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• getting rid of filesort on WordPress MySQL query

  - by Hans

  An instance of WordPress that I manage goes down about once a day due to this monster MySQL query taking far too long: SELECT SQL_CALC_FOUND_ROWS distinct wp_posts.* FROM wp_posts LEFT JOIN wp_term_relationships ON (wp_posts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy ON wp_term_taxonomy.term_taxonomy_id = wp_term_relationships.term_taxonomy_id LEFT JOIN wp_ec3_schedule ec3_sch ON ec3_sch.post_id=id WHERE 1=1 AND wp_posts.ID NOT IN ( SELECT tr.object_id FROM wp_term_relationships AS tr INNER JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy = 'category' AND tt.term_id IN ('1050') ) AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish') AND NOT EXISTS (SELECT * FROM wp_term_relationships JOIN wp_term_taxonomy ON wp_term_taxonomy.term_taxonomy_id = wp_term_relationships.term_taxonomy_id WHERE wp_term_relationships.object_id = wp_posts.ID AND wp_term_taxonomy.taxonomy = 'category' AND wp_term_taxonomy.term_id IN (533,3567) ) AND ec3_sch.post_id IS NULL GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC LIMIT 0, 10; What do I have to do to get rid of the very slow filesort? I would think that the multicolumn type_status_date index would be fast enough. The EXPLAIN EXTENDED output is below. +----+--------------------+-----------------------+--------+-----------------------------------+------------------+---------+---------------------------------------------------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------------+-----------------------+--------+-----------------------------------+------------------+---------+---------------------------------------------------------------------------------+------+----------------------------------------------+ | 1 | PRIMARY | wp_posts | ref | type_status_date | type_status_date | 124 | const,const | 7034 | Using where; Using temporary; Using filesort | | 1 | PRIMARY | wp_term_relationships | ref | PRIMARY | PRIMARY | 8 | bwog_wordpress_w.wp_posts.ID | 373 | Using index | | 1 | PRIMARY | wp_term_taxonomy | eq_ref | PRIMARY | PRIMARY | 8 | bwog_wordpress_w.wp_term_relationships.term_taxonomy_id | 1 | Using index | | 1 | PRIMARY | ec3_sch | ref | post_id_index | post_id_index | 9 | bwog_wordpress_w.wp_posts.ID | 1 | Using where; Using index | | 3 | DEPENDENT SUBQUERY | wp_term_taxonomy | range | PRIMARY,term_id_taxonomy,taxonomy | term_id_taxonomy | 106 | NULL | 2 | Using where | | 3 | DEPENDENT SUBQUERY | wp_term_relationships | eq_ref | PRIMARY,term_taxonomy_id | PRIMARY | 16 | bwog_wordpress_w.wp_posts.ID,bwog_wordpress_w.wp_term_taxonomy.term_taxonomy_id | 1 | Using index | | 2 | DEPENDENT SUBQUERY | tt | const | PRIMARY,term_id_taxonomy,taxonomy | term_id_taxonomy | 106 | const,const | 1 | | | 2 | DEPENDENT SUBQUERY | tr | eq_ref | PRIMARY,term_taxonomy_id | PRIMARY | 16 | func,const | 1 | Using index | +----+--------------------+-----------------------+--------+-----------------------------------+------------------+---------+---------------------------------------------------------------------------------+------+----------------------------------------------+ 8 rows in set, 2 warnings (0.05 sec) And CREATE TABLE: CREATE TABLE `wp_posts` ( `ID` bigint(20) unsigned NOT NULL auto_increment, `post_author` bigint(20) unsigned NOT NULL default '0', `post_date` datetime NOT NULL default '0000-00-00 00:00:00', `post_date_gmt` datetime NOT NULL default '0000-00-00 00:00:00', `post_content` longtext NOT NULL, `post_title` text NOT NULL, `post_excerpt` text NOT NULL, `post_status` varchar(20) NOT NULL default 'publish', `comment_status` varchar(20) NOT NULL default 'open', `ping_status` varchar(20) NOT NULL default 'open', `post_password` varchar(20) NOT NULL default '', `post_name` varchar(200) NOT NULL default '', `to_ping` text NOT NULL, `pinged` text NOT NULL, `post_modified` datetime NOT NULL default '0000-00-00 00:00:00', `post_modified_gmt` datetime NOT NULL default '0000-00-00 00:00:00', `post_content_filtered` text NOT NULL, `post_parent` bigint(20) unsigned NOT NULL default '0', `guid` varchar(255) NOT NULL default '', `menu_order` int(11) NOT NULL default '0', `post_type` varchar(20) NOT NULL default 'post', `post_mime_type` varchar(100) NOT NULL default '', `comment_count` bigint(20) NOT NULL default '0', `robotsmeta` varchar(64) default NULL, PRIMARY KEY (`ID`), KEY `post_name` (`post_name`), KEY `type_status_date` (`post_type`,`post_status`,`post_date`,`ID`), KEY `post_parent` (`post_parent`), KEY `post_date` (`post_date`), FULLTEXT KEY `post_related` (`post_title`,`post_content`) )

