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Add documentation to SHAMap #341

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Add documentation to SHAMap #341

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22 changes: 22 additions & 0 deletions src/ripple_app/shamap/SHAMap.h
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Expand Up @@ -62,6 +62,28 @@ enum SHAMapState
smsInvalid = 4, // Map is known not to be valid (usually synching a corrupt ledger)
};

/** A SHAMap is both a radix tree with a fan-out of 16 and a Merkle tree.

A radix tree is a tree with two properties:

1. The key for a node is represented by the node's position in the tree
(the "prefix property").
2. A node with only one child is merged with that child
(the "merge property")

These properties in a significantly smaller memory footprint for a radix tree.

And a fan-out of 16 means that each node in the tree has at most 16 children.
See https://en.wikipedia.org/wiki/Radix_tree

A Merkle tree is a tree where each non-leaf node is labelled with the hash
of the combined labels of its children nodes.

A key property of a Merkle tree is that testing for node inclusion is
O(log(N)) where N is the number of nodes in the tree.

See https://en.wikipedia.org/wiki/Merkle_tree
*/
class SHAMap
// : public CountedObject <SHAMap>
{
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