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59 lines
1.2 KiB
C++
59 lines
1.2 KiB
C++
//
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// FILE: Adler.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.1
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// DATE: 2022-01-27
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// PURPOSE: Arduino Library for calculating Adler checksum
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// URL: https://github.com/RobTillaart/Adler
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// https://en.wikipedia.org/wiki/Adler-32
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// (no Adler16 reference, implementation is experimental)
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#include "Adler.h"
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//////////////////////////////////////////////////////////////
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//
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// STATIC FUNCTION
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//
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uint32_t adler32(uint8_t * array, uint16_t length)
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{
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uint32_t s1 = 1;
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uint32_t s2 = 0;
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for (uint16_t i = 0; i < length;)
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{
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// if S2 is halfway it is time to do modulo
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while ((i < length) && (s2 < 2147483648ULL))
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{
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s1 += array[i++];
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s2 += s1;
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}
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s1 %= ADLER32_MOD_PRIME;
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s2 %= ADLER32_MOD_PRIME;
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}
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return (s2 << 16) | s1;
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}
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uint16_t adler16(uint8_t * array, uint16_t length)
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{
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uint16_t s1 = 1;
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uint16_t s2 = 0;
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for (uint16_t i = 0; i < length;)
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{
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// if S2 is halfway it is time to do modulo
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while ((i < length) && (s2 < 32768))
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{
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s1 += array[i++];
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s2 += s1;
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}
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s1 %= ADLER16_MOD_PRIME;
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s2 %= ADLER16_MOD_PRIME;
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}
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return (s2 << 8) | s1;
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}
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// -- END OF FILE --
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