself just because Bonjour is running on this computer. I mean that the applications running on the computers need to use Bonjour to broadcast themself. So, it is applications that broadcast themself (not computers) and it is not done automatically (application needs to broadcast themself explicitly). Is it right? How exactly my application can broadcast itself? Can I use command line to register an service (so that all applications using Bonjour knows that a new service appeared)? Further, I would like to have an application which use the IP network created by Bonjour. For that my application needs to know which devices/services are present in the network. In more details, my application needs to have a list of services. Each service in the list should have a name, the IP address where it is running and the port which is used by the application. Can Bonjour provide this information in some way? If it is the case, how exactly it works. How my program can get this information from Bonjour? Can my program read some file created by Bonjour and containing the above mentioned information? Can I use some commands in command line to retrieve this information? I have a special interest in accessing the information about services from files, environment variables or commands in command line. These options seems to me to be the simplest! Since in these case I do not need to use any additional libraries to communicate with Bonjour from a particular programming language. P.S. Pleas ask questions if something is not clear in my question. I will try to formulate my question in a more clear way. P.P.S. I use Windows 7. ADDED: I plan to write my applications in PHP. Every computer should run a Apache web server. And I want to use Bonjour to help computer discover each other (computers are working in a local network).

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  • shell script over SSH ends unexpectedly after running 'ant build'

    - by YShin
    I wrote a shell script that runs on remote host to build source code with 'ant build' command, and then distribute the built binary to other servers. However, right after Ant build is over successfully(I can see the command line output saying Build was successful), the ssh session ends and whatever commands after 'ant build' does not get executed. I'm confused what might be cause of this behavior. I suspected that it might be because the 'ant build' command takes too long time, and SSH somehow quits itself after that long command. But I don't think that's correct since if I just do 'sleep 60' in place of 'ant build' command, it actually execute latter commands as intended. I'm new at shell programming, so I might have made some silly misassumption. Can someone provide a pointer to a possible cause of this problem? My shell script #!/bin/bash # Inject some variables ssh -T $SSH_USER@$SSH_URL "setenv REMOTE_BASE_DIR $REMOTE_BASE_DIR; setenv CASSANDRA_SRC_TAR_FILE $CASSANDRA_SRC_TAR_FILE; setenv CASSANDRA_SRC_DIR_NAME $CASSANDRA_SRC_DIR_NAME; setenv CLUSTER_SIZE $CLUSTER_SIZE; setenv REMOTE_REDEPLOY_SCRIPT $REMOTE_REDEPLOY_SCRIPT; /bin/bash" << 'EOF' export JAVA_HOME=/usr/lib/jvm/jdk1.7.0 cd $REMOTE_BASE_DIR/$CASSANDRA_SRC_DIR_NAME echo "## Building Cassandra source" ant clean build # Anything after this doesn't run echo "## Ant Build is over. Invoking redeploy script on remote nodes" # Invoke redeploy script for each node for (( i=0; i < CLUSTER_SIZE; i++)) do echo "## Invoking redeploy script on node-$i" done Command-line output ## Building Cassandra source Buildfile: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build.xml clean: [delete] Deleting directory /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/test [delete] Deleting directory /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/classes [delete] Deleting directory /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/gen-java [delete] Deleting directory /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/resources/org/apache/cassandra/config init: [mkdir] Created dir: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/classes/main [mkdir] Created dir: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/classes/thrift [mkdir] Created dir: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/test/lib [mkdir] Created dir: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/test/classes [mkdir] Created dir: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/gen-java maven-ant-tasks-localrepo: maven-ant-tasks-download: maven-ant-tasks-init: maven-declare-dependencies: maven-ant-tasks-retrieve-build: init-dependencies: [echo] Loading dependency paths from file: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/build-dependencies.xml check-gen-cli-grammar: gen-cli-grammar: [echo] Building Grammar /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/java/org/apache/cassandra/cli/Cli.g .... check-gen-cql2-grammar: gen-cql2-grammar: [echo] Building Grammar /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/java/org/apache/cassandra/cql/Cql.g ... check-gen-cql3-grammar: gen-cql3-grammar: [echo] Building Grammar /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/java/org/apache/cassandra/cql3/Cql.g ... build-project: [echo] apache-cassandra: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build.xml [javac] Compiling 43 source files to /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/classes/thrift [javac] Note: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/interface/thrift/gen-java/org/apache/cassandra/thrift/Cassandra.java uses or overrides a deprecated API. [javac] Note: Recompile with -Xlint:deprecation for details. [javac] Note: Some input files use unchecked or unsafe operations. [javac] Note: Recompile with -Xlint:unchecked for details. [javac] Compiling 865 source files to /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/classes/main [javac] Note: Some input files use or override a deprecated API. [javac] Note: Recompile with -Xlint:deprecation for details. [javac] Note: Some input files use unchecked or unsafe operations. [javac] Note: Recompile with -Xlint:unchecked for details. createVersionPropFile: [mkdir] Created dir: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/resources/org/apache/cassandra/config [propertyfile] Creating new property file: /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/src/resources/org/apache/cassandra/config/version.properties [copy] Copying 3 files to /scratch/ISS/shin14/repos/apache-cassandra-2.0.8-src-0713/build/classes/main build: BUILD SUCCESSFUL Total time: 32 seconds

