C++ :: Reading And Writing To File Using Same Fstream
Oct 16, 2013
I have a file of data where each line consists of 4 parameters (degree, alpha, beta and x) and a value corresponding to these, organized in increasing order of the parameters. Here's the test file I'm using:
My code is supposed to look for a certain set of parameters (currently set to 1 2 1 1.5, which is not contained in the file) and its value. If it's there (i.e. the file contains the value for the right parameters) the program is done. If not it should calculate the value using a function JacobiPoly() and insert the wanted parameters and corresponding value in the appropriate place in the file.
I have a code in which I think everything works except the writing to file. I use an fstream so I can both read and write and open it with ios::out||ios::in. I'm also aware I need something similar to fseek in between input and output but according to [URL] .... reading and writing to the same file using the same fstream, seekp() should suffice. I'm using seekp(), but the output (in the form inout << (...)) doesn't work.
I want to edit the contents of a file using fstream, but none of the modes in the fstream constructor work for me.
If I use ios::trunc, then the whole file is deleted - but I want to retain the contents and edit it. If I use ios::app, then I can only add data to the end of the file - but I want to edit the data in the middle of the file. If I use ios::ate, then the whole file is deleted again, similar to ios::trunc.
How can I create an fstream object without deleting the contents of the file, whilst still being able to move the pointer arbitrarily around in the file with seekp() (and not just placing it at the end as with ios::app)?
I would like to copy one bmp file to another using plain fstream (none 3-rd party library). I've managed to come up with something but I keep getting error:
Unhandled exception at 0x504A3442 (msvcr120d.dll) in ConsoleApplication1.exe: 0xC0000005: Access violation reading location 0x00380000.
when i try to write the content of the bmp files not the header, namely error occurs in this line:
Also i am not sure if i am doing it in a right way, meaning that even after solving this error i will copy the bmp file successfully.
Code:
// ConsoleApplication1.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <iostream> #include <fstream> using namespace std; struct BITMAPfileHEADER { unsigned short bfType;
I'm writing a program using Huffman algorithm to compress text file. I have tested my program by just printing the printing ASCII character to file and it worked fine. However, now I have to implement using bits and my program doesn't work. It seems like I'm not reading or writing the right bits. Here is the result of my testing:In the input file I put abc the input file to compress it. Then I uncompress it the out out is aaa. Below is a snippet of how I read and write bits
Code: class BitInput { istream& in; // the istream to delegate to char buf; // the buffer of bits int nbits; public:
I have a text file containing 500 signed decimal numbers. My task is to read each entry and convert into a 16-bit 2's complement representation (binary number) and write into the another text file.
Is there a way to read and write to the same file?
I'm writing a game program and I want to save the score at the end of the game to a txt file. The txt file already contains other game scores. How do I store the score without overwriting the previous scores.
I'm writing a program using Huffman algorithm to compress text file. I have tested my program by just printing the printing ASCII character to file and it worked fine. However, now I have to implement using bits and my program doesn't work. It seems like I'm not reading or writing the right bits. Here is the result of my testing:In the input file I put abc the input file to compress it. Then I uncompress it the out out is aaa. Below is a snippet of how I read and write bits
public:
BitInputStream(istream& s) : in(s), buf(0), bufi(8) { } /** Read the next bit from the bit buffer. * Return the bit read as the least significant bit of an int. */ int readBit(){ int i; if(nbits == 8){ buf = in.get();
I am attempting to read a ppm file. When i do it i try to write it back in another file just to see how's done and i get a terrible result. I assume the problem is something with the casting i do to the variables.
This is my image class
Image:: Image(unsigned int width, unsigned int height, bool interleaved) { buffer = new Component [3*width*height]; this->height=height; this->width=width; this->buffer=Component();
I am having problems either writing data to a binary file or reading from the file. Through the process of elimination I am posting the code where the data is written to file to see if I can eliminate that as an option. I know the data is being processed correctly because, through the use of another function, I can view the data.
