Package org.antlr.runtime.misc
Class LookaheadStream<T>
java.lang.Object
org.antlr.runtime.misc.FastQueue<T>
org.antlr.runtime.misc.LookaheadStream<T>
- Direct Known Subclasses:
CommonTreeNodeStream
,UnbufferedTokenStream
A lookahead queue that knows how to mark/release locations in the buffer for
backtracking purposes. Any markers force the
FastQueue
superclass to
keep all elements until no more markers; then can reset to avoid growing a
huge buffer.-
Field Summary
FieldsModifier and TypeFieldDescriptionprotected int
Absolute token index.Track object returned by nextElement upon end of stream; Return it later when they ask for LT passed end of input.protected int
Track the last mark() call result value for use in rewind().protected int
tracks how deep mark() calls are nestedprotected T
This is theLT(-1)
element for the first element inFastQueue.data
.static final int
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
consume()
Make sure we have at least one element to remove, even if EOFvoid
fill
(int n) add n elements to bufferint
index()
abstract boolean
protected T
LB
(int k) LT
(int k) int
mark()
abstract T
Implement nextElement to supply a stream of elements to this lookahead buffer.void
release
(int marker) remove()
Get and remove first element in queue; overrideFastQueue.remove()
; it's the same, just checks for backtracking.void
reset()
void
rewind()
void
rewind
(int marker) void
seek
(int index) Seek to a 0-indexed absolute token index.int
size()
Size of entire stream is unknown; we only know buffer size from FastQueue.protected void
syncAhead
(int need) Make sure we have 'need' elements from current position p.
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Field Details
-
UNINITIALIZED_EOF_ELEMENT_INDEX
public static final int UNINITIALIZED_EOF_ELEMENT_INDEX- See Also:
-
currentElementIndex
protected int currentElementIndexAbsolute token index. It's the index of the symbol about to be read viaLT(1)
. Goes from 0 to numtokens. -
prevElement
This is theLT(-1)
element for the first element inFastQueue.data
. -
eof
Track object returned by nextElement upon end of stream; Return it later when they ask for LT passed end of input. -
lastMarker
protected int lastMarkerTrack the last mark() call result value for use in rewind(). -
markDepth
protected int markDepthtracks how deep mark() calls are nested
-
-
Constructor Details
-
LookaheadStream
public LookaheadStream()
-
-
Method Details
-
reset
public void reset() -
nextElement
Implement nextElement to supply a stream of elements to this lookahead buffer. Return EOF upon end of the stream we're pulling from.- See Also:
-
isEOF
-
remove
Get and remove first element in queue; overrideFastQueue.remove()
; it's the same, just checks for backtracking. -
consume
public void consume()Make sure we have at least one element to remove, even if EOF -
syncAhead
protected void syncAhead(int need) Make sure we have 'need' elements from current position p. Last valid p index is data.size()-1. p+need-1 is the data index 'need' elements ahead. If we need 1 element, (p+1-1)==p must be < data.size(). -
fill
public void fill(int n) add n elements to buffer -
size
public int size()Size of entire stream is unknown; we only know buffer size from FastQueue. -
LT
-
index
public int index() -
mark
public int mark() -
release
public void release(int marker) -
rewind
public void rewind(int marker) -
rewind
public void rewind() -
seek
public void seek(int index) Seek to a 0-indexed absolute token index. Normally used to seek backwards in the buffer. Does not force loading of nodes.To preserve backward compatibility, this method allows seeking past the end of the currently buffered data. In this case, the input pointer will be moved but the data will only actually be loaded upon the next call to
consume()
orLT(int)
fork>0
.- Throws:
IllegalArgumentException
- ifindex
is less than 0UnsupportedOperationException
- ifindex
lies before the beginning of the moving window buffer (index <
currentElementIndex
-
p
).
-
LB
-