rcpp_framework/backends/hash_hashlib/hash-library/crc32.h

70 lines
1.7 KiB
C++

// //////////////////////////////////////////////////////////
// crc32.h
// Copyright (c) 2014,2015 Stephan Brumme. All rights reserved.
// see http://create.stephan-brumme.com/disclaimer.html
//
#pragma once
//#include "hash.h"
#include <string>
// define fixed size integer types
#ifdef _MSC_VER
// Windows
typedef unsigned __int8 uint8_t;
typedef unsigned __int32 uint32_t;
#else
// GCC
#include <stdint.h>
#endif
/// compute CRC32 hash, based on Intel's Slicing-by-8 algorithm
/** Usage:
CRC32 crc32;
std::string myHash = crc32("Hello World"); // std::string
std::string myHash2 = crc32("How are you", 11); // arbitrary data, 11 bytes
// or in a streaming fashion:
CRC32 crc32;
while (more data available)
crc32.add(pointer to fresh data, number of new bytes);
std::string myHash3 = crc32.getHash();
Note:
You can find code for the faster Slicing-by-16 algorithm on my website, too:
http://create.stephan-brumme.com/crc32/
Its unrolled version is about twice as fast but its look-up table doubled in size as well.
*/
class CRC32 //: public Hash
{
public:
/// hash is 4 bytes long
enum { HashBytes = 4 };
/// same as reset()
CRC32();
/// compute CRC32 of a memory block
std::string operator()(const void* data, size_t numBytes);
/// compute CRC32 of a string, excluding final zero
std::string operator()(const std::string& text);
/// add arbitrary number of bytes
void add(const void* data, size_t numBytes);
/// return latest hash as 8 hex characters
std::string getHash();
/// return latest hash as bytes
void getHash(unsigned char buffer[HashBytes]);
/// restart
void reset();
private:
/// hash
uint32_t m_hash;
};