include/ipmid/message.hpp - openbmc/phosphor-host-ipmid - Gitiles

 /**
  * Copyright © 2018 Intel Corporation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 #pragma once

 #include <algorithm>
 #include <boost/asio/spawn.hpp>
 #include <cstdint>
 #include <exception>
 #include <ipmid/api-types.hpp>
 #include <ipmid/message/types.hpp>
 #include <memory>
 #include <phosphor-logging/log.hpp>
 #include <tuple>
 #include <utility>
 #include <vector>

 namespace ipmi
 {

 struct Context
 {
     using ptr = std::shared_ptr<Context>;

     Context() = default;

     Context(NetFn netFn, Cmd cmd, int channel, int userId, Privilege priv,
             int rqSA = 0, boost::asio::yield_context* yield = nullptr) :
         netFn(netFn),
         cmd(cmd), channel(channel), userId(userId), priv(priv), rqSA(rqSA),
         yield(yield)
     {
     }

     // normal IPMI context (what call is this, from whence it came...)
     NetFn netFn = 0;
     Cmd cmd = 0;
     int channel = 0;
     int userId = 0;
     Privilege priv = Privilege::None;
     // srcAddr is only set on IPMB requests because
     // Platform Event Message needs it to determine the incoming format
     int rqSA = 0;
     // if non-null, use this to do blocking asynchronous asio calls
     boost::asio::yield_context* yield = nullptr;
 };

 namespace message
 {

 namespace details
 {

 template <typename A>
 struct UnpackSingle;

 template <typename T>
 using UnpackSingle_t = UnpackSingle<utility::TypeIdDowncast_t<T>>;

 template <typename A>
 struct PackSingle;

 template <typename T>
 using PackSingle_t = PackSingle<utility::TypeIdDowncast_t<T>>;

 // size to hold 64 bits plus one (possibly-)partial byte
 static constexpr size_t bitStreamSize = ((sizeof(uint64_t) + 1) * CHAR_BIT);

 } // namespace details

 /**
  * @brief a payload class that provides a mechanism to pack and unpack data
  *
  * When a new request is being executed, the Payload class is responsible for
  * attempting to unpack all the required arguments from the incoming blob. For
  * variable-length functions, it is possible to have function signature have a
  * Payload object, which will then allow the remaining data to be extracted as
  * needed.
  *
  * When creating a response, the parameters returned from the callback use a
  * newly created payload object to pack all the parameters into a buffer that is
  * then returned to the requester.
  *
  * These interfaces make calls into the message/pack.hpp and message/unpack.hpp
  * functions.
  */
 struct Payload
 {
     Payload() = default;
     Payload(const Payload&) = default;
     Payload& operator=(const Payload&) = default;
     Payload(Payload&&) = default;
     Payload& operator=(Payload&&) = default;

     explicit Payload(std::vector<uint8_t>&& data) : raw(std::move(data))
     {
     }

     ~Payload()
     {
         using namespace phosphor::logging;
         if (raw.size() != 0 && std::uncaught_exceptions() == 0 && !trailingOk &&
             !unpackCheck && !unpackError)
         {
             log<level::ERR>("Failed to check request for full unpack");
         }
     }

     /******************************************************************
      * raw vector access
      *****************************************************************/
     /**
      * @brief return the size of the underlying raw buffer
      */
     size_t size() const
     {
         return raw.size();
     }
     /**
      * @brief resize the underlying raw buffer to a new size
      *
      * @param sz - new size for the buffer
      */
     void resize(size_t sz)
     {
         raw.resize(sz);
     }
     /**
      * @brief return a pointer to the underlying raw buffer
      */
     uint8_t* data()
     {
         return raw.data();
     }
     /**
      * @brief return a const pointer to the underlying raw buffer
      */
     const uint8_t* data() const
     {
         return raw.data();
     }

