Reading text files

This is a discussion on Reading text files within the C++ Programming forums, part of the General Programming Boards category; Hi, Im sorta new to c++, so i might need things explaining but what is the best way of reading ...

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    Reading text files

    Hi, Im sorta new to c++, so i might need things explaining but what is the best way of reading a txt file, one character at a time and writing each character to a different file??

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    Programming is a form of art.

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    Ok, but how would I do that in a DLL. It comes up saying 'ofstream' undeclared

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    An ofstream undeclared error probably has nothing to do with it being a DLL. Did you #include <fstream>? Did you specify the std namespace?

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    Quote Originally Posted by Xinco
    Ok, but how would I do that in a DLL. It comes up saying 'ofstream' undeclared
    it sounds like you havn't included the <fstream> header file

    does it say this at the top of your code >

    #include <fstream>

    ^^ this header is needed for FILE IO ^^
    WhAtHA hell Is GoInG ON

  6. #6
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    Just look at those tutorials.
    Code:
    #include <fstream>
    using std::ios;
    int main()
    {
       std::fstream dll_rw("my_libs.dll",ios::binary | ios::in | ios::out);
       if(!dll_rw) 
       {
          //deal with open failure
       }
       else  //"else" usually not necessary
       {
          //....read and write to DLL file....
          dll_rw.close();   //finished -- not necessary, but tidy
       }
       return 0;
    }
    "If you tell the truth, you don't have to remember anything"
    -Mark Twain

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    Ok, i found the answer but now its saying 'invalid conversion from 'char' to 'const char''. I thinks its because im using ifstream read_file(argumen0); but I need argument0 to be an argument so how do i fix this

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    You seem to be reading a character at a time, rather than line at a time. A const char* is a c style string. You should in the else statement, read each line, preferrably into a string (#include <string>), then go on to the next. You should all do this while the file has a next line.

    Edit, I see you want to read it a character at a time, since a string can be treated as an array of char, and each char can be referenced with the [] operator, you can read the string, then do a for loop that goes through each char of the string and outputs them.

    Code:
        std::string s = "akdnknfknef";
    
        for(std::string::size_type i = 0; i < s.size(); ++i)
            std::cout << s[i] << std::endl;
    replace the cout with the output file stream
    Last edited by indigo0086; 01-08-2007 at 09:54 AM.

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    But I need it to be written 1 character at a time so I can change the ascii value. Sort of like how encryption works (I think) Unless it is possible to change the ascii value of a whole line by a set amount per character.

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    If you are getting errors it is generally better to post the exact error message and your code so you can get specific help.

    As far as reading a character at a time, I would use get() for input, then encrypt the character, then output it. That will move things along one character at a time.

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    My method;

    Code:
    int main()
    {
    ifstream fin ("your.dll", ios::in | ios:: beg |ios::binary);
    ofstream out("new.dll, ios::out | ios::binary |ios::app);
    
     // verify file open success
    
     while(!fin.eof())  
         { 
      
    
       char input = 0;
        fin.unsetf(ios::skipws); // turn off whitespace skipping
        fin >> input;
       
       //manipulate, encrypt input (1 char)
    
        out<<input;   //write encrypted byte to output file ("new.dll")
     
        } //end while loop
    
     //close files
    
     return 0;
    }
    I think I've got that right. If not, I'll hear about it!

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    Frequently Quite Prolix dwks's Avatar
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    Code:
    while(!fin.eof())
    Might want to read this. http://faq.cprogramming.com/cgi-bin/...&id=1043284351
    dwk

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  13. #13
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    Quote Originally Posted by Xinco
    But I need it to be written 1 character at a time so I can change the ascii value. Sort of like how encryption works (I think) Unless it is possible to change the ascii value of a whole line by a set amount per character.
    with my method you can write one char at a time, and manipulate it as such char by char.

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    Red face

    Quote Originally Posted by dwks
    Code:
    while(!fin.eof())
    Might want to read this. http://faq.cprogramming.com/cgi-bin/...&id=1043284351

    Actually, I have. It just continually slips my mind.

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    Quote Originally Posted by Oldman47
    My method;

    Code:
    int main()
    {
    ifstream fin ("your.dll", ios::in | ios:: beg |ios::binary);
    ofstream out("new.dll, ios::out | ios::binary |ios::app);
    
     // verify file open success
    
     while(!fin.eof())  
         { 
      
    
       char input = 0;
        fin.unsetf(ios::skipws); // turn off whitespace skipping
        fin >> input;
       
       //manipulate, encrypt input (1 char)
    
        out<<input;   //write encrypted byte to output file ("new.dll")
     
        } //end while loop
    
     //close files
    
     return 0;
    }
    I think I've got that right. If not, I'll hear about it!
    Thats an app, I need the code for a programming the DLL. Heres what I got:

    DLL.h: (Note, this is header)
    Code:
    #ifndef _DLL_H_
    #define _DLL_H_
    
    #define export extern "C" __declspec (dllexport)
    
    #if BUILDING_DLL
    # define DLLIMPORT __declspec (dllexport)
    #else 
    # define DLLIMPORT __declspec (dllimport)
    #endif 
    
    
    class DLLIMPORT DllClass
    {
      public:
        DllClass();
        virtual ~DllClass(void);
    
      private:
    
    };
    
    
    #endif
    DLLmain.cpp: (this is dll c++ code)
    Code:
    #include "dll.h"
    #include <windows.h>
    #include <fstream>
    
    using namespace std;
    
    export double func1(char argument0,char argument1)
    {
           ifstream readfile;  //Here I get the error "invalid conversion from 'char' to 'const char'"
           ofstream writefile;
           readfile.open (argument0);
           writefile.open (argument1);
           char ch;
           while (readfile.get(ch)) {
           writefile << ch;
           }
           readfile.close();
           writefile.close();
    }
    I also tried this for the dllmain.cpp
    Code:
    #include "dll.h"
    #include <windows.h>
    #include <fstream>
    
    using namespace std;
    
    export double func1(char argument0,char argument1)
    {
           ifstream read_file(argument0);  //Here I get the error "invalid conversion from 'char' to 'const char'"
           ofstream write_file(argument1);
           char ch;
           while (read_file.get(ch)) {
           write_file << ch;
           }
           read_file.close();
           write_file.close();
    }

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