Reading a file.

This is a discussion on Reading a file. within the C++ Programming forums, part of the General Programming Boards category; Hey ! I have this simple code to read a file and retrieve its content but it's not working properly ...

  1. #1
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    Reading a file.

    Hey ! I have this simple code to read a file and retrieve its content but it's not working properly (it ouputs default values instead of in-file values) = /

    Here's the content of the test file:

    Code:
        r    
    yyyyyyyyyyyyyyyy
    ggggggggggggg
    rrrrrrrrrrrrrrrrrrrrrr
    While stepping through my code with the debugger, it seems that it jumps over the while() condition loop but I don't get why. peek() isn't supposed to return EOF since I used seekg().

    Here's the function:
    Code:
    #include "game_load.h"
    
    const unsigned int* Board::OpenFileContent(const char* file_path) {
    	int cur_pos = 0;
    	std::string line;
    	std::ifstream file(file_path);
    	while(file.peek() != EOF) {
    		std::getline(file, line);
    		if(line.size() > LineLength)
    			LineLength = line.size();
    		LineNb++;
    	}
    
    	Array = new unsigned int[LineLength * LineNb];
    
    	file.seekg(0, std::ios::beg);
    	while(file.peek() != EOF) {
    		std::getline(file, line);
    		for(int i = 0; i < line.size(); i++) {
    			switch(line[ i ]) {
    				case 'g':
    					Array[cur_pos] = B_GREEN;
    					break;
    				case 'y':
    					Array[cur_pos] = B_YELLOW;
    					break;
    				case 'r':
    					Array[cur_pos] = B_RED;
    					break;
    				case ' ':
    				default:
    					Array[cur_pos] = B_EMPTY;
    			}
    			cur_pos++;
    		}
    
    		while(cur_pos < (cur_pos / LineLength + 1)) {
    			Array[cur_pos] = B_EMPTY;
    			cur_pos++;
    		}
    	}
    
    	return Array;
    }
    And here's how I use it:
    Code:
    #include "game_load.h"
    #include <iostream>
    
    int main() {
    	Board b;
    	const unsigned int* dat = b.OpenFileContent("test.dat");
    	for(int y = 0; y < b.GetLineNb(); y++) {
    		for(int x = 0; x < b.GetLineLength(); x++)
    			std::cout << dat[y*x + x];
    		std::cout << std::endl;
    	}
    }
    All of this is compiled using Microsoft's Visual C++ v7.1. Is there any obvious detail I didn't think of or is there any trick I am not aware of ?

    Edit: Closing the file and reopening doesn't change the results. The while() condition loop is still skipped. =/
    I also called fail() and it returns true which means a 'failure extracting from (the) stream'(C++ reference) occured.

    Also, calling exceptions() and catch()'ing exceptions gives me a segmentation fault which is weird...

    Thanks.

  2. #2
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    clear() reset flag bits

    check out vector no need peek()

    Kuphryn

  3. #3
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    I already tried clear() as well. No change at all. Forgot to say that.

  4. #4
    Registered User whiteflags's Avatar
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    Considering what you are doing with the data later on, you might just want to read the file character by character and make your life a bit easier, instead of peeking and grabbing whole lines.

  5. #5
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    @Citizen: I find it easier to grab whole lines as I'm used to it. Thanks, though.

    It worked when I put clear() before seekg() which is logical when I think about it. However, now it outputs a lot of junk. Stepping through the debugger tells me that line contains the right string on the getline() line... but on the for() line (which is right after), it contains a lot of junk. What the hell does that mean ?

  6. #6
    ZuK
    ZuK is offline
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    I don't understand what all this peek should be good for. Just use the normal way to read from a stream line by line

    Code:
    	while( std::getline(file, line) ) {
    		if(line.size() > LineLength)
    			LineLength = line.size();
    		LineNb++;
    	}
    Kurt

  7. #7
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    I didn't know about that trick, thanks.

    Apparently, what's messed up is how I show the content of the array. When I displayed it on a single line it displayed all the correct values. I'll have to check back my algorithm = /

    Thanks all !

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