Posts by Salem Page 142

Salem 5,265 Posting Sage

19 Years Ago

Re: remote monitoring software

http://en.wikipedia.org/wiki/VNC

Software Development c

Salem 5,265 Posting Sage

19 Years Ago

Re: memory leak problem...

Post your latest - can you make a simple example fail yet?

Software Development c

Salem 5,265 Posting Sage

19 Years Ago

Re: memory leak problem...

> the variable m_pMatriz is double* and the GetElement and SetElement are methods for CMatrix types
But those functions take and return doubles, so there should be no problem.
They're used fine in some contexts already anyway.

I've attached your code with Set/Get used in many more places, and it compiles fine here.
The //!! comments are what my g++ compiler spotted with
$ g++ -c -W -Wall -ansi -pedantic -O2 foo.cpp

Oh, you might want to rename all your loop variables from i,j to be say r,c to denote row and column. It's not always clear whether you're accessing the correct element of the array (when you're doing it directly), and r/c would make it more readable IMO.
At least by always using the set/get functions, every access is properly range checked (as it should be).

foo.cpp (6.38 KB)

#include <iostream>
class CMatrix
{
  public:
    void Identity();
    void SetMaxColRow(int nRow, int nCol);
    void SetElement(int nRow, int nCol, long double element);
    void Show();

    long double GetElement(int nRow, int nCol);

    CMatrix operator+(CMatrix tmpMatriz);
    CMatrix operator-(CMatrix tmpMatriz);
    CMatrix operator*(long double scalar);
    CMatrix operator*(CMatrix tmpMatriz);
    CMatrix Transpose();
    //!! void CMatrix::Invert();
    //!! foo.cpp: error: extra qualification CMatrix:: on member Invert ignored
    void Invert();
    CMatrix GetInverted() const;
    CMatrix(int nRows, int nCols);
    CMatrix();

    virtual ~CMatrix();

    int m_nRows;
    int m_nCols;


  private:
    long double *m_pMatriz;

};

// constructor
CMatrix::CMatrix(int nRows, int nCols)
{
  SetMaxColRow(nRows, nCols);
}

// constructor
CMatrix::CMatrix()
{
  m_nCols = 0;
  m_nRows = 0;
  m_pMatriz = NULL;
}


// destructor
CMatrix::~CMatrix()
{
  if (m_pMatriz != NULL)
    delete[] m_pMatriz;

  m_pMatriz = NULL;
}


// adding 2 matrixes
CMatrix CMatrix::operator+(CMatrix tmpMatriz)
{
  // first check for same size
  if ((m_nCols != tmpMatriz.m_nCols) || (m_nRows != tmpMatriz.m_nRows))
  {
    printf("\nError in sum: Matrices do not have same size.\n\n");
    exit(1);
  }

  CMatrix ResMatriz(m_nRows,m_nCols);

  // now add in the other matrix
  for (int i=0; i<m_nRows; i++)
  {
    for (int j=0; j<m_nCols; j++)
      ResMatriz.SetElement(i,j, GetElement(i,j) + tmpMatriz.GetElement(i,j));
  }
  return ResMatriz;
}


// subtracting 2 matrixes
CMatrix CMatrix::operator-(CMatrix tmpMatriz)
{
  // first check for same size
  if ((m_nCols != tmpMatriz.m_nCols) || (m_nRows != tmpMatriz.m_nRows))
  {
    printf("\nError in subtract: Matrices do not have same size.\n\n");
    exit(1);
  }

  CMatrix ResMatriz(m_nRows, m_nCols);

  for (int i=0; i<m_nRows; i++)
    for (int j=0; j<m_nCols; j++)
      ResMatriz.SetElement(i,j, GetElement(i,j) - tmpMatriz.GetElement(i,j));

  return ResMatriz;
}


// multiplication of a scalar with a matrix
CMatrix CMatrix::operator*(long double scalar)
{
  CMatrix ResMatriz(m_nRows, m_nCols);

  for (int i=0; i<m_nRows; i++)
    for (int j=0; j<m_nCols; j++)
      ResMatriz.SetElement(i,j, scalar * GetElement(i,j) );

  return ResMatriz;
}


// multiplication of 2 matrixes
CMatrix CMatrix::operator*(CMatrix tmpMatriz)
{
  // first check for a valid multiplication operation
  if (m_nCols != tmpMatriz.m_nRows)
  {
    printf("\nError in multipication: Matrices do not have common size.\n\n");
    exit(1);
  }

  // construct the object we are going to return
  CMatrix ResMatriz(m_nRows, tmpMatriz.m_nCols);

  // e.g.
  // [A][b][C]   [G][H]     [A*G + B*I + C*K][A*H + B*J + C*L]
  // [D][E][F] * [i][J] =   [D*G + E*I + F*K][D*H + E*J + F*L]
  //             [K][L]
  //


  long double value = 0;
  for (int i=0; i<ResMatriz.m_nCols; i++)
    for (int j=0; j<ResMatriz.m_nRows; j++)
    {
      value = 0.0 ;
      for (int k=0; k<m_nCols; k++)
        value += GetElement(j,k) * tmpMatriz.GetElement(k,i);

