llvm/Support/CRC.h

0001 //===-- llvm/Support/CRC.h - Cyclic Redundancy Check-------------*- C++ -*-===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008 //
0009 // This file contains implementations of CRC functions.
0010 //
0011 //===----------------------------------------------------------------------===//
0012
0013 #ifndef LLVM_SUPPORT_CRC_H
0014 #define LLVM_SUPPORT_CRC_H
0015
0016 #include "llvm/Support/DataTypes.h"
0017
0018 namespace llvm {
0019 template <typename T> class ArrayRef;
0020
0021 // Compute the CRC-32 of Data.
0022 uint32_t crc32(ArrayRef<uint8_t> Data);
0023
0024 // Compute the running CRC-32 of Data, with CRC being the previous value of the
0025 // checksum.
0026 uint32_t crc32(uint32_t CRC, ArrayRef<uint8_t> Data);
0027
0028 // Class for computing the JamCRC.
0029 //
0030 // We will use the "Rocksoft^tm Model CRC Algorithm" to describe the properties
0031 // of this CRC:
0032 //   Width  : 32
0033 //   Poly   : 04C11DB7
0034 //   Init   : FFFFFFFF
0035 //   RefIn  : True
0036 //   RefOut : True
0037 //   XorOut : 00000000
0038 //   Check  : 340BC6D9 (result of CRC for "123456789")
0039 //
0040 // In other words, this is the same as CRC-32, except that XorOut is 0 instead
0041 // of FFFFFFFF.
0042 //
0043 // N.B.  We permit flexibility of the "Init" value.  Some consumers of this need
0044 //       it to be zero.
0045 class JamCRC {
0046 public:
0047   JamCRC(uint32_t Init = 0xFFFFFFFFU) : CRC(Init) {}
0048
0049   // Update the CRC calculation with Data.
0050   void update(ArrayRef<uint8_t> Data);
0051
0052   uint32_t getCRC() const { return CRC; }
0053
0054 private:
0055   uint32_t CRC;
0056 };
0057
0058 } // end namespace llvm
0059
0060 #endif