jdk.nio.charset.CharsetDecoder
An engine that can transform a sequence of bytes in a specific charset into a sequence of sixteen-bit Unicode characters.
The input byte sequence is provided in a byte buffer or a series of such buffers. The output character sequence is written to a character buffer or a series of such buffers. A decoder should always be used by making the following sequence of method invocations, hereinafter referred to as a decoding operation:
Reset the decoder via the reset method, unless it has not been used before;
Invoke the decode 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 decode method one final time, passing true for the endOfInput argument; and then
Invoke the flush method so that the decoder can flush any internal state to the output buffer.
Each invocation of the decode method will decode as many bytes as possible from the input buffer, writing the resulting characters to the output buffer. The decode method returns when more input is required, when there is not enough room in the output buffer, or when a decoding 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 a decoding error, as appropriate, and try again.
There are two general types of decoding errors. If the input byte sequence is not legal for this charset then the input is considered malformed. If the input byte sequence is legal but cannot be mapped to a valid Unicode character then an unmappable character has been encountered.
How a decoding 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 string. The replacement
has the initial value "\uFFFD";
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 decoding process, including the implementation of error actions. A decoder for a specific charset, which is a concrete subclass of this class, need only implement the abstract decodeLoop method, which encapsulates the basic decoding 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 bytes in a specific charset into a sequence of sixteen-bit Unicode characters. The input byte sequence is provided in a byte buffer or a series of such buffers. The output character sequence is written to a character buffer or a series of such buffers. A decoder should always be used by making the following sequence of method invocations, hereinafter referred to as a decoding operation: Reset the decoder via the reset method, unless it has not been used before; Invoke the decode 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 decode method one final time, passing true for the endOfInput argument; and then Invoke the flush method so that the decoder can flush any internal state to the output buffer. Each invocation of the decode method will decode as many bytes as possible from the input buffer, writing the resulting characters to the output buffer. The decode method returns when more input is required, when there is not enough room in the output buffer, or when a decoding 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 a decoding error, as appropriate, and try again. There are two general types of decoding errors. If the input byte sequence is not legal for this charset then the input is considered malformed. If the input byte sequence is legal but cannot be mapped to a valid Unicode character then an unmappable character has been encountered. How a decoding 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 string. The replacement has the initial value "\uFFFD"; 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 decoding process, including the implementation of error actions. A decoder for a specific charset, which is a concrete subclass of this class, need only implement the abstract decodeLoop method, which encapsulates the basic decoding 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.
auto-detecting?clj
(auto-detecting? this)Tells whether or not this decoder implements an auto-detecting charset.
The default implementation of this method always returns false; it should be overridden by auto-detecting decoders to return true.
returns: true if, and only if, this decoder implements an
auto-detecting charset - boolean
Tells whether or not this decoder implements an auto-detecting charset.
The default implementation of this method always returns
false; it should be overridden by auto-detecting decoders to
return true.
returns: true if, and only if, this decoder implements an
auto-detecting charset - `boolean`average-chars-per-byteclj
(average-chars-per-byte this)Returns the average number of characters that will be produced for each byte 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 characters produced
per byte of input - float
Returns the average number of characters that will be produced for each
byte 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 characters produced
per byte of input - `float`charsetclj
(charset this)Returns the charset that created this decoder.
returns: This decoder's charset - java.nio.charset.Charset
Returns the charset that created this decoder. returns: This decoder's charset - `java.nio.charset.Charset`
charset-detected?clj
(charset-detected? this)Tells whether or not this decoder has yet detected a charset (optional operation).
If this decoder implements an auto-detecting charset then at a single point during a decoding operation this method may start returning true to indicate that a specific charset has been detected in the input byte sequence. Once this occurs, the detectedCharset method may be invoked to retrieve the detected charset.
That this method returns false does not imply that no bytes have yet been decoded. Some auto-detecting decoders are capable of decoding some, or even all, of an input byte sequence without fixing on a particular charset.
