TBits.cxx

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// @(#)root/cont:$Id$
// Author: Philippe Canal 05/02/2001
//    Feb  5 2001: Creation
//    Feb  6 2001: Changed all int to unsigned int.

/** \class TBits
\ingroup Containers
Container of bits.

This class provides a simple container of bits.
Each bit can be set and tested via the functions SetBitNumber and
TestBitNumber.
                                             .
The default value of all bits is kFALSE.
The size of the container is automatically extended when a bit
number is either set or tested.  To reduce the memory size of the
container use the Compact function, this will discard the memory
occupied by the upper bits that are 0.
*/

#include "TBits.h"

#include "Riostream.h"
#include "TObject.h"

#include <string.h>

ClassImp(TBits);

////////////////////////////////////////////////////////////////////////////////
/// TBits constructor.  All bits set to 0

TBits::TBits(UInt_t nbits) : fNbits(nbits)
{
   if (nbits <= 0) nbits = 8;
   fNbytes  = ((nbits-1)/8) + 1;
   fAllBits = new UChar_t[fNbytes];
   // this is redundant only with libNew
   memset(fAllBits,0,fNbytes);
}

////////////////////////////////////////////////////////////////////////////////
/// TBits copy constructor

TBits::TBits(const TBits &original) : TObject(original), fNbits(original.fNbits),
   fNbytes(original.fNbytes)
{
   fAllBits = new UChar_t[fNbytes];
   memcpy(fAllBits,original.fAllBits,fNbytes);

}

////////////////////////////////////////////////////////////////////////////////
/// TBits assignment operator

TBits& TBits::operator=(const TBits& rhs)
{
   if (this != &rhs) {
      TObject::operator=(rhs);
      fNbits   = rhs.fNbits;
      fNbytes  = rhs.fNbytes;
      delete [] fAllBits;
      if (fNbytes != 0) {
         fAllBits = new UChar_t[fNbytes];
         memcpy(fAllBits,rhs.fAllBits,fNbytes);
      } else {
         fAllBits = 0;
      }
   }
   return *this;
}

////////////////////////////////////////////////////////////////////////////////
/// TBits destructor

TBits::~TBits()
{
   delete [] fAllBits;
}

////////////////////////////////////////////////////////////////////////////////
/// Clear the value.

void TBits::Clear(Option_t * /*option*/)
{
   delete [] fAllBits;
   fAllBits = 0;
   fNbits   = 0;
   fNbytes  = 0;
}

////////////////////////////////////////////////////////////////////////////////
/// Reduce the storage used by the object to a minimun

void TBits::Compact()
{
   if (!fNbits || !fAllBits) return;
   UInt_t needed;
   for(needed=fNbytes-1;
       needed > 0 && fAllBits[needed]==0; ) { needed--; };
   needed++;

   if (needed!=fNbytes) {
      UChar_t *old_location = fAllBits;
      fAllBits = new UChar_t[needed];

      memcpy(fAllBits,old_location,needed);
      delete [] old_location;

      fNbytes = needed;
      fNbits = 8*fNbytes;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Return number of bits set to 1 starting at bit startBit

UInt_t TBits::CountBits(UInt_t startBit) const
{
   static const Int_t nbits[256] = {
             0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,
             1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
             1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
             2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
             1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
             2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
             2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
             3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
             1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
             2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
             2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
             3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
             2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
             3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
             3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,
             4,5,5,6,5,6,6,7,5,6,6,7,6,7,7,8};

   UInt_t i,count = 0;
   if (startBit == 0) {
      for(i=0; i<fNbytes; i++) {
         count += nbits[fAllBits[i]];
      }
      return count;
   }
   if (startBit >= fNbits) return count;
   UInt_t startByte = startBit/8;
   UInt_t ibit = startBit%8;
   if (ibit) {
      for (i=ibit;i<8;i++) {
         if (fAllBits[startByte] & (1<<ibit)) count++;
      }
      startByte++;
   }
   for(i=startByte; i<fNbytes; i++) {
      count += nbits[fAllBits[i]];
   }
   return count;
}

