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The ANTLR 4 grammar compiler.

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UnbufferedCharStream (ANTLR 4 Runtime (Optimized) 4.7.3 API)













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org.antlr.v4.runtime
Class UnbufferedCharStream



java.lang.Object


org.antlr.v4.runtime.UnbufferedCharStream







All Implemented Interfaces:
CharStream, IntStream, UnicodeCharStream




public class UnbufferedCharStream
extends Object
implements UnicodeCharStream, CharStream
Do not buffer up the entire char stream. It does keep a small buffer
  for efficiency and also buffers while a mark exists (set by the
  lookahead prediction in parser). "Unbuffered" here refers to fact
  that it doesn't buffer all data, not that's it's on demand loading of char.











Field Summary

Fields 

Modifier and Type
Field and Description


protected int
currentCharIndex
Absolute character index.



protected char[]
data
A moving window buffer of the data being scanned.



protected Reader
input 


protected int
lastChar
This is the LA(-1) character for the current position.



protected int
lastCharBufferStart
When numMarkers > 0, this is the LA(-1) character for the
 first character in data.



protected int
n
The number of characters currently in data.



String
name
The name or source of this char stream.



protected int
numMarkers
Count up with mark() and down with
 release().



protected int
p
0..n-1 index into data of next character.







Fields inherited from interface org.antlr.v4.runtime.IntStream
EOF, UNKNOWN_SOURCE_NAME








Constructor Summary

Constructors 

Constructor and Description


UnbufferedCharStream()
Useful for subclasses that pull char from other than this.input.



UnbufferedCharStream(InputStream input) 


UnbufferedCharStream(InputStream input,
                    int bufferSize) 


UnbufferedCharStream(int bufferSize)
Useful for subclasses that pull char from other than this.input.



UnbufferedCharStream(Reader input) 


UnbufferedCharStream(Reader input,
                    int bufferSize) 









Method Summary

Methods 

Modifier and Type
Method and Description


protected void
add(int c) 


void
consume()
Consumes the current symbol in the stream.



protected int
fill(int n)
Add n characters to the buffer.



protected int
getBufferStartIndex() 


String
getSourceName()
Gets the name of the underlying symbol source.



String
getText(Interval interval)
This method returns the text for a range of characters within this input
 stream.



int
index()
Return the index into the stream of the input symbol referred to by
 LA(1).



int
LA(int i)
Gets the value of the symbol at offset i from the current
 position.



int
mark()
Return a marker that we can release later.



protected int
nextChar()
Override to provide different source of characters than
 input.



void
release(int marker)
Decrement number of markers, resetting buffer if we hit 0.



void
seek(int index)
Seek to absolute character index, which might not be in the current
  sliding window.



int
size()
Returns the total number of symbols in the stream, including a single EOF
 symbol.



boolean
supportsUnicodeCodePoints()
Determines if the current stream supports Unicode code points.



protected void
sync(int want)
Make sure we have 'need' elements from current position p.







Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait














Field Detail





data
protected char[] data
A moving window buffer of the data being scanned. While there's a marker,
 we keep adding to buffer. Otherwise, consume() resets so
 we start filling at index 0 again.







n
protected int n
The number of characters currently in data.

 This is not the buffer capacity, that's data.length.







p
protected int p
0..n-1 index into data of next character.

 The LA(1) character is data[p]. If p == n, we are
 out of buffered characters.







numMarkers
protected int numMarkers
Count up with mark() and down with
 release(). When we release() the last mark,
 numMarkers reaches 0 and we reset the buffer. Copy
 data[p]..data[n-1] to data[0]..data[(n-1)-p].







lastChar
protected int lastChar
This is the LA(-1) character for the current position.







lastCharBufferStart
protected int lastCharBufferStart
When numMarkers > 0, this is the LA(-1) character for the
 first character in data. Otherwise, this is unspecified.







currentCharIndex
protected int currentCharIndex
Absolute character index. It's the index of the character about to be
 read via LA(1). Goes from 0 to the number of characters in the
 entire stream, although the stream size is unknown before the end is
 reached.







input
protected Reader input







name
public String name
The name or source of this char stream.









Constructor Detail





UnbufferedCharStream
public UnbufferedCharStream()
Useful for subclasses that pull char from other than this.input.







UnbufferedCharStream
public UnbufferedCharStream(int bufferSize)
Useful for subclasses that pull char from other than this.input.







UnbufferedCharStream
public UnbufferedCharStream(InputStream input)







UnbufferedCharStream
public UnbufferedCharStream(Reader input)







UnbufferedCharStream
public UnbufferedCharStream(InputStream input,
                    int bufferSize)







UnbufferedCharStream
public UnbufferedCharStream(Reader input,
                    int bufferSize)









Method Detail





consume
public void consume()
Description copied from interface: IntStream
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).

