--- /dev/null
+package org.apache.lucene.util.packed;
+
+/**
+ * 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.
+ */
+
+import org.apache.lucene.store.DataInput;
+import org.apache.lucene.util.RamUsageEstimator;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * Space optimized random access capable array of values with a fixed number of
+ * bits. The maximum number of bits/value is 31. Use {@link Packed64} for higher
+ * numbers.
+ * </p><p>
+ * The implementation strives to avoid conditionals and expensive operations,
+ * sacrificing code clarity to achieve better performance.
+ */
+
+class Packed32 extends PackedInts.ReaderImpl implements PackedInts.Mutable {
+ static final int BLOCK_SIZE = 32; // 32 = int, 64 = long
+ static final int BLOCK_BITS = 5; // The #bits representing BLOCK_SIZE
+ static final int MOD_MASK = BLOCK_SIZE - 1; // x % BLOCK_SIZE
+
+ private static final int ENTRY_SIZE = BLOCK_SIZE + 1;
+ private static final int FAC_BITPOS = 3;
+
+ /*
+ * In order to make an efficient value-getter, conditionals should be
+ * avoided. A value can be positioned inside of a block, requiring shifting
+ * left or right or it can span two blocks, requiring a left-shift on the
+ * first block and a right-shift on the right block.
+ * </p><p>
+ * By always shifting the first block both left and right, we get exactly
+ * the right bits. By always shifting the second block right and applying
+ * a mask, we get the right bits there. After that, we | the two bitsets.
+ */
+ private static final int[][] SHIFTS =
+ new int[ENTRY_SIZE][ENTRY_SIZE * FAC_BITPOS];
+ private static final int[][] MASKS = new int[ENTRY_SIZE][ENTRY_SIZE];
+
+ static { // Generate shifts
+ for (int elementBits = 1 ; elementBits <= BLOCK_SIZE ; elementBits++) {
+ for (int bitPos = 0 ; bitPos < BLOCK_SIZE ; bitPos++) {
+ int[] currentShifts = SHIFTS[elementBits];
+ int base = bitPos * FAC_BITPOS;
+ currentShifts[base ] = bitPos;
+ currentShifts[base + 1] = BLOCK_SIZE - elementBits;
+ if (bitPos <= BLOCK_SIZE - elementBits) { // Single block
+ currentShifts[base + 2] = 0;
+ MASKS[elementBits][bitPos] = 0;
+ } else { // Two blocks
+ int rBits = elementBits - (BLOCK_SIZE - bitPos);
+ currentShifts[base + 2] = BLOCK_SIZE - rBits;
+ MASKS[elementBits][bitPos] = ~(~0 << rBits);
+ }
+ }
+ }
+ }
+
+ /*
+ * The setter requires more masking than the getter.
+ */
+ private static final int[][] WRITE_MASKS =
+ new int[ENTRY_SIZE][ENTRY_SIZE * FAC_BITPOS];
+ static {
+ for (int elementBits = 1 ; elementBits <= BLOCK_SIZE ; elementBits++) {
+ int elementPosMask = ~(~0 << elementBits);
+ int[] currentShifts = SHIFTS[elementBits];
+ int[] currentMasks = WRITE_MASKS[elementBits];
+ for (int bitPos = 0 ; bitPos < BLOCK_SIZE ; bitPos++) {
+ int base = bitPos * FAC_BITPOS;
+ currentMasks[base ] =~((elementPosMask
+ << currentShifts[base + 1])
+ >>> currentShifts[base]);
+ if (bitPos <= BLOCK_SIZE - elementBits) { // Second block not used
+ currentMasks[base+1] = ~0; // Keep all bits
+ currentMasks[base+2] = 0; // Or with 0
+ } else {
+ currentMasks[base+1] = ~(elementPosMask
+ << currentShifts[base + 2]);
+ currentMasks[base+2] = currentShifts[base + 2] == 0 ? 0 : ~0;
+ }
+ }
+ }
+ }
+
+ /* The bits */
+ private int[] blocks;
+
+ // Cached calculations
+ private int maxPos; // blocks.length * BLOCK_SIZE / bitsPerValue - 1
+ private int[] shifts; // The shifts for the current bitsPerValue
+ private int[] readMasks;
+ private int[] writeMasks;
+
+ /**
+ * Creates an array with the internal structures adjusted for the given
+ * limits and initialized to 0.
+ * @param valueCount the number of elements.
+ * @param bitsPerValue the number of bits available for any given value.
+ * Note: bitsPerValue >32 is not supported by this implementation.
