zipfile.java

来自「linux下建立JAVA虚拟机的源码KAFFE」· Java 代码 · 共 673 行 · 第 1/2 页

    catch (IOException ioe)
      {
	return EmptyEnumeration.getInstance();
      }
  }

  /**
   * Checks that the ZipFile is still open and reads entries when necessary.
   *
   * @exception IllegalStateException when the ZipFile has already been closed.
   * @exception IOException when the entries could not be read.
   */
  private HashMap getEntries() throws IOException
  {
    synchronized(raf)
      {
	checkClosed();

	if (entries == null)
	  readEntries();

	return entries;
      }
  }

  /**
   * Searches for a zip entry in this archive with the given name.
   *
   * @param name the name. May contain directory components separated by
   * slashes ('/').
   * @return the zip entry, or null if no entry with that name exists.
   *
   * @exception IllegalStateException when the ZipFile has already been closed
   */
  public ZipEntry getEntry(String name)
  {
    checkClosed();

    try
      {
	HashMap entries = getEntries();
	ZipEntry entry = (ZipEntry) entries.get(name);
        // If we didn't find it, maybe it's a directory.
        if (entry == null && !name.endsWith("/"))
            entry = (ZipEntry) entries.get(name + '/');
	return entry != null ? new ZipEntry(entry, name) : null;
      }
    catch (IOException ioe)
      {
	return null;
      }
  }

  /**
   * Creates an input stream reading the given zip entry as
   * uncompressed data.  Normally zip entry should be an entry
   * returned by getEntry() or entries().
   *
   * This implementation returns null if the requested entry does not
   * exist.  This decision is not obviously correct, however, it does
   * appear to mirror Sun's implementation, and it is consistant with
   * their javadoc.  On the other hand, the old JCL book, 2nd Edition,
   * claims that this should return a "non-null ZIP entry".  We have
   * chosen for now ignore the old book, as modern versions of Ant (an
   * important application) depend on this behaviour.  See discussion
   * in this thread:
   * http://gcc.gnu.org/ml/java-patches/2004-q2/msg00602.html
   *
   * @param entry the entry to create an InputStream for.
   * @return the input stream, or null if the requested entry does not exist.
   *
   * @exception IllegalStateException when the ZipFile has already been closed
   * @exception IOException if a i/o error occured.
   * @exception ZipException if the Zip archive is malformed.  
   */
  public InputStream getInputStream(ZipEntry entry) throws IOException
  {
    checkClosed();

    HashMap entries = getEntries();
    String name = entry.getName();
    ZipEntry zipEntry = (ZipEntry) entries.get(name);
    if (zipEntry == null)
      return null;

    PartialInputStream inp = new PartialInputStream(raf, 1024);
    inp.seek(zipEntry.offset);

    if (inp.readLeInt() != LOCSIG)
      throw new ZipException("Wrong Local header signature: " + name);

    inp.skip(4);

    if (zipEntry.getMethod() != inp.readLeShort())
      throw new ZipException("Compression method mismatch: " + name);

    inp.skip(16);

    int nameLen = inp.readLeShort();
    int extraLen = inp.readLeShort();
    inp.skip(nameLen + extraLen);

    inp.setLength(zipEntry.getCompressedSize());

    int method = zipEntry.getMethod();
    switch (method)
      {
      case ZipOutputStream.STORED:
	return inp;
      case ZipOutputStream.DEFLATED:
	return new InflaterInputStream(inp, new Inflater(true));
      default:
	throw new ZipException("Unknown compression method " + method);
      }
  }
  
  /**
   * Returns the (path) name of this zip file.
   */
  public String getName()
  {
    return name;
  }