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• function to get the file name of an URL

  - by user262325

  Hello everyone I have some source code to get the file name of an url for example: http://www.google.com/a.pdf I hope to get a.pdf because the way to join 2 NSStrings I can get is 'appendString' which only for adding a string at right side, so I planned to check each char one by one from the right side of string 'http://www.google.com/a.pdf', when it reach at the char '/', stop the checking, return string fdp.a , after that I change fdp.a to a.pdf source codes are below -(NSMutableString *) getSubStringAfterH : originalString:(NSString *)s0 { NSInteger i,l; l=[s0 length]; NSMutableString *h=[[NSMutableString alloc] init]; NSMutableString *ttt=[[NSMutableString alloc] init ]; for(i=l-1;i>=0;i--) //check each char one by one from the right side of string 'http://www.google.com/a.pdf', when it reach at the char '/', stop { ttt=[s0 substringWithRange:NSMakeRange(i, 1)]; if([ttt isEqualToString:@"/"]) { break; } else { [h appendString:ttt]; } } [ttt release]; //below are to change the sequence of char in h // txt.edcba -> abcde.txt NSMutableString *h1=[[[NSMutableString alloc] initWithFormat:@""] autorelease]; for (i=[h length]-1;i>=0;i--) { NSMutableString *t1=[[NSMutableString alloc] init ]; t1=[h substringWithRange:NSMakeRange(i, 1)]; [h1 appendString:t1]; [t1 release]; } [h release]; return h1; } h1 can reuturn the coorect string a.pdf, but if it returns to the codes where it was called, after a while system reports 'double free * set a breakpoint in malloc_error_break to debug' I checked a long time and foudn that if I removed the code ttt=[s0 substringWithRange:NSMakeRange(i, 1)]; everything will be Ok (of course getSubStringAfterH can not returns the corrent result I expected.), no error reported. I try to fix the bug a few hours, but still no clue. Welcome any comment Thanks interdev

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• Union struct produces garbage and general question about struct nomenclature

  - by SoulBeaver

  I read about unions the other day( today ) and tried the sample functions that came with them. Easy enough, but the result was clear and utter garbage. The first example is: union Test { int Int; struct { char byte1; char byte2; char byte3; char byte4; } Bytes; }; where an int is assumed to have 32 bits. After I set a value Test t; t.Int = 7; and then cout cout << t.Bytes.byte1 << etc... the individual bytes, there is nothing displayed, but my computer beeps. Which is fairly odd I guess. The second example gave me even worse results. union SwitchEndian { unsigned short word; struct { unsigned char hi; unsigned char lo; } data; } Switcher; Looks a little wonky in my opinion. Anyway, from the description it says, this should automatically store the result in a high/little endian format when I set the value like Switcher.word = 7656; and calling with cout << Switcher.data.hi << endl The result of this were symbols not even defined in the ASCII chart. Not sure why those are showing up. Finally, I had an error when I tried correcting the example by, instead of placing Bytes at the end of the struct, positioning it right next to it. So instead of struct {} Bytes; I wanted to write struct Bytes {}; This tossed me a big ol' error. What's the difference between these? Since C++ cannot have unnamed structs it seemed, at the time, pretty obvious that the Bytes positioned at the beginning and at the end are the things that name it. Except no, that's not the entire answer I guess. What is it then?

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• SIMPLE OpenSSL RSA Encryption in C/C++ is causing me headaches

  - by Josh

  Hey guys, I'm having some trouble figuring out how to do this. Basically I just want a client and server to be able to send each other encrypted messages. This is going to be incredibly insecure because I'm trying to figure this all out so I might as well start at the ground floor. So far I've got all the keys working but encryption/decryption is giving me hell. I'll start by saying I am using C++ but most of these functions require C strings so whatever I'm doing may be causing problems. Note that on the client side I receive the following error in regards to decryption. error:04065072:rsa routines:RSA_EAY_PRIVATE_DECRYPT:padding check failed I don't really understand how padding works so I don't know how to fix it. Anywho here are the relevant variables on each side followed by the code. Client: RSA *myKey; // Loaded with private key // The below will hold the decrypted message unsigned char* decrypted = (unsigned char*) malloc(RSA_size(myKey)); /* The below holds the encrypted string received over the network. Originally held in a C-string but C strings never work for me and scare me so I put it in a C++ string */ string encrypted; // The reinterpret_cast line was to get rid of an error message. // Maybe the cause of one of my problems? if(RSA_private_decrypt(sizeof(encrypted.c_str()), reinterpret_cast<const unsigned char*>(encrypted.c_str()), decrypted, myKey, RSA_PKCS1_OAEP_PADDING)==-1) { cout << "Private decryption failed" << endl; ERR_error_string(ERR_peek_last_error(), errBuf); printf("Error: %s\n", errBuf); free(decrypted); exit(1); } Server: RSA *pkey; // Holds the client's public key string key; // Holds a session key I want to encrypt and send //The below will hold the encrypted message unsigned char *encrypted = (unsigned char*)malloc(RSA_size(pkey)); // The reinterpret_cast line was to get rid of an error message. // Maybe the cause of one of my problems? if(RSA_public_encrypt(sizeof(key.c_str()), reinterpret_cast<const unsigned char*>(key.c_str()), encrypted, pkey, RSA_PKCS1_OAEP_PADDING)==-1) { cout << "Public encryption failed" << endl; ERR_error_string(ERR_peek_last_error(), errBuf); printf("Error: %s\n", errBuf); free(encrypted); exit(1); } Let me once again state, in case I didn't before, that I know my code sucks but I'm just trying to establish a framework for understanding this. I'm sorry if this offends you veteran coders. Thanks in advance for any help you guys can provide!

