C++ :: Write Cross-platform File IO
Aug 21, 2013
I discussed a topic about how to write cross-platform file IO code with a member named Disch for about a year ago. Since I am a beginner I am not sure if the "rules" for doing this has changed or not within C++.
He taught me that differenct CPU:s use different endianness when reading and writing to files. However, why can't the C++ standard file IO functions detect what endianness should be used on the current machine that is running the program? Why didn't the developers who created the standard library develop file IO functions that are cross-platform from the beginning? Have the rules changed since last year?
What I learn is that if you need to store data in files that will be read and written to on different machines, you have to define in the program what endianness should be used. For example, if I needed to store 4 bytes, I had to do this manually with my own functions and define in those which endianness is used.
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Nov 10, 2014
I am overriding OnSaveDocument in my MFC document class to strip out the carriage returns when saving my app's document to a UNIX file system but not when the user is saving a file to a Windows file system.
Is there a way to determine if the lpszPathName in OnSaveDocument(LPCTSTR lpszPathName) is a UNIX or Windows file system?
Note, I want to avoid hard coding server names and I want to avoid overriding the FileSave dialog and forcing the user to select Windows or UNIX.
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Apr 18, 2014
System();is bad, I get that. Is there another way, that works across platforms I can use to execute an external program. If not, is there a windows specific way.
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Aug 28, 2013
I am planning to develop a GUI that will run on Windows, Linux, Android & iOS. If am right, VC++ apps don't work on Linux, Android & iOS. Is that correct?
Is there an alternative to that? Which other tool works for GUI development on above mentioned 4 platforms?
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Oct 17, 2013
In my game, I want to display dialogues for exceptions, and I don't really want to use something heavy like Qt, but then I also don't want to write and maintain my own platform-specific code to do it. Is there any library that can display simple message dialogues, just a few lines of text and an OK button, without being complete overkill like a full-blown GUI library?
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Feb 10, 2014
Suppose:
cin >> number;
pointer = new type[number + (rand()%number);
So, I wont know the memory allocated for pointer. How can I check it in all OS?
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Mar 29, 2013
(C++ question) I need to be able make a compiled code (like a .dll?) which other programmers can use on linux, win,, mac, etc.
The compiled code would simply do calculations and spit out an answer in memory.
I need it to have certain functions that they can easily call and understand (without actually seeing the source).
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Sep 12, 2014
I am starting a turn based battle (similar to pokemon) app. How could i make this and make it cross platform. Also is it possible to make it access gps and allow other devices with the same app communicate with each other?
I have done things on the command line but i never made anything with images so i dont even know where to start for this app.
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Nov 4, 2013
I'm working on a project which uses gtk+ and gtkmm. We use them in preference to MFC because the program needs to be cross-platform. For quite a long time, customers on OS-X and Linux have sometimes complained that the program would crash during shutdown but the Windows version (which I work on) never seemed to suffer. However, I'm now transferring my build environment to a new PC and I'm noticing the same shutdown crashes. It's a bit complicated so let me start with a small example:-
Code:
namespace Whatever {
class B {
public:
virtual ~B();
private:
int bb;
[Code] ....
Suppose I run the above program. When it stops at breakpoint #1 I make a note of the value of pA. Eventually the program reaches breakpoints #2 and #3. At each point my this pointer is exactly the same number. If the value of pA was 0x03604fb0, my this pointer is identical at both stages.
Now let's consider the real example:-
Code:
namespace Gtk {
class Widget {
public:
virtual ~Widget() {}
[Code] .....
Suppose I run the real example. At breakpoint #1 the value of pW is 0x03604fb0. But by the time I reach breakpoint #2 my this point is slightly different:- 0x03604fcc. It doesn't seem right to me and I'm wondering if it might be contributing to our shutdown crashes.
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Jul 6, 2014
I am an experience C programmer but never implement GUI.
I need to make a demo implementation that will be run on Linux and will implement GUI.
I searched the WEB and found lot of information, among is implementing the GUI in HTML and run the API through web browser.
How can I make such implementation in C?
