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  • MySQL : incrementing text id in DB

    - by BarsMonster
    I need to have text IDs in my application. For example, we have acceptable charset azAZ09, and allowed range of IDs [aaa] - [cZ9]. First generated id would be aaa, then aab, aac, aad e.t.c. How one can return ID & increment lower bound in transaction-fashion? (provided that there are hundreds of concurrent requests and all should have correct result) To lower the load I guess it's possible to define say 20 separate ranges, and return id from random range - this should reduce contention, but it's not clear how to do single operation in the first place. Also, please note that number of IDs in range might exceed 2^32. Another idea is having ranges of 64-bit integers, and converting integer-char id in software code, where it could be done asyncroniously. Any ideas?

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  • The shortest way to convert infix expressions to postfix (RPN) in C

    - by kuszi
    Original formulation is given here (you can try also your program for correctness) . Additional rules: 1. The program should read from standard input and write do standard output. 2. The program should return zero to the calling system/program. 3. The program should compile and run with gcc -O2 -lm -s -fomit-frame-pointer. The challenge has some history: the call for short implementations has been announced at the Polish programming contest blog in September 2009. After the contest, the shortest code was 81 chars long. Later on the second call has been made for even shorter code and after the year matix2267 published his solution in 78 bytes: main(c){read(0,&c,1)?c-41&&main(c-40&&(c%96<27||main(c),putchar(c))):exit(0);} Anyone to make it even shorter or prove this is impossible?

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  • Why does a delegate with no parameters compile?

    - by Ryan
    I'm confused why this compiles: private delegate int MyDelegate(int p1, int p2); private void testDelegate() { MyDelegate imp = delegate { return 1; }; } MyDelegate should be a pointer to a method that takes two int parameters and returns another int, right? Why am I allowed to assign a method that takes no parameters? Interestingly, these doesn't compile (it complains about the signature mismatches, as I'd expect) private void testDelegate() { // Missing param MyDelegate imp = delegate(int p1) { return 1; }; // Wrong return type MyDelegate imp2 = delegate(int p1, int p2) { return "String"; }; } Thanks for any help! Ryan

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  • parsing/matching string occurrence in C

    - by David
    I have the following string: const char *str = "\"This is just some random text\" 130 28194 \"Some other string\" \"String 3\"" I would like to get the the integer 28194 of course the integer varies, so I can't do strstr("20194"). So I was wondering what would be a good way to get that part of the string? I was thinking to use #include <regex.h> which I already have a procedure to match regexp's but not sure how the regexp in C will look like using the POSIX style notation. [:alpha:]+[:digit:] and if performance will be an issue. Or will it be better using strchr,strstr? Any ideas will be appreciate it

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  • compare function for dates

    - by Chris
    I have struct as: struct stored { char *dates; // 12/May/2010, 10/Jun/2010 etc.. int ctr; }; // const struct stored structs[] = {{"12/May/2010", 1}, {"12/May/2011", 1}, {"21/May/2009", 4}, {"12/May/2011", 3}, {"10/May/2011", 8}, {"12/May/2011", 4 }}; What I want to do is to sort struct 'stored' by stored.dates. qsort(structs, 9, sizeof(struct stored*), sortdates); // sortdates function I'm not quite sure what would be a good way to sort those days? Compare them as c-strings?

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  • Resources for memory management in embedded application

    - by Elazar Leibovich
    How should I manage memory in my mission critical embedded application? I found some articles with google, but couldn't pinpoint a really useful practical guide. The DO-178b forbids dynamic memory allocations, but how will you manage the memory than? preallocate everything in advance and send a pointer to each function that needs allocation? Allocate it on the stack? Use a global static allocator (but then it's very similar to dynamic allocation)? Answers can be of the form of regular answer, reference to a resource, or reference to good opensource embedded system for example. clarification: The issue here is not whether or not memory management is availible for the embedded system. But what is a good design for an embedded system, to maximize reliability.

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  • How do i use a transparent image in a transparent image using GD?

