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/*
* Copyright (c) 2007 Sun Microsystems, Inc. All rights reserved.
*
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* modification, are permitted provided that the following conditions
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* from this software without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any
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package com.sun.j3d.utils.compression;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
/**
* This class maintains a map from compression stream elements (tokens) onto
* HuffmanNode objects. A HuffmanNode contains a tag describing the
* associated token's data length, right shift value, and absolute/relative
* status.
*
* The tags are computed using Huffman's algorithm to build a binary tree with
* a minimal total weighted path length. The frequency of each token is
* used as its node's weight when building the tree. The path length from the
* root to the token's node then indicates the bit length that should be used
* for that token's tag in order to minimize the total size of the compressed
* stream.
*/
class HuffmanTable {
private static final int MAX_TAG_LENGTH = 6 ;
private HuffmanNode positions[] ;
private HuffmanNode normals[] ;
private HuffmanNode colors[] ;
/**
* Create a new HuffmanTable with entries for all possible position,
* normal, and color tokens.
*/
HuffmanTable() {
//
// Position and color components can have data lengths up to 16
// bits, with right shifts up to 15 bits. The position and color
// lookup tables are therefore 2*17*16=544 entries in length to
// account for all possible combinations of data lengths, shifts,
// and relative or absolute status.
//
colors = new HuffmanNode[544] ;
positions = new HuffmanNode[544] ;
//
// Delta normals can have uv components up to 7 bits in length with
// right shifts up to 6 bits. Absolute normals can have uv components
// up to 6 bits in length with right shifts up to 5 bits. The normal
// lookup table is therefore 2*8*7=112 entries in length.
//
normals = new HuffmanNode[112] ;
}
private final int getPositionIndex(int len, int shift, boolean absolute) {
return (absolute? 1:0)*272 + len*16 + shift ;
}
private final int getNormalIndex(int length, int shift, boolean absolute) {
return (absolute? 1:0)*56 + length*7 + shift ;
}
private final int getColorIndex(int length, int shift, boolean absolute) {
return getPositionIndex(length, shift, absolute) ;
}
/**
* Add a position entry with the given length, shift, and absolute
* status.
*
* @param length number of bits in each X, Y, and Z component
* @param shift number of trailing zeros in each component
* @param absolute if false, value represented is a delta from the
* previous vertex in the compression stream
*/
void addPositionEntry(int length, int shift, boolean absolute) {
addEntry(positions, getPositionIndex(length, shift, absolute),
length, shift, absolute) ;
}
/**
* Get the position entry associated with the specified length, shift, and
* absolute status. This will contain a tag indicating the actual
* encoding to be used in the compression command stream, not necessarily
* the same as the original length and shift with which the the entry was
* created.
*
* @param length number of bits in each X, Y, and Z component
* @param shift number of trailing zeros in each component
* @param absolute if false, value represented is a delta from the
* previous vertex in the compression stream
* @return HuffmanNode mapped to the specified parameters
*/
HuffmanNode getPositionEntry(int length, int shift, boolean absolute) {
return getEntry(positions, getPositionIndex(length, shift, absolute)) ;
}
/**
* Add a color entry with the given length, shift, and absolute
* status.
*
* @param length number of bits in each R, G, B, and A component
* @param shift number of trailing zeros in each component
* @param absolute if false, value represented is a delta from the
* previous color in the compression stream
*/
void addColorEntry(int length, int shift, boolean absolute) {
addEntry(colors, getColorIndex(length, shift, absolute),
length, shift, absolute) ;
}
/**
* Get the color entry associated with the specified length, shift, and
* absolute status. This will contain a tag indicating the actual
* encoding to be used in the compression command stream, not necessarily
* the same as the original length and shift with which the the entry was
* created.
*
* @param length number of bits in each R, G, B, and A component
* @param shift number of trailing zeros in each component
* @param absolute if false, value represented is a delta from the
* previous color in the compression stream
* @return HuffmanNode mapped to the specified parameters
*/
HuffmanNode getColorEntry(int length, int shift, boolean absolute) {
return getEntry(colors, getColorIndex(length, shift, absolute)) ;
}
/**
* Add a normal entry with the given length, shift, and absolute
* status.
