/***********************************************************************
**
**  fletcher4.c
**
**  Copyright (C) 2024 Herbert Poetzl
**
**  gcc -Wall -O3 -march=armv8-a+crc -o fletcher4 fletcher4.c
**
**  This program is free software; you can redistribute it and/or modify
**  it under the terms of the GNU General Public License version 2 as
**  published by the Free Software Foundation.
**
***********************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#include <arm_neon.h>
#include <arm_acle.h>

uint64_t fletcher4(const uint8_t *data, size_t len)
{
    uint32x4_t vzero = (uint32x4_t){0, 0, 0, 0};
    register uint32x4_t v0, v1, v2, v3, v4;

    v0 = v1 = v2 = v3 = v4 = vzero;
    len >>= 4;

    while (len--) {
	v0 = vld1q_u32((uint32_t *)(data));
	v1 = vaddq_u32(v1, v0);
	v2 = vaddq_u32(v2, v1);
	v3 = vaddq_u32(v3, v2);
	v4 = vaddq_u32(v4, v3);

	data += 16;
    }

    uint32_t a, b, c, d;

    a = 1*vgetq_lane_u32(v1, 0) +
	1*vgetq_lane_u32(v1, 1) +
	1*vgetq_lane_u32(v1, 2) +
	1*vgetq_lane_u32(v1, 3);

    b = 4*vgetq_lane_u32(v2, 0) +
	4*vgetq_lane_u32(v2, 1) +
	4*vgetq_lane_u32(v2, 2) +
	4*vgetq_lane_u32(v2, 3) -
	1*vgetq_lane_u32(v1, 1) -
	2*vgetq_lane_u32(v1, 2) -
	3*vgetq_lane_u32(v1, 3);

    c = 16*vgetq_lane_u32(v3, 0) +
	16*vgetq_lane_u32(v3, 1) +
	16*vgetq_lane_u32(v3, 2) +
	16*vgetq_lane_u32(v3, 3) -
        6*vgetq_lane_u32(v2, 0) -
	10*vgetq_lane_u32(v2, 1) -
	14*vgetq_lane_u32(v2, 2) -
	18*vgetq_lane_u32(v2, 3) +
	1*vgetq_lane_u32(v1, 2) +
	3*vgetq_lane_u32(v1, 3);

    d = 64*vgetq_lane_u32(v4, 0) +
	64*vgetq_lane_u32(v4, 1) +
	64*vgetq_lane_u32(v4, 2) +
	64*vgetq_lane_u32(v4, 3) -
        48*vgetq_lane_u32(v3, 0) -
	64*vgetq_lane_u32(v3, 1) -
	80*vgetq_lane_u32(v3, 2) -
	96*vgetq_lane_u32(v3, 3) +
        4*vgetq_lane_u32(v2, 0) +
	10*vgetq_lane_u32(v2, 1) +
	20*vgetq_lane_u32(v2, 2) +
	34*vgetq_lane_u32(v2, 3) -
	1*vgetq_lane_u32(v1, 3);

    uint64_t result = 0;

    result = a ^ c;
    result <<= 32;
    result ^= b ^ d;

    return result;
}

int main(int argc, char* argv[])
{
    size_t len = 256;
    char *endptr;
    
    if (argc > 1)
        len = strtoull(argv[1], &endptr, 10);

    uint8_t *buf = malloc(len);

    if (!buf)
	exit(1);
    
    size_t cnt = 0;
    do {
	cnt = fread(buf, 1, len, stdin);

	if (cnt != len)
	    break;

	uint64_t fl4 = fletcher4(buf, len);

	printf("%016lX\n", fl4);


    } while (cnt == len); 
    
    exit(0);
}