    - by hogofwar
    I have tried every way I can find but the background is always black. Is there any way to keep the transparency of the first image when GD ises it in PHP? I'm using imagecopymerge to use the image. though i am not sure if this is the right way. imagecopymerge($dest, $char, 0, 0, 0, 0, 150, 300, 100); The image is like so: http://filesmelt.com/dl/draw7.php.png See that the background is black whereas the roginal picture was transparent as the modified picture should be aswell

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  • SDL+OpenGL app: blank screen

    - by Lococo
    I spent the last three days trying to create a small app using SDL + OpenGL. The app itself runs fine -- except it never outputs any graphics; just a black screen. I've condensed it down to a minimal C file, and I'm hoping someone can give me some guidance. I'm running out of ideas. I'm using Windows Vista, MinGW & MSYS. Thanks in advance for any advice! #include <SDL/SDL.h> #include <SDL_opengl.h> size_t sx=600, sy=600, bpp=32; void render(void) { glEnable(GL_DEPTH_TEST); // enable depth testing glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // clear to black glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear color/depth buffer glLoadIdentity(); // reset modelview matrix glColor3b(255, 0, 0); // red glLineWidth(3.0); // line width=3 glRecti(10, 10, sx-10, sy-10); // draw rectangle glFlush(); SDL_GL_SwapBuffers(); } int input(void) { SDL_Event event; while (SDL_PollEvent(&event)) if (event.type == SDL_QUIT || (event.type == SDL_KEYUP && event.key.keysym.sym == SDLK_ESCAPE)) return 0; return 1; } int main(int argc, char *argv[]) { SDL_Surface* surf; if (SDL_Init(SDL_INIT_EVERYTHING) != 0) return 0; if (!(surf = SDL_SetVideoMode(sx, sy, bpp, SDL_HWSURFACE|SDL_DOUBLEBUF))) return 0; glViewport(0, 0, sx, sy); // reset the viewport to new dimensions glMatrixMode(GL_PROJECTION); // set projection matrix to be current glLoadIdentity(); // reset projection matrix glOrtho(0, sx, sy, 0, -1.0, 1.0); // create ortho view glMatrixMode(GL_MODELVIEW); // set modelview matrix glLoadIdentity(); // reset modelview matrix for (;;) { if (!input()) break; render(); SDL_Delay(10); } SDL_FreeSurface(surf); SDL_Quit(); exit(0); } UPDATE: I have a version that works, but it changes orthographic to perspective. I'm not sure why this works and the other doesn't, but for future reference, here's a version that works: #include <SDL/SDL.h> #include <SDL_opengl.h> size_t sx=600, sy=600, bpp=32; void render(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); // set location in front of camera glTranslated(0, 0, -10); glBegin(GL_QUADS); // draw a square glColor3d(1, 0, 0); glVertex3d(-2, 2, 0); glVertex3d( 2, 2, 0); glVertex3d( 2, -2, 0); glVertex3d(-2, -2, 0); glEnd(); glFlush(); SDL_GL_SwapBuffers(); } int input(void) { SDL_Event event; while (SDL_PollEvent(&event)) if (event.type == SDL_QUIT || (event.type == SDL_KEYUP && event.key.keysym.sym == SDLK_ESCAPE)) return 0; return 1; } int main(int argc, char *argv[]) { SDL_Surface *surf; if (SDL_Init(SDL_INIT_EVERYTHING) != 0) return 0; if (!(surf = SDL_SetVideoMode(sx, sy, bpp, SDL_OPENGL))) return 0; glViewport(0, 0, sx, sy); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0, (float)sx / (float)sy, 1.0, 100.0); glMatrixMode(GL_MODELVIEW); glClearColor(0, 0, 0, 1); glClearDepth(1.0); glEnable(GL_DEPTH_TEST); for (;;) { if (!input()) break; render(); SDL_Delay(10); } SDL_FreeSurface(surf); SDL_Quit(); return 0; }

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  • Column.DbType affecting runtime behavior

    - by leppie
    Hi According to the MSDN docs, the DbType property/attribute of a Column type/element is only used for database creation. Yet, today, when trying to submit data to an IMAGE column on a SQLCE database (not sure if only on CE), I got an exception of 'Data truncated to 8000 bytes'. This was due to the DbType still being defined as VARBINARY(MAX) which SQLCE does not support. Changing the type to IMAGE in the DbType fixes the issue. So what other surprises does Linq2SQL attributes hold in store? Is this a bug or intended? Should I report it to MS? UPDATE After getting the answer from Guffa, I tested it, but it seems for NVARCHAR(10) adding a 11 char length string causes a SQL exception, and not Linq2SQL one. The data was truncated while converting from one data type to another. [ Name of function(if known) = ] A first chance exception of type 'System.Data.SqlServerCe.SqlCeException' occurred in System.Data.SqlServerCe.dll

