CharsetEncoder

See also:

• ByteBuffer
• CharBuffer
• Charset
• CharsetDecoder

CharsetEncoder

protected CharsetEncoder (Charset cs, 
                float averageBytesPerChar, 
                float maxBytesPerChar, 
                byte[] replacement)

Initializes a new encoder. The new encoder will have the given bytes-per-char and replacement values.

CharsetEncoder

protected CharsetEncoder (Charset cs, 
                float averageBytesPerChar, 
                float maxBytesPerChar)

Initializes a new encoder. The new encoder will have the given bytes-per-char values and its replacement will be the byte array { (byte)'?' }.

averageBytesPerChar

public final float averageBytesPerChar ()

Returns the average number of bytes that will be produced for each character of input. This heuristic value may be used to estimate the size of the output buffer required for a given input sequence.

canEncode

public boolean canEncode (char c)

Tells whether or not this encoder can encode the given character.

This method returns false if the given character is a surrogate character; such characters can be interpreted only when they are members of a pair consisting of a high surrogate followed by a low surrogate. The canEncode(CharSequence) method may be used to test whether or not a character sequence can be encoded.

This method may modify this encoder's state; it should therefore not be invoked if an encoding operation is already in progress.

The default implementation of this method is not very efficient; it should generally be overridden to improve performance.

canEncode

public boolean canEncode (CharSequence cs)

Tells whether or not this encoder can encode the given character sequence.

If this method returns false for a particular character sequence then more information about why the sequence cannot be encoded may be obtained by performing a full encoding operation.

This method may modify this encoder's state; it should therefore not be invoked if an encoding operation is already in progress.

The default implementation of this method is not very efficient; it should generally be overridden to improve performance.

charset

public final Charset charset ()

Returns the charset that created this encoder.

encode

public final ByteBuffer encode (CharBuffer in)

Convenience method that encodes the remaining content of a single input character buffer into a newly-allocated byte buffer.

This method implements an entire encoding operation; that is, it resets this encoder, then it encodes the characters in the given character buffer, and finally it flushes this encoder. This method should therefore not be invoked if an encoding operation is already in progress.

encode

public final CoderResult encode (CharBuffer in, 
                ByteBuffer out, 
                boolean endOfInput)

Encodes as many characters as possible from the given input buffer, writing the results to the given output buffer.

The buffers are read from, and written to, starting at their current positions. At most in.remaining() characters will be read and at most out.remaining() bytes will be written. The buffers' positions will be advanced to reflect the characters read and the bytes written, but their marks and limits will not be modified.

In addition to reading characters from the input buffer and writing bytes to the output buffer, this method returns a CoderResult object to describe its reason for termination:

• CoderResult#UNDERFLOW indicates that as much of the input buffer as possible has been encoded. If there is no further input then the invoker can proceed to the next step of the encoding operation. Otherwise this method should be invoked again with further input.

• CoderResult#OVERFLOW indicates that there is insufficient space in the output buffer to encode any more characters. This method should be invoked again with an output buffer that has more remaining bytes. This is typically done by draining any encoded bytes from the output buffer.

• A malformed-input result indicates that a malformed-input error has been detected. The malformed characters begin at the input buffer's (possibly incremented) position; the number of malformed characters may be determined by invoking the result object's length method. This case applies only if the malformed action of this encoder is CodingErrorAction#REPORT; otherwise the malformed input will be ignored or replaced, as requested.

• An unmappable-character result indicates that an unmappable-character error has been detected. The characters that encode the unmappable character begin at the input buffer's (possibly incremented) position; the number of such characters may be determined by invoking the result object's length method. This case applies only if the unmappable action of this encoder is CodingErrorAction.REPORT; otherwise the unmappable character will be ignored or replaced, as requested.

The endOfInput parameter advises this method as to whether the invoker can provide further input beyond that contained in the given input buffer. If there is a possibility of providing additional input then the invoker should pass false for this parameter; if there is no possibility of providing further input then the invoker should pass true. It is not erroneous, and in fact it is quite common, to pass false in one invocation and later discover that no further input was actually available. It is critical, however, that the final invocation of this method in a sequence of invocations always pass true so that any remaining unencoded input will be treated as being malformed.

This method works by invoking the encodeLoop method, interpreting its results, handling error conditions, and reinvoking it as necessary.

flush

public final CoderResult flush (ByteBuffer out)

Flushes this encoder.

Some encoders maintain internal state and may need to write some final bytes to the output buffer once the overall input sequence has been read.

