Like Tree1Likes
  • 1 Post By SterlingM

File IO

This is a discussion on File IO within the C++ Programming forums, part of the General Programming Boards category; Hi, I am having trouble with (I think) file i/o. The relevant code is below Code: //main.cpp int main (int ...

  1. #1
    Registered User
    Join Date
    Oct 2009
    Posts
    117
    Hi, I am having trouble with (I think) file i/o. The relevant code is below

    Code:
    //main.cpp
    int main (int argc, char * const argv[]) {
    std::string filename;
    	cout<<"Please enter a filename of a map"<<endl;
    	cin>>filename;
    	
    	Room theroom(filename);
    	
    	cout<<theroom.getMap()->toString()<<endl;
    }
    Code:
    #ifndef ROOM_H
    #define ROOM_H
    #include "Grid.h"
    #include <string>
    
    class Room {
    public:
    	
    	Room(std::string&);
    	~Room();
    	
    	Grid*& getMap();
    	
    private:
    	Grid* map;
    };
    
    #endif
    Code:
    //room.cpp
    Room::Room(std::string& filename) {
    	
    	std::ifstream thefile(filename.c_str(), std::ios::in);
    	
    	if(!thefile) {
    		std::cout<<"File could not be found"<<std::endl;
    		exit(1);
    	}
    	
    	int rowcount = 0;	//row dimension var
            char colcount[256];
    	
    	while(!thefile.getline(colcount, 256).eof()) {
    		rowcount++;
    		std::cout<<colcount<<std::endl;
    	}
    	
    	//once more for last line
    	rowcount++;	
    	std::cout<<colcount<<std::endl;
    		
    	//make 2d char array
    	char** themap = new char*[rowcount];
    	for(int i=0;i<rowcount;i++)
    		themap[i] = new char[strlen(colcount)];
    	
    	std::cout<<"rowcount: "<<rowcount<<" colcount: "<<strlen(colcount)<<"\n";
    	
    	int cols = (int)strlen(colcount);
    	map = new Grid(themap, rowcount, cols);
    	
    	thefile.close();
    }
    
    
    Room::~Room() {}
    
    
    Grid*& Room::getMap() {return map;}
    Code:
    #ifndef GRID_H
    #define GRID_H
    #include<string>
    
    class Grid {
    public:
    	Grid();
    	Grid(char**&, int&, int&);
    	~Grid();
    	
    	char**& getMap();
    	char getPos(int&, int&);
    	
    	std::string toString();
    private:
    	char** map;
    	int rows;
    	int cols;
    };
    
    #endif
    Code:
    //grid.cpp
    Grid::Grid() {}
    
    Grid::Grid(char**& themap, int& r, int& c) : map(themap), rows(r), cols(c) {
    	std::cout<<"grid constructor\n";
    	std::cout<<"r: "<<r<<" c: "<<c<<"\n";
    	std::cout<<"rows: "<<rows<<" cols: "<<cols<<"\n";
    }
    
    //todo
    Grid::~Grid() {
    }
    
    char**& Grid::getMap() {return map;}
    
    char Grid::getPos(int& row, int& col) {return map[row][col];}
    
    
    std::string Grid::toString() {
    	std::ostringstream result;
    	
    	result<<"rows: "<<rows<<" cols: "<<cols<<"\n";
    	
    	for(int row=0;row<rows;row++) {
    		for(int col=0;col<cols;col++) {
    			result<<getPos(row, col);
    			std::cout<<"grid("<<row<<","<<col<<"): "<<map[row][col]<<std::endl;
    			if(col == cols-1)
    				result<<"\n";
    		}	//end inner for
    	}	//end outter for
    
    	return result.str();
    }
    I want to pass a string with a filename to Room. Then Room should create a 2D char array and pass that to a Grid constructor to make a Grid. Whenever I run this, the grid constructor cout lines print correct information. My file is just a square outlined with # symbols and a path going up through the middle.
    Code:
    ########### ########
    #         # #      #
    #         # #      #
    #         # #      #
    #         # #      #
    #         # #      #
    #         # #      #
    #         # #      #
    #         # #      #
    ########### ########
    However, whenever I print the grid toString in main, I get nothing. The cout line in the function prints the correct row and column numbers, but everything is blank. Even if I call the toString right after I initialize map at the bottom of the Room constructor. I don't see why its not giving the map variable the right value. Can anyone explain to me whats wrong here? Any help is appreciated.

    The # symbols are formatted wrong in the post. In my file, they form a square.

