/* InflaterHuffmanTree.java -- Copyright (C) 2001, 2004 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version. */ package java.util.zip; class InflaterHuffmanTree { private static final int MAX_BITLEN = 15; private short[] tree; static InflaterHuffmanTree defLitLenTree, defDistTree; static { try { byte[] codeLengths = new byte[288]; int i = 0; while (i < 144) codeLengths[i++] = 8; while (i < 256) codeLengths[i++] = 9; while (i < 280) codeLengths[i++] = 7; while (i < 288) codeLengths[i++] = 8; defLitLenTree = new InflaterHuffmanTree(codeLengths); codeLengths = new byte[32]; i = 0; while (i < 32) codeLengths[i++] = 5; defDistTree = new InflaterHuffmanTree(codeLengths); } catch (DataFormatException ex) { throw new InternalError ("InflaterHuffmanTree: static tree length illegal"); } } /** * Constructs a Huffman tree from the array of code lengths. * * @param codeLengths the array of code lengths */ InflaterHuffmanTree(byte[] codeLengths) throws DataFormatException { buildTree(codeLengths); } private void buildTree(byte[] codeLengths) throws DataFormatException { int[] blCount = new int[MAX_BITLEN+1]; int[] nextCode = new int[MAX_BITLEN+1]; for (int i = 0; i < codeLengths.length; i++) { int bits = codeLengths[i]; if (bits > 0) blCount[bits]++; } int max = 0; int code = 0; int treeSize = 512; for (int bits = 1; bits <= MAX_BITLEN; bits++) { nextCode[bits] = code; if (blCount[bits] > 0) max = bits; code += blCount[bits] << (16 - bits); if (bits >= 10) { /* We need an extra table for bit lengths >= 10. */ int start = nextCode[bits] & 0x1ff80; int end = code & 0x1ff80; treeSize += (end - start) >> (16 - bits); } } if (code != 65536 && max > 1) throw new DataFormatException("incomplete dynamic bit lengths tree"); /* Now create and fill the extra tables from longest to shortest * bit len. This way the sub trees will be aligned. */ tree = new short[treeSize]; int treePtr = 512; for (int bits = MAX_BITLEN; bits >= 10; bits--) { int end = code & 0x1ff80; code -= blCount[bits] << (16 - bits); int start = code & 0x1ff80; for (int i = start; i < end; i += 1 << 7) { tree[DeflaterHuffman.bitReverse(i)] = (short) ((-treePtr << 4) | bits); treePtr += 1 << (bits-9); } } for (int i = 0; i < codeLengths.length; i++) { int bits = codeLengths[i]; if (bits == 0) continue; code = nextCode[bits]; int revcode = DeflaterHuffman.bitReverse(code); if (bits <= 9) { do { tree[revcode] = (short) ((i << 4) | bits); revcode += 1 << bits; } while (revcode < 512); } else { int subTree = tree[revcode & 511]; int treeLen = 1 << (subTree & 15); subTree = -(subTree >> 4); do { tree[subTree | (revcode >> 9)] = (short) ((i << 4) | bits); revcode += 1 << bits; } while (revcode < treeLen); } nextCode[bits] = code + (1 << (16 - bits)); } } /** * Reads the next symbol from input. The symbol is encoded using the * huffman tree. * @param input the input source. * @return the next symbol, or -1 if not enough input is available. */ int getSymbol(StreamManipulator input) throws DataFormatException { int lookahead, symbol; if ((lookahead = input.peekBits(9)) >= 0) { if ((symbol = tree[lookahead]) >= 0) { input.dropBits(symbol & 15); return symbol >> 4; } int subtree = -(symbol >> 4); int bitlen = symbol & 15; if ((lookahead = input.peekBits(bitlen)) >= 0) { symbol = tree[subtree | (lookahead >> 9)]; input.dropBits(symbol & 15); return symbol >> 4; } else { int bits = input.getAvailableBits(); lookahead = input.peekBits(bits); symbol = tree[subtree | (lookahead >> 9)]; if ((symbol & 15) <= bits) { input.dropBits(symbol & 15); return symbol >> 4; } else return -1; } } else { int bits = input.getAvailableBits(); lookahead = input.peekBits(bits); symbol = tree[lookahead]; if (symbol >= 0 && (symbol & 15) <= bits) { input.dropBits(symbol & 15); return symbol >> 4; } else return -1; } } }