     /******************************************************************
      * Response operations
      *****************************************************************/
     /**
      * @brief append a series of bytes to the buffer
      *
      * @tparam T - the type pointer to return; must be compatible to a byte
      *
      * @param begin - a pointer to the beginning of the series
      * @param end - a pointer to the end of the series
      */
     template <typename T>
     void append(T* begin, T* end)
     {
         static_assert(
             std::is_same_v<utility::TypeIdDowncast_t<T>, int8_t> ||
                 std::is_same_v<utility::TypeIdDowncast_t<T>, uint8_t> ||
                 std::is_same_v<utility::TypeIdDowncast_t<T>, char>,
             "begin and end must be signed or unsigned byte pointers");
         // this interface only allows full-byte access; pack in partial bytes
         drain();
         raw.insert(raw.end(), reinterpret_cast<const uint8_t*>(begin),
                    reinterpret_cast<const uint8_t*>(end));
     }

     /**
      * @brief append a series of bits to the buffer
      *
      * Only the lowest @count order of bits will be appended, with the most
      * significant of those bits getting appended first.
      *
      * @param count - number of bits to append
      * @param bits - a byte with count significant bits to append
      */
     void appendBits(size_t count, uint8_t bits)
     {
         // drain whole bytes out
         drain(true);

         // add in the new bits as the higher-order bits, filling LSBit first
         fixed_uint_t<details::bitStreamSize> tmp = bits;
         tmp <<= bitCount;
         bitStream |= tmp;
         bitCount += count;

         // drain any whole bytes we have appended
         drain(true);
     }

     /**
      * @brief empty out the bucket and pack it as bytes LSB-first
      *
      * @param wholeBytesOnly - if true, only the whole bytes will be drained
      */
     void drain(bool wholeBytesOnly = false)
     {
         while (bitCount > 0)
         {
             uint8_t retVal;
             if (bitCount < CHAR_BIT)
             {
                 if (wholeBytesOnly)
                 {
                     break;
                 }
             }
             size_t bitsOut = std::min(static_cast<size_t>(CHAR_BIT), bitCount);
             retVal = static_cast<uint8_t>(bitStream);
             raw.push_back(retVal);
             bitStream >>= bitsOut;
             bitCount -= bitsOut;
         }
     }

     // base empty pack
     int pack()
     {
         return 0;
     }

     /**
      * @brief pack arbitrary values (of any supported type) into the buffer
      *
      * @tparam Arg - the type of the first argument
      * @tparam Args - the type of the optional remaining arguments
      *
      * @param arg - the first argument to pack
      * @param args... - the optional remaining arguments to pack
      *
      * @return int - non-zero on pack errors
      */
     template <typename Arg, typename... Args>
     int pack(Arg&& arg, Args&&... args)
     {
         int packRet =
             details::PackSingle_t<Arg>::op(*this, std::forward<Arg>(arg));
         if (packRet)
         {
             return packRet;
         }
         packRet = pack(std::forward<Args>(args)...);
         drain();
         return packRet;
     }

     /**
      * @brief Prepends another payload to this one
      *
      * Avoid using this unless absolutely required since it inserts into the
      * front of the response payload.
      *
      * @param p - The payload to prepend
      *
      * @retunr int - non-zero on prepend errors
      */
     int prepend(const ipmi::message::Payload& p)
     {
         if (bitCount != 0 || p.bitCount != 0)
         {
             return 1;
         }
         raw.reserve(raw.size() + p.raw.size());
         raw.insert(raw.begin(), p.raw.begin(), p.raw.end());
         return 0;
     }