    The actual output is -
    ########### ########
    # # # #
    # # # #
    # # # #
    # # # #
    # # # #
    # # # #
    # # # #
    # # # #
    ########### ########
    rowcount: 10 colcount: 20
    grid constructor
    r: 10 c: 20
    rows: 10 cols: 20
    grid(0,0):
    grid(0,1):
    grid(0,2):
    grid(0,3):
    grid(0,4):
    grid(0,5):
    grid(0,6):
    grid(0,7):
    grid(0,8):
    grid(0,9):
    grid(0,10):
    grid(0,11):
    grid(0,12):
    grid(0,13):
    grid(0,14):
    grid(0,15):
    grid(0,16):
    grid(0,17):
    grid(0,18):
    grid(0,19):
    grid(1,0):
    grid(1,1):
    grid(1,2):
    grid(1,3):
    grid(1,4):
    grid(1,5):
    grid(1,6):
    grid(1,7):
    grid(1,8):
    grid(1,9):
    grid(1,10):
    grid(1,11):
    grid(1,12):
    grid(1,13):
    grid(1,14):
    grid(1,15):
    grid(1,16):
    grid(1,17):
    grid(1,18): \377
    grid(1,19): \377
    grid(2,0):
    grid(2,1):
    grid(2,2):
    grid(2,3):
    grid(2,4):
    grid(2,5):
    grid(2,6):
    grid(2,7):
    grid(2,8):
    grid(2,9):
    grid(2,10):
    grid(2,11):
    grid(2,12):
    grid(2,13):
    grid(2,14):
    grid(2,15):
    grid(2,16):
    grid(2,17):
    grid(2,18):
    grid(2,19):
    grid(3,0):
    grid(3,1):
    grid(3,2):
    grid(3,3):
    grid(3,4):
    grid(3,5):
    grid(3,6):
    grid(3,7):
    grid(3,8):
    grid(3,9):
    grid(3,10):
    grid(3,11):
    grid(3,12):
    grid(3,13):
    grid(3,14):
    grid(3,15):
    grid(3,16):
    grid(3,17):
    grid(3,18):
    grid(3,19):
    grid(4,0):
    grid(4,1):
    grid(4,2):
    grid(4,3):
    grid(4,4):
    grid(4,5):
    grid(4,6):
    grid(4,7):
    grid(4,8):
    grid(4,9):
    grid(4,10):
    grid(4,11):
    grid(4,12):
    grid(4,13):
    grid(4,14):
    grid(4,15):
    grid(4,16):
    grid(4,17):
    grid(4,18):
    grid(4,19):
    grid(5,0):
    grid(5,1):
    grid(5,2):
    grid(5,3):
    grid(5,4):
    grid(5,5):
    grid(5,6):
    grid(5,7):
    grid(5,8):
    grid(5,9):
    grid(5,10):
    grid(5,11):
    grid(5,12):
    grid(5,13):
    grid(5,14):
    grid(5,15):
    grid(5,16):
    grid(5,17):
    grid(5,18):
    grid(5,19):
    grid(6,0):
    grid(6,1):
    grid(6,2):
    grid(6,3):
    grid(6,4):
    grid(6,5):
    grid(6,6):
    grid(6,7):
    grid(6,8):
    grid(6,9):
    grid(6,10):
    grid(6,11):
    grid(6,12):
    grid(6,13):
    grid(6,14):
    grid(6,15):
    grid(6,16):
    grid(6,17):
    grid(6,18):
    grid(6,19):
    grid(7,0):
    grid(7,1):
    grid(7,2):
    grid(7,3):
    grid(7,4):
    grid(7,5):
    grid(7,6):
    grid(7,7):
    grid(7,8):
    grid(7,9):
    grid(7,10):
    grid(7,11):
    grid(7,12):
    grid(7,13):
    grid(7,14):
    grid(7,15):
    grid(7,16):
    grid(7,17):
    grid(7,18):
    grid(7,19):
    grid(8,0):
    grid(8,1):
    grid(8,2):
    grid(8,3):
    grid(8,4):
    grid(8,5):
    grid(8,6):
    grid(8,7):
    grid(8,8):
    grid(8,9):
    grid(8,10):
    grid(8,11):
    grid(8,12):
    grid(8,13):
    grid(8,14):
    grid(8,15):
    grid(8,16):
    grid(8,17):
    grid(8,18):
    grid(8,19):
    grid(9,0):
    grid(9,1):
    grid(9,2):
    grid(9,3):
    grid(9,4):
    grid(9,5):
    grid(9,6):
    grid(9,7):
    grid(9,8):
    grid(9,9):
    grid(9,10):
    grid(9,11):
    grid(9,12):
    grid(9,13):
    grid(9,14):
    grid(9,15):
    grid(9,16):
    grid(9,17):
    grid(9,18):
    grid(9,19):
    rows: 10 cols: 20


    Except the #s are formatted right. I don't know what the \377 means.
    Last edited by Salem; 03-22-2011 at 08:47 AM. Reason: Added the proper 'map', from the attached file

  2. #2
    and the hat of wrongness Salem's Avatar
    Join Date
    Aug 2001
    Location
    The edge of the known universe
    Posts
    32,452
    \377 is the octal (base 8) representation of a single character (usually a non-printable character).

