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  • Wierdness debugging Visual Studio C++ 2008

    - by Jeff Dege
    I have a legacy C++ app, that in its most incarnation we've been building with makefiles and VS2003's command-line tool. I'm trying to get it to build using VS2008 and MsBuild. The build is working OK, but I'm getting errors where I'd never seen errors, before, and stepping through in VS2008's debugger only confuses me. The app links a number of static libraries, which fall into two categories: those that are part of the same application suite, and those that are shared between a number of application suites. Originally, I had a .csproj file for each static library, and two .sln files, one for the application suite (including the suite-specific libraries) and one for the non-suite-specific shared libraries. The shared libraries were included in the link, their projects were not included in the application suite .sln. The application instantiates an object from a class that is defined in one of the shared libraries. The class has a member object of a class that wraps a linked list. The constructor of the linked list class sets its "head" pointer to null. When I run the app, and try to add an element to the linked list, I get an error - the head pointer contains the value 0xCCCCCCCC. So I step through with the debugger. And see weirdness. When the current line in the debugger is in a source file belonging to the static library, the head pointer contains 0x00000000. When I step into the constructor, I can see the pointer being set to that value, and when I'm stepped into any other method of the class, I can see that the head pointer still contains 0x00000000. But when I step out into methods that are defined in the application suite .sln, it contains 0xCCCCCCCC. It's not like it's being overwritten. It changes back and forth depending upon which source file I am currently debugging. So I included the shared library's project in the application suite .sln, and now I see the head pointer containing 0xCCCCCCCC all the time. It looks like the constructor of the linked list class is not being called. So now, I'm entirely confused. Anyone have any ideas?

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  • Make: how make all hidden files in the current makefile?

    - by HH
    It traverses to bottom dirs for some unknown reason: Errorsome /bin/sh: .??*: not found make[23]: Entering directory `/m/user/files/dir' make clean Makefile all: make clean #The wildcard is the bug. I want to make all hidden files in the current makefile. #It should match .<some char><some char><any char arbitrary times> make $$(.??*) #I want to replace below-like-tihngs with a wildcard above # make .lambda # make .lambda_t clean: -rm .??* .lambda: #do something .lambda_t:

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  • C++ string sort like a human being?

    - by Walter Nissen
    I would like to sort alphanumeric strings the way a human being would sort them. I.e., "A2" comes before "A10", and "a" certainly comes before "Z"! Is there any way to do with without writing a mini-parser? Ideally it would also put "A1B1" before "A1B10". I see the question "Natural (human alpha-numeric) sort in Microsoft SQL 2005" with a possible answer, but it uses various library functions, as does "Sorting Strings for Humans with IComparer". Below is a test case that currently fails: #include <set> #include <iterator> #include <iostream> #include <vector> #include <cassert> template <typename T> struct LexicographicSort { inline bool operator() (const T& lhs, const T& rhs) const{ std::ostringstream s1,s2; s1 << toLower(lhs); s2 << toLower(rhs); bool less = s1.str() < s2.str(); std::cout<<s1.str()<<" "<<s2.str()<<" "<<less<<"\n"; return less; } inline std::string toLower(const std::string& str) const { std::string newString(""); for (std::string::const_iterator charIt = str.begin(); charIt!=str.end();++charIt) { newString.push_back(std::tolower(*charIt)); } return newString; } }; int main(void) { const std::string reference[5] = {"ab","B","c1","c2","c10"}; std::vector<std::string> referenceStrings(&(reference[0]), &(reference[5])); //Insert in reverse order so we know they get sorted std::set<std::string,LexicographicSort<std::string> > strings(referenceStrings.rbegin(), referenceStrings.rend()); std::cout<<"Items:\n"; std::copy(strings.begin(), strings.end(), std::ostream_iterator<std::string>(std::cout, "\n")); std::vector<std::string> sortedStrings(strings.begin(), strings.end()); assert(sortedStrings == referenceStrings); }

