jdk.nio.charset.CharsetEncoder
An engine that can transform a sequence of sixteen-bit Unicode characters into a sequence of bytes in a specific charset.
The input character sequence is provided in a character buffer or a series of such buffers. The output byte sequence is written to a byte buffer or a series of such buffers. An encoder should always be used by making the following sequence of method invocations, hereinafter referred to as an encoding operation:
Reset the encoder via the reset method, unless it has not been used before;
Invoke the encode method zero or more times, as long as additional input may be available, passing false for the endOfInput argument and filling the input buffer and flushing the output buffer between invocations;
Invoke the encode method one final time, passing true for the endOfInput argument; and then
Invoke the flush method so that the encoder can flush any internal state to the output buffer.
Each invocation of the encode method will encode as many characters as possible from the input buffer, writing the resulting bytes to the output buffer. The encode method returns when more input is required, when there is not enough room in the output buffer, or when an encoding error has occurred. In each case a CoderResult object is returned to describe the reason for termination. An invoker can examine this object and fill the input buffer, flush the output buffer, or attempt to recover from an encoding error, as appropriate, and try again.
There are two general types of encoding errors. If the input character sequence is not a legal sixteen-bit Unicode sequence then the input is considered malformed. If the input character sequence is legal but cannot be mapped to a valid byte sequence in the given charset then an unmappable character has been encountered.
How an encoding error is handled depends upon the action requested for that type of error, which is described by an instance of the CodingErrorAction class. The possible error actions are to ignore the erroneous input, report the error to the invoker via the returned CoderResult object, or replace the erroneous input with the current value of the replacement byte array. The replacement
is initially set to the encoder's default replacement, which often (but not always) has the initial value { (byte)'?' };
its value may be changed via the replaceWith method.
The default action for malformed-input and unmappable-character errors is to report them. The malformed-input error action may be changed via the onMalformedInput method; the unmappable-character action may be changed via the onUnmappableCharacter method.
This class is designed to handle many of the details of the encoding process, including the implementation of error actions. An encoder for a specific charset, which is a concrete subclass of this class, need only implement the abstract encodeLoop method, which encapsulates the basic encoding loop. A subclass that maintains internal state should, additionally, override the implFlush and implReset methods.
Instances of this class are not safe for use by multiple concurrent threads.
An engine that can transform a sequence of sixteen-bit Unicode characters into a sequence of
bytes in a specific charset.
The input character sequence is provided in a character buffer or a series
of such buffers. The output byte sequence is written to a byte buffer
or a series of such buffers. An encoder should always be used by making
the following sequence of method invocations, hereinafter referred to as an
encoding operation:
Reset the encoder via the reset method, unless it
has not been used before;
Invoke the encode method zero or more times, as
long as additional input may be available, passing false for the
endOfInput argument and filling the input buffer and flushing the
output buffer between invocations;
Invoke the encode method one final time, passing
true for the endOfInput argument; and then
Invoke the flush method so that the encoder can
flush any internal state to the output buffer.
Each invocation of the encode method will encode as many
characters as possible from the input buffer, writing the resulting bytes
to the output buffer. The encode method returns when more
input is required, when there is not enough room in the output buffer, or
when an encoding error has occurred. In each case a CoderResult
object is returned to describe the reason for termination. An invoker can
examine this object and fill the input buffer, flush the output buffer, or
attempt to recover from an encoding error, as appropriate, and try again.
There are two general types of encoding errors. If the input character
sequence is not a legal sixteen-bit Unicode sequence then the input is considered malformed. If
the input character sequence is legal but cannot be mapped to a valid
byte sequence in the given charset then an unmappable character has been encountered.
How an encoding error is handled depends upon the action requested for
that type of error, which is described by an instance of the CodingErrorAction class. The possible error actions are to ignore the erroneous input, report the error to the invoker via
the returned CoderResult object, or replace the erroneous input with the current value of the
replacement byte array. The replacement
is initially set to the encoder's default replacement, which often
(but not always) has the initial value { (byte)'?' };
its value may be changed via the replaceWith method.
The default action for malformed-input and unmappable-character errors
is to report them. The
malformed-input error action may be changed via the onMalformedInput method; the
unmappable-character action may be changed via the onUnmappableCharacter method.
This class is designed to handle many of the details of the encoding
process, including the implementation of error actions. An encoder for a
specific charset, which is a concrete subclass of this class, need only
implement the abstract encodeLoop method, which
encapsulates the basic encoding loop. A subclass that maintains internal
state should, additionally, override the implFlush and
implReset methods.
Instances of this class are not safe for use by multiple concurrent
threads.average-bytes-per-charclj
(average-bytes-per-char this)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.
returns: The average number of bytes produced
per character of input - float
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.
returns: The average number of bytes produced
per character of input - `float`can-encode?clj
(can-encode? this 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.
c - The given character - char
returns: true if, and only if, this encoder can encode
the given character - boolean
throws: java.lang.IllegalStateException - If an encoding operation is already in progress
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.
c - The given character - `char`
returns: true if, and only if, this encoder can encode
the given character - `boolean`
throws: java.lang.IllegalStateException - If an encoding operation is already in progresscharsetclj
(charset this)Returns the charset that created this encoder.
returns: This encoder's charset - java.nio.charset.Charset
Returns the charset that created this encoder. returns: This encoder's charset - `java.nio.charset.Charset`
encodeclj
(encode this in)(encode this in out end-of-input)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.
In any case, if this method is to be reinvoked in the same encoding operation then care should be taken to preserve any characters remaining in the input buffer so that they are available to the next invocation.