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Oct 10, 2014
I am trying to compute the cross product of an 1x6 column vector "D" with a 6xN matrix "S".
vector< vector<float> > D(1, vector<float>(6));
vector< vector<float> > S(6, vector<float>(10)); // Example where N = 10
float cProduct = D*S; // ?
The last line fails, so I'm wondering how you would get the cross product?
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Feb 10, 2013
I have Mq4 platform calling functions from DLL some how it doesnt make any differents when I make the call....
// DLL Code
#define WIN32_LEAN_AND_MEAN
#define MT4_EXPFUNC __declspec(dllexport)
using namespace std;
std::string My_String;
#define stringify(mymonths ) # mymonths
[Code] ....
I call this function
bool counts = StartRulls(bars);
Print("counts =",counts );
2013.02.09 23:03:242010.03.31 16:37 My_Mq4.mq4 EURCAD,M5: counts = 1
My result always stays 1
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Mar 6, 2015
Consider the situation where you're writing a cross-platform library that has functions for creating and manipulating windows. To create a window suitable for OpenGL rendering on Windows you need to call a bunch of different functions such as GetModuleHandle, RegisterClass, CreateWindow, SetPixelFormat, GetDC, wglCreateContextGetDC and so on. All of these functions can potentially fail in one way or another and the Windows documentation doesn't even attempt to list all the different error codes that these functions return.
Let's say your function for creating a window is called create_window(). What kind of error message should you return if any of these platform specific functions fail? It could be something as simple as MultiByteToWideChar failing for some reason when you convert the UTF-8 string your API uses internally to the UTF-16 string that the Windows API expects. I've read that you're not supposed to leak implementation details from your API but what are you suppose to return when an encoding conversion fails that is supposed to be completely transparent to the user of your library?
I've decided to simply return an error code indicating a platform specific error in those cases because there's no way I can anticipate all the different errors that the Windows API might return. The problem with that is that almost all the errors end up being platform errors and without a way to actually tell what the error is then you're basically saying that some unknown error happened. That's not very useful. You could have a function called get_platform_error() that you call to obtain the exact platform error that occurred, but I'm not a fan of such a design and I've had enough trouble with GetLastError() style error handling as it is.
An alternative to that is to create a struct that represents errors and have a field in it where you can store platform specific errors. I believe this is what Apple do with their NSError error object but I'm not sure how I feel about that approach.
Assuming you implement a way to return the platform specific error code then the next part is obtaining a string that describes the error. Your library can obviously not implement error strings for every single error code that Windows might return so you're forced to use FormatMessage. The problem with that function is that you can't force it to return error messages in a specific language and it's not even guaranteed that you can get an English translation of the error string. I don't want to display error messages that mixes English with the current language the operating system uses so how do I solve this problem?
Are there any good open source libraries I could study? The ones I've looked at so far have subpar error handling at best. Many of them don't even check the return values from platform specific functions.
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Oct 26, 2013
I'm creating a small command line game in C. I have never done anything cross platforms, but this is small enough (so far) that it might not be too bad.
When I am done, I'm not sure how it will be distributed: Either I will just send people the C files and say "compile on your system with these options", or I will just have executables for various systems. Probably Windows 7/8, Ubuntu, CentOS, and whatever I can find to test on.
I right now I'm testing/developing on Windows 7 using MinGW. So my questions are: while I'm developing, how should I be compiling/testing it?
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Mar 1, 2014
I have cross sections in the form of rectangles in the XY plane formed from two point (top left, bottom right) as well as their Z position. I'd like finding some sort of API that can extrude a basic linear-average-approximated 3D shape (preferably eventually into STL format) from these points. I've tried googling but to no avail. The aim is to build a 3D shape from 2D wireframes.
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Jul 11, 2014
The project builds on Win32 platform, but not on x64.
