Package org.antlr.runtime.tree

Class RewriteRuleElementStream

java.lang.Object

org.antlr.runtime.tree.RewriteRuleElementStream

Direct Known Subclasses:

RewriteRuleNodeStream, RewriteRuleSubtreeStream, RewriteRuleTokenStream

public abstract class RewriteRuleElementStream
extends Object

A generic list of elements tracked in an alternative to be used in a -> rewrite rule. We need to subclass to fill in the next() method, which returns either an AST node wrapped around a token payload or an existing subtree. Once you start next()ing, do not try to add more elements. It will break the cursor tracking I believe.

See Also:

RewriteRuleSubtreeStream, TODO: add mechanism to detect/puke on modification after reading from stream

Field Summary

Fields

Modifier and Type	Field	Description
protected TreeAdaptor	adaptor
protected int	cursor	Cursor 0..n-1.
protected boolean	dirty	Once a node / subtree has been used in a stream, it must be dup'd from then on.
protected String	elementDescription	The element or stream description; usually has name of the token or rule reference that this list tracks.
protected List<Object>	elements	The list of tokens or subtrees we are tracking
protected Object	singleElement	Track single elements w/o creating a list.

Constructor Summary

Constructors

Constructor	Description
RewriteRuleElementStream(TreeAdaptor adaptor, String elementDescription)
RewriteRuleElementStream(TreeAdaptor adaptor, String elementDescription, Object oneElement)	Create a stream with one element
RewriteRuleElementStream(TreeAdaptor adaptor, String elementDescription, List<Object> elements)	Create a stream, but feed off an existing list

Method Summary

Modifier and Type	Method	Description
protected Object	_next()	do the work of getting the next element, making sure that it's a tree node or subtree.
void	add(Object el)
protected abstract Object	dup(Object el)	When constructing trees, sometimes we need to dup a token or AST subtree.
String	getDescription()
boolean	hasNext()
Object	nextTree()	Return the next element in the stream.
void	reset()	Reset the condition of this stream so that it appears we have not consumed any of its elements.
int	size()
protected Object	toTree(Object el)	Ensure stream emits trees; tokens must be converted to AST nodes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

cursor

protected int cursor

Cursor 0..n-1. If singleElement!=null, cursor is 0 until you next(), which bumps it to 1 meaning no more elements.

singleElement

protected Object singleElement

Track single elements w/o creating a list. Upon 2nd add, alloc list

elements

protected List<Object> elements

The list of tokens or subtrees we are tracking

dirty

protected boolean dirty

Once a node / subtree has been used in a stream, it must be dup'd from then on. Streams are reset after subrules so that the streams can be reused in future subrules. So, reset must set a dirty bit. If dirty, then next() always returns a dup. I wanted to use "naughty bit" here, but couldn't think of a way to use "naughty". TODO: unused?

elementDescription

protected String elementDescription

The element or stream description; usually has name of the token or rule reference that this list tracks. Can include rulename too, but the exception would track that info.

adaptor

protected TreeAdaptor adaptor

Constructor Detail

RewriteRuleElementStream

public RewriteRuleElementStream(TreeAdaptor adaptor,
                                String elementDescription)

RewriteRuleElementStream

public RewriteRuleElementStream(TreeAdaptor adaptor,
                                String elementDescription,
                                Object oneElement)

Create a stream with one element

RewriteRuleElementStream

public RewriteRuleElementStream(TreeAdaptor adaptor,
                                String elementDescription,
                                List<Object> elements)

Create a stream, but feed off an existing list

Method Detail

reset

public void reset()

Reset the condition of this stream so that it appears we have not consumed any of its elements. Elements themselves are untouched. Once we reset the stream, any future use will need duplicates. Set the dirty bit.

add

public void add(Object el)

nextTree

public Object nextTree()

Return the next element in the stream. If out of elements, throw an exception unless size()==1. If size is 1, then return elements[0]. Return a duplicate node/subtree if stream is out of elements and size==1. If we've already used the element, dup (dirty bit set).

_next

protected Object _next()

do the work of getting the next element, making sure that it's a tree node or subtree. Deal with the optimization of single- element list versus list of size > 1. Throw an exception if the stream is empty or we're out of elements and size>1. protected so you can override in a subclass if necessary.

dup

protected abstract Object dup(Object el)

When constructing trees, sometimes we need to dup a token or AST subtree. Dup'ing a token means just creating another AST node around it. For trees, you must call the adaptor.dupTree() unless the element is for a tree root; then it must be a node dup.

toTree

protected Object toTree(Object el)

Ensure stream emits trees; tokens must be converted to AST nodes. AST nodes can be passed through unmolested.

hasNext

public boolean hasNext()

size

public int size()

getDescription

public String getDescription()