packing::utility::CRC Class Reference

The HGC ROC and FPGA use a CRC checksum to double check that the data transfer has been done correctly. More...

#include <CRC.h>

Public Member Functions
template<typename WordType , std::enable_if_t< std::is_integral< WordType >::value, bool > = true>
CRC &	operator<< (const WordType &w)
	Stream an integral type into the calculator.
template<typename ObjectType , std::enable_if_t< std::is_class< ObjectType >::value, bool > = true>
CRC &	operator<< (const ObjectType &o)
	Stream an instance of a class into the calculator.
template<typename ContentType >
CRC &	operator<< (const std::vector< ContentType > &vec)
	Stream a vector of objects into the calculator.
uint32_t	get ()
	Get the calculate checksum from the calculator.

Private Attributes
boost::crc_32_type	crc
	the object from Boost doing the summing

Detailed Description

The HGC ROC and FPGA use a CRC checksum to double check that the data transfer has been done correctly.

Boost has a CRC checksum library that we can use to do this checking here as well.

Idea for this helper struct was found on StackOverflow https://stackoverflow.com/a/63237679 I've actually simplified it by limiting its use-case to our type of data which is integral types, classes with the 'add' method defined, and vectors of those types.

This is a very light class and is meant to be used as a calculator. It involves some fancy-shamncy template specialization using std::enable_if in order for the streaming operator to function.

Example

class MyObject { public: CRC& add(CRC& c) { c << my_member_int_; } private: uint64_t my_member_int_; } my_object;

CRC c; c << 0xffff << std::vector<uint16_t>({0xffff, 0x00ff}) << my_object; uint32_t the_sum = c.get();

Limitations

This design limits the inputs to the calculator to two main categories.

1. Integral types (e.g. bool, int, unsigned int, long, char, ...)
2. Classes with the 'CRC& add(CRC&)' method defined
3. A std::vector of objects in (1) or (2) This means you will get a compiler error if you attempt to stream an object not fitting into one of these categories.

Definition at line 50 of file CRC.h.

Member Function Documentation

get()

uint32_t packing::utility::CRC::get ( )

inline

Get the calculate checksum from the calculator.

Returns

uint32_t checksum

Definition at line 110 of file CRC.h.

{ return crc.checksum(); }

References crc.

Referenced by packing::rawdatafile::File::close(), packing::rawdatafile::EventPacket::EventPacket(), packing::rawdatafile::File::File(), ecal::EcalRawEncoder::produce(), hcal::HcalRawDecoder::read(), and packing::rawdatafile::SubsystemPacket::SubsystemPacket().

operator<<() [1/3]

template<typename ObjectType , std::enable_if_t< std::is_class< ObjectType >::value, bool > = true>

CRC & packing::utility::CRC::operator<< ( const ObjectType &  o )

inline

Stream an instance of a class into the calculator.

Here, we assume that the class we are streaming into the calculator has a specific public method defined.

CRC& add(CRC& c)

and the user can insert the subcomponents to the calculator within this method.

Parameters

o	instance of an arbitrary class

Returns

CRC modified calculator

Definition at line 86 of file CRC.h.

                                       {
    return o.add(*this);
  }

operator<<() [2/3]

template<typename ContentType >

CRC & packing::utility::CRC::operator<< ( const std::vector< ContentType > &  vec )

inline

Stream a vector of objects into the calculator.

When the compiler deduces that the input to the stream is a vector, we simply call the stream operator on all members of the vector in sequence.

Parameters

[in]

vec

vector of objects to insert into calculator

Returns

CRC modified calculator

Definition at line 101 of file CRC.h.

                                                     {
    for (auto const& w : vec) *this << w;
    return *this;
  }

operator<<() [3/3]

template<typename WordType , std::enable_if_t< std::is_integral< WordType >::value, bool > = true>

CRC & packing::utility::CRC::operator<< ( const WordType &  w )

inline

Stream an integral type into the calculator.

This is only enabled for integral types i.e. it looks like this definition doesn't exist for types that are non-integral. Look at the C++ reference for std::is_integral to see a full list of integral types.

Parameters

w	integral-type word to insert into calculator

Returns

CRC modified calculator

Definition at line 65 of file CRC.h.

                                     {
    crc.process_bytes(&w, sizeof(WordType));
    return *this;
  }

References crc.

Member Data Documentation

crc

boost::crc_32_type packing::utility::CRC::crc

private

the object from Boost doing the summing

Definition at line 114 of file CRC.h.

Referenced by get(), and operator<<().

---

The documentation for this class was generated from the following file:

• Packing/include/Packing/Utility/CRC.h