nio/charset/CharsetEncoder.java

/* CharsetEncoder.java --
   Copyright (C) 2002 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
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02110-1301 USA.

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making a combined work based on this library.  Thus, the terms and
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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
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package java.nio.charset;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;

/**
 * @author Jesse Rosenstock
 * @since 1.4
 */
public abstract class CharsetEncoder
{
  private static final int STATE_RESET   = 0;
  private static final int STATE_CODING  = 1;
  private static final int STATE_END     = 2;
  private static final int STATE_FLUSHED = 3;

  private static final byte[] DEFAULT_REPLACEMENT = {(byte)'?'};

  private final Charset charset;
  private final float averageBytesPerChar;
  private final float maxBytesPerChar;
  private byte[] replacement;

  private int state = STATE_RESET;

  private CodingErrorAction malformedInputAction
    = CodingErrorAction.REPORT;
  private CodingErrorAction unmappableCharacterAction
    = CodingErrorAction.REPORT;

  protected CharsetEncoder (Charset cs, float averageBytesPerChar,
                            float maxBytesPerChar)
  {
    this (cs, averageBytesPerChar, maxBytesPerChar, DEFAULT_REPLACEMENT);
  }

  protected CharsetEncoder (Charset cs, float averageBytesPerChar,
                            float maxBytesPerChar, byte[] replacement)
  {
    if (averageBytesPerChar <= 0.0f)
      throw new IllegalArgumentException ("Non-positive averageBytesPerChar");
    if (maxBytesPerChar <= 0.0f)
      throw new IllegalArgumentException ("Non-positive maxBytesPerChar");

    this.charset = cs;
    this.averageBytesPerChar
      = averageBytesPerChar;
    this.maxBytesPerChar
      = maxBytesPerChar;
    this.replacement = replacement;
    implReplaceWith (replacement);
  }

  public final float averageBytesPerChar ()
  {
    return averageBytesPerChar;
  }

  public boolean canEncode (char c)
  {
    CharBuffer cb = CharBuffer.allocate (1).put (c);
    cb.flip ();
    return canEncode (cb);
  }

  public boolean canEncode (CharSequence cs)
  {
    CharBuffer cb;
    if (cs instanceof CharBuffer)
      cb = ((CharBuffer) cs).duplicate ();
    else
      cb = CharBuffer.wrap (cs);
    return canEncode (cb);
  }

  private boolean canEncode (CharBuffer cb)
  {
    // It is an error if a coding operation is "in progress"
    // I take that to mean the state is not reset or flushed.
    // XXX: check "in progress" everywhere
    if (state == STATE_FLUSHED)
      reset ();
    else if (state != STATE_RESET)
      throw new IllegalStateException ();

    CodingErrorAction oldMalformedInputAction = malformedInputAction;
    CodingErrorAction oldUnmappableCharacterAction
      = unmappableCharacterAction;

    try
      {
        if (oldMalformedInputAction != CodingErrorAction.REPORT)
          onMalformedInput (CodingErrorAction.REPORT);
        if (oldUnmappableCharacterAction != CodingErrorAction.REPORT)
          onUnmappableCharacter (CodingErrorAction.REPORT);
      }
    catch (Exception e)
      {
        return false;
      }
    finally
      {
        if (oldMalformedInputAction != CodingErrorAction.REPORT)
          onMalformedInput (oldMalformedInputAction);
        if (oldUnmappableCharacterAction != CodingErrorAction.REPORT)
          onUnmappableCharacter (oldUnmappableCharacterAction);
      }

    return true;
  }

  public final Charset charset ()
  {
    return charset;
  }

  public final ByteBuffer encode (CharBuffer in)
    throws CharacterCodingException
  {
    // XXX: Sun's Javadoc seems to contradict itself saying an
    // IllegalStateException is thrown "if a decoding operation is already
    // in progress" and also that "it resets this Encoder".
    // Should we check to see that the state is reset, or should we
    // call reset()?
    if (state != STATE_RESET)
      throw new IllegalStateException ();

    // REVIEW: Using max instead of average may allocate a very large
    // buffer.  Maybe we should do something more efficient?
    int remaining = in.remaining ();
    int n = (int) (remaining * maxBytesPerChar ());
    ByteBuffer out = ByteBuffer.allocate (n);

    if (remaining == 0)
      {
        state = STATE_FLUSHED;
        return out;
      }

    CoderResult cr = encode (in, out, true);
    if (cr.isError ())
      cr.throwException ();

    cr = flush (out);
    if (cr.isError ())
      cr.throwException ();

    out.flip ();