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  • Confusion in MIPS code

    - by Haya Hallian
    While going through the MIPS code I got some confusion. Code is shown as follows .data key: .ascii "key: " # "key: \n" char: .asciiz " \n" .text .globl main main: jal getchar la $a0, char # $a0 contains address of char variable (" \n") sb $v0, ($a0) # replace " " in char with v0, which is read_character (X) la $a0, key # now a0 will contain, address of "key: " "X\n" What I dont understand is that how load address instruction works. First a0 contained address of char variable. In next line we are storing value of v0 in that location. there is no offset with ($a0), is that assumed to be 0 like in 0($a0)? Why only the " " empty space is replaced with v0, and why not the "\n" get replaced? or It may also have been the case that both the empty space and \n character get replced by v0. Secondly when we load the address of key in a0, the previous address should be overwritten. a0 should have contained the address of key only, but from comment it seems that the two strings are concatenated. How does that happen.

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  • How to get proper alignment when printing to file

    - by user1067334
    I have this Structure the elements of which that I need to write in a text file struct Stage3ADisplay { int nSlot; char *Item; char *Type; int nIndex; unsigned char attributesMD[17]; //the last character is \0 unsigned char contentsMD[17]; //only for regular files - //the last character is \0 }; buffer = malloc(sizeof(Stage3ADisplayVar[nIterator]->nSlot) + sizeof(Stage3ADisplayVar[nIterator]->Item) + sizeof(Stage3ADisplayVar[nIterator]->Type) + sizeof(Stage3ADisplayVar[nIterator]->nIndex) + sizeof(Stage3ADisplayVar[nIterator]->attributesMD) + sizeof(Stage3ADisplayVar[nIterator]->contentsMD) + 1); sprintf (buffer,"%d %s %s %d %x %x",Stage3ADisplayVar[nIterator]->nSlot, Stage3ADisplayVar[nIterator]->Item,Stage3ADisplayVar[nIterator]->Type,Stage3ADisplayVar[nIterator]->nIndex,Stage3ADisplayVar[nIterator]->attributesMD,Stage3ADisplayVar[nIterator]->contentsMD); How do I make sure the rows in the file are properly aligned. Thank you.

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  • C++ memory management of reference types

    - by Russel
    Hello, I'm still a fairly novice programmer and I have a question about c++ memory management with refence types. First of all, my understanding of reference types: A pointer is put on the stack and the actual data that the pointer points to is created and placed on the heap. Standard arrays and user defined classes are refence types. Is this correct? Second, my main question is do c and c++'s memory management mechanisms (malloc, free and new, delete) always handle this properly and free the memory that a class or array is pointing to? Does everything still work if those pointers get reassigned somehow to other objects of the same size/type on the heap? What if a class has a pointer member that points to another object? I am assuming that delete/freeing the class object doesn't free what it's member pointer points to, is that correct? Thanks all! -R

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  • shop by brand name in magento