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• Initialize byte array from a portion of existing byte array c#

  - by volody

  Is there are an easy way to initialize byte array from portion of existing byte array. In C language it is possible to use pointer to say like char s[10] = new char[10]; char* b = s + 5; Is it possible to do that in c#, like: byte[] b = new byte[buffersize]; byte* header = b + 5; byte* data = b + 25;

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• Best way to create SEO friendly URI string

  - by Mat Banik

  The method below allows only "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-" chars in URI strings. What better way is there to make nice SEO URI string? import org.apache.commons.lang.StringUtils; public static String safeChar(String input) { input = input.trim(); input = StringUtils.replace(input, " -", "-"); input = StringUtils.replace(input, "- ", "-"); input = StringUtils.replace(input, " - ", "-"); input = StringUtils.replaceChars(input, '\'', '-'); input = StringUtils.replaceChars(input, ' ', '-'); char[] allowed = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-".toCharArray(); char[] charArray = input.toCharArray(); StringBuilder result = new StringBuilder(); for (char c : charArray) { for (char a : allowed) { if (c == a) result.append(a); } } return result.toString(); }

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• Need help with basic ASM

  - by Malfist

  Hello, I'm trying to convert some c code to assmebly, and I need some help. char encode(char plain){ __asm{ mov eax, plain add eax, 2 ret } //C code /* char code; code = plain+2; return code;*/ } First problem is that visual studio complains that the register size doesn't match, i.e. eax is too small/large for char. I was under the impression that they were both DWORDs. Also, if I leave the variable in eax, and ret in assembly, it'll actually return that variable, right?

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• Problems with this stack implementation

  - by Andersson Melo

  where is the mistake? My code here: typedef struct _box { char *dados; struct _box * proximo; } Box; typedef struct _pilha { Box * topo; }Stack; void Push(Stack *p, char * algo) { Box *caixa; if (!p) { exit(1); } caixa = (Box *) calloc(1, sizeof(Box)); caixa->dados = algo; caixa->proximo = p->topo; p->topo = caixa; } char * Pop(Stack *p) { Box *novo_topo; char * dados; if (!p) { exit(1); } if (p->topo==NULL) return NULL; novo_topo = p->topo->proximo; dados = p->topo->dados; free(p->topo); p->topo = novo_topo; return dados; } void StackDestroy(Stack *p) { char * c; if (!p) { exit(1); } c = NULL; while ((c = Pop(p)) != NULL) { free(c); } free(p); } int main() { int conjunto = 1; char p[30]; int flag = 0; Stack *pilha = (Stack *) calloc(1, sizeof(Stack)); FILE* arquivoIN = fopen("L1Q3.in","r"); FILE* arquivoOUT = fopen("L1Q3.out","w"); if (arquivoIN == NULL) { printf("Erro na leitura do arquivo!\n\n"); exit(1); } fprintf(arquivoOUT,"Conjunto #%d\n",conjunto); while (fscanf(arquivoIN,"%s", p) != EOF ) { if (pilha->topo == NULL && flag != 0) { conjunto++; fprintf(arquivoOUT,"\nConjunto #%d\n",conjunto); } if(strcmp(p, "return") != 0) { Push(pilha, p); } else { p = Pop(pilha); if(p != NULL) { fprintf(arquivoOUT, "%s\n", p); } } flag = 1; } StackDestroy(pilha); return 0; } The Pop function returns the string value read from file. But is not correct and i don't know why.

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• creating Object equality "HashMap" in ActionScript3 as java HashMap

  - by jason

  const jonny1 : Person = new Person("jonny", 26); const jonny2 : Person = new Person("jonny", 26); const table : Dictionary = new Dictionary(); table[jonny1] = "That's me"; trace(table[jonny1]) // traces: "That's me" trace(table[jonny2]) // traces: undefined. But I want use Dictionary like this way: trace(table[jonny2]) // traces: "That's me". in a word, I want implements a data-structure works like HashMap in java

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• C++: Declaration of template class member specialization

