java.nio.charset.CharsetEncoder Maven / Gradle / Ivy
/* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.nio.charset;
import java.nio.BufferOverflowException;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.util.Arrays;
/**
* Transforms a sequence of 16-bit Java characters to a byte sequence in some encoding.
*
* The input character sequence is a {@link java.nio.CharBuffer CharBuffer} and the
* output byte sequence is a {@link java.nio.ByteBuffer ByteBuffer}.
*
*
Use {@link #encode(CharBuffer)} to encode an entire {@code CharBuffer} to a
* new {@code ByteBuffer}, or {@link #encode(CharBuffer, ByteBuffer, boolean)} for more
* control. When using the latter method, the entire operation proceeds as follows:
*
* - Invoke {@link #reset()} to reset the encoder if this instance has been used before.
* - Invoke {@link #encode(CharBuffer, ByteBuffer, boolean) encode} with the {@code endOfInput}
* parameter set to false until additional input is not needed (as signaled by the return value).
* The input buffer must be filled and the output buffer must be flushed between invocations.
*
The {@link #encode(CharBuffer, ByteBuffer, boolean) encode} method will
* convert as many characters as possible, and the process won't stop until the
* input buffer has been exhausted, the output buffer has been filled, or an
* error has occurred. A {@link CoderResult CoderResult} instance will be
* returned to indicate the current state. The caller should fill the input buffer, flush
* the output buffer, or recovering from an error and try again, accordingly.
*
* - Invoke {@link #encode(CharBuffer, ByteBuffer, boolean) encode} for the last time with
* {@code endOfInput} set to true.
* - Invoke {@link #flush(ByteBuffer)} to flush remaining output.
*
*
* There are two classes of encoding error: malformed input
* signifies that the input character sequence is not legal, while unmappable character
* signifies that the input is legal but cannot be mapped to a byte sequence (because the charset
* cannot represent the character, for example).
*
*
Errors can be handled in three ways. The default is to
* {@link CodingErrorAction#REPORT report} the error to the caller. The alternatives are to
* {@link CodingErrorAction#IGNORE ignore} the error or {@link CodingErrorAction#REPLACE replace}
* the problematic input with the byte sequence returned by {@link #replacement}. The disposition
* for each of the two kinds of error can be set independently using the {@link #onMalformedInput}
* and {@link #onUnmappableCharacter} methods.
*
*
The default replacement bytes depend on the charset but can be overridden using the
* {@link #replaceWith} method.
*
*
This class is abstract and encapsulates many common operations of the
* encoding process for all charsets. Encoders for a specific charset should
* extend this class and need only to implement the
* {@link #encodeLoop(CharBuffer, ByteBuffer) encodeLoop} method for basic
* encoding. If a subclass maintains internal state, it should also override the
* {@link #implFlush(ByteBuffer) implFlush} and {@link #implReset() implReset} methods.
*
*
This class is not thread-safe.
*
* @see java.nio.charset.Charset
* @see java.nio.charset.CharsetDecoder
*/
public abstract class CharsetEncoder {
private static final String RESET = "RESET";
private static final String ONGOING = "ONGOING";
private static final String END_OF_INPUT = "END_OF_INPUT";
private static final String FLUSHED = "FLUSHED";
private final Charset charset;
private final float averageBytesPerChar;
private final float maxBytesPerChar;
private byte[] replacementBytes;
private String state = RESET;
private CodingErrorAction malformedInputAction = CodingErrorAction.REPORT;
private CodingErrorAction unmappableCharacterAction = CodingErrorAction.REPORT;
// decoder instance for this encoder's charset, used for replacement value checking
private CharsetDecoder decoder;
/**
* Constructs a new {@code CharsetEncoder} using the given parameters and
* the replacement byte array {@code { (byte) '?' }}.
*/
protected CharsetEncoder(Charset cs, float averageBytesPerChar, float maxBytesPerChar) {
this(cs, averageBytesPerChar, maxBytesPerChar, new byte[] { (byte) '?' });
}
/**
* Constructs a new CharsetEncoder using the given
* Charset, replacement byte array, average number and
* maximum number of bytes created by this encoder for one input character.
*
* @param cs
* the Charset to be used by this encoder.
* @param averageBytesPerChar
* average number of bytes created by this encoder for one single
* input character, must be positive.
* @param maxBytesPerChar
* maximum number of bytes which can be created by this encoder
* for one single input character, must be positive.
