Question

I was trying for the first time to read data from a file, a .txt file. Below is my code:

Level::ReadStream(std::fstream data)
{
bool write = false;
char* p = data.tellg();

while(!data.eof())
{
    int i = 0, j = 0;

    if(&p == '[')
    {
        write == true;
    }

    if(write == true)
    {
        mapX[i] = p;
        mapY[j] = p;
    }

    if(&p == '/n')
    {
        i++;
        j++;
    }

    else
    {
        i++;
    }

    *p++
}
};

void Level::SetMapSize(std::fstream data)
{
int* p = data.tellg();
int sizeX = 0;
int sizeY = 0;

while(!data.eof())
{
    if(&p != '[' && &p != ']' && &p != '\n')
    {
        sizeX++;
    }

    else if(&p != '\n')
    {
        sizeY++;
    }
}

mapX.resize(sizeX);
mapY.resize(sizeY);

std::cout << sizeX << '\n' << sizeY;
};

The goal of these two functions are to:
1- read all the chars in the file and, if the current character is not a bracket, add it to an index map(X, Y), then increase the counter so the next non-bracket value will be put in the correct index.

2- read all the file and, as before, count the non-bracket values, so it can make mapX and mapY the correct size.

However, it’s not working, and I got these errors:

 C:\...\Level.cpp|58|warning: multi-character character constant|

 c:\...\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\bits\ios_base.h|790|error: 'std::ios_base::ios_base(const std::ios_base&)' is private|

 c:\...\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\iosfwd|47|error: within this context|

 c:...\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\iosfwd|87|note: synthesized method 'std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)' first required here |

 c:...\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\streambuf|770|error: 'std::basic_streambuf<_CharT, _Traits>::basic_streambuf(const std::basic_streambuf<_CharT, _Traits>&) [with _CharT = char, _Traits = std::char_traits<char>]' is private|

 c:...\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\iosfwd|78|error: within this context|

 c:...\mingw\bin\..\lib\gcc\mingw32\4.4.1\include\c++\iosfwd|87|note: synthesized method 'std::basic_filebuf<char, std::char_traits<char> >::basic_filebuf(const std::basic_filebuf<char, std::char_traits<char> >&)' first required here |

C:...\Level.cpp||In constructor 'Level::Level()':|

C:...\Level.cpp|24|note: synthesized method 'std::basic_fstream<char, std::char_traits<char> >::basic_fstream(const std::basic_fstream<char, std::char_traits<char> >&)' first required here |

C:...\Level.cpp|24|error:   initializing argument 1 of 'void Level::SetMapSize(std::fstream)'|

C:...\Level.cpp|29|error: 'cout' was not declared in this scope|

C:...\Level.cpp|38|error: ISO C++ forbids declaration of 'ReadStream' with no type|

C:...\Level.cpp|38|error: prototype for 'int Level::ReadStream(std::fstream)' does not match any in class 'Level'|

C :...\Level.cpp|17|error: candidate is: void Level::ReadStream(std::fstream)|
C:...\Level.cpp||In member function 'void Level::SetMapSize(std::fstream)':|
C:...\Level.cpp|75|error: invalid conversion from 'std::streamoff' to 'int*'|
C:...\Level.cpp|81|error: ISO C++ forbids comparison between pointer and integer|
C:...\Level.cpp|81|error: ISO C++ forbids comparison between pointer and integer|
C:...\Level.cpp|81|error: ISO C++ forbids comparison between pointer and integer|
C:...\Level.cpp|86|error: ISO C++ forbids comparison between pointer and integer|
C:...\Level.cpp|95|error: 'cout' is not a member of 'std'|
||=== Build finished: 15 errors, 1 warnings ===|

Can anyone help?

EDIT: Ok, I changed everything. My new code is:

void Level::ReadStream()
{
long p = textData.tellg();
int counter = 0;
int i = 0;
int j = 0;
char ch;

while(p != textData.eof())
{
    textData.seekg(counter);
    textData >> ch;

    if(ch != '[' && ch != ']')
    {
        mapX[i] = ch;
        mapY[j] = ch;

        i++;

        if(ch == '\n')
        {
            i = 0;
            j++;
        }
    }

    counter++;
    p = textData.tellg();
}
};

with mapX and mapY being 5 int long. Now it compiles, but hangs and crashes. I don’t see why… Is there anyone that can help me?

Answer 1

It’s \n not /n! That should clear some errors.

Also, you can’t just take the pointer from tellg — it returns the position, not the pointer to the position!

Basically try to read up on IO in C++, maybe start with this question:

How to read from a file char by char in C++?