From 7c56be8a724e2b0647e5a6cbd55c7b0eb948206b Mon Sep 17 00:00:00 2001
From: Sebastian Muszytowski <sebastian@muszytowski.net>
Date: Fri, 3 Jun 2016 15:48:16 +0200
Subject: initial commit of all data

---
 src/Hamming/HammingCalculateParitySmallAndFast.c | 64 ++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 src/Hamming/HammingCalculateParitySmallAndFast.c

(limited to 'src/Hamming/HammingCalculateParitySmallAndFast.c')

diff --git a/src/Hamming/HammingCalculateParitySmallAndFast.c b/src/Hamming/HammingCalculateParitySmallAndFast.c
new file mode 100644
index 0000000..ad27bf8
--- /dev/null
+++ b/src/Hamming/HammingCalculateParitySmallAndFast.c
@@ -0,0 +1,64 @@
+/*
+Hamming Error-Correcting Code (ECC)
+Optimized for avr-gcc 4.8.1 in Atmel AVR Studio 6.2
+August 12, 2014
+
+You should include Hamming.c, Hamming.h, and only one of the other Hamming files in your project.
+The other Hamming files implement the same methods in different ways, that may be better or worse for your needs.
+
+This was created for LoFi in the TheHackadayPrize contest.
+http://hackaday.io/project/1552-LoFi
+
+Copyright 2014 David Cook
+RobotRoom.com
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include <avr/pgmspace.h>
+
+#include "Hamming.h"
+
+/****************************/
+/*                          */
+/*     Global variables     */
+/*                          */
+/****************************/
+
+// This contains all of the precalculated parity values for a nibble (4 bits).
+static const byte _hammingCalculateParityLowNibble[] PROGMEM =
+{ 0,  3,  5,  6,  6,  5,  3,  0,  7,  4,  2,  1,  1,  2,  4,  7 };
+
+static const byte _hammingCalculateParityHighNibble[] PROGMEM =
+{ 0,  9, 10,  3, 11,  2,  1,  8, 12,  5,  6, 15,  7, 14, 13,  4 };
+
+
+/****************************/
+/*                          */
+/*      Public  methods     */
+/*                          */
+/****************************/
+
+// Given a byte to transmit, this returns the parity as a nibble
+nibble HammingCalculateParity128(byte value)
+{
+	return pgm_read_byte(&(_hammingCalculateParityLowNibble[value&0x0F])) ^ pgm_read_byte(&(_hammingCalculateParityHighNibble[value >> 4]));
+}
+
+// Given two bytes to transmit, this returns the parity
+// as a byte with the lower nibble being for the first byte,
+// and the upper nibble being for the second byte.
+byte HammingCalculateParity2416(byte first, byte second)
+{
+	return HammingCalculateParity128(second) << 4 | HammingCalculateParity128(first);
+}
-- 
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