| US 7,539,153 B1 | ||
| Method and apparatus for longest prefix matching based on a trie | ||
| Jun Liang, Shenzhen (China); Shijun Shen, Shenzhen (China); Meng Li, Shenzhen (China); Juan Zhang, Shenzhen (China); Rui Hu, Shenzhen (China); and Jun Gong, Shenzhen (China) | ||
| Assigned to Huawei Technologies Co., Ltd., Shenzhen, Guangdong (China) | ||
| Filed on Sep. 30, 2008, as Appl. No. 12/241,513. | ||
| Claims priority of application No. 2008 1 0096906 (CN), filed on May 05, 2008. | ||
| Int. Cl. G01R 31/08 (2006.01) | ||
| U.S. Cl. 370—255 [370/256; 370/389] | 15 Claims |
| 1. A method for longest prefix matching based on a trie, wherein the trie represents multiple prefixes with a prefix distinguished
by at least one step and each step indicated by one node, the method comprising the steps of:
(A) reading a current-level trie node (TNODE) from a memory in the trie by a search engine;
(B) determining whether an offset field of the TNODE indicates that a matched prefix exists in an upper level node by the
search engine, if a matched prefix exists in the upper level node, adding the offset field of the TNODE to a pointer that
points to a leaf array in the upper level node, updating a current best match pointer with the computation result and executing
step (C); or, if no matched prefix exists in the upper level node, executing step (C);
(C) determining whether the TNODE has a child node according to a child bitmap, when a branch flag of the TNODE matches a
corresponding bit of a search keyword, by the search engine; and
(D) when the TNODE has no child node, reading an internal bitmap of the TNODE, computing a longest matched prefix in the TNODE
according to the internal bitmap and a pointer that points to a leaf array in the TNODE, updating the current best match pointer
with the computation result, and computing an address of a leaf node (LNODE) associated with the current best match pointer
by the search engine.
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