Specified by:
consume in interface IntStream








sync
protected void sync(int want)
Make sure we have 'need' elements from current position p.
 Last valid p index is data.length-1. p+need-1 is
 the char index 'need' elements ahead. If we need 1 element,
 (p+1-1)==p must be less than data.length.







fill
protected int fill(int n)
Add n characters to the buffer. Returns the number of characters
 actually added to the buffer. If the return value is less than n,
 then EOF was reached before n characters could be added.







nextChar
protected int nextChar()
                throws IOException
Override to provide different source of characters than
 input.
Throws:
IOException







add
protected void add(int c)







LA
public int LA(int i)
Description copied from interface: IntStream
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>0
   i==-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 IntStream.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.

Specified by:
LA in interface IntStream








mark
public int mark()
Return a marker that we can release later.

 The specific marker value used for this class allows for some level of
 protection against misuse where seek() is called on a mark or
 release() is called in the wrong order.

Specified by:
mark in interface IntStream
Returns:
An opaque marker which should be passed to
 release() when the marked range is no longer required.







release
public void release(int marker)
Decrement number of markers, resetting buffer if we hit 0.

Specified by:
release in interface IntStream
Parameters:
marker - 
See Also:
IntStream.mark()







index
public int index()
Description copied from interface: IntStream
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.

Specified by:
index in interface IntStream








seek
public void seek(int index)
Seek to absolute character index, which might not be in the current
  sliding window.  Move p to index-bufferStartIndex.

Specified by:
seek in interface IntStream
Parameters:
index - The absolute index to seek to.







size
public int size()
Description copied from interface: IntStream
Returns the total number of symbols in the stream, including a single EOF
 symbol.

Specified by:
size in interface IntStream








getSourceName
public String getSourceName()
Description copied from interface: IntStream
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 IntStream.UNKNOWN_SOURCE_NAME.

Specified by:
getSourceName in interface IntStream








getText
public String getText(Interval interval)
Description copied from interface: CharStream
This method returns the text for a range of characters within this input
 stream. This method is guaranteed to not throw an exception if the
 specified interval lies entirely within a marked range. For more
 information about marked ranges, see IntStream.mark().

Specified by:
getText in interface CharStream
Parameters:
interval - an interval within the stream
Returns:
the text of the specified interval







getBufferStartIndex
protected final int getBufferStartIndex()







supportsUnicodeCodePoints
public boolean supportsUnicodeCodePoints()
Determines if the current stream supports Unicode code points.

Specified by:
supportsUnicodeCodePoints in interface UnicodeCharStream
Returns:
true if the current input stream supports Unicode code
 points; otherwise, false if the current input stream returns
 UTF-16 code units for code points above U+FFFF.
















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Copyright © 1992–2019 Tunnel Vision Laboratories, LLC. All rights reserved.

Modifier and Type	Field and Description
`protected int`	`currentCharIndex` Absolute character index.
`protected char[]`	`data` A moving window buffer of the data being scanned.
`protected Reader`	`input`
`protected int`	`lastChar` This is the `LA(-1)` character for the current position.
`protected int`	`lastCharBufferStart` When `numMarkers > 0`, this is the `LA(-1)` character for the first character in `data`.
`protected int`	`n` The number of characters currently in `data`.
`String`	`name` The name or source of this char stream.
`protected int`	`numMarkers` Count up with `mark()` and down with `release()`.
`protected int`	`p` 0..n-1 index into `data` of next character.

Modifier and Type	Method and Description
`protected void`	`add(int c)`
`void`	`consume()` Consumes the current symbol in the stream.
`protected int`	`fill(int n)` Add `n` characters to the buffer.
`protected int`	`getBufferStartIndex()`
`String`	`getSourceName()` Gets the name of the underlying symbol source.
`String`	`getText(Interval interval)` This method returns the text for a range of characters within this input stream.
`int`	`index()` Return the index into the stream of the input symbol referred to by `LA(1)`.
`int`	`LA(int i)` Gets the value of the symbol at offset `i` from the current position.
`int`	`mark()` Return a marker that we can release later.
`protected int`	`nextChar()` Override to provide different source of characters than `input`.
`void`	`release(int marker)` Decrement number of markers, resetting buffer if we hit 0.
`void`	`seek(int index)` Seek to absolute character index, which might not be in the current sliding window.
`int`	`size()` Returns the total number of symbols in the stream, including a single EOF symbol.
`boolean`	`supportsUnicodeCodePoints()` Determines if the current stream supports Unicode code points.
`protected void`	`sync(int want)` Make sure we have 'need' elements from current position `p`.