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  • Scenarios for Bazaar and SVN interaction

    - by Adam Badura
    At our company we are using SVN repository. I'm doing programming from both work (main place) and home (mostly experiments and refactoring). Those are two different machines, in different networks and almost never turned on at the same time (after all I'm either at work or at home...) I wanted to give a chance to some distributed version control system and solve some of the issues associated with SVN based process and having two machines. From git, Mercurial and Bazaar I chose to start with Bazaar since it claims that it is designed do be used by human beings. Its my first time with distributed system and having nice and easy user interface was important for me. Features I wanted to achieve were: Being able to update from SVN repository and commit to it. Being able to commit locally steps of my work on a task. Being able to have few separate tasks at the same time in their own local branches. Being able to share those branches between my work and home computer. As a means of transport between work and home computer I wanted to use a pen-drive. Company server will not work since I may not instal there anything. Neither will work a web service repository as I may not upload source code to web (especially if it would be public which seems to be a common case in free web services). This transport should be Bazaar-based (or what ever else I will end with) so it can be done more or less automatically but manual copying and pasting some folders or generating patch files (providing they would work - I have bad experience with patch files in SVN) would work as well if there is no better solution. Yet the pen-drive should only be used for transportation. I do not want to edit or build there. I tried following Bazaar guidelines for integration with SVN. But I failed. I tried both bzr svn-import and bzr checkout providing URL from my repository as both https://... and svn+https://.... In some cases it had some issues with certificates but the output specified argument to ignore them so I did that. Sometimes it asked me to log in (in other cases maybe it remembered... I don't know) which I did. All were running very slow (this could be our server issue) and at some point were interrupted due to connection interruption (this almost for sure is our server issue: it truncates the connection after some time). But since (as opposed to SVN) restarting starts a new rather than from point where it was interrupted I was unable to reach all the ~19000 revisions (ending usually somewhere around 150). What and how should I do with Bazaar? Is is possible to somehow import SVN repository from the local checkout (so that I do not suffer the connection truncation)? I was told that a colleague that used to work with us has done something similar (importing SVN repository with full history) with Mercurial like in no time. So I'm seriously considering now trying Mercurial even if only to see if that will work. But also what are your general guidelines to achieve the listed features?

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  • How to troubleshoot a PHP script that causes a Segmenation Fault?

    - by johnlai2004
    I posted this on stackoverflow.com as well because I'm not sure if this is a programming problem or a server problem. I'm using ubuntu 9.10, apache2, mysql5 and php5. I've noticed an unusual problem with some of my php programs. Sometimes when visiting a page like profile.edit.php, the browser throws a dialogue box asking to download profile.edit.php page. When I download it, there's nothing in the file. profile.edit.php is supposed to be a web form that edits user information. I've noticed this on some of my other php pages as well. I look in my apache error logs, and I see a segmentation fault message: [Mon Mar 08 15:40:10 2010] [notice] child pid 480 exit signal Segmentation fault (11) And also, the issue may or may not appear depending on which server I deploy my application too. Additonal Details This doesn't happen all the time though. It only happens sometimes. For example, profile.edit.php will load properly. But as soon as I hit the save button (form action="profile.edit.php?save=true"), then the page asks me to download profile.edit.php. Could it be that sometimes my php scripts consume too much resources? Sample code Upon save action, my profile.edit.php includes a data_access_object.php file. I traced the code in data_access_object.php to this line here if($params[$this->primaryKey]) { $q = "UPDATE $this->tableName SET ".implode(', ', $fields)." WHERE ".$this->primaryKey." = ?$this->primaryKey"; $this->bind($this->primaryKey, $params[$this->primaryKey], $this->tblFields[$this->primaryKey]['mysqlitype']); } else { $q = "INSERT $this->tableName SET ".implode(', ', $fields); } // Code executes perfectly up to this point // echo 'print this'; exit; // if i uncomment this line, profile.edit.php will actually show 'print this'. If I leave it commented, the browser will ask me to download profile.edit.php if(!$this->execute($q)){ $this->errorSave = -3; return false;} // When I jumped into the function execute(), every line executed as expected, right up to the return statement. And if it helps, here's the function execute($sql) in data_access_object.php function execute($sql) { // find all list types and explode them // eg. turn ?listId into ?listId0,?listId1,?listId2 $arrListParam = array_bubble_up('arrayName', $this->arrBind); foreach($arrListParam as $listName) if($listName) { $explodeParam = array(); $arrList = $this->arrBind[$listName]['value']; foreach($arrList as $key=>$val) { $newParamName = $listName.$key; $this->bind($newParamName,$val,$this->arrBind[$listName]['type']); $explodeParam[] = '?'.$newParamName; } $sql = str_replace("?$listName", implode(',',$explodeParam), $sql); } // replace all ?varName with ? for syntax compliance $sqlParsed = preg_replace('/\?[\w\d_\.]+/', '?', $sql); $this->stmt->prepare($sqlParsed); // grab all the parameters from the sql to create bind conditions preg_match_all('/\?[\w\d_\.]+/', $sql, $matches); $matches = $matches[0]; // store bind conditions $types = ''; $params = array(); foreach($matches as $paramName) { $types .= $this->arrBind[str_replace('?', '', $paramName)]['type']; $params[] = $this->arrBind[str_replace('?', '', $paramName)]['value']; } $input = array('types'=>$types) + $params; // bind it if(!empty($types)) call_user_func_array(array($this->stmt, 'bind_param'), $input); $stat = $this->stmt->execute(); if($GLOBALS['DEBUG_SQL']) echo '<p style="font-weight:bold;">SQL error after execution:</p> ' . $this->stmt->error.'<p>&nbsp;</p>'; $this->arrBind = array(); return $stat; }