     /******************************************************************
      * Request operations
      *****************************************************************/
     /**
      * @brief pop a series of bytes from the raw buffer
      *
      * @tparam T - the type pointer to return; must be compatible to a byte
      *
      * @param count - the number of bytes to return
      *
      * @return - a tuple of pointers (begin,begin+count)
      */
     template <typename T>
     auto pop(size_t count)
     {
         static_assert(
             std::is_same_v<utility::TypeIdDowncast_t<T>, int8_t> ||
                 std::is_same_v<utility::TypeIdDowncast_t<T>, uint8_t> ||
                 std::is_same_v<utility::TypeIdDowncast_t<T>, char>,
             "T* must be signed or unsigned byte pointers");
         // this interface only allows full-byte access; skip partial bits
         if (bitCount)
         {
             // WARN on unused bits?
             discardBits();
         }
         if (count <= (raw.size() - rawIndex))
         {
             auto range = std::make_tuple(
                 reinterpret_cast<T*>(raw.data() + rawIndex),
                 reinterpret_cast<T*>(raw.data() + rawIndex + count));
             rawIndex += count;
             return range;
         }
         unpackError = true;
         return std::make_tuple(reinterpret_cast<T*>(NULL),
                                reinterpret_cast<T*>(NULL));
     }

     /**
      * @brief fill bit stream with at least count bits for consumption
      *
      * @param count - number of bit needed
      *
      * @return - unpackError
      */
     bool fillBits(size_t count)
     {
         // add more bits to the top end of the bitstream
         // so we consume bits least-significant first
         if (count > (details::bitStreamSize - CHAR_BIT))
         {
             unpackError = true;
             return unpackError;
         }
         while (bitCount < count)
         {
             if (rawIndex < raw.size())
             {
                 fixed_uint_t<details::bitStreamSize> tmp = raw[rawIndex++];
                 tmp <<= bitCount;
                 bitStream |= tmp;
                 bitCount += CHAR_BIT;
             }
             else
             {
                 // raw has run out of bytes to pop
                 unpackError = true;
                 return unpackError;
             }
         }
         return false;
     }

     /**
      * @brief consume count bits from bitstream (must call fillBits first)
      *
      * @param count - number of bit needed
      *
      * @return - count bits from stream
      */
     uint8_t popBits(size_t count)
     {
         if (bitCount < count)
         {
             unpackError = true;
             return 0;
         }
         // consume bits low-order bits first
         auto bits = bitStream.convert_to<uint8_t>();
         bits &= ((1 << count) - 1);
         bitStream >>= count;
         bitCount -= count;
         return bits;
     }

     /**
      * @brief discard all partial bits
      */
     void discardBits()
     {
         bitStream = 0;
         bitCount = 0;
     }

     /**
      * @brief fully reset the unpack stream
      */
     void reset()
     {
         discardBits();
         rawIndex = 0;
         unpackError = false;
     }

     /**
      * @brief check to see if the stream has been fully unpacked
      *
      * @return bool - true if the stream has been unpacked and has no errors
      */
     bool fullyUnpacked()
     {
         unpackCheck = true;
         return raw.size() == rawIndex && bitCount == 0 && !unpackError;
     }

     // base empty unpack
     int unpack()
     {
         return 0;
     }

     /**
      * @brief unpack arbitrary values (of any supported type) from the buffer
      *
      * @tparam Arg - the type of the first argument
      * @tparam Args - the type of the optional remaining arguments
      *
      * @param arg - the first argument to unpack
      * @param args... - the optional remaining arguments to unpack
      *
      * @return int - non-zero for unpack error
      */
     template <typename Arg, typename... Args>
     int unpack(Arg&& arg, Args&&... args)
     {
         int unpackRet =
             details::UnpackSingle_t<Arg>::op(*this, std::forward<Arg>(arg));
         if (unpackRet)
         {
             unpackError = true;
             return unpackRet;
         }
         return unpack(std::forward<Args>(args)...);
     }

