Package org.codehaus.stax2.ri.typed
Class AsciiValueEncoder
java.lang.Object
org.codehaus.stax2.ri.typed.AsciiValueEncoder
- Direct Known Subclasses:
ValueEncoderFactory.ArrayEncoder
,ValueEncoderFactory.Base64Encoder
,ValueEncoderFactory.ScalarEncoder
This base class defines interface used for efficient encoding
of typed values, by stream writers. The abstraction is necessary
to reduce amount of duplicated code while avoiding significant
additional overhead. The idea is that the low-level stream
writer backend supplies encoder with the result buffer, while
encoder itself knows the data and state. Together these allow
for efficient serialization with light coupling.
General contract for encoding is that caller must call things in following sequence:
- First,
bufferNeedsFlush(int)
is called once; and if indicated by return value of true, caller must flush its buffer so it is completely empty (buffer also must have size of at at leastMIN_CHARS_WITHOUT_FLUSH
) - Then, one of
encodeMore(char[], int, int)
methods is to be called - After this call,
isCompleted()
should be called to determine if encoding was complete: if it was, there is nothing more to do. - Otherwise caller should flush its buffer (since encoder
has encoded as much as it can without flushing), and
repeat cycle of calls to
encodeMore(char[], int, int)
followed by a call toisCompleted()
and flushing, as long as necessary to complete encoding.
Main restrictions for use are that value serializations must produce only 7-bit ascii characters, and that the value can be produced incrementally using limited size buffers. This is true for all current value types of the Typed Access API.
Finally, details of how encoders are created and/or reused is outside scope of this public interface. Stax2 reference implementation handles this using an encoder factory that knows construction details.
- Since:
- 3.0
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Field Summary
FieldsModifier and TypeFieldDescriptionprotected static final int
Constant used to determine when caller should flush buffer before calling encode methods. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionfinal boolean
bufferNeedsFlush
(int freeChars) Method called by writer to check if it should flush its output buffer (which has specified amount of free space) before encoder can encode more data.abstract int
encodeMore
(byte[] buffer, int ptr, int end) abstract int
encodeMore
(char[] buffer, int ptr, int end) abstract boolean
Method that can alternatively be called to determine whether encoder has encoded all data it has.
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Field Details
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MIN_CHARS_WITHOUT_FLUSH
protected static final int MIN_CHARS_WITHOUT_FLUSHConstant used to determine when caller should flush buffer before calling encode methods. Strict minimum would be something like 22 (for floating point numbers), but let's pad it a bit.- See Also:
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Constructor Details
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AsciiValueEncoder
protected AsciiValueEncoder()
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Method Details
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bufferNeedsFlush
public final boolean bufferNeedsFlush(int freeChars) Method called by writer to check if it should flush its output buffer (which has specified amount of free space) before encoder can encode more data. Flushing is only needed if (a) encoder has more data to output, and (b) free space is not enough to contain smallest segment of encoded value (individual array element or encoded primitive value).- Parameters:
freeChars
- Amount of free space (in characters) in the output buffer- Returns:
- True if encoder still has data to output and specified amount of free space is insufficient for encoding any more data
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isCompleted
public abstract boolean isCompleted()Method that can alternatively be called to determine whether encoder has encoded all data it has. Generally called right after a call toencodeMore(char[], int, int)
, to figure out whether buffer flush is needed (there is more data), or encoding is complete. -
encodeMore
public abstract int encodeMore(char[] buffer, int ptr, int end) - Returns:
- Value of pointer after all remaining data (which
may be "none") that can be encoded (as constrained by
buffer length) has been encoded. Has to exceed 'ptr'
value sent in; will be equal to it if nothing was
encoded (which should only occur when everything has
been encoded, as long as
bufferNeedsFlush(int)
is appropriately called once before calling this method)
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encodeMore
public abstract int encodeMore(byte[] buffer, int ptr, int end) - Returns:
- Value of pointer after all remaining data (which
may be "none") that can be encoded (as constrained by
buffer length) has been encoded. Has to exceed 'ptr'
value sent in; will be equal to it if nothing was
encoded (which should only occur when everything has
been encoded, as long as
bufferNeedsFlush(int)
is appropriately called once before calling this method)
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