110 lines
2.9 KiB
Python
110 lines
2.9 KiB
Python
"""A merkle tree generator."""
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from typing import Any, Callable, Iterator, List
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import attr
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from flat_tree import FlatTreeAccessor
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from merkle_tree_stream.node import MerkleTreeNode
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EMPTY_DATA = b''
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EMPTY_HASH = None
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__all__ = ['MerkleTreeGenerator']
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flat_tree = FlatTreeAccessor()
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@attr.s(auto_attribs=True)
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class MerkleTreeGenerator:
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"""A merkle tree generator.
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:param leaf: The leaf hash generation function
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:param parent: The parent hash generation function
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:param roots: The tree roots
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"""
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leaf: Callable[[MerkleTreeNode], bytes]
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parent: Callable[[MerkleTreeNode, MerkleTreeNode], bytes]
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roots: List[MerkleTreeNode] = attr.Factory(list)
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_position: int = 0
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_nodes: List[MerkleTreeNode] = attr.Factory(list)
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def __attrs_post_init__(self) -> Any:
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"""Initialise parent and block defaults."""
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try:
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index = self.roots[len(self.roots) - 1].index
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except IndexError:
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index = 0
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right_span = flat_tree.right_span(index)
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self.blocks = (1 + (right_span / 2)) if self.roots else 0
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for root in self.roots:
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if not root.parent:
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root.parent = flat_tree.parent(root.index)
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def __iter__(self) -> Iterator:
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"""The iterator initialisation."""
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return self
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def __next__(self) -> MerkleTreeNode:
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"""The following node."""
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try:
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node = self._nodes[self._position]
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except IndexError:
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raise StopIteration
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self._position += 1
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return node
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def __len__(self) -> int:
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"""The number of nodes stored in the tree."""
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return len(self._nodes)
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# TODO(decentral1se): we need to take pass on async capability. Please see
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# https://datprotocol.github.io/book/ch02-02-merkle-tree-stream.html#async
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def write(self, data: bytes):
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"""Write a new node to the tree and compute the new hashes.
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:param data: The new tree data
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"""
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index = 2 * self.blocks
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self.blocks += 1
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leaf_node = MerkleTreeNode(
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index=index,
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parent=flat_tree.parent(index),
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hash=EMPTY_HASH,
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data=data,
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size=len(data),
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)
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leaf_node.hash = self.leaf(leaf_node)
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self.roots.append(leaf_node)
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self._nodes.append(leaf_node)
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while len(self.roots) > 1:
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left = self.roots[len(self.roots) - 2]
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right = self.roots[len(self.roots) - 1]
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if left.parent != right.parent:
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break
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self.roots.pop()
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new_node = MerkleTreeNode(
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index=left.parent,
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parent=flat_tree.parent(left.parent),
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hash=self.parent(left, right),
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size=left.size + right.size,
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data=EMPTY_DATA,
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)
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self.roots[len(self.roots) - 1] = new_node
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self._nodes.append(new_node)
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