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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.
  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
  61.