Any additional output is written to the output buffer beginning at its current position. At most out.remaining() bytes will be written. The buffer's position will be advanced appropriately, but its mark and limit will not be modified.

If this method completes successfully then it returns CoderResult.UNDERFLOW. If there is insufficient room in the output buffer then it returns CoderResult#OVERFLOW. If this happens then this method must be invoked again, with an output buffer that has more room, in order to complete the current encoding operation.

If this encoder has already been flushed then invoking this method has no effect.

This method invokes the implFlush method to perform the actual flushing operation.

isLegalReplacement

public boolean isLegalReplacement (byte[] repl)

Tells whether or not the given byte array is a legal replacement value for this encoder.

A replacement is legal if, and only if, it is a legal sequence of bytes in this encoder's charset; that is, it must be possible to decode the replacement into one or more sixteen-bit Unicode characters.

The default implementation of this method is not very efficient; it should generally be overridden to improve performance.

malformedInputAction

public CodingErrorAction malformedInputAction ()

Returns this encoder's current action for malformed-input errors.

maxBytesPerChar

public final float maxBytesPerChar ()

Returns the maximum number of bytes that will be produced for each character of input. This value may be used to compute the worst-case size of the output buffer required for a given input sequence. This value accounts for any necessary content-independent prefix or suffix bytes, such as byte-order marks.

onMalformedInput

public final CharsetEncoder onMalformedInput (CodingErrorAction newAction)

Changes this encoder's action for malformed-input errors.

This method invokes the implOnMalformedInput method, passing the new action.

onUnmappableCharacter

public final CharsetEncoder onUnmappableCharacter (CodingErrorAction newAction)

Changes this encoder's action for unmappable-character errors.

This method invokes the implOnUnmappableCharacter method, passing the new action.

replaceWith

public final CharsetEncoder replaceWith (byte[] newReplacement)

Changes this encoder's replacement value.

This method invokes the implReplaceWith method, passing the new replacement, after checking that the new replacement is acceptable.

replacement

public final byte[] replacement ()

Returns this encoder's replacement value.

reset

public final CharsetEncoder reset ()

Resets this encoder, clearing any internal state.

This method resets charset-independent state and also invokes the implReset method in order to perform any charset-specific reset actions.

unmappableCharacterAction

public CodingErrorAction unmappableCharacterAction ()

Returns this encoder's current action for unmappable-character errors.

encodeLoop

protected abstract CoderResult encodeLoop (CharBuffer in, 
                ByteBuffer out)

Encodes one or more characters into one or more bytes.

This method encapsulates the basic encoding loop, encoding as many characters as possible until it either runs out of input, runs out of room in the output buffer, or encounters an encoding error. This method is invoked by the encode method, which handles result interpretation and error recovery.

The buffers are read from, and written to, starting at their current positions. At most in.remaining() characters will be read, and at most out.remaining() bytes will be written. The buffers' positions will be advanced to reflect the characters read and the bytes written, but their marks and limits will not be modified.

This method returns a CoderResult object to describe its reason for termination, in the same manner as the encode method. Most implementations of this method will handle encoding errors by returning an appropriate result object for interpretation by the encode method. An optimized implementation may instead examine the relevant error action and implement that action itself.

An implementation of this method may perform arbitrary lookahead by returning CoderResult#UNDERFLOW until it receives sufficient input.

implFlush

protected CoderResult implFlush (ByteBuffer out)

Flushes this encoder.

The default implementation of this method does nothing, and always returns CoderResult#UNDERFLOW. This method should be overridden by encoders that may need to write final bytes to the output buffer once the entire input sequence has been read.

implOnMalformedInput

protected void implOnMalformedInput (CodingErrorAction newAction)

Reports a change to this encoder's malformed-input action.

The default implementation of this method does nothing. This method should be overridden by encoders that require notification of changes to the malformed-input action.

implOnUnmappableCharacter

protected void implOnUnmappableCharacter (CodingErrorAction newAction)

Reports a change to this encoder's unmappable-character action.

The default implementation of this method does nothing. This method should be overridden by encoders that require notification of changes to the unmappable-character action.

implReplaceWith

protected void implReplaceWith (byte[] newReplacement)

Reports a change to this encoder's replacement value.

The default implementation of this method does nothing. This method should be overridden by encoders that require notification of changes to the replacement.

implReset

protected void implReset ()

Resets this encoder, clearing any charset-specific internal state.

The default implementation of this method does nothing. This method should be overridden by encoders that maintain internal state.