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  are met:
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

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#include <stdint.h>
#include "igzip_checksums.h"

uint32_t
adler32_base(uint32_t adler32, uint8_t *start, uint64_t length)
{
        uint8_t *end, *next = start;
        uint64_t A, B;

        A = adler32 & 0xffff;
        B = adler32 >> 16;

        while (length > MAX_ADLER_BUF) {
                end = next + MAX_ADLER_BUF;
                for (; next < end; next++) {
                        A += *next;
                        B += A;
                }

                A = A % ADLER_MOD;
                B = B % ADLER_MOD;
                length -= MAX_ADLER_BUF;
        }

        end = next + length;
        for (; next < end; next++) {
                A += *next;
                B += A;
        }

        A = A % ADLER_MOD;
        B = B % ADLER_MOD;

        return B << 16 | A;
}