////////////////////////////////////////////////////////////////////////////////
/// Execute `(*this) &= rhs;`
/// Extra bits in rhs are ignored
/// Missing bits in rhs are assumed to be zero.

void TBits::DoAndEqual(const TBits& rhs)
{
   UInt_t min = (fNbytes<rhs.fNbytes) ? fNbytes : rhs.fNbytes;
   for(UInt_t i=0; i<min; ++i) {
      fAllBits[i] &= rhs.fAllBits[i];
   }
   if (fNbytes>min) {
      memset(&(fAllBits[min]),0,fNbytes-min);
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Execute `(*this) &= rhs;`
/// Extra bits in rhs are ignored
/// Missing bits in rhs are assumed to be zero.

void TBits::DoOrEqual(const TBits& rhs)
{
   UInt_t min = (fNbytes<rhs.fNbytes) ? fNbytes : rhs.fNbytes;
   for(UInt_t i=0; i<min; ++i) {
      fAllBits[i] |= rhs.fAllBits[i];
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Execute `(*this) ^= rhs;`
/// Extra bits in rhs are ignored
/// Missing bits in rhs are assumed to be zero.

void TBits::DoXorEqual(const TBits& rhs)
{
   UInt_t min = (fNbytes<rhs.fNbytes) ? fNbytes : rhs.fNbytes;
   for(UInt_t i=0; i<min; ++i) {
      fAllBits[i] ^= rhs.fAllBits[i];
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Execute `~(*this)`

void TBits::DoFlip()
{
   for(UInt_t i=0; i<fNbytes; ++i) {
      fAllBits[i] = ~fAllBits[i];
   }
   // NOTE: out-of-bounds bit were also flipped!
}

////////////////////////////////////////////////////////////////////////////////
/// Execute the left shift operation.
/// Note: This does extent the number of bits (i.e. no data loss)

void TBits::DoLeftShift(UInt_t shift)
{
   if (shift==0) return;
   const UInt_t wordshift = shift / 8;
   const UInt_t offset = shift % 8;
   Resize(fNbits + shift);
   if (offset==0) {
      for(UInt_t n = fNbytes - 1; n >= wordshift; --n) {
         fAllBits[n] = fAllBits[ n - wordshift ];
      }
   } else {
      const UInt_t sub_offset = 8 - offset;
      for(UInt_t n = fNbytes - 1; n > wordshift; --n) {
         fAllBits[n] = (fAllBits[n - wordshift] << offset) |
                       (fAllBits[n - wordshift - 1] >> sub_offset);
      }
      fAllBits[wordshift] = fAllBits[0] << offset;
   }
   memset(fAllBits,0,wordshift);
   fNbits += shift;
}

////////////////////////////////////////////////////////////////////////////////
/// Execute the left shift operation.

void TBits::DoRightShift(UInt_t shift)
{
   if (shift==0) return;
   const UInt_t wordshift = shift / 8;
   const UInt_t offset = shift % 8;
   if (fNbytes < (wordshift + 1)) {
      memset(fAllBits, 0, fNbytes);
      fNbits = 0;
   } else {
      const UInt_t limit = fNbytes - wordshift - 1;

      if (offset == 0)
         for (UInt_t n = 0; n <= limit; ++n)
            fAllBits[n] = fAllBits[n + wordshift];
      else {
         const UInt_t sub_offset = 8 - offset;
         for (UInt_t n = 0; n < limit; ++n)
            fAllBits[n] = (fAllBits[n + wordshift] >> offset) |
                          (fAllBits[n + wordshift + 1] << sub_offset);
         fAllBits[limit] = fAllBits[fNbytes - 1] >> offset;
      }

      memset(&(fAllBits[limit + 1]), 0, fNbytes - limit - 1);
      if (fNbits < shift)
         fNbits = 0;
      else
         fNbits -= shift;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Return position of first null bit (starting from position 0 and up)

