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IntStream (ANTLR 4 Runtime (Optimized) 4.13.1.3 API)
org.antlr.v4.runtime
Interface IntStream
-
- All Known Subinterfaces:
- CharStream, TokenStream, UnicodeCharStream
- All Known Implementing Classes:
- ANTLRFileStream, ANTLRInputStream, BufferedTokenStream, CodePointCharStream, CommonTokenStream, UnbufferedCharStream, UnbufferedTokenStream
public interface IntStream
A simple stream of symbols whose values are represented as integers. This
interface provides marked ranges with support for a minimum level
of buffering necessary to implement arbitrary lookahead during prediction.
For more information on marked ranges, see mark().
Initializing Methods: Some methods in this interface have
unspecified behavior if no call to an initializing method has occurred after
the stream was constructed. The following is a list of initializing methods:
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-
Field Summary
Fields
Modifier and Type
Field and Description
static intEOF
The value returned by LA() when the end of the stream is
reached.
static StringUNKNOWN_SOURCE_NAME
The value returned by getSourceName() when the actual name of the
underlying source is not known.
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Method Summary
All Methods Instance Methods Abstract Methods
Modifier and Type
Method and Description
voidconsume()
Consumes the current symbol in the stream.
StringgetSourceName()
Gets the name of the underlying symbol source.
intindex()
Return the index into the stream of the input symbol referred to by
LA(1).
intLA(int i)
Gets the value of the symbol at offset i from the current
position.
intmark()
voidrelease(int marker)
This method releases a marked range created by a call to
mark().
voidseek(int index)
Set the input cursor to the position indicated by index.
intsize()
Returns the total number of symbols in the stream, including a single EOF
symbol.
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Field Detail
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EOF
static final int EOF
The value returned by LA() when the end of the stream is
reached.
- See Also:
- Constant Field Values
-
UNKNOWN_SOURCE_NAME
static final String UNKNOWN_SOURCE_NAME
The value returned by getSourceName() when the actual name of the
underlying source is not known.
- See Also:
- Constant Field Values
-
Method Detail
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consume
void consume()
Consumes the current symbol in the stream. This method has the following
effects:
- Forward movement: The value of
index()
before calling this method is less than the value of index()
after calling this method.
- Ordered lookahead: The value of
LA(1) before
calling this method becomes the value of LA(-1) after calling
this method.
Note that calling this method does not guarantee that index() is
incremented by exactly 1, as that would preclude the ability to implement
filtering streams (e.g. CommonTokenStream which distinguishes
between "on-channel" and "off-channel" tokens).
- Throws:
IllegalStateException - if an attempt is made to consume the
end of the stream (i.e. if LA(1)==EOF before calling
consume).
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LA
int LA(int i)
Gets the value of the symbol at offset i from the current
position. When i==1, this method returns the value of the current
symbol in the stream (which is the next symbol to be consumed). When
i==-1, this method returns the value of the previously read
symbol in the stream. It is not valid to call this method with
i==0, but the specific behavior is unspecified because this
method is frequently called from performance-critical code.
This method is guaranteed to succeed if any of the following are true:
i>0i==-1 and index() returns a value greater
than the value of index() after the stream was constructed
and LA(1) was called in that order. Specifying the current
index() relative to the index after the stream was created
allows for filtering implementations that do not return every symbol
from the underlying source. Specifying the call to LA(1)
allows for lazily initialized streams.LA(i) refers to a symbol consumed within a marked region
that has not yet been released.
If i represents a position at or beyond the end of the stream,
this method returns EOF.
The return value is unspecified if i<0 and fewer than -i
calls to consume() have occurred from the beginning of
the stream before calling this method.
- Throws:
UnsupportedOperationException - if the stream does not support
retrieving the value of the specified symbol
-
mark
int mark()
A mark provides a guarantee that seek() operations will be
valid over a "marked range" extending from the index where mark()
was called to the current index(). This allows the use of
streaming input sources by specifying the minimum buffering requirements
to support arbitrary lookahead during prediction.
The returned mark is an opaque handle (type int) which is passed
to release() when the guarantees provided by the marked
range are no longer necessary. When calls to
mark()/release() are nested, the marks must be released
in reverse order of which they were obtained. Since marked regions are
used during performance-critical sections of prediction, the specific
behavior of invalid usage is unspecified (i.e. a mark is not released, or
a mark is released twice, or marks are not released in reverse order from
which they were created).
The behavior of this method is unspecified if no call to an
initializing method has occurred after this stream was
constructed.
This method does not change the current position in the input stream.
The following example shows the use of mark(),
release(mark), index(), and
seek(index) as part of an operation to safely work within a
marked region, then restore the stream position to its original value and
release the mark.
IntStream stream = ...;
int index = -1;
int mark = stream.mark();
try {
index = stream.index();
// perform work here...
} finally {
if (index != -1) {
stream.seek(index);
}
stream.release(mark);
}
- Returns:
- An opaque marker which should be passed to
release() when the marked range is no longer required.
-
release
void release(int marker)
This method releases a marked range created by a call to
mark(). Calls to release() must appear in the
reverse order of the corresponding calls to mark(). If a mark is
released twice, or if marks are not released in reverse order of the
corresponding calls to mark(), the behavior is unspecified.
For more information and an example, see mark().
- Parameters:
marker - A marker returned by a call to mark().- See Also:
mark()
-
index
int index()
Return the index into the stream of the input symbol referred to by
LA(1).
The behavior of this method is unspecified if no call to an
initializing method has occurred after this stream was
constructed.
-
seek
void seek(int index)
Set the input cursor to the position indicated by index. If the
specified index lies past the end of the stream, the operation behaves as
though index was the index of the EOF symbol. After this method
returns without throwing an exception, then at least one of the following
will be true.
index() will return the index of the first symbol
appearing at or after the specified index. Specifically,
implementations which filter their sources should automatically
adjust index forward the minimum amount required for the
operation to target a non-ignored symbol.LA(1) returns EOF
This operation is guaranteed to not throw an exception if index
lies within a marked region. For more information on marked regions, see
mark(). The behavior of this method is unspecified if no call to
an initializing method has occurred after this stream
was constructed.
- Parameters:
index - The absolute index to seek to.- Throws:
IllegalArgumentException - if index is less than 0UnsupportedOperationException - if the stream does not support
seeking to the specified index
-
size
int size()
Returns the total number of symbols in the stream, including a single EOF
symbol.
- Throws:
UnsupportedOperationException - if the size of the stream is
unknown.
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getSourceName
@NotNull
String getSourceName()
Gets the name of the underlying symbol source. This method returns a
non-null, non-empty string. If such a name is not known, this method
returns UNKNOWN_SOURCE_NAME.
Copyright © 1992–2023 Daniel Sun. All rights reserved.