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#ifndef TENSORFLOW_LIB_HASH_CRC32C_H_
#define TENSORFLOW_LIB_HASH_CRC32C_H_
#include <stddef.h>
#include "tensorflow/core/platform/port.h"
namespace tensorflow {
namespace crc32c {
// Return the crc32c of concat(A, data[0,n-1]) where init_crc is the
// crc32c of some string A. Extend() is often used to maintain the
// crc32c of a stream of data.
extern uint32 Extend(uint32 init_crc, const char* data, size_t n);
// Return the crc32c of data[0,n-1]
inline uint32 Value(const char* data, size_t n) { return Extend(0, data, n); }
static const uint32 kMaskDelta = 0xa282ead8ul;
// Return a masked representation of crc.
//
// Motivation: it is problematic to compute the CRC of a string that
// contains embedded CRCs. Therefore we recommend that CRCs stored
// somewhere (e.g., in files) should be masked before being stored.
inline uint32 Mask(uint32 crc) {
// Rotate right by 15 bits and add a constant.
return ((crc >> 15) | (crc << 17)) + kMaskDelta;
}
// Return the crc whose masked representation is masked_crc.
inline uint32 Unmask(uint32 masked_crc) {
uint32 rot = masked_crc - kMaskDelta;
return ((rot >> 17) | (rot << 15));
}
} // namespace crc32c
} // namespace tensorflow
#endif // TENSORFLOW_LIB_HASH_CRC32C_H_
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