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/**
* Copyright (c) Rich Hickey. All rights reserved.
* The use and distribution terms for this software are covered by the
* Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
* which can be found in the file epl-v10.html at the root of this distribution.
* By using this software in any fashion, you are agreeing to be bound by
* the terms of this license.
* You must not remove this notice, or any other, from this software.
**/
/* rich Mar 5, 2009 */
package clojure.lang;
final public class Stream implements Seqable, Streamable, Sequential {
static final ISeq NO_SEQ = new Cons(null, null);
ISeq sequence = NO_SEQ;
final IFn src;
final IFn xform;
IFn tap = null;
public Stream(IFn src){
this.src = src;
this.xform = null;
}
public Stream(IFn xform, Stream src) {
this.src = src.tap();
this.xform = xform;
}
final public ISeq seq(){
return sequence().seq();
}
final synchronized public ISeq sequence(){
if(sequence == NO_SEQ)
{
tap();
sequence = makeSequence(tap);
}
return sequence;
}
static ISeq makeSequence(final IFn tap){
return new LazySeq(new AFn(){
public Object invoke() throws Exception{
Object v = tap.invoke();
if(v == RT.EOS)
return null;
return new Cons(v, new LazySeq(this));
}
});
}
final synchronized public Stream stream() throws Exception {
return this;
}
final synchronized public IFn tap() {
if (tap != null)
throw new IllegalStateException("Stream already tapped");
return tap = makeTap(xform, src);
}
static IFn makeTap(final IFn xform, final IFn src){
return new AFn(){
final synchronized public Object invoke() throws Exception{
if(xform == null)
return src.invoke();
Object v;
Object xv;
do {
v = src.invoke();
if(v == RT.EOS)
return v;
xv = xform.invoke(v);
} while(xv == RT.SKIP);
return xv;
}
};
}
}
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