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73 lines
1.6 KiB
C++
73 lines
1.6 KiB
C++
//
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// FILE: Adler.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.5
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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, uint32_t s1, uint32_t s2)
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{
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uint32_t _s1 = s1;
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uint32_t _s2 = s2;
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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 < 2147483648UL)) // MAGIC NUMBER 2^31
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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, uint16_t s1, uint16_t s2)
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{
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uint16_t _s1 = s1;
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uint16_t _s2 = s2;
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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)) // MAGIC NUMBER 2^15
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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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// char array wrappers
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uint32_t adler32(char * array, uint16_t length, uint32_t s1, uint32_t s2)
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{
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return adler32((uint8_t *) array, length, s1, s2);
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}
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uint16_t adler16(char * array, uint16_t length, uint16_t s1, uint16_t s2)
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{
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return adler16((uint8_t *) array, length, s1, s2);
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}
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// -- END OF FILE --
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