ch.cern.hbase.thirdparty.io.netty.handler.codec.compression.Bzip2HuffmanAllocator Maven / Gradle / Ivy
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Pulls down netty.io, relocates nd then makes a fat new jar with them all in it.
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/*
* Copyright 2014 The Netty Project
*
* The Netty Project 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.
*/
package ch.cern.hbase.thirdparty.io.netty.handler.codec.compression;
/**
* An in-place, length restricted Canonical Huffman code length allocator.
* Based on the algorithm proposed by R. L. Milidi'u, A. A. Pessoa and E. S. Laber in
* In-place Length-Restricted Prefix Coding
* and incorporating additional ideas from the implementation of
* shcodec by Simakov Alexander.
*/
final class Bzip2HuffmanAllocator {
/**
* @param array The code length array
* @param i The input position
* @param nodesToMove The number of internal nodes to be relocated
* @return The smallest {@code k} such that {@code nodesToMove <= k <= i} and
* {@code i <= (array[k] % array.length)}
*/
private static int first(final int[] array, int i, final int nodesToMove) {
final int length = array.length;
final int limit = i;
int k = array.length - 2;
while (i >= nodesToMove && array[i] % length > limit) {
k = i;
i -= limit - i + 1;
}
i = Math.max(nodesToMove - 1, i);
while (k > i + 1) {
int temp = i + k >>> 1;
if (array[temp] % length > limit) {
k = temp;
} else {
i = temp;
}
}
return k;
}
/**
* Fills the code array with extended parent pointers.
* @param array The code length array
*/
private static void setExtendedParentPointers(final int[] array) {
final int length = array.length;
array[0] += array[1];
for (int headNode = 0, tailNode = 1, topNode = 2; tailNode < length - 1; tailNode++) {
int temp;
if (topNode >= length || array[headNode] < array[topNode]) {
temp = array[headNode];
array[headNode++] = tailNode;
} else {
temp = array[topNode++];
}
if (topNode >= length || (headNode < tailNode && array[headNode] < array[topNode])) {
temp += array[headNode];
array[headNode++] = tailNode + length;
} else {
temp += array[topNode++];
}
array[tailNode] = temp;
}
}
/**
* Finds the number of nodes to relocate in order to achieve a given code length limit.
* @param array The code length array
* @param maximumLength The maximum bit length for the generated codes
* @return The number of nodes to relocate
*/
private static int findNodesToRelocate(final int[] array, final int maximumLength) {
int currentNode = array.length - 2;
for (int currentDepth = 1; currentDepth < maximumLength - 1 && currentNode > 1; currentDepth++) {
currentNode = first(array, currentNode - 1, 0);
}
return currentNode;
}
/**
* A final allocation pass with no code length limit.
* @param array The code length array
*/
private static void allocateNodeLengths(final int[] array) {
int firstNode = array.length - 2;
int nextNode = array.length - 1;
for (int currentDepth = 1, availableNodes = 2; availableNodes > 0; currentDepth++) {
final int lastNode = firstNode;
firstNode = first(array, lastNode - 1, 0);
for (int i = availableNodes - (lastNode - firstNode); i > 0; i--) {
array[nextNode--] = currentDepth;
}
availableNodes = (lastNode - firstNode) << 1;
}
}
/**
* A final allocation pass that relocates nodes in order to achieve a maximum code length limit.
* @param array The code length array
* @param nodesToMove The number of internal nodes to be relocated
* @param insertDepth The depth at which to insert relocated nodes
*/
private static void allocateNodeLengthsWithRelocation(final int[] array,
final int nodesToMove, final int insertDepth) {
int firstNode = array.length - 2;
int nextNode = array.length - 1;
int currentDepth = insertDepth == 1 ? 2 : 1;
int nodesLeftToMove = insertDepth == 1 ? nodesToMove - 2 : nodesToMove;
for (int availableNodes = currentDepth << 1; availableNodes > 0; currentDepth++) {
final int lastNode = firstNode;
firstNode = firstNode <= nodesToMove ? firstNode : first(array, lastNode - 1, nodesToMove);
int offset = 0;
if (currentDepth >= insertDepth) {
offset = Math.min(nodesLeftToMove, 1 << (currentDepth - insertDepth));
} else if (currentDepth == insertDepth - 1) {
offset = 1;
if (array[firstNode] == lastNode) {
firstNode++;
}
}
for (int i = availableNodes - (lastNode - firstNode + offset); i > 0; i--) {
array[nextNode--] = currentDepth;
}
nodesLeftToMove -= offset;
availableNodes = (lastNode - firstNode + offset) << 1;
}
}
/**
* Allocates Canonical Huffman code lengths in place based on a sorted frequency array.
* @param array On input, a sorted array of symbol frequencies; On output, an array of Canonical
* Huffman code lengths
* @param maximumLength The maximum code length. Must be at least {@code ceil(log2(array.length))}
*/
static void allocateHuffmanCodeLengths(final int[] array, final int maximumLength) {
switch (array.length) {
case 2:
array[1] = 1;
// fall through
case 1:
array[0] = 1;
return;
}
/* Pass 1 : Set extended parent pointers */
setExtendedParentPointers(array);
/* Pass 2 : Find number of nodes to relocate in order to achieve maximum code length */
int nodesToRelocate = findNodesToRelocate(array, maximumLength);
/* Pass 3 : Generate code lengths */
if (array[0] % array.length >= nodesToRelocate) {
allocateNodeLengths(array);
} else {
int insertDepth = maximumLength - (32 - Integer.numberOfLeadingZeros(nodesToRelocate - 1));
allocateNodeLengthsWithRelocation(array, nodesToRelocate, insertDepth);
}
}
private Bzip2HuffmanAllocator() { }
}