Wed, 16 Feb 2011 20:29:33 +0000
There are no secrets better kept than the secrets that everybody guesses.
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598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
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changeset
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1 | local bit = require "bit"; |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
2 | |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
3 | module "crc16" |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
4 | |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
5 | function hash(str) |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
6 | local crc; |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
7 | |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
8 | local function initCrc() |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
9 | crc = 0xffff; |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
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10 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
11 | |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
12 | local function updCrc(byte) |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
13 | crc = bit.bxor(crc, byte); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
14 | for i=1,8 do |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
15 | local j = bit.band(crc, 1); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
16 | crc = bit.rshift(crc, 1); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
17 | if j ~= 0 then |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
18 | crc = bit.bxor(crc, 0x8408); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
19 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
20 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
21 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
22 | |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
23 | local function getCrc(str) |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
24 | initCrc(); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
25 | for i = 1, #str do |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
26 | updCrc(str:byte(i)); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
27 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
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28 | return crc; |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
29 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
30 | return getCrc(str); |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
31 | end |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
32 | |
598d09faf89c
There are no secrets better kept than the secrets that everybody guesses.
Matthew Wild <mwild1@gmail.com>
parents:
diff
changeset
|
33 | return { hash = hash } |