*
* @param length number of bits in each U and V component
* @param shift number of trailing zeros in each component
* @param absolute if false, value represented is a delta from the
* previous normal in the compression stream
*/
void addNormalEntry(int length, int shift, boolean absolute) {
addEntry(normals, getNormalIndex(length, shift, absolute),
length, shift, absolute) ;
}
/**
* Get the normal entry associated with the specified length, shift, and
* absolute status. This will contain a tag indicating the actual
* encoding to be used in the compression command stream, not necessarily
* the same as the original length and shift with which the the entry was
* created.
*
* @param length number of bits in each U and V component
* @param shift number of trailing zeros in each component
* @param absolute if false, value represented is a delta from the
* previous normal in the compression stream
* @return HuffmanNode mapped to the specified parameters
*/
HuffmanNode getNormalEntry(int length, int shift, boolean absolute) {
return getEntry(normals, getNormalIndex(length, shift, absolute)) ;
}
private void addEntry(HuffmanNode table[], int index,
int length, int shift, boolean absolute) {
if (table[index] == null)
table[index] = new HuffmanNode(length, shift, absolute) ;
else if (table[index].cleared())
table[index].set(length, shift, absolute) ;
table[index].addCount() ;
}
private HuffmanNode getEntry(HuffmanNode table[], int index) {
HuffmanNode t = table[index] ;
while (t.merged())
t = t.getMergeNode() ;
return t ;
}
private void getEntries(HuffmanNode table[], Collection c) {
for (int i = 0 ; i < table.length ; i++)
if (table[i] != null && !table[i].cleared() &&
table[i].hasCount() && !table[i].merged())
c.add(table[i]) ;
}
/**
* Clear this HuffmanTable instance.
*/
void clear() {
for (int i = 0 ; i < positions.length ; i++)
if (positions[i] != null)
positions[i].clear() ;
for (int i = 0 ; i < colors.length ; i++)
if (colors[i] != null)
colors[i].clear() ;
for (int i = 0 ; i < normals.length ; i++)
if (normals[i] != null)
normals[i].clear() ;
}
/**
* Compute optimized tags for each position, color, and normal entry.
*/
void computeTags() {
LinkedList nodeList = new LinkedList() ;
getEntries(positions, nodeList) ;
computeTags(nodeList, 3) ;
nodeList.clear() ;
getEntries(colors, nodeList) ;
computeTags(nodeList, 3) ;
nodeList.clear() ;
getEntries(normals, nodeList) ;
computeTags(nodeList, 2) ;
}
//
// Compute tags for a list of Huffman tokens.
//
private void computeTags(LinkedList nodes, int minComponentCount) {
HuffmanNode node0, node1, node2 ;
// Return if there's nothing to do.
if (nodes.isEmpty())
return ;
while (true) {
// Sort the nodes in ascending order by frequency.
Collections.sort(nodes, HuffmanNode.frequencyComparator) ;
// Apply Huffman's algorithm to construct a binary tree with a
// minimum total weighted path length.
node0 = (HuffmanNode)nodes.removeFirst() ;
while (nodes.size() > 0) {
node1 = (HuffmanNode)nodes.removeFirst() ;
node2 = new HuffmanNode() ;
node2.addChildren(node0, node1) ;
addNodeInOrder(nodes, node2, HuffmanNode.frequencyComparator) ;
node0 = (HuffmanNode)nodes.removeFirst() ;
}
// node0 is the root of the resulting binary tree. Traverse it
// assigning tags and lengths to the leaf nodes. The leaves are
// collected into the now empty node list.
node0.collectLeaves(0, 0, nodes) ;
// Sort the nodes in descending order by tag length.
Collections.sort(nodes, HuffmanNode.tagLengthComparator) ;
// Check for tag length overrun.
if (((HuffmanNode)nodes.getFirst()).tagLength > MAX_TAG_LENGTH) {
// Tokens need to be merged and the tree rebuilt with the new
// combined frequencies.
merge(nodes) ;
} else {
// Increase tag length + data length if they're too small.
expand(nodes, minComponentCount) ;
break ;
}
}
}
//
// Merge a token with a long tag into some other token. The merged token
// will be removed from the list along with any duplicate node the merge
// created, reducing the size of the list by 1 or 2 elements until only
// unmergeable tokens are left.
//
private void merge(LinkedList nodes) {
ListIterator i = nodes.listIterator(0) ;
HuffmanNode node0, node1, node2 ;
int index = 0 ;
while (i.hasNext()) {
// Get the node with the longest possibly mergeable tag.
node0 = (HuffmanNode)i.next() ;
if (node0.unmergeable()) continue ;
// Try to find a node that can be merged with node0. This is any
// node that matches its absolute/relative status.
i.remove() ;
while (i.hasNext()) {
node1 = (HuffmanNode)i.next() ;
if (node0.mergeInto(node1)) {
// Search for a duplicate of the possibly modified node1
// and merge into it so that node weights remain valid.
