splitIterator - split an iterator into parallel iterators with dynamic buffering [1013600]

// iterators are not thread-safe
static <A> L<IterableIterator<A>> splitIterator(final int n, final Iterator<A> it) {
  class SplitIterator {
    final int[] positions = repIntAsArray(n, -1);
    new CircularArrayList<A> buffer;
    int first;
    bool done;
  
    L<IterableIterator<A>> iterators() {
      new L<IterableIterator<A>> l;
      for _i to n: {
        final int i = _i;
        l.add((IterableIterator) iteratorFF(func {
          positions[i]++;
          updateBuffer();
          int idx = positions[i]-first;
          ret idx >= l(buffer) ? endMarker() : buffer.get(idx);
        }));
      }
      ret l;
    }
    
    int last() { ret first+l(buffer); }
    
    void updateBuffer {
      int min = min(positions), max = max(positions);
      while (min > first) { buffer.remove(0); ++first; }
      while (!done && max >= last()) {
        if (!it.hasNext())
          done = true;
        else
          buffer.add(it.next());
      }
    }
  }
  ret new SplitIterator().iterators();
}

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Snippet ID:	#1013600
Snippet name:	splitIterator - split an iterator into parallel iterators with dynamic buffering
Eternal ID of this version:	#1013600/13
Text MD5:	5679d53cd7a64bc35079495a2f3a6e58
Author:	stefan
Category:	javax
Type:	JavaX fragment (include)
Public (visible to everyone):	Yes
Archived (hidden from active list):	No
Created/modified:	2018-01-11 14:21:31
Source code size:	1047 bytes / 37 lines
Pitched / IR pitched:	No / No
Views / Downloads:	469 / 475
Version history:	12 change(s)
Referenced in:	[show references]

1	// iterators are not thread-safe
2	static <A> L<IterableIterator<A>> splitIterator(final int n, final Iterator<A> it) {
3	class SplitIterator {
4	final int[] positions = repIntAsArray(n, -1);
5	new CircularArrayList<A> buffer;
6	int first;
7	bool done;
8
9	L<IterableIterator<A>> iterators() {
10	new L<IterableIterator<A>> l;
11	for _i to n: {
12	final int i = _i;
13	l.add((IterableIterator) iteratorFF(func {
14	positions[i]++;
15	updateBuffer();
16	int idx = positions[i]-first;
17	ret idx >= l(buffer) ? endMarker() : buffer.get(idx);
18	}));
19	}
20	ret l;
21	}
22
23	int last() { ret first+l(buffer); }
24
25	void updateBuffer {
26	int min = min(positions), max = max(positions);
27	while (min > first) { buffer.remove(0); ++first; }
28	while (!done && max >= last()) {
29	if (!it.hasNext())
30	done = true;
31	else
32	buffer.add(it.next());
33	}
34	}
35	}
36	ret new SplitIterator().iterators();
37	}

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JavaX fragment (include)