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.
in - The input character buffer - java.nio.CharBuffer
out - The output byte buffer - java.nio.ByteBuffer
end-of-input - true if, and only if, the invoker can provide no additional input characters beyond those in the given buffer - boolean
returns: A coder-result object describing the reason for termination - java.nio.charset.CoderResult
throws: java.lang.IllegalStateException - If an encoding operation is already in progress and the previous step was an invocation neither of the reset method, nor of this method with a value of false for the endOfInput parameter, nor of this method with a value of true for the endOfInput parameter but a return value indicating an incomplete encoding operation
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.
In any case, if this method is to be reinvoked in the same encoding
operation then care should be taken to preserve any characters remaining
in the input buffer so that they are available to the next invocation.
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.
in - The input character buffer - `java.nio.CharBuffer`
out - The output byte buffer - `java.nio.ByteBuffer`
end-of-input - true if, and only if, the invoker can provide no additional input characters beyond those in the given buffer - `boolean`
returns: A coder-result object describing the reason for termination - `java.nio.charset.CoderResult`
throws: java.lang.IllegalStateException - If an encoding operation is already in progress and the previous step was an invocation neither of the reset method, nor of this method with a value of false for the endOfInput parameter, nor of this method with a value of true for the endOfInput parameter but a return value indicating an incomplete encoding operationflushclj
(flush this 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.
out - The output byte buffer - java.nio.ByteBuffer
returns: A coder-result object, either CoderResult.UNDERFLOW or
CoderResult.OVERFLOW - java.nio.charset.CoderResult
throws: java.lang.IllegalStateException - If the previous step of the current encoding operation was an invocation neither of the flush method nor of the three-argument encode method with a value of true for the endOfInput parameter
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.
out - The output byte buffer - `java.nio.ByteBuffer`
returns: A coder-result object, either CoderResult.UNDERFLOW or
CoderResult.OVERFLOW - `java.nio.charset.CoderResult`
throws: java.lang.IllegalStateException - If the previous step of the current encoding operation was an invocation neither of the flush method nor of the three-argument encode method with a value of true for the endOfInput parameterlegal-replacement?clj
(legal-replacement? this 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.
repl - The byte array to be tested - byte[]
returns: true if, and only if, the given byte array
is a legal replacement value for this encoder - boolean
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.
repl - The byte array to be tested - `byte[]`
returns: true if, and only if, the given byte array
is a legal replacement value for this encoder - `boolean`malformed-input-actionclj
(malformed-input-action this)Returns this encoder's current action for malformed-input errors.
returns: The current malformed-input action, which is never null - java.nio.charset.CodingErrorAction
Returns this encoder's current action for malformed-input errors. returns: The current malformed-input action, which is never null - `java.nio.charset.CodingErrorAction`
max-bytes-per-charclj
(max-bytes-per-char this)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.
returns: The maximum number of bytes that will be produced per
character of input - float
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.
returns: The maximum number of bytes that will be produced per
character of input - `float`on-malformed-inputclj
(on-malformed-input this new-action)Changes this encoder's action for malformed-input errors.
This method invokes the implOnMalformedInput method, passing the new action.
new-action - The new action; must not be null - java.nio.charset.CodingErrorAction
returns: This encoder - java.nio.charset.CharsetEncoder
throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
Changes this encoder's action for malformed-input errors. This method invokes the implOnMalformedInput method, passing the new action. new-action - The new action; must not be null - `java.nio.charset.CodingErrorAction` returns: This encoder - `java.nio.charset.CharsetEncoder` throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
on-unmappable-characterclj
(on-unmappable-character this new-action)Changes this encoder's action for unmappable-character errors.
This method invokes the implOnUnmappableCharacter method, passing the new action.
new-action - The new action; must not be null - java.nio.charset.CodingErrorAction
returns: This encoder - java.nio.charset.CharsetEncoder
throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
Changes this encoder's action for unmappable-character errors. This method invokes the implOnUnmappableCharacter method, passing the new action. new-action - The new action; must not be null - `java.nio.charset.CodingErrorAction` returns: This encoder - `java.nio.charset.CharsetEncoder` throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
replace-withclj
(replace-with this new-replacement)Changes this encoder's replacement value.
This method invokes the implReplaceWith method, passing the new replacement, after checking that the new replacement is acceptable.
new-replacement - The replacement value The new replacement; must not be null, must have non-zero length, must not be longer than the value returned by the maxBytesPerChar method, and must be legal - byte[]
returns: This encoder - java.nio.charset.CharsetEncoder
throws: java.lang.IllegalArgumentException - If the preconditions on the parameter do not hold
Changes this encoder's replacement value. This method invokes the implReplaceWith method, passing the new replacement, after checking that the new replacement is acceptable. new-replacement - The replacement value The new replacement; must not be null, must have non-zero length, must not be longer than the value returned by the maxBytesPerChar method, and must be legal - `byte[]` returns: This encoder - `java.nio.charset.CharsetEncoder` throws: java.lang.IllegalArgumentException - If the preconditions on the parameter do not hold
replacementclj
(replacement this)Returns this encoder's replacement value.
returns: This encoder's current replacement,
which is never null and is never empty - byte[]
Returns this encoder's replacement value.
returns: This encoder's current replacement,
which is never null and is never empty - `byte[]`resetclj
(reset this)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.
returns: This encoder - java.nio.charset.CharsetEncoder
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. returns: This encoder - `java.nio.charset.CharsetEncoder`
unmappable-character-actionclj
(unmappable-character-action this)Returns this encoder's current action for unmappable-character errors.
returns: The current unmappable-character action, which is never
null - java.nio.charset.CodingErrorAction
Returns this encoder's current action for unmappable-character errors.
returns: The current unmappable-character action, which is never
null - `java.nio.charset.CodingErrorAction`cljdoc is a website building & hosting documentation for Clojure/Script libraries
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