     /**
      * @brief unpack a tuple of values (of any supported type) from the buffer
      *
      * This will unpack the elements of the tuple as if each one was passed in
      * individually, as if passed into the above variadic function.
      *
      * @tparam Types - the implicitly declared list of the tuple element types
      *
      * @param t - the tuple of values to unpack
      *
      * @return int - non-zero on unpack error
      */
     template <typename... Types>
     int unpack(std::tuple<Types...>& t)
     {
         // roll back checkpoint so that unpacking a tuple is atomic
         size_t priorBitCount = bitCount;
         size_t priorIndex = rawIndex;
         fixed_uint_t<details::bitStreamSize> priorBits = bitStream;

         int ret =
             std::apply([this](Types&... args) { return unpack(args...); }, t);
         if (ret)
         {
             bitCount = priorBitCount;
             bitStream = priorBits;
             rawIndex = priorIndex;
         }

         return ret;
     }

     // partial bytes in the form of bits
     fixed_uint_t<details::bitStreamSize> bitStream;
     size_t bitCount = 0;
     std::vector<uint8_t> raw;
     size_t rawIndex = 0;
     bool trailingOk = true;
     bool unpackCheck = false;
     bool unpackError = false;
 };

 /**
  * @brief high-level interface to an IPMI response
  *
  * Make it easy to just pack in the response args from the callback into a
  * buffer that goes back to the requester.
  */
 struct Response
 {
     /* Define all of the basic class operations:
      *     Not allowed:
      *         - Default constructor to avoid nullptrs.
      *     Allowed:
      *         - Copy operations.
      *         - Move operations.
      *         - Destructor.
      */
     Response() = delete;
     Response(const Response&) = default;
     Response& operator=(const Response&) = default;
     Response(Response&&) = default;
     Response& operator=(Response&&) = default;
     ~Response() = default;

     using ptr = std::shared_ptr<Response>;

     explicit Response(Context::ptr& context) :
         payload(), ctx(context), cc(ccSuccess)
     {
     }

     /**
      * @brief pack arbitrary values (of any supported type) into the payload
      *
      * @tparam Args - the type of the optional arguments
      *
      * @param args... - the optional arguments to pack
      *
      * @return int - non-zero on pack errors
      */
     template <typename... Args>
     int pack(Args&&... args)
     {
         return payload.pack(std::forward<Args>(args)...);
     }

     /**
      * @brief pack a tuple of values (of any supported type) into the payload
      *
      * This will pack the elements of the tuple as if each one was passed in
      * individually, as if passed into the above variadic function.
      *
      * @tparam Types - the implicitly declared list of the tuple element types
      *
      * @param t - the tuple of values to pack
      *
      * @return int - non-zero on pack errors
      */
     template <typename... Types>
     int pack(std::tuple<Types...>& t)
     {
         return payload.pack(t);
     }

     /**
      * @brief Prepends another payload to this one
      *
      * Avoid using this unless absolutely required since it inserts into the
      * front of the response payload.
      *
      * @param p - The payload to prepend
      *
      * @retunr int - non-zero on prepend errors
      */
     int prepend(const ipmi::message::Payload& p)
     {
         return payload.prepend(p);
     }

     Payload payload;
     Context::ptr ctx;
     Cc cc;
 };

 /**
  * @brief high-level interface to an IPMI request
  *
  * Make it easy to unpack the buffer into the request args for the callback.
  */
 struct Request
 {
     /* Define all of the basic class operations:
      *     Not allowed:
      *         - Default constructor to avoid nullptrs.
      *     Allowed:
      *         - Copy operations.
      *         - Move operations.
      *         - Destructor.
      */
     Request() = delete;
     Request(const Request&) = default;
     Request& operator=(const Request&) = default;
     Request(Request&&) = default;
     Request& operator=(Request&&) = default;
     ~Request() = default;

     using ptr = std::shared_ptr<Request>;

     explicit Request(Context::ptr context, std::vector<uint8_t>&& d) :
         payload(std::forward<std::vector<uint8_t>>(d)), ctx(context)
     {
     }

