1 files changed, 40 insertions, 5 deletions
diff --git a/include/llvm/Support/CRC.h b/include/llvm/Support/CRC.h
index 6ea8e3edcea4..210890ae06d4 100644
--- a/include/llvm/Support/CRC.h
+++ b/include/llvm/Support/CRC.h
@@ -6,20 +6,55 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file contains basic functions for calculating Cyclic Redundancy Check
-// or CRC.
+// This file contains implementations of CRC functions.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_CRC_H
 #define LLVM_SUPPORT_CRC_H
 
-#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/DataTypes.h"
 
 namespace llvm {
-/// zlib independent CRC32 calculation.
-uint32_t crc32(uint32_t CRC, StringRef S);
+template <typename T> class ArrayRef;
+
+// Compute the CRC-32 of Data.
+uint32_t crc32(ArrayRef<uint8_t> Data);
+
+// Compute the running CRC-32 of Data, with CRC being the previous value of the
+// checksum.
+uint32_t crc32(uint32_t CRC, ArrayRef<uint8_t> Data);
+
+// Class for computing the JamCRC.
+//
+// We will use the "Rocksoft^tm Model CRC Algorithm" to describe the properties
+// of this CRC:
+//   Width  : 32
+//   Poly   : 04C11DB7
+//   Init   : FFFFFFFF
+//   RefIn  : True
+//   RefOut : True
+//   XorOut : 00000000
+//   Check  : 340BC6D9 (result of CRC for "123456789")
+//
+// In other words, this is the same as CRC-32, except that XorOut is 0 instead
+// of FFFFFFFF.
+//
+// N.B.  We permit flexibility of the "Init" value.  Some consumers of this need
+//       it to be zero.
+class JamCRC {
+public:
+  JamCRC(uint32_t Init = 0xFFFFFFFFU) : CRC(Init) {}
+
+  // Update the CRC calculation with Data.
+  void update(ArrayRef<uint8_t> Data);
+
+  uint32_t getCRC() const { return CRC; }
+
+private:
+  uint32_t CRC;
+};
+
 } // end namespace llvm
 
 #endif