faststringbuffer.java

来自「java jdk 1.4的源码」· Java 代码 · 共 1,377 行 · 第 1/4 页

    int copyfrom = start;
    char[] chunk = m_array[m_lastChunk];
    int available = m_chunkSize - m_firstFree;

    // Repeat while data remains to be copied
    while (strlen > 0)
    {

      // Copy what fits
      if (available > strlen)
        available = strlen;

      System.arraycopy(chars, copyfrom, m_array[m_lastChunk], m_firstFree,
                       available);

      strlen -= available;
      copyfrom += available;

      // If there's more left, allocate another chunk and continue
      if (strlen > 0)
      {

        // Extend array?
        int i = m_array.length;

        if (m_lastChunk + 1 == i)
        {
          char[][] newarray = new char[i + 16][];

          System.arraycopy(m_array, 0, newarray, 0, i);

          m_array = newarray;
        }

        // Advance one chunk
        chunk = m_array[++m_lastChunk];

        if (chunk == null)
        {

          // Hierarchical encapsulation
          if (m_lastChunk == 1 << m_rebundleBits
                  && m_chunkBits < m_maxChunkBits)
          {

            // Should do all the work of both encapsulating
            // existing data and establishing new sizes/offsets
            m_innerFSB = new FastStringBuffer(this);
          }

          // Add a chunk.
          chunk = m_array[m_lastChunk] = new char[m_chunkSize];
        }

        available = m_chunkSize;
        m_firstFree = 0;
      }
    }

    // Adjust the insert point in the last chunk, when we've reached it.
    m_firstFree += available;
  }

  /**
   * Append the contents of another FastStringBuffer onto
   * this FastStringBuffer, growing the storage if necessary.
   * <p>
   * NOTE THAT after calling append(), previously obtained
   * references to m_array[] may no longer be valid.
   *
   * @param value FastStringBuffer whose contents are
   * to be appended.
   */
  public final void append(FastStringBuffer value)
  {

    // Complicating factor here is that the two buffers may use
    // different chunk sizes, and even if they're the same we're
    // probably on a different alignment due to previously appended
    // data. We have to work through the source in bite-sized chunks.
    if (value == null) 
      return;
    int strlen = value.length();

    if (0 == strlen)
      return;

    int copyfrom = 0;
    char[] chunk = m_array[m_lastChunk];
    int available = m_chunkSize - m_firstFree;

    // Repeat while data remains to be copied
    while (strlen > 0)
    {

      // Copy what fits
      if (available > strlen)
        available = strlen;

      int sourcechunk = (copyfrom + value.m_chunkSize - 1)
                        >>> value.m_chunkBits;
      int sourcecolumn = copyfrom & value.m_chunkMask;
      int runlength = value.m_chunkSize - sourcecolumn;

      if (runlength > available)
        runlength = available;

      System.arraycopy(value.m_array[sourcechunk], sourcecolumn,
                       m_array[m_lastChunk], m_firstFree, runlength);

      if (runlength != available)
        System.arraycopy(value.m_array[sourcechunk + 1], 0,
                         m_array[m_lastChunk], m_firstFree + runlength,
                         available - runlength);

      strlen -= available;
      copyfrom += available;

      // If there's more left, allocate another chunk and continue
      if (strlen > 0)
      {

        // Extend array?
        int i = m_array.length;

        if (m_lastChunk + 1 == i)
        {
          char[][] newarray = new char[i + 16][];

          System.arraycopy(m_array, 0, newarray, 0, i);

          m_array = newarray;
        }

        // Advance one chunk
        chunk = m_array[++m_lastChunk];

        if (chunk == null)
        {

          // Hierarchical encapsulation
          if (m_lastChunk == 1 << m_rebundleBits
                  && m_chunkBits < m_maxChunkBits)
          {

            // Should do all the work of both encapsulating
            // existing data and establishing new sizes/offsets
            m_innerFSB = new FastStringBuffer(this);
          }

          // Add a chunk. 
          chunk = m_array[m_lastChunk] = new char[m_chunkSize];
        }

        available = m_chunkSize;
        m_firstFree = 0;
      }
    }

    // Adjust the insert point in the last chunk, when we've reached it.
    m_firstFree += available;
  }

  /**
   * @return true if the specified range of characters are all whitespace,
   * as defined by XMLCharacterRecognizer.
   * <p>
   * CURRENTLY DOES NOT CHECK FOR OUT-OF-RANGE.
   *
   * @param start Offset of first character in the range.
   * @param length Number of characters to send.
   */
  public boolean isWhitespace(int start, int length)
  {

    int sourcechunk = start >>> m_chunkBits;
    int sourcecolumn = start & m_chunkMask;
    int available = m_chunkSize - sourcecolumn;
    boolean chunkOK;

    while (length > 0)
    {
      int runlength = (length <= available) ? length : available;

      if (sourcechunk == 0 && m_innerFSB != null)
        chunkOK = m_innerFSB.isWhitespace(sourcecolumn, runlength);
      else
        chunkOK = org.apache.xml.utils.XMLCharacterRecognizer.isWhiteSpace(
          m_array[sourcechunk], sourcecolumn, runlength);

      if (!chunkOK)
        return false;

      length -= runlength;

