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/* 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 code = 0;

    int treeSize = 512;

    for (int bits = 1; bits <= MAX_BITLEN; bits++)

      {

        nextCode[bits] = code;

        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)

      throw new DataFormatException("Code lengths don't add up properly.");

    /* 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;

      }

  }

}