include/llvm/Support/CRC.h

   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.
  50   void update(ArrayRef<uint8_t> 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