MurmurHash3.cpp

#include <iostream>
#include <string>
#include <cstdint>
#include <stdint.h>
#include "MurmurHash3.h"
using namespace std;

#ifdef __cplusplus
extern "C" {
#endif

void MurmurHash3::reset() {
	_len = 0;
	_h1 = _seed;
    data.i = 0;
}

int32_t MurmurHash3::pushByte(int8_t b) 
{
	//store the current byte of input
	data.c[_len % 4] = b;
	_len++;

	static const int32_t c1 = 0xcc9e2d51;
	static const int32_t c2 = 0x1b873593;

	/**
	 * We will use this as the value of _h1 to dirty for returning to the caller
	 */
	int32_t h1_as_if_done;
	if (_len > 0 && _len % 4 == 0)    //we have a valid history of 4 items!
    {
		// little endian load order
        int32_t k1 = data.i;
        k1 *= c1;
        k1 = ROTL32(k1,15);
        k1 *= c2;

        _h1 ^= k1;
        _h1 = ROTL32(_h1,13); 
        _h1 = _h1*5+0xe6546b64;
        
		h1_as_if_done = _h1;
        data.i = 0;//data is out the window now
	} 
    else  //tail case
	{
		// tail
		int32_t k1 = data.i;
		h1_as_if_done = _h1;

        k1 *= c1;
        k1 = ROTL32(k1, 15);
        k1 *= c2;
        h1_as_if_done ^= k1;
	}

	// finalization
    h1_as_if_done ^= (int32_t)_len;

    h1_as_if_done = fmix32(h1_as_if_done);

    //  *(uint32_t*)out = h1;
    return h1_as_if_done;
}

MurmurHash3::MurmurHash3(int32_t _seed) {
	this->_seed = _seed;
    this->reset();
}

#ifdef __cplusplus
}
#endif