GY-63_MS5611/libraries/Adler/Adler16.cpp
2023-01-16 16:33:37 +01:00

134 lines
2.3 KiB
C++

//
// FILE: Adler16.cpp
// AUTHOR: Rob Tillaart
// VERSION: 0.2.3
// DATE: 2022-06-14
// PURPOSE: Arduino Library for calculating Adler-16 checksum
// URL: https://github.com/RobTillaart/Adler
// https://en.wikipedia.org/wiki/Adler-32
// (no Adler16 reference, implementation is experimental)
#include "Adler16.h"
Adler16::Adler16()
{
begin(1, 0);
}
void Adler16::begin(uint16_t s1, uint16_t s2)
{
_s1 = s1;
_s2 = s2;
_count = 0;
}
// reference implementation
// void Adler16::add(uint8_t value)
// {
// _count++;
// _s1 += value;
// if (_s1 >= ADLER16_MOD_PRIME) _s1 -= ADLER16_MOD_PRIME;
// _s2 += _s1;
// if (_s2 >= ADLER16_MOD_PRIME) _s2 -= ADLER16_MOD_PRIME;
// }
// optimized version (~10% faster)
void Adler16::add(uint8_t value)
{
_count++;
_s1 += value;
_s2 += _s1;
if (_s2 >= ADLER16_MOD_PRIME)
{
_s2 -= ADLER16_MOD_PRIME;
if (_s1 >= ADLER16_MOD_PRIME) _s1 -= ADLER16_MOD_PRIME;
}
}
// straightforward going through the array.
// small footprint
// returns current Adler value
uint16_t Adler16::add(uint8_t * array, uint16_t length)
{
while (length--)
{
add(*array++);
}
return (_s2 << 8) | _s1;
}
// Optimized version
// S1 grows linear
// S2 grows quadratic
// only do modulo when S2 reaches halfway uint16_t
// and at the end of the loop.
// returns current Adler value
uint16_t Adler16::addFast(uint8_t * array, uint16_t length)
{
_count += length;
uint16_t s1 = _s1;
uint16_t s2 = _s2;
for (uint16_t i = 0; i < length;)
{
// if S2 is halfway it is time to do modulo
while ((i < length) && (s2 < 32768))
{
s1 += array[i++];
s2 += s1;
}
if (s2 >= ADLER16_MOD_PRIME)
{
s2 %= ADLER16_MOD_PRIME;
if (s1 >= ADLER16_MOD_PRIME) s1 %= ADLER16_MOD_PRIME;
}
}
_s1 = s1;
_s2 = s2;
return (s2 << 8) | s1;
}
uint16_t Adler16::getAdler()
{
return (_s2 << 8) | _s1;
};
uint16_t Adler16::count()
{
return _count;
};
//////////////////////////////////////////////////////////////
//
// wrappers for strings.
//
void Adler16::add(char value)
{
add((uint8_t) value);
}
uint16_t Adler16::add(char * array, uint16_t length)
{
return add((uint8_t *) array, length);
}
uint16_t Adler16::addFast(char * array, uint16_t length)
{
return addFast((uint8_t *) array, length);
}
// -- END OF FILE --