      ResMatriz.SetElement(j, i, value) ;
    }

  return ResMatriz;
}



// sets a specific element
void CMatrix::SetElement(int nRow, int nCol, long double element)
{
  if ((nCol >= m_nCols) || (nRow >= m_nRows) || (nRow < 0 ) || (nCol < 0))
  {
    printf("\nError in SetElement.\n\n");
    exit(1);
  }

  *(m_pMatriz + nRow * m_nCols + nCol) = element;
}

// gets one specific element
long double CMatrix::GetElement(int nRow, int nCol)
{
  long double element = 0;

  if ((nCol >= m_nCols) || (nRow >= m_nRows) || (nRow < 0 ) || (nCol < 0))
  {
    printf("\nError in GetElement.\n\n");
    exit(1);
  }

  element = *(m_pMatriz + nRow * m_nCols + nCol);

  return element;
}



// prints a matrix
void CMatrix::Show()
{
  for (int i=0; i<m_nRows; i++)
  {
    for (int j=0; j<m_nCols; j++)
      //!! printf("%8lf\t", *(m_pMatriz + i * m_nCols + j));
      //!! foo.cpp: warning: ISO C++ does not support the %lf printf format
      //!! foo.cpp: warning: format %8lf expects type double, but argument 2 has type long double
      printf("%8Lf\t", GetElement(i,j) );
    printf("\n");
  }
  printf("\n");
}

void CMatrix::SetMaxColRow(int nRows, int nCols)
{
  m_nCols = nCols;
  m_nRows = nRows;

  m_pMatriz = new long double[m_nRows * m_nCols];

  for (int i=0; i<m_nRows; i++)
    for (int j=0; j<m_nRows; j++)
      SetElement(i,j,0.0);
  //!!int lim = m_nRows * m_nCols;
  //!!for ( int i = 0 ; i < lim ; i++ )
  //!!  m_pMatriz[i] = 0.0;
}

void CMatrix::Identity()
{
  // first check if matrix is square
  if (m_nCols != m_nRows)
  {
    printf("\nMatrix is not square.\n\n");
    exit(1);
  }

  for (int i=0; i<m_nRows; i++)
    for (int j=0; j<m_nRows; j++)
      SetElement(i,j,0.0);

  //memset(m_pMatriz, 0.0, sizeof(long double)  * m_nRows * m_nCols);

  for (int k=0; k<m_nRows; k++)
    SetElement(k,k,1.0);
}

// matrix tranpose
CMatrix CMatrix::Transpose()
{
  // construct the object we are going to return
  CMatrix ResMatriz(m_nCols, m_nRows);

  // copy across the transposed data
  for (int i=0; i<m_nCols; i++)
    for (int j=0; j<m_nRows; j++)
      ResMatriz.SetElement(i, j, GetElement(j,i) );

  return ResMatriz;
}

CMatrix CMatrix::GetInverted() const
{
  // matrix inversion will only work on square matrices
  if (m_nCols != m_nRows)
  {
    printf("\nMatrix is not square.\n\n");
    exit(1);
  }

  // construct the object we are going to return
  CMatrix ResMatriz(m_nCols, m_nCols);

  // return this matrix inverted
  CMatrix copy(*this);
  copy.Invert();

  return copy;
}

void CMatrix::Invert()
{
  // matrix inversion will only work on square matrices
  // invert ourselves
  if (m_nCols != m_nRows)
  {
    printf("\nMatrix is not square.\n\n");
    exit(1);
  }
  long double e = 0;

  for (int k = 0 ; k < m_nCols ; ++k)
  {
    e = GetElement(k, k) ;
    SetElement(k, k, 1.0) ;
    if (e == 0.0)
    {
      printf("\nMatrix inversion error\n");
      exit(1);
    }

    for (int j = 0 ; j < m_nCols ; ++j)
      SetElement(k, j, GetElement(k, j) / e) ;
    for (int i = 0 ; i < m_nCols ; ++i)
    {
      if (i != k)
      {
        e = GetElement(i, k) ;
        SetElement(i, k, 0.0) ;
        //!!for (j = 0 ; j < m_nCols ; ++j)
        //!!foo.cpp: error: name lookup of j changed for new ISO for scoping
        for (int j = 0 ; j < m_nCols ; ++j)
          SetElement(i, j, GetElement(i, j) - e * GetElement(k, j)) ;
      }
    }
  }
}

Software Development c

Salem 5,265 Posting Sage

19 Years Ago

Re: My c++ cgi-bin program wont allow access to files

http://www.faqs.org/docs/securing/chap29sec254.html
Are you entirely sure that apache is seeing the same directory structure that you're seeing?
Which real / effective user ID's is apache running with, and do these have appropriate permissions to access the files?

Create a simple C++ program which allows you to log all this information, and send it back out as a response.
Use API calls like perror() to tell you why a file could not be accessed - like could it be found, or is it permissions?