UInt_t TBits::FirstNullBit(UInt_t startBit) const
{
   static const Int_t fbits[256] = {
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,6,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,7,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,6,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,
             0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,8};

   UInt_t i;
   if (startBit == 0) {
      for(i=0; i<fNbytes; i++) {
         if (fAllBits[i] != 255) return 8*i + fbits[fAllBits[i]];
      }
      return fNbits;
   }
   if (startBit >= fNbits) return fNbits;
   UInt_t startByte = startBit/8;
   UInt_t ibit = startBit%8;
   if (ibit) {
      for (i=ibit;i<8;i++) {
         if ((fAllBits[startByte] & (1<<i)) == 0) return 8*startByte+i;
      }
      startByte++;
   }
   for(i=startByte; i<fNbytes; i++) {
      if (fAllBits[i] != 255) return 8*i + fbits[fAllBits[i]];
   }
   return fNbits;
}

////////////////////////////////////////////////////////////////////////////////
/// Return position of first null bit (starting from position 0 and up)

UInt_t TBits::LastNullBit(UInt_t startBit) const
{
   static const Int_t fbits[256] = {
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
             5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
             4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
             3,3,3,3,3,3,3,3,2,2,2,2,1,1,0,8};

   UInt_t i;
   if (startBit>=fNbits) startBit = fNbits-1;
   UInt_t startByte = startBit/8;
   UInt_t ibit = startBit%8;
   if (ibit<7) {
      for (i=ibit+1;i>0;i--) {
         if ((fAllBits[startByte] & (1<<(i-1))) == 0) return 8*startByte+i-1;
      }
      startByte--;
   }
   for(i=startByte+1; i>0; i--) {
      if (fAllBits[i-1] != 255) return 8*(i-1) + fbits[fAllBits[i-1]];
   }
   return fNbits;
}

////////////////////////////////////////////////////////////////////////////////
/// Return position of first non null bit (starting from position 0 and up)

UInt_t TBits::FirstSetBit(UInt_t startBit) const
{
   static const Int_t fbits[256] = {
             8,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             7,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             6,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             5,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,
             4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0};

   UInt_t i;
   if (startBit == 0) {
      for(i=0; i<fNbytes; i++) {
         if (fAllBits[i] != 0) return 8*i + fbits[fAllBits[i]];
      }
      return fNbits;
   }
   if (startBit >= fNbits) return fNbits;
   UInt_t startByte = startBit/8;
   UInt_t ibit = startBit%8;
   if (ibit) {
      for (i=ibit;i<8;i++) {
         if ((fAllBits[startByte] & (1<<i)) != 0) return 8*startByte+i;
      }
      startByte++;
   }
   for(i=startByte; i<fNbytes; i++) {
      if (fAllBits[i] != 0) return 8*i + fbits[fAllBits[i]];
   }
   return fNbits;
}

////////////////////////////////////////////////////////////////////////////////
/// Return position of first non null bit (starting from position 0 and up)

UInt_t TBits::LastSetBit(UInt_t startBit) const
{
   static const Int_t fbits[256] = {
             8,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,
             4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
             5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
             5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
             7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7};

   UInt_t i;
   if (startBit>=fNbits) startBit = fNbits-1;
   UInt_t startByte = startBit/8;
   UInt_t ibit = startBit%8;
   if (ibit<7) {
      for (i=ibit+1;i>0;i--) {
         if ((fAllBits[startByte] & (1<<(i-1))) != 0) return 8*startByte+i-1;
      }
      startByte--;
   }
   for(i=startByte+1; i>0; i--) {
      if (fAllBits[i-1] != 0) return 8*(i-1) + fbits[fAllBits[i-1]];
   }
   return fNbits;
}

