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package com.ashardalon.pratt.tokens;
import java.util.Iterator;
import bjc.data.MarkListIterator;
/**
* Simple token stream implementation
* @author bjcul
*
* @param <K> The key type
* @param <V> The value type
*/
public class SimpleTokenStream<K, V> extends TokenStream<K, V> {
private final MarkListIterator<Token<K, V>> iter;
private Token<K, V> curr;
private Token<K, V> terminal;
/**
* Create a new token stream from a iterator.
*
* @param itr The iterator to use.
* @param terminal The terminal token to use for end-of-stream
*
*/
public SimpleTokenStream(final Iterator<Token<K, V>> itr, Token<K, V> terminal) {
this.iter = new MarkListIterator<>(itr);
this.terminal = terminal;
}
@Override
public Token<K, V> current() {
// Prime stream if necessary
if (curr == null)
return next();
return curr;
}
@Override
public Token<K, V> next() {
if (iter.hasNext()) {
curr = iter.next();
} else {
curr = terminal;
}
return curr;
}
@Override
public boolean hasNext() {
return iter.hasNext();
}
@Override
public void mark() {
iter.mark();
}
@Override
public void commit() {
iter.commit();
if (!iter.hasMark()) {
// No marks outstanding; we can release the previous state
iter.reset();
}
}
@Override
public void rollback() {
iter.rollback();
curr = iter.current();
}
@Override
public boolean hasMark() {
return iter.hasMark();
}
}
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