Full error message: dllentry.obj : error LNK2001: unresolved external symbol "class CFactoryTemplate * g_Templates" (?g_Templates@@3PAVCFactoryTemplate@@A)
The dllentry.cpp (a DirectShow base class) compiles on both platforms. It contains the external declarations:
extern CFactoryTemplate g_Templates[];
extern int g_cTemplates;
g_Templates[] is then used in two functions:
__control_entrypoint(DllExport) STDAPI DllGetClassObject(__in REFCLSID rClsID,
__in REFIID riid, __deref_out void **pv)
[Code]...
myClass.cpp contains the definitions for the two externals in dllentry.cpp, at top level, just after the includes:
CFactoryTemplate* g_Templates=0;
int g_cTemplates=0;
myClass.cpp also compiles by itself, but the project does not build. I checked all the libraries in the project settings and all seems to be OK, the 64 bit versions are used.
What should I do to make the project build for x64 platform?
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Dec 11, 2014
Why something doesn't work without setting global variables. I want to know how to deliver values for example my boolean value "ende" (means end) from the function in line 99
Code:
bool pruefeGewinn() or in line 116 Code: bool spielfeldVoll() to the main function for using it there for Code: } while (ende != true); in line 164.
How to return it correctly?
Here is the Code of the game TicTacToe.
Code:
#include <stdio.h> // In- and Output
#include <stdlib.h> // Implementation of many functions
#include <stdbool.h> // Allows in C99 True and False as Boolean
#include <time.h> // Allows using Random by time
/*----------------------- Constants -------------------------*/
#define KANTENLAENGE 3
#define STRING 100
[Code] .....
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Jan 8, 2015
I have to write some cpp program which computes area of a triangle using cross product,we give 3 vertices as R2 and 3 edges as double.
I am beginning like this;
#include <iostream>
#include "R2.h"
#include <cmath>
using namespace std;
double area ( R2 *A,double *z)
[Code] .....
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Jun 20, 2014
I'm using ubuntu 14.04 and I want to cross compile this simple GTKmm program for Windows:
#include <gtkmm.h>
int main(int argc, char *argv[])
{
Glib::RefPtr<Gtk::Application> app =
Gtk::Application::create(argc, argv,
"org.gtkmm.examples.base");
Gtk::ApplicationWindow window;
return app->run(window);
}
I don't know how to do this...When I use this command:
x86_64-w64-mingw32-g++ main.cpp -o hello.exe `x86_64-w64-mingw32-pkg-config gtkmm-3.0 --cflags --libs`
I get this error:
In file included from /usr/include/cairomm-1.0/cairomm/fontoptions.h:26:0,
from /usr/include/cairomm-1.0/cairomm/surface.h:37,
from /usr/include/gdkmm-3.0/gdkmm/pixbuf.h:40,
from /usr/include/gdkmm-3.0/gdkmm/dragcontext.h:31,
from /usr/include/gtkmm-3.0/gtkmm.h:90,
from main.cpp:1:
/usr/include/cairo/cairo-ft.h:50:35: fatal error: fontconfig/fontconfig.h: No such file or directory
#include <fontconfig/fontconfig.h>
[code]....
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Aug 29, 2014
One of my class assignments is to create a program that receive a .txt file containing a students name and their grades as follows:
John K. 99, 87, 57, 89, 90, 95
Amanda B. Jones 100, 88, 76, 99, 86, 92
etc..
The number of students is unknown until run time. You have to take those grades and average them weighing the first (4) at 10% a piece and the last (2) at 30% each.
Then return an output file with the students name and their letter grade A,B,C,D,F based on their computed score. In addition, on screen it needs to display the average scores for each Q1, Q2, etc. as well as the minimum and maximum for each test on the screen. I am having a hard time in assigning the scores to a variable so that they can then be computed as an average and then used to determine a letter grade. I have begun to write the code and am a bit stuck..here's what I have so far:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
[Code]....
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Mar 15, 2013
The Objective Of This Program Is To Create A File To Write Text And Read Back The File Content. To Do That I Have Made Two Function writeFile() To Write And readFile() To Read.The readFile() function works just fine but writeFile() doesn't.