    // Unfortunately, resizing the actual bytebuffer array is required.
    byte[] resized = new byte[out.remaining()];
    out.get(resized);
    return ByteBuffer.wrap(resized);
  }

  public final CoderResult encode (CharBuffer in, ByteBuffer out,
                                   boolean endOfInput)
  {
    int newState = endOfInput ? STATE_END : STATE_CODING;
    // XXX: Need to check for "previous step was an invocation [not] of
    // this method with a value of true for the endOfInput parameter but
    // a return value indicating an incomplete decoding operation"
    // XXX: We will not check the previous return value, just
    // that the previous call passed true for endOfInput
    if (state != STATE_RESET && state != STATE_CODING
        && !(endOfInput && state == STATE_END))
      throw new IllegalStateException ();
    state = newState;

    for (;;)
      {
        CoderResult cr;
        try
          {
            cr = encodeLoop (in, out);
          }
        catch (RuntimeException e)
          {
            throw new CoderMalfunctionError (e);
          }

        if (cr.isOverflow ())
          return cr;

        if (cr.isUnderflow ())
          {
            if (endOfInput && in.hasRemaining ())
              cr = CoderResult.malformedForLength (in.remaining ());
            else
              return cr;
          }

        CodingErrorAction action = cr.isMalformed ()
                                     ? malformedInputAction
                                     : unmappableCharacterAction;

        if (action == CodingErrorAction.REPORT)
          return cr;

        if (action == CodingErrorAction.REPLACE)
          {
            if (out.remaining () < replacement.length)
              return CoderResult.OVERFLOW;
            out.put (replacement);
          }

        in.position (in.position () + cr.length ());
      }
  }

  protected abstract CoderResult encodeLoop (CharBuffer in, ByteBuffer out);

  public final CoderResult flush (ByteBuffer out)
  {
    // It seems weird that you can flush after reset, but Sun's javadoc
    // says an IllegalStateException is thrown "If the previous step of the
    // current decoding operation was an invocation neither of the reset
    // method nor ... of the three-argument encode method with a value of
    // true for the endOfInput parameter."
    // Further note that flush() only requires that there not be
    // an IllegalStateException if the previous step was a call to
    // encode with true as the last argument.  It does not require
    // that the call succeeded.  encode() does require that it succeeded.
    // XXX: test this to see if reality matches javadoc
    if (state != STATE_RESET && state != STATE_END)
      throw new IllegalStateException ();

    state = STATE_FLUSHED;
    return implFlush (out);
  }

  protected CoderResult implFlush (ByteBuffer out)
  {
    return CoderResult.UNDERFLOW;
  }

  protected void implOnMalformedInput (CodingErrorAction newAction)
  {
    // default implementation does nothing
  }

  protected void implOnUnmappableCharacter (CodingErrorAction newAction)
  {
    // default implementation does nothing
  }

  protected void implReplaceWith (byte[] newReplacement)
  {
    // default implementation does nothing
  }

  protected void implReset ()
  {
    // default implementation does nothing
  }

  public boolean isLegalReplacement (byte[] replacement)
  {
    // TODO: cache the decoder
    // error actions will be REPORT after construction
    CharsetDecoder decoder = charset.newDecoder ();
    ByteBuffer bb = ByteBuffer.wrap (replacement);
    CharBuffer cb
      = CharBuffer.allocate ((int) (replacement.length
                                    * decoder.maxCharsPerByte ()));
    return !decoder.decode (bb, cb, true).isError ();
  }

  public CodingErrorAction malformedInputAction ()
  {
    return malformedInputAction;
  }

  public final float maxBytesPerChar ()
  {
    return maxBytesPerChar;
  }

  public final CharsetEncoder onMalformedInput (CodingErrorAction newAction)
  {
    if (newAction == null)
      throw new IllegalArgumentException ("Null action");

    malformedInputAction = newAction;
    implOnMalformedInput (newAction);
    return this;
  }

  public CodingErrorAction unmappableCharacterAction ()
  {
    return unmappableCharacterAction;
  }

  public final CharsetEncoder onUnmappableCharacter
    (CodingErrorAction newAction)
  {
    if (newAction == null)
      throw new IllegalArgumentException ("Null action");

    unmappableCharacterAction = newAction;
    implOnUnmappableCharacter (newAction);
    return this;
  }

  public final byte[] replacement ()
  {
    return replacement;
  }

  public final CharsetEncoder replaceWith (byte[] newReplacement)
  {
    if (newReplacement == null)
      throw new IllegalArgumentException ("Null replacement");
    if (newReplacement.length == 0)
      throw new IllegalArgumentException ("Empty replacement");
    // XXX: what about maxBytesPerChar?

      if (!isLegalReplacement (newReplacement))
        throw new IllegalArgumentException ("Illegal replacement");

    this.replacement = newReplacement;
    implReplaceWith (newReplacement);
    return this;
  }

  public final CharsetEncoder reset ()
  {
    state = STATE_RESET;
    implReset ();
    return this;
  }
}