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  • Help for CSS Menu Dropdown, FF OK and IE6 Problem

    - by Taruhku
    IE Problem, FF OK. Please help..???? Screen Shoot problem click here This is my CSS dolphincontainer { position:relative; height:56px; color:#E0E0E0; background:#143D55; width:100%; font-family:Tahoma; left: 0px; } dolphinnav {position:absolute;;height:33px;font-size:12px;font-weight:bold;background:#fff url(images/dolphin_bg.gif) repeat-x bottom left;padding:0 0 0 10px;width:975px;} dolphinnav ul {margin:0;padding:0;list-style-type:none;width:auto;float:left;} dolphinnav ul li {display:block;float:left;margin:0 1px;} dolphinnav ul li a {display:block;float:left;color:#001b2c;text-decoration:none;padding:0 0 0 10px;height:33px;} dolphinnav ul li a span {padding:12px 20px 0 0;height:21px;float:left;font-weight:bold;} dolphinnav ul li a:hover {color:#fff;background:transparent url(images/dolphin_bg-OVER.gif) repeat-x bottom left;} dolphinnav ul li a:hover span {display:block;width:auto;cursor:pointer;} dolphinnav ul li a.current,#dolphinnav ul li a.current:hover {color:#fff;background:#00517e url(images/dolphin_left-ON.gif) no-repeat top left;line-height:275%;} dolphinnav ul li a.current span {display:block;padding:0 20px 0 0;width:auto;background:#00517e url(images/dolphin_right-ON.gif) no-repeat top right;height:33px;} .tuckUp { display:block; width:90px; height:30px; overflow:hidden; cursor:pointer; } .pullDown { width:90px; height:56px; } .item a:link, .item a:visited { display:inline; float:left; background:#fff url(images/dolphin_bg.gif) repeat-x top left;padding:0 0 0 10px; text-align:left; color:#444; font-size:11px; font-weight:bold; text-decoration:none; line-height:25px; margin:0 5px 0px 0px; width:80px; } .item a:hover { display:inline; float:left; background:#39c; color:#FFF; text-decoration:none; text-align:left; font-size:11px; font-weight:700; font-weight:bold; line-height:25px; padding:0 0 0 10px; margin:0 5px 0px 0px; width:80px; } HTML: <div id="dolphincontainer"> <div id="dolphinnav"> <ul> <li><a href="index.php"><span>Home</span></a></li> <li><a href="chooseus.php"><span>Why Choose Us</span></a></li> <li><a href="peraturan.php"><span>Rules</span></a></li> <li class="tuckUp" onmousemove="this.className='pullDown'" onmouseout="this.className='tuckUp'"><a href="#"><span>Transaction</span></a> <div class="item"> <a href="drop1.php">Drop Down 1</a><br /> <a href="drop2.php">Drop Down 2</a></a><br /> <a href="drop3.php">Drop Down 3</a><br /> </div> </li> <li><a href="download.php"><span>Download</span></a></li> <li><a href="aboutus.php"><span>About Us</span></a></li> <li><a href="help.php" class="current"><span>Support</span></a></li> <li><a href="promo.php"><span><font color="#FF0000"><blink>PROMO</blink> </font></span></a></li> </ul> </div> </div>

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  • How to resolve error "Run-Time Check Failure #3"?