* @param replacement
* the replacement byte array, cannot be null or empty, its
* length cannot be larger than maxBytesPerChar,
* and must be a legal replacement, which can be justified by
* {@link #isLegalReplacement(byte[]) isLegalReplacement}.
* @throws IllegalArgumentException
* if any parameters are invalid.
*/
protected CharsetEncoder(Charset cs, float averageBytesPerChar, float maxBytesPerChar, byte[] replacement) {
this(cs, averageBytesPerChar, maxBytesPerChar, replacement, false);
}
CharsetEncoder(Charset cs, float averageBytesPerChar, float maxBytesPerChar, byte[] replacement, boolean trusted) {
if (averageBytesPerChar <= 0 || maxBytesPerChar <= 0) {
throw new IllegalArgumentException("averageBytesPerChar and maxBytesPerChar must both be positive");
}
if (averageBytesPerChar > maxBytesPerChar) {
throw new IllegalArgumentException("averageBytesPerChar is greater than maxBytesPerChar");
}
this.charset = cs;
this.averageBytesPerChar = averageBytesPerChar;
this.maxBytesPerChar = maxBytesPerChar;
if (trusted) {
// The RI enforces unnecessary restrictions on the replacement bytes. We trust ICU to
// know what it's doing. Doing so lets us support ICU's EUC-JP, SCSU, and Shift_JIS.
this.replacementBytes = replacement;
} else {
replaceWith(replacement);
}
}
/**
* Returns the average number of bytes created by this encoder for a single
* input character.
*/
public final float averageBytesPerChar() {
return averageBytesPerChar;
}
/**
* Tests whether the given character can be encoded by this encoder.
*
*
Note that this method may change the internal state of this encoder, so
* it should not be called when another encoding process is ongoing,
* otherwise it will throw an IllegalStateException.
*
* @throws IllegalStateException if another encode process is ongoing.
*/
public boolean canEncode(char c) {
return canEncode(CharBuffer.wrap(new char[] { c }));
}
/**
* Tests whether the given CharSequence can be encoded by this
* encoder.
*
*
Note that this method may change the internal state of this encoder, so
* it should not be called when another encode process is ongoing, otherwise
* it will throw an IllegalStateException.
*
* @throws IllegalStateException if another encode process is ongoing.
*/
public boolean canEncode(CharSequence sequence) {
CharBuffer cb;
if (sequence instanceof CharBuffer) {
cb = ((CharBuffer) sequence).duplicate();
} else {
cb = CharBuffer.wrap(sequence);
}
if (state == FLUSHED) {
reset();
}
if (state != RESET) {
throw illegalStateException();
}
CodingErrorAction originalMalformedInputAction = malformedInputAction;
CodingErrorAction originalUnmappableCharacterAction = unmappableCharacterAction;
onMalformedInput(CodingErrorAction.REPORT);
onUnmappableCharacter(CodingErrorAction.REPORT);
try {
encode(cb);
return true;
} catch (CharacterCodingException e) {
return false;
} finally {
onMalformedInput(originalMalformedInputAction);
onUnmappableCharacter(originalUnmappableCharacterAction);
reset();
}
}
/**
* Returns the {@link Charset} which this encoder uses.
*/
public final Charset charset() {
return charset;
}
/**
* This is a facade method for the encoding operation.
*
* This method encodes the remaining character sequence of the given
* character buffer into a new byte buffer. This method performs a complete
* encoding operation, resets at first, then encodes, and flushes at last.
*
* This method should not be invoked if another encode operation is ongoing.
*
* @param in
* the input buffer.
* @return a new ByteBuffer containing the bytes produced by
* this encoding operation. The buffer's limit will be the position
* of the last byte in the buffer, and the position will be zero.
* @throws IllegalStateException
* if another encoding operation is ongoing.
* @throws MalformedInputException
* if an illegal input character sequence for this charset is
* encountered, and the action for malformed error is
* {@link CodingErrorAction#REPORT CodingErrorAction.REPORT}
* @throws UnmappableCharacterException
* if a legal but unmappable input character sequence for this
* charset is encountered, and the action for unmappable
* character error is
* {@link CodingErrorAction#REPORT CodingErrorAction.REPORT}.
* Unmappable means the Unicode character sequence at the input
* buffer's current position cannot be mapped to a equivalent
* byte sequence.
* @throws CharacterCodingException
* if other exception happened during the encode operation.