    - by Jyotiranjan
    This is brand.php file having directory local/Vilpjsc/brand/Block.I want the brand name with logo(image) sholud display on home page .But I am getting the error i.e Fatal error: Call to a member function getCollection() on a non-object in /var/www/magentodemo/app/code/local/Vilpjsc/Brand/Block/Brand.php on line 25 <?php class Vilpjsc_Brand_Block_Brand extends Mage_Core_Block_Template { public function _prepareLayout() { return parent::_prepareLayout(); } //Get Collection from Brand Controller public function getBrand() { if (!$this->hasData('brand')) { $this->setData('brand', Mage::registry('brand')); } return $this->getData('brand'); } //Get Brand Featured Collection public function getFeaturedBrand() { return $this->getBrand()->getCollection()->setPageSize(12)->addFilter('status', '1'); } public function resizeImage($img,$width=100, $height=60) { if (!file_exists("./media/brand/resized")) mkdir("./media/brand/resized", 0777); $imageResized = Mage::getBaseDir('media') . DS . "brand" . DS . "resized" . DS . $width."x".$height.$img; if (!file_exists($imageResized) && file_exists("./media/brand/" . $img)) { $imageObj = new Varien_Image("./media/brand/" . $img); $imageObj->constrainOnly(TRUE); $imageObj->keepAspectRatio(TRUE); $imageObj->keepFrame(FALSE); $imageObj->resize($width, $height); $imageObj->save($imageResized); } $newImageUrl = Mage::getBaseUrl('media')."brand/resized/".$width."x".$height.$img; return $newImageUrl; } public function getNormalBrand() { return $this->getBrand()->getCollection()->addFilter('status', '0'); } public function getBrandChar() { extract($this->getBrandKey()); return $this->getBrand()->getCollection()->saveBrandcollection($char); } //Create Alphabet navigation public function navigation() { extract($this->getBrandKey()); $alphas = range('A', 'Z'); $navigation = ""; $digitClass = ""; foreach ($alphas as $key) { if ($char == $key) $class_key = "current_char"; else $class_key=""; $navigation .= "<li class='key_item " . $class_key . "'><a href='" . Mage::getBaseUrl() . "brand/index/index/brand_key/" . $key . "'>" . $key . "</a></li>"; } if ($char == "digit") { $digitClass = "current_char"; } elseif ($char == "all") $allClass = "current_char"; $navigation = "<li class='key_item " . $digitClass . "'><a href='" . Mage::getBaseUrl() . "brand/index/index/brand_key/digit'>#</a></li>" . $navigation; return $navigation; } //Get request for brand block public function getBrandKey() { $brand_key = Mage::registry('brand_key'); if ($brand_key) { $char = $brand_key->getParam('brand_key') ? $brand_key->getParam('brand_key') : 'A'; $option_id = $brand_key->getParam('option_id') ? $brand_key->getParam('option_id') : '1'; $brand = $brand_key->getParam('brand') ? $brand_key->getParam('brand') : 'Nike'; } else { $char = 'digit'; $option_id = '544'; } return compact('char', 'option_id', 'brand'); } }

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  • sending input parameters to another function

    - by Pegah
    Hi everybody, I need to send the list of the input arguments to readInput function. But the compiler gives error when I call readInput function. Could you please tell me where my mistake is? bool readInput(netcorr net,int argc, char * argv[]); int main(int argc, char * const argv[]) { netcorr net; bool error=readInput(net, argc, argv); } bool readInput(netcorr &net,int argc, char * argv[]) { } thanks for your help. Pegah

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  • Strange thing on IPv6 multicast program on Windows

