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Created Oct 12, 2018
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#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#define CST 11246805480246805480ULL
static uint64_t load64_le(uint8_t const* V)
#if !defined(__LITTLE_ENDIAN__)
#error This code only works with little endian systems
uint64_t Ret = *((uint64_t const*)V);
return Ret;
static uint64_t hash(const uint8_t* Data, const size_t Len)
uint64_t Ret = 0;
const size_t NBlocks = Len/8;
for (size_t I = 0; I < NBlocks; ++I) {
const uint64_t V = load64_le(&Data[I*sizeof(uint64_t)]);
Ret = (Ret ^ V)*CST;
uint64_t LastV = 0;
for (size_t I = 0; I < (Len-NBlocks*8); ++I) {
LastV |= ((uint64_t)Data[NBlocks*8+I]) << (I*8);
Ret = (Ret^LastV)*CST;
return Ret;
int main(int argc, char** argv)
if (argc < 2) {
fprintf(stderr, "Usage: %s string\n", argv[0]);
return 1;
const char* Str = argv[1];
const uint64_t H = hash((const uint8_t*) Str, strlen(Str));
printf("%016" PRIX64 "\n", H);
return 0;
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