From 01445c3287b5055c9f87f4596e3c7af5774247c7 Mon Sep 17 00:00:00 2001 From: Dobrica Pavlinusic Date: Sun, 4 Apr 2004 21:04:47 +0000 Subject: [PATCH] even more detail explanation git-svn-id: file:///home/dpavlin/private/svn/webpac/trunk@300 13eb9ef6-21d5-0310-b721-a9d68796d827 --- doc/exact_match.txt | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/doc/exact_match.txt b/doc/exact_match.txt index 472cb28..2dbb277 100644 --- a/doc/exact_match.txt +++ b/doc/exact_match.txt @@ -30,18 +30,22 @@ on TitleAndResponsibility, you would use: What are bit-masks? -Bit-mask is usage of one byte (8 bits) as 8 separate bits with it's own meaning. -So, 1 = 2^1, thus it's bit 1. So, for 1-3 we have: +Bit-mask is usage of one byte (8 bits) as 8 separate bits with it's own +meaning (this is simplification, but bear with me for now). + +So, 1 = 2^0, thus it's bit 1. With analogy, 2=2^1 and 3=2^0+2^1. +So, for 1-3 we use two bits and have: number bits -1 01 -2 10 -3 11 +1 01 (just begin bit set) +2 10 (just end bit set) +3 11 (begin and end bit set) -For that we are using two bits. If we want to produce wild-card match, we use -bit 3 (2^3 = 4) so we have: +Thus, with two bits (and values 1-3) we can express should we exact match from +beginning, end or both. For wild-card match, we use additional bit 3 (2^3 = 4) +so we have: -number bits +number bits exact match 1 001 begin 2 010 end 3 011 begin+end @@ -49,3 +53,4 @@ number bits 5 101 (4+1) begin+wild-card 6 110 (4+2) end+wild-card 7 111 (4+3) begin+end+wild-card + -- 2.20.1