The default implementation of this method always throws an UnsupportedOperationException; it should be overridden by auto-detecting decoders to return true once the input charset has been determined.
returns: true if, and only if, this decoder has detected a
specific charset - boolean
throws: java.lang.UnsupportedOperationException - If this decoder does not implement an auto-detecting charset
Tells whether or not this decoder has yet detected a
charset (optional operation).
If this decoder implements an auto-detecting charset then at a
single point during a decoding operation this method may start returning
true to indicate that a specific charset has been detected in
the input byte sequence. Once this occurs, the detectedCharset method may be invoked to retrieve the detected charset.
That this method returns false does not imply that no bytes
have yet been decoded. Some auto-detecting decoders are capable of
decoding some, or even all, of an input byte sequence without fixing on
a particular charset.
The default implementation of this method always throws an UnsupportedOperationException; it should be overridden by
auto-detecting decoders to return true once the input charset
has been determined.
returns: true if, and only if, this decoder has detected a
specific charset - `boolean`
throws: java.lang.UnsupportedOperationException - If this decoder does not implement an auto-detecting charsetdecodeclj
(decode this in)(decode this in out end-of-input)Decodes as many bytes 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() bytes will be read and at most out.remaining() characters will be written. The buffers' positions will be advanced to reflect the bytes read and the characters written, but their marks and limits will not be modified.
In addition to reading bytes from the input buffer and writing characters 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 decoded. If there is no further input then the invoker can proceed to the next step of the decoding operation. Otherwise this method should be invoked again with further input.
CoderResult.OVERFLOW indicates that there is
insufficient space in the output buffer to decode any more bytes. This method should be invoked again with an output buffer that has more remaining characters. This is typically done by draining any decoded characters from the output buffer.
A malformed-input result indicates that a malformed-input
error has been detected. The malformed bytes begin at the input buffer's (possibly incremented) position; the number of malformed bytes may be determined by invoking the result object's length method. This case applies only if the malformed action of this decoder 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 bytes that decode the unmappable character begin at the input buffer's (possibly incremented) position; the number of such bytes may be determined by invoking the result object's length method. This case applies only if the unmappable action of this decoder 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 decoding operation then care should be taken to preserve any bytes 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 undecoded input will be treated as being malformed.
This method works by invoking the decodeLoop method, interpreting its results, handling error conditions, and reinvoking it as necessary.
in - The input byte buffer - java.nio.ByteBuffer
out - The output character buffer - java.nio.CharBuffer
end-of-input - true if, and only if, the invoker can provide no additional input bytes 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 a decoding 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 decoding operation
Decodes as many bytes 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() bytes
will be read and at most out.remaining()
characters will be written. The buffers' positions will be advanced to
reflect the bytes read and the characters written, but their marks and
limits will not be modified.
In addition to reading bytes from the input buffer and writing
characters 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 decoded. If there is no further
input then the invoker can proceed to the next step of the
decoding operation. Otherwise this method
should be invoked again with further input.
CoderResult.OVERFLOW indicates that there is
insufficient space in the output buffer to decode any more bytes.
This method should be invoked again with an output buffer that has
more remaining characters. This is
typically done by draining any decoded characters from the output
buffer.
A malformed-input result indicates that a malformed-input
error has been detected. The malformed bytes begin at the input
buffer's (possibly incremented) position; the number of malformed
bytes may be determined by invoking the result object's length method. This case applies only if the
malformed action of this decoder
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 bytes that
decode the unmappable character begin at the input buffer's (possibly
incremented) position; the number of such bytes may be determined
by invoking the result object's length
method. This case applies only if the unmappable action of this decoder 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 decoding
operation then care should be taken to preserve any bytes 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 undecoded input will be treated
as being malformed.
This method works by invoking the decodeLoop
method, interpreting its results, handling error conditions, and
reinvoking it as necessary.
in - The input byte buffer - `java.nio.ByteBuffer`
out - The output character buffer - `java.nio.CharBuffer`
end-of-input - true if, and only if, the invoker can provide no additional input bytes 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 a decoding 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 decoding operationdetected-charsetclj
(detected-charset this)Retrieves the charset that was detected by this decoder (optional operation).
