CRC.h revision 360784 
1//===-- llvm/Support/CRC.h - Cyclic Redundancy Check-------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains implementations of CRC functions.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_SUPPORT_CRC_H
14#define LLVM_SUPPORT_CRC_H
15
16#include "llvm/Support/DataTypes.h"
17
18namespace llvm {
19template <typename T> class ArrayRef;
20
21// Compute the CRC-32 of Data.
22uint32_t crc32(ArrayRef<uint8_t> Data);
23
24// Compute the running CRC-32 of Data, with CRC being the previous value of the
25// checksum.
26uint32_t crc32(uint32_t CRC, ArrayRef<uint8_t> Data);
27
28// Class for computing the JamCRC.
29//
30// We will use the "Rocksoft^tm Model CRC Algorithm" to describe the properties
31// of this CRC:
32//   Width  : 32
33//   Poly   : 04C11DB7
34//   Init   : FFFFFFFF
35//   RefIn  : True
36//   RefOut : True
37//   XorOut : 00000000
38//   Check  : 340BC6D9 (result of CRC for "123456789")
39//
40// In other words, this is the same as CRC-32, except that XorOut is 0 instead
41// of FFFFFFFF.
42//
43// N.B.  We permit flexibility of the "Init" value.  Some consumers of this need
44//       it to be zero.
45class JamCRC {
46public:
47  JamCRC(uint32_t Init = 0xFFFFFFFFU) : CRC(Init) {}
48
49  // Update the CRC calculation with Data.
50  void update(ArrayRef<uint8_t> Data);
51
52  uint32_t getCRC() const { return CRC; }
53
54private:
55  uint32_t CRC;
56};
57
58} // end namespace llvm
59
60#endif
61