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