    - by karikari
    I am working on MS Visual Studio. I keep on getting this error: "Run-Time Check Failure #3 - The variable 'test' is being used without being initialized." I don't have any idea how to solve this. Here is the code that I'm currently tries to modify: STDMETHODIMP CButtonDemoBHO::Exec(const GUID*, DWORD nCmdID, DWORD d, VARIANTARG*, VARIANTARG* pvaOut) { CRebarHandler *test; switch (nCmdID){ case BUTTON_PRESSED: MessageBox(m_hWnd, L"You have pressed the button", L"Button Pressed", MB_OK); test->findButton(m_hWnd); test->setmenu(); break; case MENU_ITEM_SELECT: MessageBox(m_hWnd, L"You have simulated a button press with the menu ", L"Menu Pressed", MB_OK); break; } return S_OK; }

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  • Using memory mapping in C for reading binary

    - by user1320912
    I am trying to read data from a binary file and process it.It is a very large file so I thought I would use memory mapping. I am trying to use memory mapping so I can read the file byte by byte. I am getting a few compiler errors while doing this. I am doing this on a linux platform #include <unistd.h> #include <sys/types.h> #include <sys/mman.h> int fd; char *data; fd = open("data.bin", O_RDONLY); pagesize = 4000; data = mmap((caddr_t)0, pagesize, PROT_READ, MAP_SHARED, fd, pagesize); The errors i get are : caddr not initialized, R_RDONLY not initialized, mmap has too few arguments. Could someone help me out ?

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  • How to find validity of a string of parentheses, curly brackets and square brackets?

    - by Rajendra
    I recently came in contact with this interesting problem. You are given a string containing just the characters '(', ')', '{', '}', '[' and ']', for example, "[{()}]", you need to write a function which will check validity of such an input string, function may be like this: bool isValid(char* s); these brackets have to close in the correct order, for example "()" and "()[]{}" are all valid but "(]", "([)]" and "{{{{" are not! I came out with following O(n) time and O(n) space complexity solution, which works fine: Maintain a stack of characters. Whenever you find opening braces '(', '{' OR '[' push it on the stack. Whenever you find closing braces ')', '}' OR ']' , check if top of stack is corresponding opening bracket, if yes, then pop the stack, else break the loop and return false. Repeat steps 2 - 3 until end of the string. This works, but can we optimize it for space, may be constant extra space, I understand that time complexity cannot be less than O(n) as we have to look at every character. So my question is can we solve this problem in O(1) space?

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  • C++, create an instance from a static method

    - by Manux
    Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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  • SSL_CTX_set_cert_verify_callback vs. SSL_CTX_set_verify

    - by BreakPoint
    Hello, Can anyone tell me what is the difference between SSL_CTX_set_cert_verify_callback and SSL_CTX_set_verify? From OpenSSL docs: SSL_CTX_set_cert_verify_callback() sets the verification callback function for ctx. SSL objects that are created from ctx inherit the setting valid at the time when SSL_new(3) is called. and: SSL_CTX_set_verify() sets the verification flags for ctx to be mode and specifies the verify_callback function to be used. If no callback function shall be specified, the NULL pointer can be used for verify_callback. So I'm trying to understand which callback to send for each one (from client side). Thanks experts.

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  • C optimization breaks algorithm

    - by Halpo
    I am programming an algorithm that contains 4 nested for loops. The problem is at at each level a pointer is updated. The innermost loop only uses 1 of the pointers. The algorithm does a complicated count. When I include a debugging statement that logs the combination of the indexes and the results of the count I get the correct answer. When the debugging statement is omitted, the count is incorrect. The program is compiled with the -O3 option on gcc. Why would this happen?

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  • Is there a leak in this copy code?

    - by Don Wilson
    Is there a leak in this code? // Move the group Group *movedGroup = [[Group alloc] init]; movedGroup = [[[[GroupList sharedGroupList] groups] objectAtIndex:fromIndex] copy]; [[GroupList sharedGroupList] deleteGroup:fromIndex]; [[GroupList sharedGroupList] insertGroup:movedGroup atIndex:toIndex]; // Update the loadedGroupIndex pointer if (loadedGroupIndex < fromIndex & loadedGroupIndex >= toIndex) { loadedGroupIndex = loadedGroupIndex + 1; } else if (loadedGroupIndex > fromIndex & loadedGroupIndex < toIndex) { loadedGroupIndex = loadedGroupIndex - 1; } else if (loadedGroupIndex == fromIndex) { loadedGroupIndex = toIndex; } [movedGroup release]

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  • Usage of atoi in the c language

    - by maddy
    I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi val is shown as 0. But I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array.? Please correct me if I am wrong.

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  • Why doesn't Perl threading work when I call readdir beforehand?

