LLVM  8.0.0svn
JamCRC.cpp
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1 //===-- JamCRC.cpp - Cyclic Redundancy Check --------------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains an implementation of JamCRC.
11 //
12 //===----------------------------------------------------------------------===//
13 //
14 // The implementation technique is the one mentioned in:
15 // D. V. Sarwate. 1988. Computation of cyclic redundancy checks via table
16 // look-up. Commun. ACM 31, 8 (August 1988)
17 //
18 //===----------------------------------------------------------------------===//
19 
20 #include "llvm/Support/JamCRC.h"
21 #include "llvm/ADT/ArrayRef.h"
22 
23 using namespace llvm;
24 
25 static const uint32_t CRCTable[256] = {
26  0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
27  0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
28  0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
29  0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
30  0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
31  0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
32  0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
33  0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
34  0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
35  0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
36  0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
37  0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
38  0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
39  0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
40  0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
41  0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
42  0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
43  0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
44  0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
45  0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
46  0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
47  0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
48  0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
49  0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
50  0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
51  0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
52  0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
53  0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
54  0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
55  0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
56  0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
57  0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
58  0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
59  0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
60  0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
61  0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
62  0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
63  0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
64  0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
65  0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
66  0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
67  0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
68  0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
69  0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
70  0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
71  0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
72  0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
73  0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
74  0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
75  0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
76  0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
77  0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
78  0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
79  0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
80  0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
81  0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
82  0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
83  0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
84  0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
85  0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
86  0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
87  0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
88  0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
89  0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
90 };
91 
93  for (char Byte : Data) {
94  int TableIdx = (CRC ^ Byte) & 0xff;
95  CRC = CRCTable[TableIdx] ^ (CRC >> 8);
96  }
97 }
This class represents lattice values for constants.
Definition: AllocatorList.h:24
static const uint32_t CRCTable[256]
Definition: JamCRC.cpp:25
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
void update(ArrayRef< char > Data)
Definition: JamCRC.cpp:92