    - by zhanglistar
    I have written an ipv6 multicast program on windows xp sp3. But a problem bothers me a lot. The sendto function implies no error, but I can't capture the packet using wireshark. I am sure the filter is right. Thanks in advance. And the code is as follows: #include "stdafx.h" #include <stdio.h> /* for printf() and fprintf() */ #include <winsock2.h> /* for socket(), connect(), sendto(), and recvfrom() */ #include <ws2tcpip.h> /* for ip_mreq */ #include <stdlib.h> /* for atoi() and exit() */ #include <string.h> /* for memset() */ #include <time.h> /* for timestamps */ #include <pcap.h> #include <Iphlpapi.h> #pragma comment(lib, "Ws2_32.lib") #pragma comment(lib, "wpcap.lib") #pragma comment(lib, "Iphlpapi.lib") int _tmain(int argc, _TCHAR* argv[]) { int sfd; int on, length, iResult; WSADATA wsaData; struct addrinfo Hints; struct addrinfo *multicastAddr, *localAddr; char buf[46]; // Initialize Winsock iResult = WSAStartup(MAKEWORD(2, 2), &wsaData); if (iResult != 0) { printf("WSAStartup failed: %d\n", iResult); return 1; } /* Resolve destination address for multicast datagrams */ memset(&Hints, 0, sizeof (Hints)); Hints.ai_family = AF_INET6; Hints.ai_socktype = SOCK_DGRAM; Hints.ai_protocol = IPPROTO_UDP; Hints.ai_flags = AI_NUMERICHOST; iResult = getaddrinfo("FF02::1:2", "547", &Hints, &multicastAddr); if (iResult != 0) { /* error handling */ printf("socket error: %d\n", WSAGetLastError()); return -1; } /* Get a local address with the same family (IPv4 or IPv6) as our multicast group */ Hints.ai_family = multicastAddr->ai_family; Hints.ai_socktype = SOCK_DGRAM; Hints.ai_flags = AI_PASSIVE; /* Return an address we can bind to */ if ( getaddrinfo(NULL, "546", &Hints, &localAddr) != 0 ) { printf("getaddrinfo() failed: %d\n", WSAGetLastError()); exit(-1); } // Create sending socket //sfd = socket (multicastAddr->ai_family, multicastAddr->ai_socktype, multicastAddr->ai_protocol); sfd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP); if (sfd == -1) { printf("socket error: %d\n", WSAGetLastError()); return 0; } /* Bind to the multicast port */ if ( bind(sfd, localAddr->ai_addr, localAddr->ai_addrlen) != 0 ) { printf("bind() failed: %d\n", WSAGetLastError()); exit(-1); } if (multicastAddr->ai_family == AF_INET6 && multicastAddr->ai_addrlen == sizeof(struct sockaddr_in6)) /* IPv6 */ { on = 1; if (setsockopt (sfd, IPPROTO_IPV6, IPV6_MULTICAST_IF, (char *)&on, sizeof (on) /*(char *)&interface_addr, sizeof(interface_addr)*/) == -1) { printf("setsockopt error:%d\n", WSAGetLastError()); return -1; } if (setsockopt (sfd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, (char *)&on, sizeof (on) /*(char *)&interface_addr, sizeof(interface_addr)*/) == -1) { printf("setsockopt error:%d\n", WSAGetLastError()); return -1; } struct ipv6_mreq multicastRequest; /* Multicast address join structure */ /* Specify the multicast group */ memcpy(&multicastRequest.ipv6mr_multiaddr, &((struct sockaddr_in6*)(multicastAddr->ai_addr))->sin6_addr, sizeof(struct in6_addr)); /* Accept multicast from any interface */ multicastRequest.ipv6mr_interface = 0; /* Join the multicast address */ if ( setsockopt(sfd, IPPROTO_IPV6, IPV6_JOIN_GROUP, (char*) &multicastRequest, sizeof(multicastRequest)) != 0 ) { printf("setsockopt() failed: %d\n", WSAGetLastError()); return -1; } on = 1; if (setsockopt (sfd, IPPROTO_IPV6, IPV6_MULTICAST_IF, (char *)&on, sizeof (on)) == -1) { printf("setsockopt error:%d\n", WSAGetLastError()); return 0; } } memset(buf, 0, sizeof(buf)); strcpy(buf, "hello world"); iResult = sendto(sfd, buf, strlen(buf), 0, (LPSOCKADDR) multicastAddr->ai_addr, multicastAddr->ai_addrlen); if (iResult == SOCKET_ERROR) { printf("setsockopt error:%d\n", WSAGetLastError()); return -1; /* Error handling */ } return 0; }

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  • C# to unmanaged dll data structures interop

    - by Shane Powell
    I have a unmanaged DLL that exposes a function that takes a pointer to a data structure. I have C# code that creates the data structure and calls the dll function without any problem. At the point of the function call to the dll the pointer is correct. My problem is that the DLL keeps the pointer to the structure and uses the data structure pointer at a later point in time. When the DLL comes to use the pointer it has become invalid (I assume the .net runtime has moved the memory somewhere else). What are the possible solutions to this problem? The possible solutions I can think of are: Fix the memory location of the data structure somehow? I don't know how you would do this in C# or even if you can. Allocate memory manually so that I have control over it e.g. using Marshal.AllocHGlobal Change the DLL function contract to copy the structure data (this is what I'm currently doing as a short term change, but I don't want to change the dll at all if I can help it as it's not my code to begin with). Are there any other better solutions?

