Interface LookaheadTokenSource<D,T,L>
- Type Parameters:
D
- the type of source document identifiersT
- the type of token typesL
- the type of lookahead data
- All Superinterfaces:
AutoCloseable
,Closeable
,Supplier<Token<D,
T>>
- All Known Subinterfaces:
TokenSource<D,
T>
- All Known Implementing Classes:
LookaheadTokenFilter
,LookaheadTokenMultiplexer
,LookaheadTokenProcessor
,LookaheadTokenSourceProxy
,Screener
,TokenFilter
,TokenProcessor
Token sources must not return null
or throw an exception to
indicate that there are no more tokens available. Instead, it must supply an
infinite number of special tokens that indicate the end of the input stream.
Instead of creating multiple such tokens, a token source may return multiple
references to the same token object. How the client recognizes end-of-stream
tokens is application-dependent; it is recommended that a distinguished token
type be defined for the purpose.
Lookahead data can be transferred from the internal buffer of one instance of this interface to another. This is useful for transfer of control if both share the same input source.
This interface extends Closeable
, but the default implementation
of close()
does nothing. Implementing classes are assumed by default
not to expect explicit closing. An implementing class for which closing is
beneficial or even required should be documented explicitly as such. Note
that this interfaces restricts the contract of close()
to
not throw IOException
.
-
Method Summary
Modifier and TypeMethodDescriptiondefault void
close()
Closes this source and releases any resources associated with it.default TokenSource
<D, T> Returns a token source that forwards tokens and does not use lookahead.Clear the internal lookahead buffer and return its contents.default LookaheadTokenSource
<D, T, L> removeTypes
(Set<T> types) Returns a secondary token source that forwards all tokens from this token source that have none of the given types.default LookaheadTokenSource
<D, T, L> removeTypes
(T... types) Returns a secondary token source that forwards all tokens from this token source that have none of the given types.void
takeOverLookahead
(L lookaheadData) Fill the internal lookahead buffer with data.static <L> void
transferLookahead
(LookaheadTokenSource<?, ?, ? extends L> first, LookaheadTokenSource<?, ?, ? super L> second) Transfers lookahead buffer data between two compatible token sources.
-
Method Details
-
relinquishLookahead
L relinquishLookahead()Clear the internal lookahead buffer and return its contents.- Returns:
- the former contents of the internal lookahead buffer
-
takeOverLookahead
Fill the internal lookahead buffer with data.The buffer must be empty before this method is invoked. After return, the given data will be consumed from the buffer before the usual input is considered.
- Parameters:
lookaheadData
- the lookahead data to fill in- Throws:
IllegalStateException
- if the internal lookahead buffer is not empty
-
transferLookahead
static <L> void transferLookahead(LookaheadTokenSource<?, ?, ? extends L> first, LookaheadTokenSource<?, ?, ? super L> second) Transfers lookahead buffer data between two compatible token sources.This method calls
relinquishLookahead()
on the first source, followed bytakeOverLookahead(L)
on the second.Two sources are compatible if the lookahead data type of the first is assignable to the lookahead data type of the second. Source document identifier and token types are irrelevant.
- Type Parameters:
L
- the type of lookahead data- Parameters:
first
- the first token sourcesecond
- token source- See Also:
-
forgetLookahead
Returns a token source that forwards tokens and does not use lookahead.- Returns:
- a token source that forwards tokens from this token source
-
removeTypes
Returns a secondary token source that forwards all tokens from this token source that have none of the given types.- Parameters:
types
- the types of tokens to remove- Returns:
- a token source that forwards all tokens from this token source that have none of the given types
-
removeTypes
Returns a secondary token source that forwards all tokens from this token source that have none of the given types.- Parameters:
types
- the types of tokens to remove- Returns:
- a token source that forwards all tokens from this token source that have none of the given types
-
close
default void close()Closes this source and releases any resources associated with it.The default implementation does nothing.
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
-