*/
public final ByteBuffer encode(CharBuffer in) throws CharacterCodingException {
int length = (int) (in.remaining() * averageBytesPerChar);
ByteBuffer out = ByteBuffer.allocate(length);
reset();
while (state != FLUSHED) {
CoderResult result = encode(in, out, true);
if (result == CoderResult.OVERFLOW) {
out = allocateMore(out);
continue; // No point trying to flush to an already-full buffer.
} else {
checkCoderResult(result);
}
result = flush(out);
if (result == CoderResult.OVERFLOW) {
out = allocateMore(out);
} else {
checkCoderResult(result);
}
}
out.flip();
return out;
}
private void checkCoderResult(CoderResult result) throws CharacterCodingException {
if (malformedInputAction == CodingErrorAction.REPORT && result.isMalformed()) {
throw new MalformedInputException(result.length());
} else if (unmappableCharacterAction == CodingErrorAction.REPORT && result.isUnmappable()) {
throw new UnmappableCharacterException(result.length());
}
}
private ByteBuffer allocateMore(ByteBuffer output) {
if (output.capacity() == 0) {
return ByteBuffer.allocate(1);
}
ByteBuffer result = ByteBuffer.allocate(output.capacity() * 2);
output.flip();
result.put(output);
return result;
}
/**
* Encodes characters starting at the current position of the given input
* buffer, and writes the equivalent byte sequence into the given output
* buffer from its current position.
*
* The buffers' position will be changed with the reading and writing
* operation, but their limits and marks will be kept intact.
*
* A CoderResult instance will be returned according to
* following rules:
*
* - A {@link CoderResult#malformedForLength(int) malformed input} result
* indicates that some malformed input error was encountered, and the
* erroneous characters start at the input buffer's position and their
* number can be got by result's {@link CoderResult#length() length}. This
* kind of result can be returned only if the malformed action is
* {@link CodingErrorAction#REPORT CodingErrorAction.REPORT}.
* - {@link CoderResult#UNDERFLOW CoderResult.UNDERFLOW} indicates that
* as many characters as possible in the input buffer have been encoded. If
* there is no further input and no characters left in the input buffer then
* this task is complete. If this is not the case then the client should
* call this method again supplying some more input characters.
* - {@link CoderResult#OVERFLOW CoderResult.OVERFLOW} indicates that the
* output buffer has been filled, while there are still some characters
* remaining in the input buffer. This method should be invoked again with a
* non-full output buffer.
* - A {@link CoderResult#unmappableForLength(int) unmappable character}
* result indicates that some unmappable character error was encountered,
* and the erroneous characters start at the input buffer's position and
* their number can be got by result's {@link CoderResult#length() length}.
* This kind of result can be returned only on
* {@link CodingErrorAction#REPORT CodingErrorAction.REPORT}.
*
*
* The endOfInput parameter indicates if the invoker can
* provider further input. This parameter is true if and only if the
* characters in the current input buffer are all inputs for this encoding
* operation. Note that it is common and won't cause an error if the invoker
* sets false and then has no more input available, while it may cause an
* error if the invoker always sets true in several consecutive invocations.
* This would make the remaining input to be treated as malformed input.
* input.
*
* This method invokes the
* {@link #encodeLoop(CharBuffer, ByteBuffer) encodeLoop} method to
* implement the basic encode logic for a specific charset.
*
* @param in
* the input buffer.
* @param out
* the output buffer.
* @param endOfInput
* true if all the input characters have been provided.
* @return a CoderResult instance indicating the result.
* @throws IllegalStateException
* if the encoding operation has already started or no more
* input is needed in this encoding process.
* @throws CoderMalfunctionError
* If the {@link #encodeLoop(CharBuffer, ByteBuffer) encodeLoop}
* method threw an BufferUnderflowException or
* BufferUnderflowException.
*/
public final CoderResult encode(CharBuffer in, ByteBuffer out, boolean endOfInput) {
if (state != RESET && state != ONGOING && !(endOfInput && state == END_OF_INPUT)) {
throw illegalStateException();
}
state = endOfInput ? END_OF_INPUT : ONGOING;
while (true) {
CoderResult result;
try {
result = encodeLoop(in, out);
} catch (BufferOverflowException ex) {
throw new CoderMalfunctionError(ex);
} catch (BufferUnderflowException ex) {
throw new CoderMalfunctionError(ex);
}
if (result == CoderResult.UNDERFLOW) {
if (endOfInput && in.hasRemaining()) {
result = CoderResult.malformedForLength(in.remaining());
} else {
return result;
}
} else if (result == CoderResult.OVERFLOW) {
return result;
}
// We have a real error, so do what the appropriate action tells us what to do...