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  • C++ Word-Number to int

    - by Andrew
    I'm developing a program that makes basic calculations using words instead of numbers. E.g. five + two would output seven. The program becomes more complex, taking input such as two_hundred_one + five_thousand_six (201 + 5006) Through operator overloading methods, I split each number and assign it to it's own array index. two would be [0], hundred is [1], and one is [2]. Then the array recycles for 5006. My problem is, to perform the actual calculation, I need to convert the words stored in the array to actual integers. I have const string arrays such as this as a library of the words: const string units[] = { "", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" }; const string teens[] = { "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" }; const string tens[] = { "", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" }; If my 'token' array has stored in it two hundred one in index 0, 1, and 2, I'm not sure what the best way to convert these to ints would involve.

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  • Type for use in template object to compare double values

    - by DaClown
    I got this n-dimensional point object: template <class T, unsigned int dimension> class Obj { protected: T coords[dimension]; static const unsigned int size = dimension; public: Obj() { }; Obj(T def) { for (unsigned int i = 0; i < size; ++i) coords[i]=def; }; Obj(const Obj& o) { for (unsigned int i = 0; i < size; ++i) coords[i] = o.coords[i]; } const Obj& operator= (const Obj& rhs) { if (this != &rhs) for (unsigned int i = 0; i < size; ++i) coords[i] = rhs.coords[i]; return *this; } virtual ~Obj() { }; T get (unsigned int id) { if (id >= size) throw std::out_of_range("out of range"); return coords[id]; } void set (unsigned int id, T t) { if (id >= size) throw std::out_of_range("out of range"); coords[id] = t; } }; and a 3D point class which uses Obj as base class: template <class U> class Point3DBase : public Obj<U,3> { typedef U type; public: U &x, &y, &z; public: Point3DBase() : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { }; Point3DBase(U def) : Obj<U,3>(def), x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { }; Point3DBase(U x_, U y_, U z_) : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { x = x_; y = y_; z= z_; }; Point3DBase(const Point3DBase& other) : x(Obj<U,3>::coords[0]), y(Obj<U,3>::coords[1]), z(Obj<U,3>::coords[2]) { x = other.x; y = other.y; z = other.z; } // several operators ... }; The operators, basically the ones for comparison, use the simple compare-the-member-object approach like: virtual friend bool operator== (const Point3DBase<U> &lhs, const Point3DBase<U> rhs) { return (lhs.x == rhs.x && lhs.y == rhs.y && lhs.z == rhs.z); } Then it occured to me that for the comparion of double values the simply equality approach is not very useful since double values should be compared with an error margin. What would be the best approach to introduce an error margin into the point? I thought about an epsDouble type as template parameter but I can't figure out how to achieve this.

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  • Argc/Argv C Problems

    - by Salman
    Hey all, If I have the following code: main(int argc, char *argv[]){ char serveradd[20]; strcpy(serveradd, argv[1]); int port = atoi(argv[2]); printf("%s %d \n", serveradd, port); The first two arguments to the command line are printed. However, if I do this: char serveradd[20]; strcpy(serveradd, argv[1]); int port = atoi(argv[2]); char versionnum[1]; strcpy(versionnum, argv[3]); printf("%s %d %s \n", serveradd, port, versionnum);` The first argument (serveradd) does not print out to the screen and is not being stored... Why is this happening and how can I fix it? Thanks!

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  • Returning and printing string array index in C

    - by user1781966
    I've got a function that searches through a list of names and I'm trying to get the search function to return the index of the array back to the main function and print out the starting location of the name found. Everything I've tried up to this point either crashes the program or results in strange output. Here is my search function: #include<stdio.h> #include<conio.h> #include<string.h> #define MAX_NAMELENGTH 10 #define MAX_NAMES 5 void initialize(char names[MAX_NAMES][MAX_NAMELENGTH], int Number_entrys, int i); int search(char names[MAX_NAMES][MAX_NAMELENGTH], int Number_entrys); int main() { char names[MAX_NAMES][MAX_NAMELENGTH]; int i, Number_entrys,search_result,x; printf("How many names would you like to enter to the list?\n"); scanf("%d",&Number_entrys); initialize(names,Number_entrys,i); search_result= search(names,Number_entrys); if (search_result==-1){ printf("Found no names.\n"); }else { printf("%s",search_result); } getch(); return 0; } void initialize(char names[MAX_NAMES][MAX_NAMELENGTH],int Number_entrys,int i) { if(Number_entrys>MAX_NAMES){ printf("Please choose a smaller entry\n"); }else{ for (i=0; i<Number_entrys;i++){ scanf("%s",names[i]); } } } int search(char names[MAX_NAMES][MAX_NAMELENGTH],int Number_entrys) { int x; char new_name[MAX_NAMELENGTH]; printf("Now enter a name in which you would like to search the list for\n"); scanf("%s",new_name); for(x = 0; x < Number_entrys; x++) { if ( strcmp( new_name, names[x] ) == 0 ) { return x; } } return -1; } Like I mentioned before I have tried a lot of different ways to try and fix this issue, but I cant seem to get them to work. Printing X like what I have above is just the last thing I tried, and therefor know that it doesn't work. Any suggestions on the simplest way to do this?