////////////////////////////////////////////////////////////////////////////////
/// Print the value to the std::ostream

void TBits::Output(std::ostream &os) const
{
   for(UInt_t i=0; i<fNbytes; ++i) {
      UChar_t val = fAllBits[fNbytes - 1 - i];
      for (UInt_t j=0; j<8; ++j) {
         os << (Bool_t)(val&0x80);
         val <<= 1;
      }
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Once implemented, it will draw the bit field as an histogram.
/// use the TVirtualPainter as the usual trick

void TBits::Paint(Option_t *)
{
}

////////////////////////////////////////////////////////////////////////////////
/// Print the list of active bits

void TBits::Print(Option_t *) const
{
   Int_t count = 0;
   for(UInt_t i=0; i<fNbytes; ++i) {
      UChar_t val = fAllBits[i];
      for (UInt_t j=0; j<8; ++j) {
         if (val & 1) printf(" bit:%4d = 1\n",count);
         count++;
         val = val >> 1;
      }
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Reset all bits to 0 (false).

void TBits::ResetAllBits(Bool_t)
{
   if (fAllBits) memset(fAllBits,0,fNbytes);
}

////////////////////////////////////////////////////////////////////////////////
/// Reverse each bytes.

void TBits::ReserveBytes(UInt_t nbytes)
{
   if (nbytes > fNbytes) {
      // do it in this order to remain exception-safe.
      UChar_t *newBits=new UChar_t[nbytes];
      delete[] fAllBits;
      fNbytes=nbytes;
      fAllBits=newBits;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Set all the bytes.

void TBits::Set(UInt_t nbits, const Char_t *array)
{
   UInt_t nbytes=(nbits+7)>>3;

   ReserveBytes(nbytes);

   fNbits=nbits;
   memcpy(fAllBits, array, nbytes);
}

////////////////////////////////////////////////////////////////////////////////
/// Copy all the byes.

void TBits::Get(Char_t *array) const
{
   memcpy(array, fAllBits, (fNbits+7)>>3);
}

 #ifdef R__BYTESWAP  /* means we are on little endian */

 /*
 If we are on a little endian machine, a bitvector represented using
 any integer type is identical to a bitvector represented using bytes.
 -- FP.
 */

void TBits::Set(UInt_t nbits, const Short_t *array)
{
   // Set all the bytes.

   Set(nbits, (const Char_t*)array);
}

void TBits::Set(UInt_t nbits, const Int_t *array)
{
   // Set all the bytes.

   Set(nbits, (const Char_t*)array);
}

void TBits::Set(UInt_t nbits, const Long64_t *array)
{
   // Set all the bytes.

   Set(nbits, (const Char_t*)array);
}

void TBits::Get(Short_t *array) const
{
   // Get all the bytes.

   Get((Char_t*)array);
}

void TBits::Get(Int_t *array) const
{
   // Get all the bytes.

   Get((Char_t*)array);
}

void TBits::Get(Long64_t *array) const
{
   // Get all the bytes.

   Get((Char_t*)array);
}

#else

 /*
 If we are on a big endian machine, some swapping around is required.
 */

void TBits::Set(UInt_t nbits, const Short_t *array)
{
   // make nbytes even so that the loop below is neat.
   UInt_t nbytes = ((nbits+15)>>3)&~1;

   ReserveBytes(nbytes);

   fNbits=nbits;

   const UChar_t *cArray = (const UChar_t*)array;
   for (UInt_t i=0; i<nbytes; i+=2) {
      fAllBits[i] = cArray[i+1];
      fAllBits[i+1] = cArray[i];
   }
}

void TBits::Set(UInt_t nbits, const Int_t *array)
{
   // make nbytes a multiple of 4 so that the loop below is neat.
   UInt_t nbytes = ((nbits+31)>>3)&~3;

