115 lines
3.1 KiB
Python
115 lines
3.1 KiB
Python
"""Stateful iterator for flat trees."""
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__all__ = ["FlatTreeIterator"]
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import attr
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from flat_tree.accessor import FlatTreeAccessor
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@attr.s(auto_attribs=True)
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class FlatTreeIterator:
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"""Stateful iterator for flat trees."""
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index: int = 0
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offset: int = 0
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factor: int = 0
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accessor: FlatTreeAccessor = FlatTreeAccessor()
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def __attrs_post_init__(self):
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self.seek(self.index)
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# TODO(decentral1se): Once we get to the point of actually using this
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# module in hypercore, we should consider whether or not to make this a
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# real Python iterator using the protocol methods of __iter__ and __next__
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def next(self) -> int:
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"""The next index in the tree."""
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self.offset += 1
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self.index += self.factor
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return self.index
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def prev(self) -> int:
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"""The previous index in the tree."""
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if not self.offset:
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return self.index
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self.offset -= 1
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self.index = self.factor
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return self.index
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def seek(self, index: int) -> None:
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"""Move iterator to the given index.
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:param index: The index to move to
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"""
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self.index = index
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if self.index & 1:
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self.offset = self.accessor.offset(index)
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self.factor = 2 ** (self.accessor.depth(index) + 1)
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else:
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self.offset = int(index / 2)
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self.factor = 2
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def parent(self) -> int:
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"""Move iterator to the parent index."""
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if self.offset & 1:
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self.index -= int(self.factor / 2)
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self.offset = int((self.offset - 1) / 2)
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else:
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self.index += int(self.factor / 2)
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self.offset = int(self.offset / 2)
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self.factor *= 2
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return self.index
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def left_child(self) -> int:
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"""Move iterator to the left child."""
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if self.factor == 2:
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return self.index
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self.factor = int(self.factor / 2)
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self.index -= int(self.factor / 2)
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self.offset *= 2
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return self.index
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def right_child(self) -> int:
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"""Move iterator to the right child."""
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if self.factor == 2:
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return self.index
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self.factor = int(self.factor / 2)
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self.index += int(self.factor / 2)
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self.offset = (2 * self.offset) + 1
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return self.index
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def left_span(self) -> int:
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"""Move iterator to the left span."""
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self.index = int(self.index - (self.factor / 2)) + 1
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self.offset = int(self.index / 2)
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self.factor = 2
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return self.index
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def right_span(self) -> int:
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"""Move iterator to the right span."""
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self.index = int((self.index - self.factor) / 2) - 1
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self.offset = int(self.index / 2)
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self.factor = 2
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return self.index
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def sibling(self) -> int:
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"""Move iterator to the sibling."""
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return self.next() if self.is_left() else self.prev()
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def is_left(self) -> bool:
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"""Is this index a left sibling?"""
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return not self.offset & 1
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def is_right(self) -> bool:
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"""Is this index a right sibling?"""
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return not self.is_left()
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