LLVM  10.0.0svn
CRC.h
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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 
18 namespace llvm {
19 template <typename T> class ArrayRef;
20 
21 // Compute the CRC-32 of Data.
22 uint32_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.
26 uint32_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.
45 class JamCRC {
46 public:
47  JamCRC(uint32_t Init = 0xFFFFFFFFU) : CRC(Init) {}
48 
49  // Update the CRC calculation with Data.
51 
52  uint32_t getCRC() const { return CRC; }
53 
54 private:
55  uint32_t CRC;
56 };
57 
58 } // end namespace llvm
59 
60 #endif
uint32_t crc32(ArrayRef< uint8_t > Data)
Definition: CRC.cpp:93
uint32_t getCRC() const
Definition: CRC.h:52
JamCRC(uint32_t Init=0xFFFFFFFFU)
Definition: CRC.h:47
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void update(ArrayRef< uint8_t > Data)
Definition: CRC.cpp:95