/* $Id: bitarray.h,v 1.11 1998/10/16 03:15:04 bsmith Exp bsmith $ */

/*    

          BT - Bit array objects: used to compactly store logical arrays of variables.

     BTCreate(m,bt)        - creates a bit array with enough room to hold m values
     BTDestroy(bt)         - destroys the bit array
     BTMemzero(m,bt)       - zeros the entire bit array (sets all values to false)
     BTSet(bt,index)       - sets a particular entry as true
     BTClear(bt,index)     - sets a particular entry as false
     BTLookup(bt,index)    - returns the value 
     BTLookupSet(bt,index) - returns the value and then sets it true
     BTLength(m)           - returns number of bytes in array with m bits
     BTView(m,bt)          - prints all the entries in a bit array

    These routines do not currently have manual pages.

    The are all implemented as macros with the trivial data structure for efficiency.

    These are not thread safe since they use a few global variables.

*/
#if !defined(__BITARRAY_H)
#define __BITARRAY_H

#if !defined(BITSPERBYTE)
#define BITSPERBYTE 8
#endif

typedef char* BT;

extern char _BT_mask, _BT_c;
extern int  _BT_idx;

#define BTView(m,bt) {\
  int __i; \
  for (__i=0; __i<m; __i++) { \
    printf("%d %d\n",__i,BTLookup(bt,__i)); \
  }}

#define BTLength(m)        ((m)/BITSPERBYTE+1)*sizeof(char)

#define BTCreate(m,array)  (array = (char *)PetscMalloc(((m)/BITSPERBYTE+1)*sizeof(char)),\
                           ( !array ) ? 1 : (BTMemzero(m,array),0) )

#define BTMemzero(m,array) PetscMemzero(array,(m)/BITSPERBYTE+1)

#define BTLookupSet(array, index)    (_BT_idx           = (index)/BITSPERBYTE, \
                                        _BT_c           = array[_BT_idx], \
                                        _BT_mask        = (char)1 << ((index)%BITSPERBYTE), \
                                        array[_BT_idx]  = _BT_c | _BT_mask, \
                                        _BT_c & _BT_mask )

#define BTSet(array, index)    (_BT_idx          = (index)/BITSPERBYTE, \
                                 _BT_c           = array[_BT_idx], \
                                 _BT_mask        = (char)1 << ((index)%BITSPERBYTE), \
                                 array[_BT_idx]  = _BT_c | _BT_mask,0)


#define BTClear(array, index)  (_BT_idx          = (index)/BITSPERBYTE, \
                                 _BT_c           = array[_BT_idx], \
                                 _BT_mask        = (char)1 << ((index)%BITSPERBYTE), \
                                 array[_BT_idx]  = _BT_c & (~_BT_mask),0)

#define BTLookup(array, index) (_BT_idx          = (index)/BITSPERBYTE, \
                                 _BT_c           = array[_BT_idx], \
                                 _BT_mask        = (char)1 << ((index)%BITSPERBYTE), \
                                 (_BT_c & _BT_mask) != 0 )

#define BTDestroy(array) PetscFree(array)

#endif