     /**
      * @brief unpack arbitrary values (of any supported type) from the payload
      *
      * @tparam Args - the type of the optional arguments
      *
      * @param args... - the optional arguments to unpack
      *
      * @return int - non-zero for unpack error
      */
     template <typename... Args>
     int unpack(Args&&... args)
     {
         int unpackRet = payload.unpack(std::forward<Args>(args)...);
         if (unpackRet == ipmi::ccSuccess)
         {
             if (!payload.trailingOk)
             {
                 if (!payload.fullyUnpacked())
                 {
                     // not all bits were consumed by requested parameters
                     return ipmi::ccReqDataLenInvalid;
                 }
             }
         }
         return unpackRet;
     }

     /**
      * @brief unpack a tuple of values (of any supported type) from the payload
      *
      * This will unpack the elements of the tuple as if each one was passed in
      * individually, as if passed into the above variadic function.
      *
      * @tparam Types - the implicitly declared list of the tuple element types
      *
      * @param t - the tuple of values to unpack
      *
      * @return int - non-zero on unpack error
      */
     template <typename... Types>
     int unpack(std::tuple<Types...>& t)
     {
         return std::apply([this](Types&... args) { return unpack(args...); },
                           t);
     }

     /** @brief Create a response message that corresponds to this request
      *
      * @return A shared_ptr to the response message created
      */
     Response::ptr makeResponse()
     {
         return std::make_shared<Response>(ctx);
     }

     Payload payload;
     Context::ptr ctx;
 };

 } // namespace message

 } // namespace ipmi

 // include packing and unpacking of types
 #include <ipmid/message/pack.hpp>
 #include <ipmid/message/unpack.hpp>
	/**
	* Copyright © 2018 Intel Corporation
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	#pragma once

	#include <algorithm>
	#include <boost/asio/spawn.hpp>
	#include <cstdint>
	#include <exception>
	#include <ipmid/api-types.hpp>
	#include <ipmid/message/types.hpp>
	#include <memory>
	#include <phosphor-logging/log.hpp>
	#include <tuple>
	#include <utility>
	#include <vector>

	namespace ipmi
	{

	struct Context
	{
	using ptr = std::shared_ptr<Context>;

	Context() = default;

	Context(NetFn netFn, Cmd cmd, int channel, int userId, Privilege priv,
	int rqSA = 0, boost::asio::yield_context* yield = nullptr) :
	netFn(netFn),
	cmd(cmd), channel(channel), userId(userId), priv(priv), rqSA(rqSA),
	yield(yield)
	{
	}

	// normal IPMI context (what call is this, from whence it came...)
	NetFn netFn = 0;
	Cmd cmd = 0;
	int channel = 0;
	int userId = 0;
	Privilege priv = Privilege::None;
	// srcAddr is only set on IPMB requests because
	// Platform Event Message needs it to determine the incoming format
	int rqSA = 0;
	// if non-null, use this to do blocking asynchronous asio calls
	boost::asio::yield_context* yield = nullptr;
	};

	namespace message
	{

	namespace details
	{

	template <typename A>
	struct UnpackSingle;

	template <typename T>
	using UnpackSingle_t = UnpackSingle<utility::TypeIdDowncast_t<T>>;

	template <typename A>
	struct PackSingle;

	template <typename T>
	using PackSingle_t = PackSingle<utility::TypeIdDowncast_t<T>>;

	// size to hold 64 bits plus one (possibly-)partial byte
	static constexpr size_t bitStreamSize = ((sizeof(uint64_t) + 1) * CHAR_BIT);

	} // namespace details

	/**
	* @brief a payload class that provides a mechanism to pack and unpack data
	*
	* When a new request is being executed, the Payload class is responsible for
	* attempting to unpack all the required arguments from the incoming blob. For
	* variable-length functions, it is possible to have function signature have a
	* Payload object, which will then allow the remaining data to be extracted as
	* needed.
	*
	* When creating a response, the parameters returned from the callback use a
	* newly created payload object to pack all the parameters into a buffer that is
	* then returned to the requester.
	*
	* These interfaces make calls into the message/pack.hpp and message/unpack.hpp
	* functions.
	*/
	struct Payload
	{
	Payload() = default;
	Payload(const Payload&) = default;
	Payload& operator=(const Payload&) = default;
	Payload(Payload&&) = default;
	Payload& operator=(Payload&&) = default;