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  • php-fpm + persistent sockets = 502 bad gateway

    - by leeoniya
    Put on your reading glasses - this will be a long-ish one. First, what I'm doing. I'm building a web-app interface for some particularly slow tcp devices. Opening a socket to them takes 200ms and an fwrite/fread cycle takes another 300ms. To reduce the need for both of these actions on each request, I'm opening a persistent tcp socket which reduces the response time by the aforementioned 200ms. I was hoping PHP-FPM would share the persistent connections between requests from different clients (and indeed it does!), but there are some issues which I havent been able to resolve after 2 days of interneting, reading logs and modifying settings. I have somewhat narrowed it down though. Setup: Ubuntu 13.04 x64 Server (fully updated) on Linode PHP 5.5.0-6~raring+1 (fpm-fcgi) nginx/1.5.2 Relevent config: nginx worker_processes 4; php-fpm/pool.d pm = dynamic pm.max_children = 2 pm.start_servers = 2 pm.min_spare_servers = 2 Let's go from coarse to fine detail of what happens. After a fresh start I have 4x nginx processes and 2x php5-fpm processes waiting to handle requests. Then I send requests every couple seconds to the script. The first take a while to open the socket connection and returns with the data in about 500ms, the second returns data in 300ms (yay it's re-using the socket), the third also succeeds in about 300ms, the fourth request = 502 Bad Gateway, same with the 5th. Sixth request once again returns data, except now it took 500ms again. The process repeats for several cycles after which every 4 requests result in 2x 502 Bad Gateways and 2x 500ms Data responses. If I double all the fpm pool values and have 4x php-fpm processes running, the cycles settles in with 4x successful 500ms responses followed by 4x Bad Gateway errors. If I don't use persistent sockets, this issue goes away but then every request is 500ms. What I suspect is happening is the persistent socket keeps each php-fpm process from idling and ties it up, so the next one gets chosen until none are left and as they error out, maybe they are restarted and become available on the next round-robin loop ut the socket dies with the process. I haven't yet checked the 'slowlog', but the nginx error log shows lots of this: *188 recv() failed (104: Connection reset by peer) while reading response header from upstream, client:... All the suggestions on the internet regarding fixing nginx/php-fpm/502 bad gateway relate to high load or fcgi_pass misconfiguration. This is not the case here. Increasing buffers/sizes, changing timeouts, switching from unix socket to tcp socket for fcgi_pass, upping connection limits on the system....none of this stuff applies here. I've had some other success with setting pm = ondemand rather than dynamic, but as soon as the initial fpm-process gets killed off after idling, the persistent socket is gone for all subsequent php-fpm spawns. For the php script, I'm using stream_socket_client() with a STREAM_CLIENT_PERSISTENT flag. A while/stream_select() loop to detect socket data and fread($sock, 4096) to grab the data. I don't call fclose() obviously. If anyone has some additional questions or advice on how to get a persistent socket without tying up the php-fpm processes beyond the request completion, or maybe some other things to try, I'd appreciate it. some useful links: Nginx + php-fpm - recv() error Nginx + php-fpm "504 Gateway Time-out" error with almost zero load (on a test-server) Nginx + PHP-FPM "error 104 Connection reset by peer" causes occasional duplicate posts http://www.linuxquestions.org/questions/programming-9/php-pfsockopen-552084/ http://stackoverflow.com/questions/14268018/concurrent-use-of-a-persistent-php-socket http://devzone.zend.com/303/extension-writing-part-i-introduction-to-php-and-zend/#Heading3 http://stackoverflow.com/questions/242316/how-to-keep-a-php-stream-socket-alive http://php.net/manual/en/install.fpm.configuration.php https://www.google.com/search?q=recv%28%29+failed+%28104:+Connection+reset+by+peer%29+while+reading+response+header+from+upstream+%22502%22&ei=mC1XUrm7F4WQyAHbv4H4AQ&start=10&sa=N&biw=1920&bih=953&dpr=1

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