If this decoder implements an auto-detecting charset then this method returns the actual charset once it has been detected. After that point, this method returns the same value for the duration of the current decoding operation. If not enough input bytes have yet been read to determine the actual charset then this method throws an IllegalStateException.
The default implementation of this method always throws an UnsupportedOperationException; it should be overridden by auto-detecting decoders to return the appropriate value.
returns: The charset detected by this auto-detecting decoder,
or null if the charset has not yet been determined - java.nio.charset.Charset
throws: java.lang.IllegalStateException - If insufficient bytes have been read to determine a charset
Retrieves the charset that was detected by this
decoder (optional operation).
If this decoder implements an auto-detecting charset then this
method returns the actual charset once it has been detected. After that
point, this method returns the same value for the duration of the
current decoding operation. If not enough input bytes have yet been
read to determine the actual charset then this method throws an IllegalStateException.
The default implementation of this method always throws an UnsupportedOperationException; it should be overridden by
auto-detecting decoders to return the appropriate value.
returns: The charset detected by this auto-detecting decoder,
or null if the charset has not yet been determined - `java.nio.charset.Charset`
throws: java.lang.IllegalStateException - If insufficient bytes have been read to determine a charsetflushclj
(flush this out)Flushes this decoder.
Some decoders maintain internal state and may need to write some final characters 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() characters 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 decoding operation.
If this decoder 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 character buffer - java.nio.CharBuffer
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 decoding operation was an invocation neither of the flush method nor of the three-argument decode method with a value of true for the endOfInput parameter
Flushes this decoder.
Some decoders maintain internal state and may need to write some
final characters 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()
characters 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 decoding
operation.
If this decoder 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 character buffer - `java.nio.CharBuffer`
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 decoding operation was an invocation neither of the flush method nor of the three-argument decode method with a value of true for the endOfInput parametermalformed-input-actionclj
(malformed-input-action this)Returns this decoder's current action for malformed-input errors.
returns: The current malformed-input action, which is never null - java.nio.charset.CodingErrorAction
Returns this decoder's current action for malformed-input errors. returns: The current malformed-input action, which is never null - `java.nio.charset.CodingErrorAction`
max-chars-per-byteclj
(max-chars-per-byte this)Returns the maximum number of characters that will be produced for each byte 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 characters that will be produced per
byte of input - float
Returns the maximum number of characters that will be produced for each
byte 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 characters that will be produced per
byte of input - `float`on-malformed-inputclj
(on-malformed-input this new-action)Changes this decoder'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 decoder - java.nio.charset.CharsetDecoder
throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
Changes this decoder'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 decoder - `java.nio.charset.CharsetDecoder` throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
on-unmappable-characterclj
(on-unmappable-character this new-action)Changes this decoder'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 decoder - java.nio.charset.CharsetDecoder
throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
Changes this decoder'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 decoder - `java.nio.charset.CharsetDecoder` throws: java.lang.IllegalArgumentException - If the precondition on the parameter does not hold
replace-withclj
(replace-with this new-replacement)Changes this decoder'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 and must have non-zero length - java.lang.String
returns: This decoder - java.nio.charset.CharsetDecoder
throws: java.lang.IllegalArgumentException - If the preconditions on the parameter do not hold
Changes this decoder'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 and must have non-zero length - `java.lang.String` returns: This decoder - `java.nio.charset.CharsetDecoder` throws: java.lang.IllegalArgumentException - If the preconditions on the parameter do not hold
replacementclj
(replacement this)Returns this decoder's replacement value.
returns: This decoder's current replacement,
which is never null and is never empty - java.lang.String
Returns this decoder's replacement value.
returns: This decoder's current replacement,
which is never null and is never empty - `java.lang.String`resetclj
(reset this)Resets this decoder, 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 decoder - java.nio.charset.CharsetDecoder
Resets this decoder, 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 decoder - `java.nio.charset.CharsetDecoder`
unmappable-character-actionclj
(unmappable-character-action this)Returns this decoder's current action for unmappable-character errors.
returns: The current unmappable-character action, which is never
null - java.nio.charset.CodingErrorAction
Returns this decoder'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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