Commit 3e5f1310aaf2b3f3e5ce84ef70c9d91a24657bde
Update spec.md
Mahnush Movahedi authored on 12/21/2017, 8:16:30 PMGitHub committed on 12/21/2017, 8:16:30 PM
Parent: 89398824f10c7485f1839296a5d994e9b852aef9
Files changed
| docs/spec.md | changed |
| docs/spec.md | ||
|---|---|---|
| @@ -1,30 +1,29 @@ | ||
| 1 | -This is a simple Merkle Binary [Radix Tree](https://ipfs.io/ipns/QmdJiuMWp2FxyaerfLrtdLF6Nr1EWpL7dPAxA9oKSPYYgV/wiki/Radix_tree.html). | |
| 1 … | +This documnet provides the structure of the Dfinities Radix Tree which is type of the Merkle tree.(https://ipfs.io/ipns/QmdJiuMWp2FxyaerfLrtdLF6Nr1EWpL7dPAxA9oKSPYYgV/wiki/Radix_tree.html). | |
| 2 … | +The radix tree data structure consists of nodes. | |
| 2 | 3 … | |
| 3 | - | |
| 4 | 4 … | ## Node |
| 5 | -Each node contains at the most four elements | |
| 5 … | +Each node has a type and contains at the most four elements | |
| 6 | 6 … | "extension", "left branch", "right branch" and "value". |
| 7 | 7 … | |
| 8 | 8 … | ``` |
| 9 | -node : = EXTENSION | LBRANCH | RBRANCH | VALUE | |
| 9 … | +node : = TYPE | EXTENSION | LBRANCH | RBRANCH | VALUE | |
| 10 | 10 … | ``` |
| 11 | 11 … | |
| 12 | -A prefix byte is used a bit field to signify which elements a node contains. | |
| 13 | -The bit field is defined a the following. The first nibble is reserved for | |
| 14 | -merkle proofs. | |
| 12 … | +###Type | |
| 13 … | +Contains a byte that the last 4 bits are used to signify which elements a node contains. | |
| 14 … | +The bit field is defined a the following. The first 4 bits are paded to zero while in storage. These bits are reserved as insicators of type when sending the nodes to other clients which we will describe later. | |
| 15 | 15 … | |
| 16 | 16 … | ``` |
| 17 | -PREFIX := reserved | reserved | reserved | reserved | EXTENSION | LBRANCH | RBRANCH | VALUE | |
| 17 … | +Type := 0 | 0 | 0 | 0 | HasEXTENSION | HasLBRANCH | HasRBRANCH | HasVALUE | |
| 18 | 18 … | ``` |
| 19 | 19 … | |
| 20 | -For example a node that contained a left branch and a value would have a prefix byte | |
| 21 | -of 00000101 or 0x07 | |
| 20 … | +For example a node that contained a left branch and a value would have a prefix byte of 00000101 or 0x07 | |
| 22 | 21 … | |
| 23 | 22 … | The full encoded node would then look something like. `0x07<20_bytes_for_lbranch><remaing_bytes_for_value>` |
| 24 | 23 … | |
| 25 | 24 … | |
| 26 | -## Branches | |
| 25 … | +### Branches | |
| 27 | 26 … | |
| 28 | 27 … | The branch elements point to the next node in the tree using a merkle link. |
| 29 | 28 … | A merkle link is defined by the first 20 bytes of the result SHA2-256 of an encoded node. |
| 30 | 29 … | |
| @@ -37,13 +36,13 @@ | ||
| 37 | 36 … | link := SHA2(encoded_node)[0..20] |
| 38 | 37 … | ``` |
| 39 | 38 … | |
| 40 | 39 … | |
| 41 | -## Extensions | |
| 42 | -Extensions encode shared paths. Extensions are defined as | |
| 40 … | +### Extensions | |
| 41 … | +For optimization, we use the Extension element that encodes shared paths in the tree. Extensions are defined as | |
| 43 | 42 … | |
| 44 | 43 … | ``` |
| 45 | -extension := length | extension | |
| 44 … | +extension := Length | ExtensionValue | |
| 46 | 45 … | |
| 47 | 46 … | ``` |
| 48 | 47 … | Where the length is the number of bits that extension repesents. This varuint32 |
| 49 | 48 … | encoded with leb128. And the extension is bit array padded with 0's to the nearst byte. |
| @@ -55,14 +54,14 @@ | ||
| 55 | 54 … | |
| 56 | 55 … | where 3 is the the shared path length and the `0x04` is the shared path encoded |
| 57 | 56 … | as a little endian byte array. |
| 58 | 57 … | |
| 59 | -# Examples | |
| 58 … | +## Examples | |
| 60 | 59 … | |
| 61 | -An empty tree is hash a merkle link of sha256(0x00) or `6e340b9cffb37a989ca544e6bb780a2c78901d3f` | |
| 60 … | +An empty tree has a merkle root which is a hash of sha256(0x00) or `6e340b9cffb37a989ca544e6bb780a2c78901d3f`. | |
| 62 | 61 … | |
| 63 | 62 … | |
| 64 | -A tree with a single key 'binary' and value of 'tree' is encoded as | |
| 63 … | +A tree with a single node with key 'binary' and value of 'tree' is encoded as | |
| 65 | 64 … | |
| 66 | 65 … | ``` |
| 67 | 66 … | 0x093062696e61727974726565 |
| 68 | 67 … | |
| @@ -71,9 +70,9 @@ | ||
| 71 | 70 … | 0x62696e617279 the key 'binary' |
| 72 | 71 … | 0x4726565 the value 'tree' |
| 73 | 72 … | ``` |
| 74 | 73 … | |
| 75 | -If an other key "bin" with the value "number" is add the tree will have two nodes | |
| 74 … | +If we add another key-value with the key "bin" and the value "number" to the tree, the tree will have two nodes | |
| 76 | 75 … | |
| 77 | 76 … | The root node will be |
| 78 | 77 … | |
| 79 | 78 … | ``` |
Built with git-ssb-web