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/**
* Copyright (c) David Miller. 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.
**/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.CompilerServices;
namespace clojure.lang
{
public sealed class Stream : Seqable, Streamable, Sequential
{
#region Data
static readonly ISeq NO_SEQ = new Cons(null, null);
ISeq _sequence = NO_SEQ;
readonly IFn _src;
readonly IFn _xform;
//Cons _pushed = null;
IFn _tap = null;
#endregion
#region C-tors and factory methods
public Stream(IFn src)
{
_src = src;
_xform = null;
}
public Stream(IFn xform, Stream src)
{
_src = src.tap();
_xform = xform;
}
#endregion
#region Seqable Members
public ISeq seq()
{
return sequence().seq();
}
[MethodImpl(MethodImplOptions.Synchronized)]
public ISeq sequence()
{
if (_sequence == NO_SEQ)
{
tap();
_sequence = makeSequence(_tap);
}
return _sequence;
}
class Seqer : AFn
{
IFn _tap;
public Seqer(IFn tap)
{
_tap = tap;
}
public override object invoke()
{
object v = _tap.invoke();
if (v == RT.EOS)
return null;
return new Cons(v, new LazySeq(this));
}
}
static ISeq makeSequence(IFn tap)
{
return RT.seq(new LazySeq(new Seqer(tap)));
}
#endregion
#region Streamable Members
[MethodImpl(MethodImplOptions.Synchronized)]
public Stream stream()
{
return this;
}
#endregion
#region Tapping
[MethodImpl(MethodImplOptions.Synchronized)]
public IFn tap()
{
if (_tap != null)
throw new InvalidOperationException("Stream already tapped");
return _tap = makeTap(_xform, _src);
}
class Tapper : AFn
{
IFn _xform;
IFn _src;
public Tapper(IFn xform, IFn src)
{
_xform = xform;
_src = src;
}
public override object invoke()
{
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;
}
}
static IFn makeTap(IFn xform, IFn src)
{
return new Tapper(xform,src);
}
#endregion
}
}
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