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  • Gtk, whether destroying GtkBuilder destroies all the screens and widgets?

    - by PP
    Hi, Question regarding GtkBuilder. When we unref builder pointer does it destroys all the screens/widgets the builder had created? if( builder_ptr ) g_object_unref(G_OBJECT(builder_ptr)); Suppose we have created one screen using Glade/XML with some 2-3 top_level windows in it gtk_builder_add_from_file(builder_ptr, "Test.glade", &error ) and generated GtkBuilder pointer (as above) so after deleting this pointer does it deletes created Windows or do we need to manually delete these windows? Thanks, PP.

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  • Reading data from text file in C

    - by themake
    I have a text file which contains words separated by space. I want to take each word from the file and store it. So i have opened the file but am unsure how to assign the word to a char. FILE *fp; fp = fopen("file.txt", "r"); //then i want char one = the first word in the file char two = the second word in the file

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  • Linked lists in Java - help with assignment

    - by user368241
    Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (I will add methods gradually according to my specific questions) (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations. Here is my try to write the method indexOf (int ch). Kindly assist me with fixing the bugs so I can move on. public int indexOf (int ch) { int count = 0; charNode pose = _head; if (pose == null ) { return -1; } for (pose = _head; pose!=null && pose.getNext()!='ch'; pose = pose.getNext()) { count++; } if (pose!=null) return count; else return -1; }

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  • optimize output value using a class and public member

    - by wiso
    Suppose you have a function, and you call it a lot of times, every time the function return a big object. I've optimized the problem using a functor that return void, and store the returning value in a public member: #include <vector> const int N = 100; std::vector<double> fun(const std::vector<double> & v, const int n) { std::vector<double> output = v; output[n] *= output[n]; return output; } class F { public: F() : output(N) {}; std::vector<double> output; void operator()(const std::vector<double> & v, const int n) { output = v; output[n] *= n; } }; int main() { std::vector<double> start(N,10.); std::vector<double> end(N); double a; // first solution for (unsigned long int i = 0; i != 10000000; ++i) a = fun(start, 2)[3]; // second solution F f; for (unsigned long int i = 0; i != 10000000; ++i) { f(start, 2); a = f.output[3]; } } Yes, I can use inline or optimize in an other way this problem, but here I want to stress on this problem: with the functor I declare and construct the output variable output only one time, using the function I do that every time it is called. The second solution is two time faster than the first with g++ -O1 or g++ -O2. What do you think about it, is it an ugly optimization?

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  • deep or shallow copying?

    - by Dervin Thunk
    Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value (deep copy) in C. For instance, passing a char to a function is usually cheaper in space than passing a char* (if there's no need to share the value), since char is 1 byte and pointers are, well, whatever they are in the architecture (4 in my 32 bit machine). ?(When) do you want to pass (big) deep copies to functions? if so, why?

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  • Useless variable name in C struct type definition

    - by user1210233
    I'm implementing a linked list in C. Here's a struct that I made, which represents the linked list: typedef struct llist { struct lnode* head; /* Head pointer either points to a node with data or NULL */ struct lnode* tail; /* Tail pointer either points to a node with data or NULL */ unsigned int size; /* Size of the linked list */ } list; Isn't the "llist" basically useless. When a client uses this library and makes a new linked list, he would have the following declaration: list myList; So typing llist just before the opening brace is practically useless, right? The following code basically does the same job: typedef struct { struct lnode* head; /* Head pointer either points to a node with data or NULL */ struct lnode* tail; /* Tail pointer either points to a node with data or NULL */ unsigned int size; /* Size of the linked list */ } list;

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  • Image/"most resembling pixel" search optimization?