  - by Ziv

  When I specialize a (static) member function/constant in a template class, I'm confused as to where the declaration is meant to go. Here's an example of what I what to do - yoinked directly from IBM's reference on template specialization: ===IBM Member Specialization Example=== template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } int main() { X<char*> a, b; X<float> c; c.f(10); // X<float>::v now set to 20 } The question is, how do I divide this into header/cpp files? The generic implementation is obviously in the header, but what about the specialization? It can't go in the header file, because it's concrete, leading to multiple definition. But if it goes into the .cpp file, is code which calls X::f() aware of the specialization, or might it rely on the generic X::f()? So far I've got the specialization in the .cpp only, with no declaration in the header. I'm not having trouble compiling or even running my code (on gcc, don't remember the version at the moment), and it behaves as expected - recognizing the specialization. But A) I'm not sure this is correct, and I'd like to know what is, and B) my Doxygen documentation comes out wonky and very misleading (more on that in a moment a later question). What seems most natural to me would be something like this, declaring the specialization in the header and defining it in the .cpp: ===XClass.hpp=== #ifndef XCLASS_HPP #define XCLASS_HPP template<class T> class X { public: static T v; static void f(T); }; template<class T> T X<T>::v = 0; template<class T> void X<T>::f(T arg) { v = arg; } /* declaration of specialized functions */ template<> char* X<char*>::v; template<> void X<float>::f(float arg); #endif ===XClass.cpp=== #include <XClass.hpp> /* concrete implementation of specialized functions */ template<> char* X<char*>::v = "Hello"; template<> void X<float>::f(float arg) { v = arg * 2; } ...but I have no idea if this is correct. Any ideas? Thanks much, Ziv

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• 2d array, using calloc in C

  - by BigBirdy

  Hi, I'm trying to create a 2D array of chars to storage lines of chars. For Example: lines[0]="Hello"; lines[1]="Your Back"; lines[2]="Bye"; Since lines has to be dynamically cause i don't know how many lines i need at first. Here is the code i have: int i; char **lines= (char**) calloc(size, sizeof(char*)); for ( i = 0; i < size; i++ ){ lines[i] = (char*) calloc(200, sizeof(char)); } for ( i = 0; i < size; i++ ){ free(lines[i]); } free(lines); I know that each line can't go over 200 chars. I keep getting errors like "error C2059: syntax error : 'for'" and such. Any ideas of what i did wrong?

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• Polynomial division overloading operator

  - by Vlad

  Ok. here's the operations i successfully code so far thank's to your help: Adittion: polinom operator+(const polinom& P) const { polinom Result; constIter i = poly.begin(), j = P.poly.begin(); while (i != poly.end() && j != P.poly.end()) { //logic while both iterators are valid if (i->pow > j->pow) { //if the current term's degree of the first polynomial is bigger Result.insert(i->coef, i->pow); i++; } else if (j->pow > i->pow) { // if the other polynomial's term degree is bigger Result.insert(j->coef, j->pow); j++; } else { // if both are equal Result.insert(i->coef + j->coef, i->pow); i++; j++; } } //handle the remaining items in each list //note: at least one will be equal to end(), but that loop will simply be skipped while (i != poly.end()) { Result.insert(i->coef, i->pow); ++i; } while (j != P.poly.end()) { Result.insert(j->coef, j->pow); ++j; } return Result; } Subtraction: polinom operator-(const polinom& P) const //fixed prototype re. const-correctness { polinom Result; constIter i = poly.begin(), j = P.poly.begin(); while (i != poly.end() && j != P.poly.end()) { //logic while both iterators are valid if (i->pow > j->pow) { //if the current term's degree of the first polynomial is bigger Result.insert(-(i->coef), i->pow); i++; } else if (j->pow > i->pow) { // if the other polynomial's term degree is bigger Result.insert(-(j->coef), j->pow); j++; } else { // if both are equal Result.insert(i->coef - j->coef, i->pow); i++; j++; } } //handle the remaining items in each list //note: at least one will be equal to end(), but that loop will simply be skipped while (i != poly.end()) { Result.insert(i->coef, i->pow); ++i; } while (j != P.poly.end()) { Result.insert(j->coef, j->pow); ++j; } return Result; } Multiplication: polinom operator*(const polinom& P) const { polinom Result; constIter i, j, lastItem = Result.poly.end(); Iter it1, it2, first, last; int nr_matches; for (i = poly.begin() ; i != poly.end(); i++) { for (j = P.poly.begin(); j != P.poly.end(); j++) Result.insert(i->coef * j->coef, i->pow + j->pow); } Result.poly.sort(SortDescending()); lastItem--; while (true) { nr_matches = 0; for (it1 = Result.poly.begin(); it1 != lastItem; it1++) { first = it1; last = it1; first++; for (it2 = first; it2 != Result.poly.end(); it2++) { if (it2->pow == it1->pow) { it1->coef += it2->coef; nr_matches++; } } nr_matches++; do { last++; nr_matches--; } while (nr_matches != 0); Result.poly.erase(first, last); } if (nr_matches == 0) break; } return Result; } Division(Edited): polinom operator/(const polinom& P) { polinom Result, temp; Iter i = poly.begin(); constIter j = P.poly.begin(); if (poly.size() < 2) { if (i->pow >= j->pow) { Result.insert(i->coef, i->pow - j->pow); *this = *this - Result; } } else { while (true) { if (i->pow >= j->pow) { Result.insert(i->coef, i->pow - j->pow); temp = Result * P; *this = *this - temp; } else break; } } return Result; } The first three are working correctly but division doesn't as it seems the program is in a infinite loop. Update Because no one seems to understand how i thought the algorithm, i'll explain: If the dividend contains only one term, we simply insert the quotient in Result, then we multiply it with the divisor ans subtract it from the first polynomial which stores the remainder. If the polynomial we do this until the second polynomial( P in this case) becomes bigger. I think this algorithm is called long division, isn't it? So based on these, can anyone help me with overloading the / operator correctly for my class? Thanks!

