--- trunk/doc/exact_match.txt 2004/04/04 20:48:56 299
+++ trunk/doc/exact_match.txt 2004/04/04 21:04:47 300
@@ -30,18 +30,22 @@
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 @@
5 101 (4+1) begin+wild-card
6 110 (4+2) end+wild-card
7 111 (4+3) begin+end+wild-card
+