// If a duplicate exists it must be further in the list,
// otherwise node0 would have merged into it.
i.remove() ;
while (i.hasNext()) {
node2 = (HuffmanNode)i.next() ;
if (node1.tokenEquals(node2)) {
node1.mergeInto(node2) ;
return ;
}
}
// node1 has no duplicate, so return it to the list.
i.add(node1) ;
return ;
}
}
// node0 can't be merged with any other node; it must be the only
// relative or absolute node in the list. Mark it as unmergeable
// to avoid unnecessary searches on subsequent calls to merge()
// and return it to the list.
node0.setUnmergeable() ;
i.add(node0) ;
// Restart the iteration.
i = nodes.listIterator(0) ;
}
}
//
// Empty bits within a compression command header are not allowed. If
// the tag length plus the total data length is less than 6 bits then
// the token's length must be increased.
//
private void expand(LinkedList nodes, int minComponentCount) {
Iterator i = nodes.iterator() ;
while (i.hasNext()) {
HuffmanNode n = (HuffmanNode)i.next() ;
while (n.tagLength +
(minComponentCount * (n.dataLength - n.shift)) < 6) {
n.incrementLength() ;
}
}
}
//
// Insert a node into the correct place in a sorted list of nodes.
//
private void addNodeInOrder(LinkedList l, HuffmanNode node, Comparator c) {
ListIterator i = l.listIterator(0) ;
while (i.hasNext()) {
HuffmanNode n = (HuffmanNode)i.next() ;
if (c.compare(n, node) > 0) {
n = (HuffmanNode)i.previous() ;
break ;
}
}
i.add(node) ;
}
/**
* Create compression stream commands for decompressors to use to set up
* their decompression tables.
*
* @param output CommandStream which receives the compression commands
*/
void outputCommands(CommandStream output) {
LinkedList nodeList = new LinkedList() ;
getEntries(positions, nodeList) ;
outputCommands(nodeList, output, CommandStream.POSITION_TABLE) ;
nodeList.clear() ;
getEntries(colors, nodeList) ;
outputCommands(nodeList, output, CommandStream.COLOR_TABLE) ;
nodeList.clear() ;
getEntries(normals, nodeList) ;
outputCommands(nodeList, output, CommandStream.NORMAL_TABLE) ;
}
//
// Output a setTable command for each unique token.
//
private void outputCommands(Collection nodes,
CommandStream output, int tableId) {
Iterator i = nodes.iterator() ;
while (i.hasNext()) {
HuffmanNode n = (HuffmanNode)i.next() ;
int addressRange = (1 << n.tagLength) | n.tag ;
int dataLength = (n.dataLength == 16? 0 : n.dataLength) ;
int command =
CommandStream.SET_TABLE | (tableId << 1) | (addressRange >> 6) ;
long body =
((addressRange & 0x3f) << 9) | (dataLength << 5) |
(n.absolute? 0x10 : 0) | n.shift ;
output.addCommand(command, 8, body, 15) ;
}
}
/**
* Print a collection of HuffmanNode objects to standard out.
*
* @param header descriptive string
* @param nodes Collection of HuffmanNode objects to print
*/
void print(String header, Collection nodes) {
System.out.println(header + "\nentries: " + nodes.size() + "\n") ;
Iterator i = nodes.iterator() ;
while(i.hasNext()) {
HuffmanNode n = (HuffmanNode)i.next() ;
System.out.println(n.toString() + "\n") ;
}
}
/**
* Print the contents of this instance to standard out.
*/
void print() {
LinkedList nodeList = new LinkedList() ;
getEntries(positions, nodeList) ;
Collections.sort(nodeList, HuffmanNode.frequencyComparator) ;
print("\nposition tokens and tags", nodeList) ;
nodeList.clear() ;
getEntries(colors, nodeList) ;
Collections.sort(nodeList, HuffmanNode.frequencyComparator) ;
print("\ncolor tokens and tags", nodeList) ;
nodeList.clear() ;
getEntries(normals, nodeList) ;
Collections.sort(nodeList, HuffmanNode.frequencyComparator) ;
print("\nnormal tokens and tags", nodeList) ;
}
}