+ */
+ public Packed32(int valueCount, int bitsPerValue) {
+ this(new int[(int)(((long)valueCount) * bitsPerValue / BLOCK_SIZE + 2)],
+ valueCount, bitsPerValue);
+ }
+
+ /**
+ * Creates an array with content retrieved from the given DataInput.
+ * @param in a DataInput, positioned at the start of Packed64-content.
+ * @param valueCount the number of elements.
+ * @param bitsPerValue the number of bits available for any given value.
+ * @throws java.io.IOException if the values for the backing array could not
+ * be retrieved.
+ */
+ public Packed32(DataInput in, int valueCount, int bitsPerValue)
+ throws IOException {
+ super(valueCount, bitsPerValue);
+ int size = size(bitsPerValue, valueCount);
+ blocks = new int[size + 1]; // +1 due to non-conditional tricks
+ // TODO: find a faster way to bulk-read ints...
+ for(int i = 0 ; i < size ; i++) {
+ blocks[i] = in.readInt();
+ }
+ if (size % 2 == 1) {
+ in.readInt(); // Align to long
+ }
+ updateCached();
+ }
+
+ private static int size(int bitsPerValue, int valueCount) {
+ final long totBitCount = (long) valueCount * bitsPerValue;
+ return (int) (totBitCount/32 + ((totBitCount % 32 == 0 ) ? 0:1));
+ }
+
+
+ /**
+ * Creates an array backed by the given blocks.
+ * </p><p>
+ * Note: The blocks are used directly, so changes to the given block will
+ * affect the Packed32-structure.
+ * @param blocks used as the internal backing array.
+ * @param valueCount the number of values.
+ * @param bitsPerValue the number of bits available for any given value.
+ * Note: bitsPerValue >32 is not supported by this implementation.
+ */
+ public Packed32(int[] blocks, int valueCount, int bitsPerValue) {
+ // TODO: Check that blocks.length is sufficient for holding length values
+ super(valueCount, bitsPerValue);
+ if (bitsPerValue > 31) {
+ throw new IllegalArgumentException(String.format(
+ "This array only supports values of 31 bits or less. The "
+ + "required number of bits was %d. The Packed64 "
+ + "implementation allows values with more than 31 bits",
+ bitsPerValue));
+ }
+ this.blocks = blocks;
+ updateCached();
+ }
+
+ private void updateCached() {
+ readMasks = MASKS[bitsPerValue];
+ maxPos = (int)((((long)blocks.length) * BLOCK_SIZE / bitsPerValue) - 2);
+ shifts = SHIFTS[bitsPerValue];
+ writeMasks = WRITE_MASKS[bitsPerValue];
+ }
+
+ /**
+ * @param index the position of the value.
+ * @return the value at the given index.
+ */
+ public long get(final int index) {
+ final long majorBitPos = (long)index * bitsPerValue;
+ final int elementPos = (int)(majorBitPos >>> BLOCK_BITS); // / BLOCK_SIZE
+ final int bitPos = (int)(majorBitPos & MOD_MASK); // % BLOCK_SIZE);
+
+ final int base = bitPos * FAC_BITPOS;
+
+ return ((blocks[elementPos] << shifts[base]) >>> shifts[base+1]) |
+ ((blocks[elementPos+1] >>> shifts[base+2]) & readMasks[bitPos]);
+ }
+
+ public void set(final int index, final long value) {
+ final int intValue = (int)value;
+ final long majorBitPos = (long)index * bitsPerValue;
+ final int elementPos = (int)(majorBitPos >>> BLOCK_BITS); // / BLOCK_SIZE
+ final int bitPos = (int)(majorBitPos & MOD_MASK); // % BLOCK_SIZE);
+ final int base = bitPos * FAC_BITPOS;
+
+ blocks[elementPos ] = (blocks[elementPos ] & writeMasks[base])
+ | (intValue << shifts[base + 1] >>> shifts[base]);
+ blocks[elementPos+1] = (blocks[elementPos+1] & writeMasks[base+1])
+ | ((intValue << shifts[base + 2])
+ & writeMasks[base+2]);
+ }
+
+ public void clear() {
+ Arrays.fill(blocks, 0);
+ }
+
+ @Override
+ public String toString() {
+ return "Packed32(bitsPerValue=" + bitsPerValue + ", maxPos=" + maxPos
+ + ", elements.length=" + blocks.length + ")";
+ }
+
+ public long ramBytesUsed() {
+ return RamUsageEstimator.NUM_BYTES_ARRAY_HEADER
+ + blocks.length * RamUsageEstimator.NUM_BYTES_INT;
+ }
+}
fnp / pylucene.git / blobdiff