I also know that fwrite must be including some padding because the file size ends up being 576 bytes after it is written instead of 540 bytes (the size it would be if no padding is used). Here is my struct:
Code:
typedef struct { char teams[25]; float wins; float losses; float pct; int runsScored; int runsAgainst; } STATISTICS;
Code to write data(Double type e.g 12345.67891) in text file like pattern given below. Remember to put tab between each column.
----------------------------------------------------- Column1 Column2 Column3 Value 1 Value 2 Value 3 Value 4 Value 5 Value 6 Value 7 Value 8 Value 9 ----------------------------------------------------
I'm currently working on a server for handling clients in a 2d online game and I wrote some regular fstream file code for handling the file that stores their information and I was about to implement it into the server, then I realized there might be a problem having it open multiple times concurrently, so I googled it and came up with posts like
[URL]
I'm wondering if I can just treat it like everything else or will I have to do something specific for opening on multiple threads?
p.s. I did read those posts but I'm very new to multithreading
I'm having issues with writing to a file. more precisely, i'm trying to determine if a set of numbers are in the file. if they are already in it, don't write to the file. if not, write to the file. My problem is my program is writing all numbers, even duplicates. The sort is working.
#include <iostream> #include <fstream> #include <algorithm> using namespace std; //Counter Stats int STR;
I am using visual studio 2012.....in below code i m writing data in to a test.txt file but i dont know with which key file stop accepting char...i tried ctrl+z and ctrl+d but not working ....
For some unknown reason when i try the following code it doesn't create a file. (the program will simply get two inputs from the user and then use http to obtain the html/php text and then output it to a file)
code:
#include <SFML/Network.hpp> #include <iostream> using std::cout;
Name: Mary Smith Exam 1: 65 Exam 2: 79.1234 Exam 3: 70.24
Becomes something like this in the output file:
Name: Parker, Peter Average Score: 92.28 Grade: A
Name: Smith, Mary Average Score: 71.45 Grade: C
I know I'm supposed to read the whole file, but I'm getting really confused on how to take the name of each student separately without recording Exam 1, 2, and 3. I'll be able to do the average score and grade on my own.
I have to make a program that asks for your username (any)to register it. When you type it it will say something. I want to create a txt file also. so this is what I have:
#include <iostream> #include <fstream> using namespace std; int main() { int a; { ofstream myfile;
[Code] ....
now, how can I use the cout again to print something "Welcome to the program..."?
I'm messing around with reading and writing files. The first file creates a small txt file. Simple enough
#include <iostream> #include <fstream> #include <string> using namespace std; int main(){ string name; string desc;
[Code] ....
It does what it should. It creates a text file "items.txt" .... It reads as such:
dagger,a dagger,15,10,0,1,3,1,0,0,0,1,0,0,0,0,0,1
The second file is meant to read the file and place the data back into the variables. This happens, but the data crams itself into the first variable, and the rest of them collect the trash that's in memory.
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string name,desc;
[Code ....
I need to get "dagger" into name, "a dagger" into description, and each value with their perspective variable. I'm sure I need some type of "separator". Hopefully I can use the comma. Before it's over, I will have about a hundred items that will need to be read into a class of items.
I did some of the projects using STL container and it is pretty much efficient to retrieve the data's information quickly (i.e. sets, sets & maps). I read many C++ OOP book and none of them make me clear about the Link Between (STL) Container and (Fstream) File I/O. Can they link together ?
I am going to design a small Library Book Management Project. I am planning to develop it using the STL Algorithms & containers. Objective of this project is to keeping the records of books issued and deposited by students in a particular date. User will be given a facility to retrieve student's information, book information and he/she can modify/update specific book's, student's information by changing issue date, deposited date, Book's publication etc.
My intention is to create a File I/O where user can input & update/modify daily transaction inside the file called (xx.dat) file in project directory. Is it possible to create 'set' container inside the file (xx.dat) ? Or, It's impossible ? Or, do i have to do this in other way?
