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Stack.h

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/***************************************************************************
 *cr                                                                       
 *cr            (C) Copyright 1995-2019 The Board of Trustees of the           
 *cr                        University of Illinois                       
 *cr                         All Rights Reserved                        
 *cr                                                                   
 ***************************************************************************/

/***************************************************************************
 * RCS INFORMATION:
 *
 *      $RCSfile: Stack.h,v $
 *      $Author: johns $        $Locker:  $             $State: Exp $
 *      $Revision: 1.30 $       $Date: 2021/09/23 16:11:23 $
 *
 ***************************************************************************
 * DESCRIPTION:
 *   A template class which implements a simple stack of arbitrary data.
 * Items are pushed onto and popped off of the stack, or may just be
 * copied from the stack.
 *
 ***************************************************************************/
#ifndef STACK_TEMPLATE_H
#define STACK_TEMPLATE_H

template<class T>
class Stack {

private:
  T *data;     
  T *curr;     
  int sz;      
  int items;   
  
public:
  Stack(int s) {
    items = 0;
    data = curr = new T[sz = (s > 0 ? s : 1)];
  }


  ~Stack(void) {
    if(data)
      delete [] data;
  }

  int max_stack_size(void) { return sz; }  
  int stack_size(void) { return items; }   
  int num(void) { return items; }          

  int push(const T& a) {
    if (items < sz) {
      *curr++ = a;
      items++;
    } else {
      return -1;  // stack size exceede
    }
    return 0;
  }

  
  int dup(void) {
    if (items > 0) {
      return push(top());
    } else if(sz > 0) {
      curr++;
      items++;
    }
    return 0;  // success
  }


  T& pop(void) {
    if (items > 0) {
      items--;
      return (*--curr);
    } else {
      return *data;
    }
  }


  T& top(void) {
    if (items > 0) {
      return *(curr - 1);
    } else {
      return *data;
    }
  }


  //
  // a cleaner O(1) alternative to something like...
  //   while (transMat.num()) {  stack.pop(); }
  //
  void clear(void) {
    items = 0;
    curr = data;
    // std::fill_n(data, sz, 0);
    memset(data, 0, sizeof(T)*sz);
  }

};

#endif

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