9 releases

0.4.0 May 22, 2019
0.3.1 Jun 10, 2018
0.2.3 Jun 10, 2018
0.2.2 Jan 12, 2017
0.1.1 Jan 29, 2016

#79 in Data structures

Download history 2172/week @ 2019-07-27 2305/week @ 2019-08-03 677/week @ 2019-08-10 795/week @ 2019-08-17 237/week @ 2019-08-24 1063/week @ 2019-08-31 864/week @ 2019-09-07 269/week @ 2019-09-14 661/week @ 2019-09-21 712/week @ 2019-09-28 946/week @ 2019-10-05 490/week @ 2019-10-12 672/week @ 2019-10-19 377/week @ 2019-10-26 160/week @ 2019-11-02

648 downloads per month
Used in 1 crate

MIT license

78KB
1.5K SLoC

Tree-Bitmap: Fast lookup table for IPv4/IPv6 prefixes

This crate provides a datastructure for fast IP address lookups. It aims at fast lookup times, and a reasonable memory footprint.

The internal datastructure is based on the Tree-bitmap algorithm described by W. Eatherton, Z. Dittia, G. Varghes.

Documentation

Rustdoc: https://docs.rs/treebitmap/

Illustration

An example illustration of a trie representing a routing table containing 0.0.0.0/0 (foo), 10.0.0.0/8 (bar), 172.16.0.0/12 (baz) and 192.168.0.0/16 (quux).

rfc1918 trie illustration

Internal trie datastructure basics

Node encodes result and child node pointers in a bitmap.

A trie node can encode up to 31 results when acting as an "end node", or 15 results and 16 children/subtrees when acting as a normal/internal node.

Each bit in the bitmap indicates a bit matching pattern:

bit 0 1 2 3 4 5 6 7
match * 0* 1* 00* 01* 10* 11* 000*
bit 8 9 10 11 12 13 14 15
match 001* 010* 011* 100* 101* 110* 111* endnode-bit

The last bit here does not indicate a pattern. It instead indicates if this node is an "end node". End nodes carry double the amount of results but can't encode any child pointers.

bit 16 17 18 19 20 21 22 23
match 0000* 0001* 0010* 0011* 0100* 0101* 0110* 0111*
bit 24 25 26 27 28 29 30 31
match 1000* 1001* 1010* 1011* 1100* 1101* 1110* 1111*

The location of the result value is computed by adding the result_ptr base pointer and its position among set bits.

If the endnode bit is not set, the last 16 bits encodes pointers to child nodes. If bit N is set it means that a child node with segment value N is present. The pointer to the child node is then computed by adding the child_ptr base pointer and its position among set bits.

No runtime deps