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

source code of llvm/include/llvm/Support/CRC.h