  /**
   * Returns the number of entries in this zip file.
   *
   * @exception IllegalStateException when the ZipFile has already been closed
   */
  public int size()
  {
    checkClosed();
    
    try
      {
	return getEntries().size();
      }
    catch (IOException ioe)
      {
	return 0;
      }
  }
  
  private static class ZipEntryEnumeration implements Enumeration
  {
    private final Iterator elements;

    public ZipEntryEnumeration(Iterator elements)
    {
      this.elements = elements;
    }

    public boolean hasMoreElements()
    {
      return elements.hasNext();
    }

    public Object nextElement()
    {
      /* We return a clone, just to be safe that the user doesn't
       * change the entry.  
       */
      return ((ZipEntry)elements.next()).clone();
    }
  }

  private static final class PartialInputStream extends InputStream
  {
    private final RandomAccessFile raf;
    private final byte[] buffer;
    private long bufferOffset;
    private int pos;
    private long end;

    public PartialInputStream(RandomAccessFile raf, int bufferSize)
      throws IOException
    {
      this.raf = raf;
      buffer = new byte[bufferSize];
      bufferOffset = -buffer.length;
      pos = buffer.length;
      end = raf.length();
    }

    void setLength(long length)
    {
      end = bufferOffset + pos + length;
    }

    private void fillBuffer() throws IOException
    {
      synchronized (raf)
        {
          raf.seek(bufferOffset);
          raf.readFully(buffer, 0, (int) Math.min(buffer.length, end - bufferOffset));
        }
    }
    
    public int available()
    {
      long amount = end - (bufferOffset + pos);
      if (amount > Integer.MAX_VALUE)
	return Integer.MAX_VALUE;
      return (int) amount;
    }
    
    public int read() throws IOException
    {
      if (bufferOffset + pos >= end)
	return -1;
      if (pos == buffer.length)
        {
          bufferOffset += buffer.length;
          pos = 0;
          fillBuffer();
        }
      return buffer[pos++] & 0xFF;
    }

    public int read(byte[] b, int off, int len) throws IOException
    {
      if (len > end - (bufferOffset + pos))
	{
	  len = (int) (end - (bufferOffset + pos));
	  if (len == 0)
	    return -1;
	}

      int totalBytesRead = Math.min(buffer.length - pos, len);
      System.arraycopy(buffer, pos, b, off, totalBytesRead);
      pos += totalBytesRead;
      off += totalBytesRead;
      len -= totalBytesRead;

      while (len > 0)
        {
          bufferOffset += buffer.length;
          pos = 0;
          fillBuffer();
          int remain = Math.min(buffer.length, len);
          System.arraycopy(buffer, pos, b, off, remain);
          pos += remain;
          off += remain;
          len -= remain;
          totalBytesRead += remain;
        }

      return totalBytesRead;
    }

    public long skip(long amount) throws IOException
    {
      if (amount < 0)
	return 0;
      if (amount > end - (bufferOffset + pos))
	amount = end - (bufferOffset + pos);
      seek(bufferOffset + pos + amount);
      return amount;
    }

    void seek(long newpos) throws IOException
    {
      long offset = newpos - bufferOffset;
      if (offset >= 0 && offset <= buffer.length)
        {
          pos = (int) offset;
        }
      else
        {
          bufferOffset = newpos;
          pos = 0;
          fillBuffer();
        }
    }

    void readFully(byte[] buf) throws IOException
    {
      if (read(buf, 0, buf.length) != buf.length)
        throw new EOFException();
    }

    void readFully(byte[] buf, int off, int len) throws IOException
    {
      if (read(buf, off, len) != len)
        throw new EOFException();
    }

    int readLeShort() throws IOException
    {
      int b0 = read();
      int b1 = read();
      if (b1 == -1)
        throw new EOFException();
      return (b0 & 0xff) | (b1 & 0xff) << 8;
    }

    int readLeInt() throws IOException
    {
      int b0 = read();
      int b1 = read();
      int b2 = read();
      int b3 = read();
      if (b3 == -1)
        throw new EOFException();
      return ((b0 & 0xff) | (b1 & 0xff) << 8)
            | ((b2 & 0xff) | (b3 & 0xff) << 8) << 16;
    }

    String readString(int length) throws IOException
    {
      if (length > end - (bufferOffset + pos))
        throw new EOFException();

      try
        {
          if (buffer.length - pos >= length)
            {
              String s = new String(buffer, pos, length, "UTF-8");
              pos += length;
              return s;
            }
          else
            {
              byte[] b = new byte[length];
              readFully(b);
              return new String(b, 0, length, "UTF-8");
            }
        }
      catch (UnsupportedEncodingException uee)
        {
          throw new AssertionError(uee);
        }
    }
  }
}