    In hex, this is 0xFF and decimal 255.

    What it usually means is that you've read past the end of the file, and you have the casted value of EOF (typically -1) stored.

    In short, look at your eof() handling. It seems overly complicated and messy to me.
    Code:
    while ( thefile.getline(colcount, 256) ) {
    }
    loops until the end of the file.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  3. #3
    Registered User
    Join Date
    Oct 2009
    Posts
    117
    Well whenever I use that for my while condition, it only reads 11 for my rows and 0 for my columns.

  4. #4
    and the hat of wrongness Salem's Avatar
    Join Date
    Aug 2001
    Location
    The edge of the known universe
    Posts
    32,452
    OK - start with the basics, just write some code to read each line of the file.

    Also, if the forum isn't rendering your room input file properly, then attach it to your post so we can see exactly what it looks like.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  5. #5
    Registered User
    Join Date
    Oct 2009
    Posts
    117

    map

    Okay, I'll go back to the basics and try to solve the problem. In the meantime, here is the file.
    Attached Files Attached Files

  6. #6
    and the hat of wrongness Salem's Avatar
    Join Date
    Aug 2001
    Location
    The edge of the known universe
    Posts
    32,452
    I updated your post to show the correct map file. Just so you know, it might look poor when you paste to the edit window, but the code tags will make it right again.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  7. #7
    Registered User
    Join Date
    Oct 2009
    Posts
    117
    Okay, I got it working. In case anyone has the same problem, the code (with some debug lines I haven't taken out yet) is -
    Code:
    Room::Room(std::string& filename) {
    	std::stringstream tempmap;	//temporary hold map
    	int colcount = 0;	//col dimsension var
    	int rowcount = 0;	//row dimension var
    	char receive[256];	//get lines from file
    	std::ifstream thefile(filename.c_str(), std::ios::in);	//file input stream
    	
    	//make sure the file exists
    	if(!thefile) {
    		std::cout<<"File could not be found"<<std::endl;
    		exit(1);
    	}
    	
    	//go through file and get map
    	while(thefile.getline(receive, 256)) {
    		rowcount++;	//add a row
    		std::cout<<receive<<std::endl;
    		tempmap<<receive<<std::endl;	//pass line into tempmap
    		//set column dimension
    		colcount = strlen(receive);
    	}	//end while
    	
    	/*
    	std::cout<<tempmap.str()<<std::endl;
    	std::cout<<"colcount: "<<colcount<<std::endl;
    	std::cout<<"rowcount: "<<rowcount<<std::endl;
    	tempmap.getline(receive, 256);
    	std::cout<<receive<<std::endl;
    	*/
    	
    	std::cout<<"\n\n";
    	
    	
    	//make 2d char array
    	char** themap = new char*[rowcount];
    	for(int i=0;i<rowcount;i++)
    		themap[i] = new char[colcount];
    	
    	//initialize char array
    	for(int r=0;r<rowcount;r++) 
    		for(int c=0;c<colcount;c++) {
    			//if newline char, conusme that
    			if((char)tempmap.peek() == '\n')
    				tempmap.get();
    			themap[r][c] = (char)tempmap.get();
    		}
    	
    	
    	std::cout<<"\n\n";
    	
    	for(int r=0;r<rowcount;r++)
    		for(int c=0;c<colcount;c++) {
    			std::cout<<themap[r][c];
    			if(c == colcount-1)
    				std::cout<<"\n";
    		}
    	
    	map = new Grid(themap, rowcount, colcount);
    	
    	thefile.close();
    }
    Salem likes this.

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. A development process
    By Noir in forum C Programming
    Replies: 37
    Last Post: 07-10-2011, 10:39 PM
  2. Can you help me about tolower() in file
    By nctar in forum C Programming
    Replies: 7
    Last Post: 05-12-2010, 10:04 AM
  3. Formatting the contents of a text file
    By dagorsul in forum C++ Programming
    Replies: 2
    Last Post: 04-29-2008, 12:36 PM
  4. Can we have vector of vector?
    By ketu1 in forum C++ Programming
    Replies: 24
    Last Post: 01-03-2008, 04:02 AM
  5. File IO with .Net SDK and platform SDK
    By AtomRiot in forum Windows Programming
    Replies: 5
    Last Post: 12-14-2004, 09:18 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21