/*
* @(#)CoderResult.java 1.8 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.nio.charset;
import java.lang.ref.WeakReference;
import java.nio.*;
import java.util.Map;
import java.util.HashMap;
/**
* A description of the result state of a coder.
*
* <p> A charset coder, that is, either a decoder or an encoder, consumes bytes
* (or characters) from an input buffer, translates them, and writes the
* resulting characters (or bytes) to an output buffer. A coding process
* terminates for one of four categories of reasons, which are described by
* instances of this class:
*
* <ul>
*
* <li><p> <i>Underflow</i> is reported when there is no more input to be
* processed, or there is insufficient input and additional input is
* required. This condition is represented by the unique result object
* {@link #UNDERFLOW}, whose {@link #isUnderflow() isUnderflow} method
* returns <tt>true</tt>. </p></li>
*
* <li><p> <i>Overflow</i> is reported when there is insufficient room
* remaining in the output buffer. This condition is represented by the
* unique result object {@link #OVERFLOW}, whose {@link #isOverflow()
* isOverflow} method returns <tt>true</tt>. </p></li>
*
* <li><p> A <i>malformed-input error</i> is reported when a sequence of
* input units is not well-formed. Such errors are described by instances of
* this class whose {@link #isMalformed() isMalformed} method returns
* <tt>true</tt> and whose {@link #length() length} method returns the length
* of the malformed sequence. There is one unique instance of this class for
* all malformed-input errors of a given length. </p></li>
*
* <li><p> An <i>unmappable-character error</i> is reported when a sequence
* of input units denotes a character that cannot be represented in the
* output charset. Such errors are described by instances of this class
* whose {@link #isUnmappable() isUnmappable} method returns <tt>true</tt> and
* whose {@link #length() length} method returns the length of the input
* sequence denoting the unmappable character. There is one unique instance
* of this class for all unmappable-character errors of a given length.
* </p></li>
*
* </ul>
*
* For convenience, the {@link #isError() isError} method returns <tt>true</tt>
* for result objects that describe malformed-input and unmappable-character
* errors but <tt>false</tt> for those that describe underflow or overflow
* conditions. </p>
*
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @version 1.8, 03/12/19
* @since 1.4
*/
public class CoderResult {
private static final int CR_UNDERFLOW = 0;
private static final int CR_OVERFLOW = 1;
private static final int CR_ERROR_MIN = 2;
private static final int CR_MALFORMED = 2;
private static final int CR_UNMAPPABLE = 3;
private static final String[] names
= { "UNDERFLOW", "OVERFLOW", "MALFORMED", "UNMAPPABLE" };
private final int type;
private final int length;
private CoderResult(int type, int length) {
this.type = type;
this.length = length;
}
/**
* Returns a string describing this coder result.
*
* @return A descriptive string
*/
public String toString() {
String nm = names[type];
return isError() ? nm + "[" + length + "]" : nm;
}
/**
* Tells whether or not this object describes an underflow condition. </p>
*
* @return <tt>true</tt> if, and only if, this object denotes underflow
*/
public boolean isUnderflow() {
return (type == CR_UNDERFLOW);
}
/**
* Tells whether or not this object describes an overflow condition. </p>
*
* @return <tt>true</tt> if, and only if, this object denotes overflow
*/
public boolean isOverflow() {
return (type == CR_OVERFLOW);
}
/**
* Tells whether or not this object describes an error condition. </p>
*
* @return <tt>true</tt> if, and only if, this object denotes either a
* malformed-input error or an unmappable-character error
*/
public boolean isError() {
return (type >= CR_ERROR_MIN);
}
/**
* Tells whether or not this object describes a malformed-input error.
* </p>
*
* @return <tt>true</tt> if, and only if, this object denotes a
* malformed-input error
*/
public boolean isMalformed() {
return (type == CR_MALFORMED);
}
/**
* Tells whether or not this object describes an unmappable-character
* error. </p>
*
* @return <tt>true</tt> if, and only if, this object denotes an
* unmappable-character error
*/
public boolean isUnmappable() {
return (type == CR_UNMAPPABLE);
}
/**
* Returns the length of the erroneous input described by this
* object <i>(optional operation)</i>. </p>
*
* @return The length of the erroneous input, a positive integer
*
* @throws UnsupportedOperationException
* If this object does not describe an error condition, that is,
* if the {@link #isError() isError} does not return <tt>true</tt>
*/
public int length() {
if (!isError())
throw new UnsupportedOperationException();
return length;
}
/**
* Result object indicating underflow, meaning that either the input buffer
* has been completely consumed or, if the input buffer is not yet empty,
* that additional input is required. </p>
*/
public static final CoderResult UNDERFLOW
= new CoderResult(CR_UNDERFLOW, 0);
/**
* Result object indicating overflow, meaning that there is insufficient
* room in the output buffer. </p>
*/
public static final CoderResult OVERFLOW
= new CoderResult(CR_OVERFLOW, 0);
private static abstract class Cache {
private Map cache = null;
protected abstract CoderResult create(int len);
private synchronized CoderResult get(int len) {
if (len <= 0)
throw new IllegalArgumentException("Non-positive length");
Integer k = new Integer(len);
WeakReference w;
CoderResult e = null;
if (cache == null) {
cache = new HashMap();
} else if ((w = (WeakReference)cache.get(k)) != null) {
e = (CoderResult)w.get();
}
if (e == null) {
e = create(len);
cache.put(k, new WeakReference(e));
}
return e;
}
}
private static Cache malformedCache
= new Cache() {
public CoderResult create(int len) {
return new CoderResult(CR_MALFORMED, len);
}};
/**
* Static factory method that returns the unique object describing a
* malformed-input error of the given length. </p>
*
* @return The requested coder-result object
*/
public static CoderResult malformedForLength(int length) {
return malformedCache.get(length);
}
private static Cache unmappableCache
= new Cache() {
public CoderResult create(int len) {
return new CoderResult(CR_UNMAPPABLE, len);
}};
/**
* Static factory method that returns the unique result object describing
* an unmappable-character error of the given length. </p>
*
* @return The requested coder-result object
*/
public static CoderResult unmappableForLength(int length) {
return unmappableCache.get(length);
}
/**
* Throws an exception appropriate to the result described by this object.
* </p>
*
* @throws BufferUnderflowException
* If this object is {@link #UNDERFLOW}
*
* @throws BufferOverflowException
* If this object is {@link #OVERFLOW}
*
* @throws MalformedInputException
* If this object represents a malformed-input error; the
* exception's length value will be that of this object
*
* @throws UnmappableCharacterException
* If this object represents an unmappable-character error; the
* exceptions length value will be that of this object
*/
public void throwException()
throws CharacterCodingException
{
switch (type) {
case CR_UNDERFLOW: throw new BufferUnderflowException();
case CR_OVERFLOW: throw new BufferOverflowException();
case CR_MALFORMED: throw new MalformedInputException(length);
case CR_UNMAPPABLE: throw new UnmappableCharacterException(length);
default:
assert false;
}
}
}
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