CRC16 in erlang

[Rudolph van Graan]

Hi Joe,

Here is one which I wrote some time ago. It does work, but there  
might be some issues. (No guarantees on speed!)

Rudolph van Graan

Telecommunications Specialist
Pattern Matched Technologies

E-Mail:  rvg@REDACTED
Mobile:  +27 83 390 7767
Fax:     +27 12 667 5342
Web:     www.patternmatched.com

On 31 Jan 2006, at 10:14 AM, Joe Armstrong ((AL/EAB)) wrote:



%%% File    : crc16.erl
%%% Author  : Rudolph van Graan <rvg@REDACTED>
%%% Description :
%%% Created : 18 Nov 2003 by Rudolph van Graan  
<rvg@REDACTED>

-module(crc16).

-define(CRC16Def,[16#0000, 16#C0C1, 16#C181, 16#0140, 16#C301,  
16#03C0, 16#0280, 16#C241,
                    16#C601, 16#06C0, 16#0780, 16#C741, 16#0500,  
16#C5C1, 16#C481, 16#0440,
                    16#CC01, 16#0CC0, 16#0D80, 16#CD41, 16#0F00,  
16#CFC1, 16#CE81, 16#0E40,
                    16#0A00, 16#CAC1, 16#CB81, 16#0B40, 16#C901,  
16#09C0, 16#0880, 16#C841,
                    16#D801, 16#18C0, 16#1980, 16#D941, 16#1B00,  
16#DBC1, 16#DA81, 16#1A40,
                    16#1E00, 16#DEC1, 16#DF81, 16#1F40, 16#DD01,  
16#1DC0, 16#1C80, 16#DC41,
                    16#1400, 16#D4C1, 16#D581, 16#1540, 16#D701,  
16#17C0, 16#1680, 16#D641,
                    16#D201, 16#12C0, 16#1380, 16#D341, 16#1100,  
16#D1C1, 16#D081, 16#1040,
                    16#F001, 16#30C0, 16#3180, 16#F141, 16#3300,  
16#F3C1, 16#F281, 16#3240,
                    16#3600, 16#F6C1, 16#F781, 16#3740, 16#F501,  
16#35C0, 16#3480, 16#F441,
                    16#3C00, 16#FCC1, 16#FD81, 16#3D40, 16#FF01,  
16#3FC0, 16#3E80, 16#FE41,
                    16#FA01, 16#3AC0, 16#3B80, 16#FB41, 16#3900,  
16#F9C1, 16#F881, 16#3840,
                    16#2800, 16#E8C1, 16#E981, 16#2940, 16#EB01,  
16#2BC0, 16#2A80, 16#EA41,
                    16#EE01, 16#2EC0, 16#2F80, 16#EF41, 16#2D00,  
16#EDC1, 16#EC81, 16#2C40,
                    16#E401, 16#24C0, 16#2580, 16#E541, 16#2700,  
16#E7C1, 16#E681, 16#2640,
                    16#2200, 16#E2C1, 16#E381, 16#2340, 16#E101,  
16#21C0, 16#2080, 16#E041,
                    16#A001, 16#60C0, 16#6180, 16#A141, 16#6300,  
16#A3C1, 16#A281, 16#6240,
                    16#6600, 16#A6C1, 16#A781, 16#6740, 16#A501,  
16#65C0, 16#6480, 16#A441,
                    16#6C00, 16#ACC1, 16#AD81, 16#6D40, 16#AF01,  
16#6FC0, 16#6E80, 16#AE41,
                    16#AA01, 16#6AC0, 16#6B80, 16#AB41, 16#6900,  
16#A9C1, 16#A881, 16#6840,
                    16#7800, 16#B8C1, 16#B981, 16#7940, 16#BB01,  
16#7BC0, 16#7A80, 16#BA41,
                    16#BE01, 16#7EC0, 16#7F80, 16#BF41, 16#7D00,  
16#BDC1, 16#BC81, 16#7C40,
                    16#B401, 16#74C0, 16#7580, 16#B541, 16#7700,  
16#B7C1, 16#B681, 16#7640,
                    16#7200, 16#B2C1, 16#B381, 16#7340, 16#B101,  
16#71C0, 16#7080, 16#B041,
                    16#5000, 16#90C1, 16#9181, 16#5140, 16#9301,  
16#53C0, 16#5280, 16#9241,
                    16#9601, 16#56C0, 16#5780, 16#9741, 16#5500,  
16#95C1, 16#9481, 16#5440,
                    16#9C01, 16#5CC0, 16#5D80, 16#9D41, 16#5F00,  
16#9FC1, 16#9E81, 16#5E40,
                    16#5A00, 16#9AC1, 16#9B81, 16#5B40, 16#9901,  
16#59C0, 16#5880, 16#9841,
                    16#8801, 16#48C0, 16#4980, 16#8941, 16#4B00,  
16#8BC1, 16#8A81, 16#4A40,
                    16#4E00, 16#8EC1, 16#8F81, 16#4F40, 16#8D01,  
16#4DC0, 16#4C80, 16#8C41,
                    16#4400, 16#84C1, 16#8581, 16#4540, 16#8701,  
16#47C0, 16#4680, 16#8641,
                    16#8201, 16#42C0, 16#4380, 16#8341, 16#4100,  
16#81C1, 16#8081, 16#4040]).

-export([calc/1]).

calc(List) ->
   calc(List,16#5555).
calc(<<>>,CRC) ->
   CRC;
calc([],CRC) ->
   CRC;
calc(<<Value:8,Rest/binary>>,CRC) when Value =< 255->
   Index = (CRC bxor Value) band 255,
   NewCRC = (CRC bsr 8) bxor crc_index(Index),
   calc(Rest,NewCRC);
calc([Value|Rest],CRC) when Value =< 255->
   Index = (CRC bxor Value) band 255,
   NewCRC = (CRC bsr 8) bxor crc_index(Index),
   calc(Rest,NewCRC).

crc_index(N) ->
   lists:nth(N+1,?CRC16Def).