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#ifndef _nsMsgKeySet_H_
#define _nsMsgKeySet_H_

#include "msgCore.h"

class nsMsgKeyArray;

// nsMsgKeySet represents a set of articles.  Typically, it is the set of
// read articles from a .newsrc file, but it can be used for other purposes
// too.

#if 0
// If a MSG_NewsHost* is supplied to the creation routine, then that
// MSG_NewsHost will be notified whenever a change is made to set.
class MSG_NewsHost;
#endif

class NS_MSG_BASE nsMsgKeySet {
public:
  // Creates an empty set.
  static nsMsgKeySet* Create(/* MSG_NewsHost* host = NULL*/);

  // Creates a set from the list of numbers, as might be found in a
  // newsrc file.
  static nsMsgKeySet* Create(const char* str/* , MSG_NewsHost* host = NULL*/);
  ~nsMsgKeySet();
  
  // FirstNonMember() returns the lowest non-member of the set that is
  // greater than 0.
  PRInt32 FirstNonMember();

  // Output() converts to a string representation suitable for writing to a
  // .newsrc file.  
  nsresult Output(char **outputStr);		

  // IsMember() returns whether the given article is a member of this set.
  PRBool IsMember(PRInt32 art);
  
  // Add() adds the given article to the set.  (Returns 1 if a change was
  // made, 0 if it was already there, and negative on error.)
  int Add(PRInt32 art);
  
  // Remove() removes the given article from the set. 
  int Remove(PRInt32 art);
  
  // AddRange() adds the (inclusive) given range of articles to the set.
  int AddRange(PRInt32 first, PRInt32 last);
  
  // CountMissingInRange() takes an inclusive range of articles and returns
  // the number of articles in that range which are not in the set.
  PRInt32 CountMissingInRange(PRInt32 start, PRInt32 end);
  
  // FirstMissingRange() takes an inclusive range and finds the first range
  // of articles that are not in the set.  If none, return zeros. 
  int FirstMissingRange(PRInt32 min, PRInt32 max, PRInt32* first, PRInt32* last);
  

  // LastMissingRange() takes an inclusive range and finds the last range
  // of articles that are not in the set.  If none, return zeros. 
  int LastMissingRange(PRInt32 min, PRInt32 max, PRInt32* first, PRInt32* last);
  
  PRInt32 GetLastMember();
  PRInt32 GetFirstMember();
  void  SetLastMember(PRInt32 highWaterMark);
  // For debugging only...
  PRInt32 getLength() {return m_length;}

  /**
   * Return a copy of this as an nsMsgKeyArray, which is much easier for
   * callers to manipulate.  Normal XPCOM calling conventions, although the
   * array itself isn't refcounted, so the caller should free when done
   * using NS_DELETEXPCOM().
   */
  nsresult ToMsgKeyArray(nsMsgKeyArray **aArray);
  
#ifdef DEBUG
  static void RunTests();
#endif

protected:
  nsMsgKeySet(/* MSG_NewsHost* host */);
  nsMsgKeySet(const char* /* , MSG_NewsHost* host */);
  PRBool Grow();
  PRBool Optimize();
  
#ifdef DEBUG
  static void test_decoder(const char*);
  static void test_adder();
  static void test_ranges();
  static void test_member(PRBool with_cache);
#endif
  
  PRInt32 *m_data;					/* the numbers composing the `chunks' */
  PRInt32 m_data_size;				/* size of that malloc'ed block */
  PRInt32 m_length;				/* active area */
  
  PRInt32 m_cached_value;			/* a potential set member, or -1 if unset*/
  PRInt32 m_cached_value_index;		/* the index into `data' at which a search
									   to determine whether `cached_value' was
									   a member of the set ended. */
#ifdef NEWSRC_DOES_HOST_STUFF
  MSG_NewsHost* m_host;
#endif
};


#endif /* _nsMsgKeySet_H_ */