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Diffstat (limited to 'src/Hamming/HammingCalculateParityFast.c')
| -rw-r--r-- | src/Hamming/HammingCalculateParityFast.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/src/Hamming/HammingCalculateParityFast.c b/src/Hamming/HammingCalculateParityFast.c new file mode 100644 index 0000000..6cc5df6 --- /dev/null +++ b/src/Hamming/HammingCalculateParityFast.c @@ -0,0 +1,67 @@ +/* +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" + + +// This contains all of the precalculated parity values for a byte (8 bits). +// This is very fast, but takes up more program space than calculating on the fly. +static const byte _hammingCalculateParityFast128[256] PROGMEM = +{ + 0, 3, 5, 6, 6, 5, 3, 0, 7, 4, 2, 1, 1, 2, 4, 7, + 9, 10, 12, 15, 15, 12, 10, 9, 14, 13, 11, 8, 8, 11, 13, 14, + 10, 9, 15, 12, 12, 15, 9, 10, 13, 14, 8, 11, 11, 8, 14, 13, + 3, 0, 6, 5, 5, 6, 0, 3, 4, 7, 1, 2, 2, 1, 7, 4, + 11, 8, 14, 13, 13, 14, 8, 11, 12, 15, 9, 10, 10, 9, 15, 12, + 2, 1, 7, 4, 4, 7, 1, 2, 5, 6, 0, 3, 3, 0, 6, 5, + 1, 2, 4, 7, 7, 4, 2, 1, 6, 5, 3, 0, 0, 3, 5, 6, + 8, 11, 13, 14, 14, 13, 11, 8, 15, 12, 10, 9, 9, 10, 12, 15, + 12, 15, 9, 10, 10, 9, 15, 12, 11, 8, 14, 13, 13, 14, 8, 11, + 5, 6, 0, 3, 3, 0, 6, 5, 2, 1, 7, 4, 4, 7, 1, 2, + 6, 5, 3, 0, 0, 3, 5, 6, 1, 2, 4, 7, 7, 4, 2, 1, + 15, 12, 10, 9, 9, 10, 12, 15, 8, 11, 13, 14, 14, 13, 11, 8, + 7, 4, 2, 1, 1, 2, 4, 7, 0, 3, 5, 6, 6, 5, 3, 0, + 14, 13, 11, 8, 8, 11, 13, 14, 9, 10, 12, 15, 15, 12, 10, 9, + 13, 14, 8, 11, 11, 8, 14, 13, 10, 9, 15, 12, 12, 15, 9, 10, + 4, 7, 1, 2, 2, 1, 7, 4, 3, 0, 6, 5, 5, 6, 0, 3, +}; + +// Given a byte to transmit, this returns the parity as a nibble +nibble HammingCalculateParity128(byte value) +{ + return pgm_read_byte(&(_hammingCalculateParityFast128[value])); +} + +// 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 (pgm_read_byte(&(_hammingCalculateParityFast128[second]))<<4) | pgm_read_byte(&(_hammingCalculateParityFast128[first])); +} |