   ReserveBytes(nbytes);

   fNbits=nbits;

   const UChar_t *cArray = (const UChar_t*)array;
   for (UInt_t i=0; i<nbytes; i+=4) {
      fAllBits[i] = cArray[i+3];
      fAllBits[i+1] = cArray[i+2];
      fAllBits[i+2] = cArray[i+1];
      fAllBits[i+3] = cArray[i];
   }
}

void TBits::Set(UInt_t nbits, const Long64_t *array)
{
   // make nbytes a multiple of 8 so that the loop below is neat.
   UInt_t nbytes = ((nbits+63)>>3)&~7;

   ReserveBytes(nbytes);

   fNbits=nbits;

   const UChar_t *cArray = (const UChar_t*)array;
   for (UInt_t i=0; i<nbytes; i+=8) {
      fAllBits[i] = cArray[i+7];
      fAllBits[i+1] = cArray[i+6];
      fAllBits[i+2] = cArray[i+5];
      fAllBits[i+3] = cArray[i+4];
      fAllBits[i+4] = cArray[i+3];
      fAllBits[i+5] = cArray[i+2];
      fAllBits[i+6] = cArray[i+1];
      fAllBits[i+7] = cArray[i];
   }
}

void TBits::Get(Short_t *array) const
{
   // Get all the bytes.

   UInt_t nBytes = (fNbits+7)>>3;
   UInt_t nSafeBytes = nBytes&~1;

   UChar_t *cArray=(UChar_t*)array;
   for (UInt_t i=0; i<nSafeBytes; i+=2) {
      cArray[i] = fAllBits[i+1];
      cArray[i+1] = fAllBits[i];
   }

   if (nBytes>nSafeBytes) {
      cArray[nSafeBytes+1] = fAllBits[nSafeBytes];
   }
}

void TBits::Get(Int_t *array) const
{
   // Get all the bytes.

   UInt_t nBytes = (fNbits+7)>>3;
   UInt_t nSafeBytes = nBytes&~3;

   UChar_t *cArray=(UChar_t*)array;
   UInt_t i;
   for (i=0; i<nSafeBytes; i+=4) {
      cArray[i] = fAllBits[i+3];
      cArray[i+1] = fAllBits[i+2];
      cArray[i+2] = fAllBits[i+1];
      cArray[i+3] = fAllBits[i];
   }

   for (i=0; i<nBytes-nSafeBytes; ++i) {
      cArray[nSafeBytes + (3 - i)] = fAllBits[nSafeBytes + i];
   }
}

void TBits::Get(Long64_t *array) const
{
   // Get all the bytes.

   UInt_t nBytes = (fNbits+7)>>3;
   UInt_t nSafeBytes = nBytes&~7;

   UChar_t *cArray=(UChar_t*)array;
   UInt_t i;
   for (i=0; i<nSafeBytes; i+=8) {
      cArray[i] = fAllBits[i+7];
      cArray[i+1] = fAllBits[i+6];
      cArray[i+2] = fAllBits[i+5];
      cArray[i+3] = fAllBits[i+4];
      cArray[i+4] = fAllBits[i+3];
      cArray[i+5] = fAllBits[i+2];
      cArray[i+6] = fAllBits[i+1];
      cArray[i+7] = fAllBits[i];
   }

   for (i=0; i<nBytes-nSafeBytes; ++i) {
      cArray[nSafeBytes + (7 - i)] = fAllBits[nSafeBytes + i];
   }
}

#endif

Bool_t TBits::operator==(const TBits &other) const
{
   // Compare object.

   if (fNbits == other.fNbits) {
      return !memcmp(fAllBits, other.fAllBits, (fNbits+7)>>3);
   } else if (fNbits <  other.fNbits) {
      return !memcmp(fAllBits, other.fAllBits, (fNbits+7)>>3) && other.FirstSetBit(fNbits) == other.fNbits;
   } else {
      return !memcmp(fAllBits, other.fAllBits, (other.fNbits+7)>>3) && FirstSetBit(other.fNbits) == fNbits;
   }
}