CodingErrorAction action =
result.isUnmappable() ? unmappableCharacterAction : malformedInputAction;
if (action == CodingErrorAction.REPORT) {
return result;
} else if (action == CodingErrorAction.REPLACE) {
if (out.remaining() < replacementBytes.length) {
return CoderResult.OVERFLOW;
}
out.put(replacementBytes);
}
in.position(in.position() + result.length());
}
}
/**
* Encodes characters into bytes. This method is called by
* {@link #encode(CharBuffer, ByteBuffer, boolean) encode}.
*
* This method will implement the essential encoding operation, and it won't
* stop encoding until either all the input characters are read, the output
* buffer is filled, or some exception is encountered. Then it will
* return a CoderResult object indicating the result of the
* current encoding operation. The rule to construct the
* CoderResult is the same as for
* {@link #encode(CharBuffer, ByteBuffer, boolean) encode}. When an
* exception is encountered in the encoding operation, most implementations
* of this method will return a relevant result object to the
* {@link #encode(CharBuffer, ByteBuffer, boolean) encode} method, and
* subclasses may handle the exception and
* implement the error action themselves.
*
* The buffers are scanned from their current positions, and their positions
* will be modified accordingly, while their marks and limits will be
* intact. At most {@link CharBuffer#remaining() in.remaining()} characters
* will be read, and {@link ByteBuffer#remaining() out.remaining()} bytes
* will be written.
*
* Note that some implementations may pre-scan the input buffer and return
* CoderResult.UNDERFLOW until it receives sufficient input.
*
* @param in
* the input buffer.
* @param out
* the output buffer.
* @return a CoderResult instance indicating the result.
*/
protected abstract CoderResult encodeLoop(CharBuffer in, ByteBuffer out);
/**
* Flushes this encoder.
*
* This method will call {@link #implFlush(ByteBuffer) implFlush}. Some
* encoders may need to write some bytes to the output buffer when they have
* read all input characters, subclasses can overridden
* {@link #implFlush(ByteBuffer) implFlush} to perform writing action.
*
* The maximum number of written bytes won't larger than
* {@link ByteBuffer#remaining() out.remaining()}. If some encoder wants to
* write more bytes than the output buffer's available remaining space, then
* CoderResult.OVERFLOW will be returned, and this method
* must be called again with a byte buffer that has free space. Otherwise
* this method will return CoderResult.UNDERFLOW, which
* means one encoding process has been completed successfully.
*
* During the flush, the output buffer's position will be changed
* accordingly, while its mark and limit will be intact.
*
* @param out
* the given output buffer.
* @return CoderResult.UNDERFLOW or
* CoderResult.OVERFLOW.
* @throws IllegalStateException
* if this encoder isn't already flushed or at end of input.
*/
public final CoderResult flush(ByteBuffer out) {
if (state != FLUSHED && state != END_OF_INPUT) {
throw illegalStateException();
}
CoderResult result = implFlush(out);
if (result == CoderResult.UNDERFLOW) {
state = FLUSHED;
}
return result;
}
/**
* Flushes this encoder. The default implementation does nothing and always
* returns CoderResult.UNDERFLOW; this method can be
* overridden if needed.
*
* @param out
* the output buffer.
* @return CoderResult.UNDERFLOW or
* CoderResult.OVERFLOW.
*/
protected CoderResult implFlush(ByteBuffer out) {
return CoderResult.UNDERFLOW;
}
/**
* Notifies that this encoder's CodingErrorAction specified
* for malformed input error has been changed. The default implementation
* does nothing; this method can be overridden if needed.
*
* @param newAction
* the new action.
*/
protected void implOnMalformedInput(CodingErrorAction newAction) {
// default implementation is empty
}
/**
* Notifies that this encoder's CodingErrorAction specified
* for unmappable character error has been changed. The default
* implementation does nothing; this method can be overridden if needed.
*
* @param newAction
* the new action.
*/
protected void implOnUnmappableCharacter(CodingErrorAction newAction) {
// default implementation is empty
}
/**
* Notifies that this encoder's replacement has been changed. The default
* implementation does nothing; this method can be overridden if needed.
*
* @param newReplacement
* the new replacement string.