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• QT- QImage and multi-threading problem.

  - by umanga

  Greetings all, Please refer to image at : http://i48.tinypic.com/316qb78.jpg We are developing an application to extract cell edges from MRC images from electron microscope. MRC file format stores volumetric pixel data (http://en.wikipedia.org/wiki/Voxel) and we simply use 3D char array(char***) to load and store data (gray scale values) from a MRC file. As shown in the image,there are 3 viewers to display XY,YZ and ZX planes respectively. Scrollbars on the top of the viewers use to change the image slice along an axis. Here is the steps we do when user changes the scrollbar position. 1) get the new scrollbar value.(this is the selected slice) 2) for the relavant plane (YZ,XY or ZX), generate (char* slice;) array for the selected slice by reading 3D char array (char***) 3) Create a new QImage* (Format_RGB888) and set pixel values by reading 'slice' (using img-setPixel(x,y,c);) 4) This new QImage* is painted in the paintEvent() method. We are going to execute "edge-detection" process in a seperate thread since it is an intensive process.During this process we need to draw detected curve (set of pixels) on top of above QImage*.(as a layer).This means we need to call drawPoint() methods outside the QT thread. Is it the best wayto use QImage for this case? What is the best way to execute QT drawing methods from another thread? thanks in advance,

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• Fuzzy Date algorithm in Objective-C

  - by Brock Woolf

  I would like to write a fuzzy date method for calculating dates in Objective-C for iPhone. There is a popular explanation here: http://stackoverflow.com/questions/11/how-do-i-calculate-relative-time However it contains missing arguments. How could this be used in Objective-C?. Thanks. const int SECOND = 1; const int MINUTE = 60 * SECOND; const int HOUR = 60 * MINUTE; const int DAY = 24 * HOUR; const int MONTH = 30 * DAY; if (delta < 1 * MINUTE) { return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago"; } if (delta < 2 * MINUTE) { return "a minute ago"; } if (delta < 45 * MINUTE) { return ts.Minutes + " minutes ago"; } if (delta < 90 * MINUTE) { return "an hour ago"; } if (delta < 24 * HOUR) { return ts.Hours + " hours ago"; } if (delta < 48 * HOUR) { return "yesterday"; } if (delta < 30 * DAY) { return ts.Days + " days ago"; } if (delta < 12 * MONTH) { int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30)); return months <= 1 ? "one month ago" : months + " months ago"; } else { int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365)); return years <= 1 ? "one year ago" : years + " years ago"; }

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• Sax Parser Character Array to Integer??

  - by Andy Barlow

  Hello, I am trying to get the contents of tags into variables in my java Sax parser. However, the Characters method only returns Char arrays. Is there anyway to get the Char array into an Int??? public void characters(char ch[], int start, int length) { if(this.in_total_results) { // my INT varialble would be nice here! } } Can anyone help at all? Kind regards, Andy

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• How does delete deal with pointer constness?

  - by aJ

  I was reading this question Deleting a const pointer and wanted to know more about delete behavior. Now, as per my understanding: delete expression works in two steps: invoke destructor then releases the memory (often with a call to free()) by calling operator delete. operator delete accepts a void*. As part of a test program I overloaded operator delete and found that operator delete doesn't accept const pointer. Since operator delete does not accept const pointer and delete internally calls operator delete, how does Deleting a const pointer work ? Does delete uses const_cast internally?

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• MinGW Doesn't Generate an Object File When Compiling

  - by Nathan Campos

  I've just bought a new laptop for me on the travel, then on my free time, I've started to test MinGW on it by trying to compile my own OS that is written in C++, then I've created all the files needed and the kernel.cpp: extern "C" void _main(struct multiboot_data* mbd, unsigned int magic); void _main( struct multiboot_data* mbd, unsigned int magic ) { char * boot_loader_name =(char*) ((long*)mbd)[16]; /* Print a letter to screen to see everything is working: */ unsigned char *videoram = (unsigned char *) 0xb8000; videoram[0] = 65; /* character 'A' */ videoram[1] = 0x07; /* forground, background color. */ } And tried to compile it with g++ G: g++ -o C:\kernel.o -c kernel.cpp -Wall -Wextra -Werror -nostdlib -nostartfiles -nodefaultlibs kernel.cpp: In function `void _main(multiboot_data*, unsigned int)': kernel.cpp:8: warning: unused variable 'boot_loader_name' kernel.cpp: At global scope: kernel.cpp:4: warning: unused parameter 'magic' G: But it don't create any binary file at C:/. What can I do?

