/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using DocIdSetIterator = Lucene.Net.Search.DocIdSetIterator;
namespace Lucene.Net.Util
{
/// An iterator to iterate over set bits in an OpenBitSet.
/// This is faster than nextSetBit() for iterating over the complete set of bits,
/// especially when the density of the bits set is high.
///
///
/// $Id$
///
public class OpenBitSetIterator:DocIdSetIterator
{
// The General Idea: instead of having an array per byte that has
// the offsets of the next set bit, that array could be
// packed inside a 32 bit integer (8 4 bit numbers). That
// should be faster than accessing an array for each index, and
// the total array size is kept smaller (256*sizeof(int))=1K
// NOTE: Removed protected access for CLS-Compliance
/*protected*/ internal static readonly uint[] bitlist = new uint[]
{
0x0, 0x1, 0x2, 0x21, 0x3, 0x31, 0x32, 0x321, 0x4, 0x41,
0x42, 0x421, 0x43, 0x431, 0x432, 0x4321, 0x5, 0x51,
0x52, 0x521, 0x53, 0x531, 0x532, 0x5321, 0x54, 0x541,
0x542, 0x5421, 0x543, 0x5431, 0x5432, 0x54321, 0x6,
0x61, 0x62, 0x621, 0x63, 0x631, 0x632, 0x6321, 0x64,
0x641, 0x642, 0x6421, 0x643, 0x6431, 0x6432, 0x64321,
0x65, 0x651, 0x652, 0x6521, 0x653, 0x6531, 0x6532,
0x65321, 0x654, 0x6541, 0x6542, 0x65421, 0x6543,
0x65431, 0x65432, 0x654321, 0x7, 0x71, 0x72, 0x721,
0x73, 0x731, 0x732, 0x7321, 0x74, 0x741, 0x742, 0x7421,
0x743, 0x7431, 0x7432, 0x74321, 0x75, 0x751, 0x752,
0x7521, 0x753, 0x7531, 0x7532, 0x75321, 0x754, 0x7541,
0x7542, 0x75421, 0x7543, 0x75431, 0x75432, 0x754321,
0x76, 0x761, 0x762, 0x7621, 0x763, 0x7631, 0x7632,
0x76321, 0x764, 0x7641, 0x7642, 0x76421, 0x7643,
0x76431, 0x76432, 0x764321, 0x765, 0x7651, 0x7652,
0x76521, 0x7653, 0x76531, 0x76532, 0x765321, 0x7654,
0x76541, 0x76542, 0x765421, 0x76543, 0x765431, 0x765432
, 0x7654321, 0x8, 0x81, 0x82, 0x821, 0x83, 0x831, 0x832
, 0x8321, 0x84, 0x841, 0x842, 0x8421, 0x843, 0x8431,
0x8432, 0x84321, 0x85, 0x851, 0x852, 0x8521, 0x853,
0x8531, 0x8532, 0x85321, 0x854, 0x8541, 0x8542, 0x85421
, 0x8543, 0x85431, 0x85432, 0x854321, 0x86, 0x861,
0x862, 0x8621, 0x863, 0x8631, 0x8632, 0x86321, 0x864,
0x8641, 0x8642, 0x86421, 0x8643, 0x86431, 0x86432,
0x864321, 0x865, 0x8651, 0x8652, 0x86521, 0x8653,
0x86531, 0x86532, 0x865321, 0x8654, 0x86541, 0x86542,
0x865421, 0x86543, 0x865431, 0x865432, 0x8654321, 0x87,
0x871, 0x872, 0x8721, 0x873, 0x8731, 0x8732, 0x87321,
0x874, 0x8741, 0x8742, 0x87421, 0x8743, 0x87431,
0x87432, 0x874321, 0x875, 0x8751, 0x8752, 0x87521,
0x8753, 0x87531, 0x87532, 0x875321, 0x8754, 0x87541,
0x87542, 0x875421, 0x87543, 0x875431, 0x875432,
0x8754321, 0x876, 0x8761, 0x8762, 0x87621, 0x8763,
0x87631, 0x87632, 0x876321, 0x8764, 0x87641, 0x87642,
0x876421, 0x87643, 0x876431, 0x876432, 0x8764321,
0x8765, 0x87651, 0x87652, 0x876521, 0x87653, 0x876531,
0x876532, 0x8765321, 0x87654,
0x876541, 0x876542, 0x8765421, 0x876543, 0x8765431,
0x8765432, 0x87654321
};
/// ** the python code that generated bitlist
/// def bits2int(val):
/// arr=0
/// for shift in range(8,0,-1):
/// if val & 0x80:
/// arr = (arr << 4) | shift
/// val = val << 1
/// return arr
/// def int_table():
/// tbl = [ hex(bits2int(val)).strip('L') for val in range(256) ]
/// return ','.join(tbl)
/// ****
///
// hmmm, what about an iterator that finds zeros though,
// or a reverse iterator... should they be separate classes
// for efficiency, or have a common root interface? (or
// maybe both? could ask for a SetBitsIterator, etc...
