31  * be constant to reduce overhead. All the bits of a new bitSieve are zero, and
  32  * bits are removed from it by setting them.
  33  *
  34  * To reduce storage space and increase efficiency, no even numbers are
  35  * represented in the sieve (each bit in the sieve represents an odd number).
  36  * The relationship between the index of a bit and the number it represents is
  37  * given by
  38  * N = offset + (2*index + 1);
  39  * Where N is the integer represented by a bit in the sieve, offset is some
  40  * even integer offset indicating where the sieve begins, and index is the
  41  * index of a bit in the sieve array.
  42  *
  43  * @see     BigInteger
  44  * @author  Michael McCloskey
  45  * @since   1.3
  46  */
  47 class BitSieve {
  48     /**
  49      * Stores the bits in this bitSieve.
  50      */
  51     private long bits[];
  52 
  53     /**
  54      * Length is how many bits this sieve holds.
  55      */
  56     private int length;
  57 
  58     /**
  59      * A small sieve used to filter out multiples of small primes in a search
  60      * sieve.
  61      */
  62     private static BitSieve smallSieve = new BitSieve();
  63 
  64     /**
  65      * Construct a "small sieve" with a base of 0.  This constructor is
  66      * used internally to generate the set of "small primes" whose multiples
  67      * are excluded from sieves generated by the main (package private)
  68      * constructor, BitSieve(BigInteger base, int searchLen).  The length
  69      * of the sieve generated by this constructor was chosen for performance;
  70      * it controls a tradeoff between how much time is spent constructing
  71      * other sieves, and how much time is wasted testing composite candidates

  31  * be constant to reduce overhead. All the bits of a new bitSieve are zero, and
  32  * bits are removed from it by setting them.
  33  *
  34  * To reduce storage space and increase efficiency, no even numbers are
  35  * represented in the sieve (each bit in the sieve represents an odd number).
  36  * The relationship between the index of a bit and the number it represents is
  37  * given by
  38  * N = offset + (2*index + 1);
  39  * Where N is the integer represented by a bit in the sieve, offset is some
  40  * even integer offset indicating where the sieve begins, and index is the
  41  * index of a bit in the sieve array.
  42  *
  43  * @see     BigInteger
  44  * @author  Michael McCloskey
  45  * @since   1.3
  46  */
  47 class BitSieve {
  48     /**
  49      * Stores the bits in this bitSieve.
  50      */
  51     private long[] bits;
  52 
  53     /**
  54      * Length is how many bits this sieve holds.
  55      */
  56     private int length;
  57 
  58     /**
  59      * A small sieve used to filter out multiples of small primes in a search
  60      * sieve.
  61      */
  62     private static BitSieve smallSieve = new BitSieve();
  63 
  64     /**
  65      * Construct a "small sieve" with a base of 0.  This constructor is
  66      * used internally to generate the set of "small primes" whose multiples
  67      * are excluded from sieves generated by the main (package private)
  68      * constructor, BitSieve(BigInteger base, int searchLen).  The length
  69      * of the sieve generated by this constructor was chosen for performance;
  70      * it controls a tradeoff between how much time is spent constructing
  71      * other sieves, and how much time is wasted testing composite candidates