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package bjc.pratt.tokens;
import static bjc.pratt.tokens.StringToken.litToken;
import java.util.Iterator;
import bjc.data.MarkListIterator;
/**
* Simple implementation of token stream for strings.
*
* The terminal token here is represented by a token with type and value
* '(end)'.
*
* @author EVE
*
*/
public class StringTokenStream extends TokenStream<String, String> {
private final MarkListIterator<Token<String, String>> iter;
private Token<String, String> curr;
/**
* Create a new token stream from a iterator.
*
* @param itr
* The iterator to use.
*
*/
public StringTokenStream(final Iterator<Token<String, String>> itr) {
iter = new MarkListIterator<>(itr);
}
@Override
public Token<String, String> current() {
// Prime stream if necessary
if (curr == null)
return next();
return curr;
}
@Override
public Token<String, String> next() {
if(iter.hasNext()) {
curr = iter.next();
} else {
curr = litToken("(end)");
}
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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