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• What does `const` do when combined with `readonly`?

  - by Byron Sommardahl

  The difference between const and readonly is well covered. A const can't be changed and a read only can only be changed in a constructor. But, what happens when you combine the two: public readonly const string how_does_this_behave = "I don't know"; The compiler allows it. But I'm not sure how it behaves from this point on. Thoughts?

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• C++ Mutexes and STL Lists Across Subclasses

  - by Genesis

  I am currently writing a multi-threaded C++ server using Poco and am now at the point where I need to be keeping information on which users are connected, how many connections each of them have, and given it is a proxy server, where each of those connections are proxying through to. For this purpose I have created a ServerStats class which holds an STL list of ServerUser objects. The ServerStats class includes functions which can add and remove objects from the list as well as find a user in the list an return a pointer to them so I can access member functions within any given ServerUser object in the list. The ServerUser class contains an STL list of ServerConnection objects and much like the ServerStats class it contains functions to add, remove and find elements within this list. Now all of the above is working but I am now trying to make it threadsafe. I have defined a Poco::FastMutex within the ServerStats class and can lock/unlock this in the appropriate places so that STL containers are not modified at the same time as being searched for example. I am however having an issue setting up mutexes within the ServerUser class and am getting the following compiler error: /root/poco/Foundation/include/Poco/Mutex.h: In copy constructor âServerUser::ServerUser(const ServerUser&)â: src/SocksServer.cpp:185: instantiated from âvoid __gnu_cxx::new_allocator<_Tp::construct(_Tp*, const _Tp&) [with _Tp = ServerUser]â /usr/include/c++/4.4/bits/stl_list.h:464: instantiated from âstd::_List_node<_Tp* std::list<_Tp, _Alloc::_M_create_node(const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â /usr/include/c++/4.4/bits/stl_list.h:1407: instantiated from âvoid std::list<_Tp, _Alloc::_M_insert(std::_List_iterator<_Tp, const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â /usr/include/c++/4.4/bits/stl_list.h:920: instantiated from âvoid std::list<_Tp, _Alloc::push_back(const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â src/SocksServer.cpp:301: instantiated from here /root/poco/Foundation/include/Poco/Mutex.h:164: error: âPoco::FastMutex::FastMutex(const Poco::FastMutex&)â is private src/SocksServer.cpp:185: error: within this context In file included from /usr/include/c++/4.4/x86_64-linux-gnu/bits/c++allocator.h:34, from /usr/include/c++/4.4/bits/allocator.h:48, from /usr/include/c++/4.4/string:43, from /root/poco/Foundation/include/Poco/Bugcheck.h:44, from /root/poco/Foundation/include/Poco/Foundation.h:147, from /root/poco/Net/include/Poco/Net/Net.h:45, from /root/poco/Net/include/Poco/Net/TCPServerParams.h:43, from src/SocksServer.cpp:1: /usr/include/c++/4.4/ext/new_allocator.h: In member function âvoid __gnu_cxx::new_allocator<_Tp::construct(_Tp*, const _Tp&) [with _Tp = ServerUser]â: /usr/include/c++/4.4/ext/new_allocator.h:105: note: synthesized method âServerUser::ServerUser(const ServerUser&)â first required here src/SocksServer.cpp: At global scope: src/SocksServer.cpp:118: warning: âstd::string getWord(std::string)â defined but not used make: * [/root/poco/SocksServer/obj/Linux/x86_64/debug_shared/SocksServer.o] Error 1 The code for the ServerStats, ServerUser and ServerConnection classes is below: class ServerConnection { public: bool continue_connection; int bytes_in; int bytes_out; string source_address; string destination_address; ServerConnection() { continue_connection = true; } ~ServerConnection() { } }; class ServerUser { public: string username; int connection_count; string client_ip; ServerUser() { } ~ServerUser() { } ServerConnection* addConnection(string source_address, string destination_address) { //FastMutex::ScopedLock lock(_connection_mutex); ServerConnection connection; connection.source_address = source_address; connection.destination_address = destination_address; client_ip = getWord(source_address, ":"); _connections.push_back(connection); connection_count++; return &_connections.back(); } void removeConnection(string source_address) { //FastMutex::ScopedLock lock(_connection_mutex); for(list<ServerConnection>::iterator it = _connections.begin(); it != _connections.end(); it++) { if(it->source_address == source_address) { it = _connections.erase(it); connection_count--; } } } void disconnect() { //FastMutex::ScopedLock lock(_connection_mutex); for(list<ServerConnection>::iterator it = _connections.begin(); it != _connections.end(); it++) { it->continue_connection = false; } } list<ServerConnection>* getConnections() { return &_connections; } private: list<ServerConnection> _connections; //UNCOMMENTING THIS LINE BREAKS IT: //mutable FastMutex _connection_mutex; }; class ServerStats { public: int current_users; ServerStats() { current_users = 0; } ~ServerStats() { } ServerUser* addUser(string username) { FastMutex::ScopedLock lock(_user_mutex); for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) { if(it->username == username) { return &(*it); } } ServerUser newUser; newUser.username = username; _users.push_back(newUser); current_users++; return &_users.back(); } void removeUser(string username) { FastMutex::ScopedLock lock(_user_mutex); for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) { if(it->username == username) { _users.erase(it); current_users--; break; } } } ServerUser* getUser(string username) { FastMutex::ScopedLock lock(_user_mutex); for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) { if(it->username == username) { return &(*it); } } return NULL; } private: list<ServerUser> _users; mutable FastMutex _user_mutex; }; Now I have never used C++ for a project of this size or mutexes for that matter so go easy please :) Firstly, can anyone tell me why the above is causing a compiler error? Secondly, can anyone suggest a better way of storing the information I require? Bear in mind that I need to update this info whenever connections come or go and it needs to be global to the whole server.