    - by Kevin
    Whenever I call readdir before I create a thread, I get an error that looks like this: perl(2820,0x7fff70c33ca0) malloc: * error for object 0x10082e600: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug Abort trap What's strange is that it happens when I call readdir before I create a thread (i.e. readdir is not called in any concurrent code). I don't even use the results from readdir, just making the call to it seems to screw things up. When I get rid of it, things seem to work fine. Some example code is below: opendir(DIR, $someDir); my @allFiles = readdir(DIR); close(DIR); my $thread = threads-create(\&sub1); $thread-join(); sub sub1 { print "in thread\n" }

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  • Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

    - by Shane MacLaughlin
    Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it safe to use the following? memcpy(Array1,Array2,PageSize*sizeof(MyClass)); The reason I ask, is that I'm dealing with very large collections of paged data, as decribed here, where performance is critical, and memcpy offers significant performance advantages over iterative assignment. I suspect it should be ok, as the 'this' pointer is an implicit parameter rather than anything stored, but are there any other hidden nasties I should be aware of?

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  • How to build up a lookup table in microcontroller?

    - by GiGi
    Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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  • C++ template parameter/class ambiguity

    - by aaa
    hello. while testing with different version of g++, the following problem came up template<class bra> struct Transform<bra, void> : kernel::Eri::Transform::bra { static const size_t ni = bra::A::size; bra::A is interpreted as kernel::Eri::Transform::bra::A, rather than template argument by g++ 4.1.2. on the other hand, g++ 4.3 gets it right. what should be correct behavior according to standard? Meanwhile, I refactor slightly to make problem go away.

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  • get content from website with utf8 format

    - by zahir
    i want how to get the content from websites with utf8 format,, i have writing the following code is try { String webnames = "http://pathivu.com"; URL url = new URL(webnames); URLConnection urlc = url.openConnection(); //BufferedInputStream buffer = new BufferedInputStream(urlc.getInputStream()); BufferedReader buffer = new BufferedReader(new InputStreamReader(urlc.getInputStream(), "UTF8")); StringBuilder builder = new StringBuilder(); int byteRead; while ((byteRead = buffer.read()) != -1) builder.append((char) byteRead); buffer.close(); String text=builder.toString(); System.out.println(text); } catch (IOException e) { e.printStackTrace(); } but i cant get the correct format... thanks and advance..

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  • MinGW screw up with COLORREF and RGB

    - by kjoppy
    I am trying to build a 3rd party open source project using MinGW. One of the dependencies is wxWidgets. When I try to make the project from MSYS I get a compiler error from /MinGW/msys/1.0/local/include/wx-2.8/wx/msw/private.h In function 'COLORREF wxColourToRGB(const wxColour&)': error: cannot convert 'RGB' to 'COLORREF {aka long unsigned in}' in return This is somewhat odd given that, according to Microsoft the RGB macro returns a COLORREF. In fact, looking in H:\MinGW\include I find wingdi.h with the following code #define RGB(r,g,b) ((COLORREF)((BYTE)(r)|((BYTE)(g) << 8)|((BYTE)(b) << 16))) What sort of thing would cause this error? Is there some way I can check to see if COLORREF and RGB are being included from wingdi.h and not somewhere else? Is that even worth checking? Specifications GCC version 4.7.2 wxWidgets version 2.8.12 (I'm new to C++ and MinGW specifically but generally computer and programming literate)

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  • assignment vs std::swap and merging and keeping duplicates in seperate object

    - by rubenvb
    Say I have two std::set<std::string>s. The first one, old_options, needs to be merged with additional options, contained in new_options. I can't just use std::merge (well, I do, but not only that) because I also check for doubles and warn the user about this accordingly. To this effect, I have void merge_options( set<string> &old_options, const set<string> &new_options ) { // find duplicates and create merged_options, a stringset containing the merged options // handle duplicated the way I want to // ... old_options = merged_options; } Is it better to use std::swap( merged_options, old_options ); or the assignment I have? Is there a better way to filter duplicates and return the merged set than consecutive calls to std::set_intersection and std::set_union to detect dupes and merge the sets? I know it's slower than one traversal and doing both at once, but these sets are small (performance is not critical) and I trust the Standard more than I trust myself.

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