*/
protected void implReplaceWith(byte[] newReplacement) {
// default implementation is empty
}
/**
* Resets this encoder's charset related state. The default implementation
* does nothing; this method can be overridden if needed.
*/
protected void implReset() {
// default implementation is empty
}
/**
* Tests whether the given argument is legal as this encoder's replacement byte
* array. The given byte array is legal if and only if it can be decoded into
* characters.
*/
public boolean isLegalReplacement(byte[] replacement) {
if (decoder == null) {
decoder = charset.newDecoder();
decoder.onMalformedInput(CodingErrorAction.REPORT);
decoder.onUnmappableCharacter(CodingErrorAction.REPORT);
}
ByteBuffer in = ByteBuffer.wrap(replacement);
CharBuffer out = CharBuffer.allocate((int) (replacement.length * decoder.maxCharsPerByte()));
CoderResult result = decoder.decode(in, out, true);
return !result.isError();
}
/**
* Returns this encoder's CodingErrorAction when a malformed
* input error occurred during the encoding process.
*/
public CodingErrorAction malformedInputAction() {
return malformedInputAction;
}
/**
* Returns the maximum number of bytes which can be created by this encoder for
* one input character, must be positive.
*/
public final float maxBytesPerChar() {
return maxBytesPerChar;
}
/**
* Sets this encoder's action on malformed input error.
*
* This method will call the
* {@link #implOnMalformedInput(CodingErrorAction) implOnMalformedInput}
* method with the given new action as argument.
*
* @param newAction
* the new action on malformed input error.
* @return this encoder.
* @throws IllegalArgumentException
* if the given newAction is null.
*/
public final CharsetEncoder onMalformedInput(CodingErrorAction newAction) {
if (newAction == null) {
throw new IllegalArgumentException("newAction == null");
}
malformedInputAction = newAction;
implOnMalformedInput(newAction);
return this;
}
/**
* Sets this encoder's action on unmappable character error.
*
* This method will call the
* {@link #implOnUnmappableCharacter(CodingErrorAction) implOnUnmappableCharacter}
* method with the given new action as argument.
*
* @param newAction
* the new action on unmappable character error.
* @return this encoder.
* @throws IllegalArgumentException
* if the given newAction is null.
*/
public final CharsetEncoder onUnmappableCharacter(CodingErrorAction newAction) {
if (newAction == null) {
throw new IllegalArgumentException("newAction == null");
}
unmappableCharacterAction = newAction;
implOnUnmappableCharacter(newAction);
return this;
}
/**
* Returns the replacement byte array, which is never null or empty.
*/
public final byte[] replacement() {
return replacementBytes;
}
/**
* Sets the new replacement value.
*
* This method first checks the given replacement's validity, then changes
* the replacement value and finally calls the
* {@link #implReplaceWith(byte[]) implReplaceWith} method with the given
* new replacement as argument.
*
* @param replacement
* the replacement byte array, cannot be null or empty, its
* length cannot be larger than maxBytesPerChar,
* and it must be legal replacement, which can be justified by
* calling isLegalReplacement(byte[] replacement).
* @return this encoder.
* @throws IllegalArgumentException
* if the given replacement cannot satisfy the requirement
* mentioned above.
*/
public final CharsetEncoder replaceWith(byte[] replacement) {
if (replacement == null) {
throw new IllegalArgumentException("replacement == null");
}
if (replacement.length == 0) {
throw new IllegalArgumentException("replacement.length == 0");
}
if (replacement.length > maxBytesPerChar()) {
throw new IllegalArgumentException("replacement.length > maxBytesPerChar: " +
replacement.length + " > " + maxBytesPerChar());
}
if (!isLegalReplacement(replacement)) {
throw new IllegalArgumentException("Bad replacement: " + Arrays.toString(replacement));
}
// It seems like a bug, but the RI doesn't clone, and we have tests that check we don't.
this.replacementBytes = replacement;
implReplaceWith(replacementBytes);
return this;
}
/**
* Resets this encoder. This method will reset the internal state and then
* calls {@link #implReset} to reset any state related to the
* specific charset.
*/
public final CharsetEncoder reset() {
state = RESET;
implReset();
return this;
}
/**
* Returns this encoder's CodingErrorAction when unmappable
* character occurred during encoding process.
*/
public CodingErrorAction unmappableCharacterAction() {
return unmappableCharacterAction;
}
private IllegalStateException illegalStateException() {
throw new IllegalStateException("State: " + state);
}
}