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• Overloading *(iterator + n) and *(n + iterator) in a C++ iterator class?

  - by exscape

  (Note: I'm writing this project for learning only; comments about it being redundant are... uh, redundant. ;) I'm trying to implement a random access iterator, but I've found very little literature on the subject, so I'm going by trial and error combined with Wikpedias list of operator overload prototypes. It's worked well enough so far, but I've hit a snag. Code such as exscape::string::iterator i = string_instance.begin(); std::cout << *i << std::endl; works, and prints the first character of the string. However, *(i + 1) doesn't work, and neither does *(1 + i). My full implementation would obviously be a bit too much, but here's the gist of it: namespace exscape { class string { friend class iterator; ... public: class iterator : public std::iterator<std::random_access_iterator_tag, char> { ... char &operator*(void) { return *p; // After some bounds checking } char *operator->(void) { return p; } char &operator[](const int offset) { return *(p + offset); // After some bounds checking } iterator &operator+=(const int offset) { p += offset; return *this; } const iterator operator+(const int offset) { iterator out (*this); out += offset; return out; } }; }; } int main() { exscape::string s = "ABCDEF"; exscape::string::iterator i = s.begin(); std::cout << *(i + 2) << std::endl; } The above fails with (line 632 is, of course, the *(i + 2) line): string.cpp: In function ‘int main()’: string.cpp:632: error: no match for ‘operator*’ in ‘*exscape::string::iterator::operator+(int)(2)’ string.cpp:105: note: candidates are: char& exscape::string::iterator::operator*() *(2 + i) fails with: string.cpp: In function ‘int main()’: string.cpp:632: error: no match for ‘operator+’ in ‘2 + i’ string.cpp:434: note: candidates are: exscape::string exscape::operator+(const char*, const exscape::string&) My guess is that I need to do some more overloading, but I'm not sure what operator I'm missing.

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• Insert date to database

  - by simon

  I'm trying to insert the current date to the database and i allways get the massage(when i pres the button on the form to save to my access database), that the data type is incorect in the conditional expression. the code: string conString = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=C:\Users\Simon\Desktop\save.mdb"; OleDbConnection empConnection = new OleDbConnection(conString); string insertStatement = "INSERT INTO obroki_save " + "([ID_uporabnika],[datum],[ID_zivila],[skupaj_kalorij]) " + "VALUES (@ID_uporabnika,@datum,@ID_zivila,@skupaj_kalorij)"; OleDbCommand insertCommand = new OleDbCommand(insertStatement, empConnection); insertCommand.Parameters.Add("@ID_uporabnika", OleDbType.Char).Value = users.iDTextBox.Text; insertCommand.Parameters.Add("@datum", OleDbType.Char).Value = DateTime.Now; insertCommand.Parameters.Add("@ID_zivila", OleDbType.Char).Value = iDTextBox.Text; insertCommand.Parameters.Add("@skupaj_kalorij", OleDbType.Char).Value = textBox1.Text; empConnection.Open(); try { int count = insertCommand.ExecuteNonQuery(); } catch (OleDbException ex) { MessageBox.Show(ex.Message); } finally { empConnection.Close(); textBox1.Clear(); textBox2.Clear(); textBox3.Clear(); textBox4.Clear(); textBox5.Clear(); } i tried to change the oleDbType.char to oleDbType.Dbdate and others but it doesnt work. I can save other stuff with that code but im stuck here when i wan't to save the date. Please help !

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• Concat wchar_t Unicode strings in C?

