tools_func.c

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/*
 * (C) Copyright 2017 UCAR
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 */
 
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
 
uint32_t fletcher32(uint32_t *n, uint16_t const *var)
{
  uint32_t sum1 = 0xffff, sum2 = 0xffff;
  size_t tlen; uint32_t words = *n;
  while (words) {
    tlen = ((words >= 359) ? 359 : words);
    words -= tlen;
    do {
      sum2 += sum1 += *var++;
      tlen--;
    } while (tlen);
      sum1 = (sum1 & 0xffff) + (sum1 >> 16);
      sum2 = (sum2 & 0xffff) + (sum2 >> 16);
  }
  sum1 = (sum1 & 0xffff) + (sum1 >> 16);
  sum2 = (sum2 & 0xffff) + (sum2 >> 16);
  return (sum2 << 16) | sum1;
}