      ++sourcechunk;

      sourcecolumn = 0;
      available = m_chunkSize;
    }

    return true;
  }

  /**
   * @param start Offset of first character in the range.
   * @param length Number of characters to send.
   * @return a new String object initialized from the specified range of
   * characters.
   */
  public String getString(int start, int length)
  {
    return getString(new StringBuffer(length), start >>> m_chunkBits,
                     start & m_chunkMask, length).toString();
  }

  /**
   * @param sb StringBuffer to be appended to
   * @param start Offset of first character in the range.
   * @param length Number of characters to send.
   * @return sb with the requested text appended to it
   */
  StringBuffer getString(StringBuffer sb, int start, int length)
  {
    return getString(sb, start >>> m_chunkBits, start & m_chunkMask, length);
  }

  /**
   * Internal support for toString() and getString().
   * PLEASE NOTE SIGNATURE CHANGE from earlier versions; it now appends into
   * and returns a StringBuffer supplied by the caller. This simplifies
   * m_innerFSB support.
   * <p>
   * Note that this operation has been somewhat deoptimized by the shift to a
   * chunked array, as there is no factory method to produce a String object
   * directly from an array of arrays and hence a double copy is needed.
   * By presetting length we hope to minimize the heap overhead of building
   * the intermediate StringBuffer.
   * <p>
   * (It really is a pity that Java didn't design String as a final subclass
   * of MutableString, rather than having StringBuffer be a separate hierarchy.
   * We'd avoid a <strong>lot</strong> of double-buffering.)
   *
   *
   * @param sb
   * @param startChunk
   * @param startColumn
   * @param length
   * 
   * @return the contents of the FastStringBuffer as a standard Java string.
   */
  StringBuffer getString(StringBuffer sb, int startChunk, int startColumn,
                         int length)
  {

    int stop = (startChunk << m_chunkBits) + startColumn + length;
    int stopChunk = stop >>> m_chunkBits;
    int stopColumn = stop & m_chunkMask;

    // Factored out
    //StringBuffer sb=new StringBuffer(length);
    for (int i = startChunk; i < stopChunk; ++i)
    {
      if (i == 0 && m_innerFSB != null)
        m_innerFSB.getString(sb, startColumn, m_chunkSize - startColumn);
      else
        sb.append(m_array[i], startColumn, m_chunkSize - startColumn);

      startColumn = 0;  // after first chunk
    }

    if (stopChunk == 0 && m_innerFSB != null)
      m_innerFSB.getString(sb, startColumn, stopColumn - startColumn);
    else if (stopColumn > startColumn)
      sb.append(m_array[stopChunk], startColumn, stopColumn - startColumn);

    return sb;
  }

  /**
   * Get a single character from the string buffer.
   *
   *
   * @param pos character position requested.
   * @return A character from the requested position.
   */
  public char charAt(int pos)
  {
    int startChunk = pos >>> m_chunkBits;

    if (startChunk == 0 && m_innerFSB != null)
      return m_innerFSB.charAt(pos & m_chunkMask);
    else
      return m_array[startChunk][pos & m_chunkMask];
  }

  /**
   * Sends the specified range of characters as one or more SAX characters()
   * events.
   * Note that the buffer reference passed to the ContentHandler may be
   * invalidated if the FastStringBuffer is edited; it's the user's
   * responsibility to manage access to the FastStringBuffer to prevent this
   * problem from arising.
   * <p>
   * Note too that there is no promise that the output will be sent as a
   * single call. As is always true in SAX, one logical string may be split
   * across multiple blocks of memory and hence delivered as several
   * successive events.
   *
   * @param ch SAX ContentHandler object to receive the event.
   * @param start Offset of first character in the range.
   * @param length Number of characters to send.
   * @exception org.xml.sax.SAXException may be thrown by handler's
   * characters() method.
   */
  public void sendSAXcharacters(
          org.xml.sax.ContentHandler ch, int start, int length)
            throws org.xml.sax.SAXException
  {

    int stop = start + length;
    int startChunk = start >>> m_chunkBits;
    int startColumn = start & m_chunkMask;
    int stopChunk = stop >>> m_chunkBits;
    int stopColumn = stop & m_chunkMask;

    for (int i = startChunk; i < stopChunk; ++i)
    {
      if (i == 0 && m_innerFSB != null)
        m_innerFSB.sendSAXcharacters(ch, startColumn,
                                     m_chunkSize - startColumn);
      else
        ch.characters(m_array[i], startColumn, m_chunkSize - startColumn);

      startColumn = 0;  // after first chunk
    }

    // Last, or only, chunk
    if (stopChunk == 0 && m_innerFSB != null)
      m_innerFSB.sendSAXcharacters(ch, startColumn, stopColumn - startColumn);
    else if (stopColumn > startColumn)
    {
      ch.characters(m_array[stopChunk], startColumn,
                    stopColumn - startColumn);
    }