private readonly long[] arr;
private readonly int words;
private int i = - 1;
private long word;
private int wordShift;
private int indexArray;
private int curDocId = - 1;
public OpenBitSetIterator(OpenBitSet obs):this(obs.Bits, obs.NumWords)
{
}
public OpenBitSetIterator(long[] bits, int numWords)
{
arr = bits;
words = numWords;
}
// 64 bit shifts
private void Shift()
{
if ((int) word == 0)
{
wordShift += 32; word = (long) ((ulong) word >> 32);
}
if ((word & 0x0000FFFF) == 0)
{
wordShift += 16; word = (long) ((ulong) word >> 16);
}
if ((word & 0x000000FF) == 0)
{
wordShift += 8; word = (long) ((ulong) word >> 8);
}
indexArray = (int) bitlist[word & 0xff];
}
/*/// ** alternate shift implementations
/// // 32 bit shifts, but a long shift needed at the end
/// private void shift2() {
/// int y = (int)word;
/// if (y==0) {wordShift +=32; y = (int)(word >>>32); }
/// if ((y & 0x0000FFFF) == 0) { wordShift +=16; y>>>=16; }
/// if ((y & 0x000000FF) == 0) { wordShift +=8; y>>>=8; }
/// indexArray = bitlist[y & 0xff];
/// word >>>= (wordShift +1);
/// }
/// private void shift3() {
/// int lower = (int)word;
/// int lowByte = lower & 0xff;
/// if (lowByte != 0) {
/// indexArray=bitlist[lowByte];
/// return;
/// }
/// shift();
/// }
/// ****
/// */
public override int NextDoc()
{
if (indexArray == 0)
{
if (word != 0)
{
word = (long) ((ulong) word >> 8);
wordShift += 8;
}
while (word == 0)
{
if (++i >= words)
{
return curDocId = NO_MORE_DOCS;
}
word = arr[i];
wordShift = - 1; // loop invariant code motion should move this
}
// after the first time, should I go with a linear search, or
// stick with the binary search in shift?
Shift();
}
int bitIndex = (indexArray & 0x0f) + wordShift;
indexArray = (int) ((uint) indexArray >> 4);
// should i<<6 be cached as a separate variable?
// it would only save one cycle in the best circumstances.
return curDocId = (i << 6) + bitIndex;
}
public override int Advance(int target)
{
indexArray = 0;
i = target >> 6;
if (i >= words)
{
word = 0; // setup so next() will also return -1
return curDocId = NO_MORE_DOCS;
}
wordShift = target & 0x3f;
word = (long) ((ulong) arr[i] >> wordShift);
if (word != 0)
{
wordShift--; // compensate for 1 based arrIndex
}
else
{
while (word == 0)
{
if (++i >= words)
{
return curDocId = NO_MORE_DOCS;
}
word = arr[i];
}
wordShift = - 1;
}
Shift();
int bitIndex = (indexArray & 0x0f) + wordShift;
indexArray = (int) ((uint) indexArray >> 4);
// should i<<6 be cached as a separate variable?
// it would only save one cycle in the best circumstances.
return curDocId = (i << 6) + bitIndex;
}
public override int DocID()
{
return curDocId;
}
}
}