gridstring.h

C++高级编程这本书所附的源代码

#include "Grid.h" // The file containing the Grid template definition shown above
#include <cstdlib>
#include <cstring>
using namespace std;

template <int WIDTH, int HEIGHT>
class Grid<char*, WIDTH, HEIGHT>
{
 public:
  Grid();
  Grid(const Grid<char*, WIDTH, HEIGHT>& src);
  ~Grid();

  Grid<char*, WIDTH, HEIGHT>& Grid<char*, WIDTH, HEIGHT>::operator=(
    const Grid<char*, WIDTH, HEIGHT>& rhs);
  void setElementAt(int x, int y, const char* inElem);
  char* getElementAt(int x, int y) const;
  int getHeight() const { return HEIGHT; }
  int getWidth() const { return WIDTH; }
 protected:
  void copyFrom(const Grid<char*, WIDTH, HEIGHT>& src);
  char* mCells[WIDTH][HEIGHT];
};

template <int WIDTH, int HEIGHT>
Grid<char*, WIDTH, HEIGHT>::Grid()
{
  for (int i = 0; i < WIDTH; i++) {
    for (int j = 0; j < HEIGHT; j++) {
      // initialize each element to NULL
      mCells[i][j] = NULL;
    }
  }
}

template <int WIDTH, int HEIGHT>
Grid<char*, WIDTH, HEIGHT>::Grid(const Grid<char*, WIDTH, HEIGHT>& src)
{
    copyFrom(src);
}

template <int WIDTH, int HEIGHT>
Grid<char*, WIDTH, HEIGHT>::~Grid()
{
    for (int i = 0; i < WIDTH; i++) {
        for (int j = 0; j < HEIGHT; j++) {
            delete [] mCells[i][j];
        }
    }
}

template <int WIDTH, int HEIGHT>
void Grid<char*, WIDTH, HEIGHT>::copyFrom(
    const Grid<char*, WIDTH, HEIGHT>& src)
{
    int i, j;

    for (i = 0; i < WIDTH; i++) {
        for (j = 0; j < HEIGHT; j++) {
            if (src.mCells[i][j] == NULL) {
                mCells[i][j] = NULL;
            } else {
                mCells[i][j] = new char[strlen(src.mCells[i][j]) + 1];
                strcpy(mCells[i][j], src.mCells[i][j]);
            }
        }
    }
}

template <int WIDTH, int HEIGHT>
Grid<char*, WIDTH, HEIGHT>& Grid<char*, WIDTH, HEIGHT>::operator=(
    const Grid<char*, WIDTH, HEIGHT>& rhs)
{
    int i, j;

    // check for self-assignment
    if (this == &rhs) {
        return (*this);
    }
    // free the old memory
    for (i = 0; i < WIDTH; i++) {
        for (j = 0; j < HEIGHT; j++) {
            delete [] mCells[i][j];
        }
    }

    // copy the new memory
    copyFrom(rhs);
    return (*this);
}

template <int WIDTH, int HEIGHT>
void Grid<char*, WIDTH, HEIGHT>::setElementAt(
    int x, int y, const char* inElem)
{
    delete[] mCells[x][y];
    if (inElem == NULL) {
        mCells[x][y] = NULL;
    } else {
        mCells[x][y] = new char[strlen(inElem) + 1];
        strcpy(mCells[x][y], inElem);
    }
}

template <int WIDTH, int HEIGHT>
char* Grid<char*, WIDTH, HEIGHT>::getElementAt(int x, int y) const
{
    if (mCells[x][y] == NULL) {
        return (NULL);
    }
    char* ret = new char[strlen(mCells[x][y]) + 1];
    strcpy(ret, mCells[x][y]);

    return (ret);
}