    - by SigTerm
    The situation: Let's say I have an image A, say, 512x512 pixels, and image B, 5x5 or 7x7 pixels. Both images are 24bit rgb, and B have 1bit alpha mask (so each pixel is either completely transparent or completely solid). I need to find within image A a pixel which (with its' neighbors) most closely resembles image B, OR the pixel that probably most closely resembles image B. Resemblance is calculated as "distance" which is sum of "distances" between non-transparent B's pixels and A's pixels divided by number of non-transparent B's pixels. Here is a sample SDL code for explanation: struct Pixel{ unsigned char b, g, r, a; }; void fillPixel(int x, int y, SDL_Surface* dst, SDL_Surface* src, int dstMaskX, int dstMaskY){ Pixel& dstPix = *((Pixel*)((char*)(dst->pixels) + sizeof(Pixel)*x + dst->pitch*y)); int xMin = x + texWidth - searchWidth; int xMax = xMin + searchWidth*2; int yMin = y + texHeight - searchHeight; int yMax = yMin + searchHeight*2; int numFilled = 0; for (int curY = yMin; curY < yMax; curY++) for (int curX = xMin; curX < xMax; curX++){ Pixel& cur = *((Pixel*)((char*)(dst->pixels) + sizeof(Pixel)*(curX & texMaskX) + dst->pitch*(curY & texMaskY))); if (cur.a != 0) numFilled++; } if (numFilled == 0){ int srcX = rand() % src->w; int srcY = rand() % src->h; dstPix = *((Pixel*)((char*)(src->pixels) + sizeof(Pixel)*srcX + src->pitch*srcY)); dstPix.a = 0xFF; return; } int storedSrcX = rand() % src->w; int storedSrcY = rand() % src->h; float lastDifference = 3.40282347e+37F; //unsigned char mask = for (int srcY = searchHeight; srcY < (src->h - searchHeight); srcY++) for (int srcX = searchWidth; srcX < (src->w - searchWidth); srcX++){ float curDifference = 0; int numPixels = 0; for (int tmpY = -searchHeight; tmpY < searchHeight; tmpY++) for(int tmpX = -searchWidth; tmpX < searchWidth; tmpX++){ Pixel& tmpSrc = *((Pixel*)((char*)(src->pixels) + sizeof(Pixel)*(srcX+tmpX) + src->pitch*(srcY+tmpY))); Pixel& tmpDst = *((Pixel*)((char*)(dst->pixels) + sizeof(Pixel)*((x + dst->w + tmpX) & dstMaskX) + dst->pitch*((y + dst->h + tmpY) & dstMaskY))); if (tmpDst.a){ numPixels++; int dr = tmpSrc.r - tmpDst.r; int dg = tmpSrc.g - tmpDst.g; int db = tmpSrc.g - tmpDst.g; curDifference += dr*dr + dg*dg + db*db; } } if (numPixels) curDifference /= (float)numPixels; if (curDifference < lastDifference){ lastDifference = curDifference; storedSrcX = srcX; storedSrcY = srcY; } } dstPix = *((Pixel*)((char*)(src->pixels) + sizeof(Pixel)*storedSrcX + src->pitch*storedSrcY)); dstPix.a = 0xFF; } This thing is supposed to be used for texture generation. Now, the question: The easiest way to do this is brute force search (which is used in example routine). But it is slow - even using GPU acceleration and dual core cpu won't make it much faster. It looks like I can't use modified binary search because of B's mask. So, how can I find desired pixel faster? Additional Info: It is allowed to use 2 cores, GPU acceleration, CUDA, and 1.5..2 gigabytes of RAM for the task. I would prefer to avoid some kind of lengthy preprocessing phase that will take 30 minutes to finish. Ideas?

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