/*
******************************************************************************
* Copyright (C) 1996-2002, International Business Machines Corporation and   *
* others. All Rights Reserved.                                               *
******************************************************************************
*
* $Source: /xsrl/Nsvn/icu/icu4j/src/com/ibm/icu/impl/CharTrie.java,v $
* $Date: 2002/08/08 22:43:05 $
* $Revision: 1.6 $
*
******************************************************************************
*/

package com.ibm.icu.impl;

import java.io.InputStream;
import java.io.DataInputStream;
import java.io.IOException;

/**
 * Trie implementation which stores data in char, 16 bits.
 * @author synwee
 * @see com.ibm.icu.util.Trie
 * @since release 2.1, Jan 01 2002
 */

 // note that i need to handle the block calculations later, since chartrie
 // in icu4c uses the same index array.
public class CharTrie extends Trie
{
    // public constructors ---------------------------------------------

    /**
    * <p>Creates a new Trie with the settings for the trie data.</p>
    * <p>Unserialize the 32-bit-aligned input stream and use the data for the 
    * trie.</p>
    * @param inputStream file input stream to a ICU data file, containing 
    *                    the trie
    * @param dataManipulate, object which provides methods to parse the char 
    *                        data
    * @exception IOException thrown when data reading fails
    * @draft 2.1
    */
    public CharTrie(InputStream inputStream, 
                    DataManipulate dataManipulate) throws IOException
    {
        super(inputStream, dataManipulate);
        
        if (!isCharTrie()) {
            throw new IllegalArgumentException(
                               "Data given does not belong to a char trie.");
        }
    }

    // public methods --------------------------------------------------

    /**
    * Gets the value associated with the codepoint.
    * If no value is associated with the codepoint, a default value will be
    * returned.
    * @param ch codepoint
    * @return offset to data
    * @draft 2.1
    */
    public final char getCodePointValue(int ch)
    {
        int offset = getCodePointOffset(ch);
        if (offset > 0) {
            return m_data_[offset];
        }
        return m_initialValue_;
    }

    /**
    * Gets the value to the data which this lead surrogate character points
    * to.
    * Returned data may contain folding offset information for the next
    * trailing surrogate character.
    * This method does not guarantee correct results for trail surrogates.
    * @param ch lead surrogate character
    * @return data value
    * @draft 2.1
    */
    public final char getLeadValue(char ch)
    {
       return m_data_[getLeadOffset(ch)];
    }

    /**
    * Get the value associated with the BMP code point.
    * Lead surrogate code points are treated as normal code points, with
    * unfolded values that may differ from getLeadValue() results.
    * @param ch the input BMP code point
    * @return trie data value associated with the BMP codepoint
    * @draft 2.1
    */
    public final char getBMPValue(char ch)
    {
        return m_data_[getBMPOffset(ch)];
    }

    /**
    * Get the value associated with a pair of surrogates.
    * @param lead a lead surrogate
    * @param trail a trail surrogate
    * @param trie data value associated with the surrogate characters
    * @draft 2.1
    */
    public final char getSurrogateValue(char lead, char trail)
    {
    	int offset = getSurrogateOffset(lead, trail);
    	if (offset > 0) {
            return m_data_[offset];
        }
        return m_initialValue_;
    }

    /**
    * <p>Get a value from a folding offset (from the value of a lead surrogate)
    * and a trail surrogate.</p>
    * <p>If the 
    * @param leadvalue value associated with the lead surrogate which contains
    *        the folding offset
    * @param trail surrogate
    * @return trie data value associated with the trail character
    * @draft 2.1
    */
    public final char getTrailValue(int leadvalue, char trail)
    {
        if (m_dataManipulate_ == null) {
            throw new NullPointerException(
                             "The field DataManipulate in this Trie is null");
        }
        int offset = m_dataManipulate_.getFoldingOffset(leadvalue);
        if (offset > 0) {
	        return m_data_[getRawOffset(offset,
 		                                (char)(trail & SURROGATE_MASK_))];
        }
        return m_initialValue_;
    }
    
    /**
     * <p>Gets the latin 1 fast path value.</p>
     * <p>Note this only works if latin 1 characters have their own linear 
     * array.</p>
     * @param ch latin 1 characters
     * @return value associated with latin character
     */
    public final char getLatin1LinearValue(char ch) 
    {
    	return m_data_[INDEX_STAGE_3_MASK_ + 1 + m_dataOffset_ + ch];
    }

    // protected methods -----------------------------------------------

    /**
    * <p>Parses the input stream and stores its trie content into a index and
    * data array</p>
    * @param inputStream data input stream containing trie data
    * @exception IOException thrown when data reading fails
    */
    protected final void unserialize(InputStream inputStream) 
                                                throws IOException
    {
        DataInputStream input = new DataInputStream(inputStream);
        int indexDataLength = m_dataOffset_ + m_dataLength_;
        m_index_ = new char[indexDataLength];
        for (int i = 0; i < indexDataLength; i ++) {
            m_index_[i] = input.readChar();
        }
        m_data_           = m_index_;
        m_initialValue_   = m_data_[m_dataOffset_];
    }
    
    /**
    * Gets the offset to the data which the surrogate pair points to.
    * @param lead lead surrogate
    * @param trail trailing surrogate
    * @return offset to data
    * @draft 2.1
    */
    protected final int getSurrogateOffset(char lead, char trail)
    {
        if (m_dataManipulate_ == null) {
            throw new NullPointerException(
                             "The field DataManipulate in this Trie is null");
        }
        
        // get fold position for the next trail surrogate
        int offset = m_dataManipulate_.getFoldingOffset(getLeadValue(lead));

        // get the real data from the folded lead/trail units
        if (offset > 0) {
            return getRawOffset(offset, (char)(trail & SURROGATE_MASK_));
        }

        // return -1 if there is an error, in this case we return the default
        // value: m_initialValue_
        return -1;
    }
    
    /**
    * Gets the value at the argument index.
    * For use internally in com.ibm.icu.util.TrieEnumeration.
    * @param index value at index will be retrieved
    * @return 32 bit value
    * @see com.ibm.icu.util.TrieEnumeration
    * @draft 2.1
    */
    protected final int getValue(int index)
    {
        return m_data_[index];
    }

    /**
    * Gets the default initial value
    * @return 32 bit value 
    * @draft 2.1
    */
    protected final int getInitialValue()
    {
        return m_initialValue_;
    }
  
    // private data members --------------------------------------------

    /**
    * Default value
    */
    private char m_initialValue_;
    /**
    * Array of char data
    */
    protected char m_data_[];
}