C Programming Starter Kit 2.0/SamsPublishing-CProgrammingStarterKit-v2.0-Win31.iso/tybc4/ioerr1.cpp

C/C++ Source or Header | 1994-01-26 | 5KB | 213 lines

/*
   C++ program that demonstrates sequential binary file I/O
*/

#include <iostream.h>
#include <fstream.h>

const unsigned MIN_SIZE = 10;
const double BAD_VALUE = -1.0e+30;
enum boolean { false, true };

class TErrIO
{};

class TErrIndex
{};

class Array
{
    protected:
      double *dataPtr;
      unsigned size;
      double badIndex;
      TErrIO ErrIO;
      TErrIndex ErrIndex;

    public:
      Array(unsigned Size = MIN_SIZE);
      ~Array()
         { delete [] dataPtr; }
      unsigned getSize() const { return size; }
      double& operator [](unsigned index)
      { return (index < size) ? *(dataPtr + index) : badIndex; }
      void writeElem(fstream& os, unsigned index)
          throw(TErrIO, TErrIndex);
      void readElem(fstream& is, unsigned index)
          throw(TErrIO, TErrIndex);
      void writeArray(const char* filename)
          throw(TErrIO);
      void readArray(const char* filename)
          throw(TErrIO);
};

Array::Array(unsigned Size)
{
  size = (Size < MIN_SIZE) ? MIN_SIZE : Size;
  badIndex = BAD_VALUE;
  dataPtr = new double[size];
}

void Array::writeElem(fstream& os, unsigned index)
  throw(TErrIO, TErrIndex)
{
    if (index < size) {
      os.write((unsigned char*)(dataPtr + index), sizeof(double));
      if(!os.good())
         throw(ErrIO);
    }
    else
      throw(ErrIndex);
}

void Array::readElem(fstream& is, unsigned index)
  throw(TErrIO, TErrIndex)
{
    if (index < size) {
      is.read((unsigned char*)(dataPtr + index), sizeof(double));
      if (!is.good())
         throw(ErrIO);
    }
    else
      throw(ErrIndex);
}

void Array::writeArray(const char* filename)
  throw(TErrIO)
{
    fstream f(filename, ios::out | ios::binary);

    if (f.fail())
      throw(ErrIO);
    f.write((unsigned char*) &size, sizeof(size));
    f.write((unsigned char*)dataPtr, size * sizeof(double));
    f.close();
    if (!f.good())
      throw(ErrIO);
}

void Array::readArray(const char* filename)
  throw(TErrIO)
{
    fstream f(filename, ios::in | ios::binary);
    unsigned sz;

    if (f.fail())
      throw(ErrIO);
    f.read((unsigned char*) &sz, sizeof(sz));
    // need to expand the array
    if (sz != size) {
      delete [] dataPtr;
      dataPtr = new double[sz];
      size = sz;
    }
    f.read((unsigned char*)dataPtr, size * sizeof(double));
    f.close();
    if (!f.good())
      throw(ErrIO);
}

main()
{
  const unsigned SIZE1 = 10;
  const unsigned SIZE2 = 20;
  char* filename1 = "array1.dat";
  char* filename2 = "array3.dat";
  int hiIndex = 10;
  Array arr1(SIZE1), arr2(SIZE1), arr3(SIZE2);
  fstream f(filename1, ios::out | ios::binary);

  // assign values to array arr1
  for (unsigned i = 0; i < arr1.getSize(); i++)
     arr1[i] = 10 * i;

  // assign values to array arr3
  for (i = 0; i < SIZE2; i++)
     arr3[i] = i;

  cout << "Array arr1 has the following values:\n";
  for (i = 0; i < arr1.getSize(); i++)
     cout << arr1[i] << "  ";
  cout << "\n\n";

  try {
     // write elements of array arr1 to the stream
     for (i = 0; i < arr1.getSize(); i++)
        arr1.writeElem(f, i);
  }
  catch(TErrIO e) {
     cout << "Bad stream output\n";
  }
  catch(TErrIndex e) {
     cout << "Error in writing element " << i << "\n";
  }
  f.close();

  // reopen the stream for input
  f.open(filename1, ios::in | ios::binary);

  try {
     for (i = 0; i < arr1.getSize(); i++)
         arr2.readElem(f, i);
  }
  catch(TErrIO e) {
     cout << "Bad stream output\n";
  }
  catch(TErrIndex e) {
     cout << "Error in writing element " << i << "\n";
  }
  f.close();

  // display the elements of array arr2
  cout << "Array arr2 has the following values:\n";
  for (i = 0; i < arr2.getSize(); i++)
     cout << arr2[i] << "  ";
  cout << "\n\n";

  // display the elements of array arr3
  cout << "Array arr3 has the following values:\n";
  for (i = 0; i < arr3.getSize(); i++)
     cout << arr3[i] << "  ";
  cout << "\n\n";

  // write the array arr3 to file ARRAY3.DAT
  try {
     arr3.writeArray(filename2);
  }
  catch(TErrIO e) {
     cout << "Cannot write the entire array\n";
  }

  try {
     // read the array arr1 from file ARRAY3.DAT
     arr1.readArray(filename2);
  }
  catch(TErrIO e) {
     cout << "Cannot read the entire array\n";
  }

  // display the elements of array arr1
  cout << "Array arr1 now has the following values:\n";
  for (i = 0; i < arr1.getSize(); i++)
     cout << arr1[i] << "  ";
  cout << "\n\n";

  // reopen the stream for input
  f.open(filename1, ios::in | ios::binary);

  for (i = 0; i < 3; i++) {
     hiIndex *= 10;
     // attempt to read an element at index hiIndex
     try {
        arr1.readElem(f, hiIndex);
        cout << "Element at index " << hiIndex << " = "
              << arr1[hiIndex] << "\n";
     }
     catch(TErrIndex) {
        cout << "Failed to read element at index "
            << hiIndex << "\n";
     }
  }
  f.close();
  return 0;
}