How writeFile() function Works? when writeFile() function Execute It Takes Characters User Type And When Hit Enter(ASC|| 10) It Ask "More?(Y/N)" That Means What User Want? Want To Go Next Line Or End Input?
If "Y" Than Inputs Are Taken From Next Line Else Input Ends.
But The Problem Is When Program Encounters ch==10 It Shows "More?(Y/N)" And Takes Input In cmd variable.If cmd=='Y' I Mean More From Next Line Than It Should Execute Scanf Again To Take ch I Mean User Input.But Its Not!!! Its Always Showing "More?(Y/N)" Again And Again Like A Loop.
Code:
#include <stdio.h>
void writeFile(void);
void readFile(void);
int main(){
[Code].....
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Jul 8, 2013
how do i decompress an input file and write the results into an output file?
also my do while loop is supposed to keep going unless the user selects the option to exit the program, instead it exits after finishing ay of the options.
here's my code so far...
#include <iostream>
#include <iomanip>
#include <fstream>
[Code]....
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Jun 11, 2014
I have a .txt file which I want to read from and then write a new text file, this time with sorted lines. It is easy to sort one value, but what about sorting entire lines based on one value?
I want to sort the lines based on the FIRST value.
Example text file contents:
values;data
5.01 100
2.9 342
2.69 43534
10.1 43
6.8 45324
Output: Text file containing
2.69 43534
2.9 342
5.01 100
6.8 45324
10.1 43
It's easy to do this if there was only 1 number on each line, but I do I sort all the lines based on the first number in each line?
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Aug 31, 2014
We have to write a program that reads an input file containing data in the form:
Martha J, 80, 90, 90, 100, 89, 99, 85
Anna Smith, 65, 72, 77, 68, 62, 70, 65
Bill Gates, 60, 54, 89, 62, 65, 60, 50
...etc...
and then use that information to determine their letter grade and write that information to a .txt file. I have been able to successfully pass that information to a function to determine their letter grade and have been able to successfully compute their letter grade. However, I can get this information to successfully post within the *computeGrade () function. Yet, I don't know how to pass this information back to the main() on a student by student basis so that I can open a new .txt file and write just their name and letter grade to it.
Another issue I'm having is when it comes to computing the averages of the class. Each score is either a quiz (there are 4), a midterm (there are 2) or a final (there is 1). I'm a little stuck on how to pass say all of the quiz 1 grades as one entity to the function averagesminmax(). Is there a way to compile each of the grades for a specific quiz or midterm as one array and pass that to the function to then do the computation. Also we need the min and max so again from compiling the grades of a particular quiz or exam together as one.
Here's the code that I have so far.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
const char *computeGrade();
int averagesminmax();
int main() {
char fName[20];
char lName[20];
[code]....
Do I need to re-read the input file and assign them to different variables?
Here's a sample of the output so far:
Enter input .txt file name
Graded
Thui Bhu, 91, A
Ariana B. Smith, 96, A
Emily Gonzales, 83, B
Jennifer L, 89, B
Maria Jones, 67, D
Bill Gates, 55, F
Escobar Morris, 78, C
Anne Latner, 88, B
Program ended with exit code: 0
Also in my output file, the only thing that it prints will be the first name of whatever the last student in the input file list is.
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Apr 22, 2013
I am trying to get the code to read from the txt file one bite at a time and then write this bite into the binary file but i cant seem to get it working.
FILE *fpcust, *fpcustbin; //<<<<<-----point to both sales and customers text files, and the new .bin files for both
char buffer;
int ch;
int ch1;
fpcust = fopen("c:customers.txt", "r"); //<<<<-----pointing to the file
fpcustbin = fopen("c:customers.bin", "wb"); //<<<<<-----pointing to the new binary file, opening in writing binary
[Code]...
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Dec 11, 2013
im supposed to create a program that reads in a list of integers from the terminal and writes the negative numbers to one file and the positive numbers to another file.
i got most of it doen but for some reason its not writting the negative numbers. on what im doing wrong?
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(){
int pos_num = 0;
int neg_num = 0;
int positive_numbers = pos_num % 5;
[Code]...
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