  - by Doori Bar

  I'm a beginner, I play with FindFirstFileW() of the winapi - C. The unicoded path is: " \\?\c:\Français\", and I would like to concat "*" to this path of type wchar_t (then I will use it as an arg for FindFirstFileW()). I made two test cases of mine, the first is ansi_string() which seem to work fine, the second is unicode_string() - which I don't quite understand how should I concat the additional "*" char to the unicoded path. I write the strings to a file, because I'm not able to print Unicoded characters to stdout. Note: my goal is to learn, which means I'll appreciate guidance and references to the appropriate resources regards my scenario, I'm very much a beginner and this is my first attempt with Unicode. Thanks, Doori Bar #include <stdio.h> #include <stdlib.h> #include <wchar.h> #include <string.h> #include <errno.h> void *error_malloc(int size); void ansi_string(char **str1, char **str2); void unicode_string(wchar_t **wstr1, wchar_t **wstr2); void unicode_string(wchar_t **wstr1, wchar_t **wstr2) { /* assign wstr1 with the path: \\?\c:\Français\ */ *wstr1 = error_malloc((wcslen(L"\\\\?\\c:\\Français\\")+1) *sizeof(**wstr1)); wcscpy(*wstr1,L"\\\\?\\c:\\Français\\"); /* concat wstr1+"*" , assign wstr2 with: \\?\c:\Français\* */ *wstr2 = error_malloc((wcslen(*wstr1) + 1 + 1) * sizeof(**wstr1)); /* swprintf(*wstr2,"%ls*",*wstr1); */ /* how should I concat wstr1+"*"? */ wcscpy(*wstr2,L"\\\\?\\c:\\Français\\"); } void ansi_string(char **str1, char **str2) { /* assign str1 with the path: c:\English\ */ *str1 = error_malloc(strlen("c:\\English\\") + 1); strcpy(*str1,"c:\\English\\"); /* concat str1+"*" , assign str2 with: c:\English\* */ *str2 = error_malloc(strlen(*str1) + 1 + 1); sprintf(*str2,"%s*",*str1); } void *error_malloc(int size) { void *ptr; int errornumber; if ((ptr = malloc(size)) == NULL) { errornumber = errno; fprintf(stderr,"Error: malloc(): %d; Error Message: %s;\n", errornumber,strerror(errornumber)); exit(1); } return ptr; } int main(void) { FILE *outfile; char *str1; char *str2; wchar_t *wstr1; wchar_t *wstr2; if ((outfile = fopen("out.bin","w")) == NULL) { printf("Error: fopen failed."); return 1; } ansi_string(&str1,&str2); fwrite(str2, sizeof(*str2), strlen(str2), outfile); printf("strlen: %d\n",strlen(str2)); printf("sizeof: %d\n",sizeof(*str2)); free(str1); free(str2); unicode_string(&wstr1,&wstr2); fwrite(wstr2, sizeof(*wstr2), wcslen(wstr2), outfile); printf("wcslen: %d\n",wcslen(wstr2)); printf("sizeof: %d\n",sizeof(*wstr2)); free(wstr1); free(wstr2); fclose(outfile); return 0; }

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• Accessing a file on a network drive

  - by Rekreativc

  Hello. Background: I have an application that has to read from files on a network drive (Z:) This works great in my office domain, however it does not work on site (in a different domain). As far as I can tell the domain users and network drives are set in the same way, however I do not have access to users etc in the customers domain. When I couldn't access the network drive I figured I needed a token for a user. This is how I impersionate the user: [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)] public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken); ... const string userName = "Razvoj02"; const string pass = "Programer02"; const string domainName = null; const int LOGON32_PROVIDER_DEFAULT = 0; const int LOGON32_LOGON_INTERACTIVE = 2; IntPtr tokenHandle = new IntPtr(0); bool returnValue = LogonUser(userName, domainName, pass, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref tokenHandle); if (!returnValue) throw new Exception("Logon failed."); WindowsImpersonationContext impersonatedUser = null; try { WindowsIdentity wid = new WindowsIdentity(tokenHandle); impersonatedUser = wid.Impersonate(); } finally { if (impersonatedUser != null) impersonatedUser.Undo(); } Now here is the interesting/weird part. In my network the application can already access the network drive, and if I try to impersonate the active user (exactly the same user, including the same domain) it will not be able to access the network drive. This leaves me helpless since now I have no idea what works and what doesn't, and more to the point, will it work on site? What am I missing?

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• boost lambda::bind return type selection

  - by psaghelyi

  I would like to call a member through lambda::bind. Unfortunately I have got to members with the same name but different return type. Is there a way to help the lambda::bind to deduce the right return type for a member function call? #include <vector> #include <iostream> #include <algorithm> #include <boost/bind.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> using namespace std; using namespace boost; struct A { A (const string & name) : m_name(name) {} string & name () { return m_name; } const string & name () const { return m_name; } string m_name; }; vector<A> av; int main () { av.push_back (A ("some name")); // compiles fine find_if(av.begin(), av.end(), bind<const string &>(&A::name, _1) == "some name"); // error: call of overloaded 'bind(<unresolved overloaded function type>, const boost::lambda::lambda_functor<boost::lambda::placeholder<1> >&)' is ambiguous find_if(av.begin(), av.end(), lambda::bind(&A::name, lambda::_1) == "some name"); return 0; }

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• Wingding chars in sql server 2005

  - by Savvas Sopiadis

  Hi everybody! In a winforms application i 'm storing one Wingdings char in a SQL Server 2005 field of type NVARCHAR(1). Storing, retrieving and showing up this char in a control works fine. The problem i'm facing is this: how to search for records which have a specific wingding char value: for example Select * from table where FieldWithWingding = valueOfLeftArrowChar How to achieve this? Thanks in advance

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