	explicit Payload(std::vector<uint8_t>&& data) : raw(std::move(data))
	{
	}

	~Payload()
	{
	using namespace phosphor::logging;
	if (raw.size() != 0 && std::uncaught_exceptions() == 0 && !trailingOk &&
	!unpackCheck && !unpackError)
	{
	log<level::ERR>("Failed to check request for full unpack");
	}
	}

	/******************************************************************
	* raw vector access
	*****************************************************************/
	/**
	* @brief return the size of the underlying raw buffer
	*/
	size_t size() const
	{
	return raw.size();
	}
	/**
	* @brief resize the underlying raw buffer to a new size
	*
	* @param sz - new size for the buffer
	*/
	void resize(size_t sz)
	{
	raw.resize(sz);
	}
	/**
	* @brief return a pointer to the underlying raw buffer
	*/
	uint8_t* data()
	{
	return raw.data();
	}
	/**
	* @brief return a const pointer to the underlying raw buffer
	*/
	const uint8_t* data() const
	{
	return raw.data();
	}

	/******************************************************************
	* Response operations
	*****************************************************************/
	/**
	* @brief append a series of bytes to the buffer
	*
	* @tparam T - the type pointer to return; must be compatible to a byte
	*
	* @param begin - a pointer to the beginning of the series
	* @param end - a pointer to the end of the series
	*/
	template <typename T>
	void append(T* begin, T* end)
	{
	static_assert(
	std::is_same_v<utility::TypeIdDowncast_t<T>, int8_t> \|\|
	std::is_same_v<utility::TypeIdDowncast_t<T>, uint8_t> \|\|
	std::is_same_v<utility::TypeIdDowncast_t<T>, char>,
	"begin and end must be signed or unsigned byte pointers");
	// this interface only allows full-byte access; pack in partial bytes
	drain();
	raw.insert(raw.end(), reinterpret_cast<const uint8_t*>(begin),
	reinterpret_cast<const uint8_t*>(end));
	}

	/**
	* @brief append a series of bits to the buffer
	*
	* Only the lowest @count order of bits will be appended, with the most
	* significant of those bits getting appended first.
	*
	* @param count - number of bits to append
	* @param bits - a byte with count significant bits to append
	*/
	void appendBits(size_t count, uint8_t bits)
	{
	// drain whole bytes out
	drain(true);

	// add in the new bits as the higher-order bits, filling LSBit first
	fixed_uint_t<details::bitStreamSize> tmp = bits;
	tmp <<= bitCount;
	bitStream \|= tmp;
	bitCount += count;

	// drain any whole bytes we have appended
	drain(true);
	}

	/**
	* @brief empty out the bucket and pack it as bytes LSB-first
	*
	* @param wholeBytesOnly - if true, only the whole bytes will be drained
	*/
	void drain(bool wholeBytesOnly = false)
	{
	while (bitCount > 0)
	{
	uint8_t retVal;
	if (bitCount < CHAR_BIT)
	{
	if (wholeBytesOnly)
	{
	break;
	}
	}
	size_t bitsOut = std::min(static_cast<size_t>(CHAR_BIT), bitCount);
	retVal = static_cast<uint8_t>(bitStream);
	raw.push_back(retVal);
	bitStream >>= bitsOut;
	bitCount -= bitsOut;
	}
	}

	// base empty pack
	int pack()
	{
	return 0;
	}

	/**
	* @brief pack arbitrary values (of any supported type) into the buffer
	*
	* @tparam Arg - the type of the first argument
	* @tparam Args - the type of the optional remaining arguments
	*
	* @param arg - the first argument to pack
	* @param args... - the optional remaining arguments to pack
	*
	* @return int - non-zero on pack errors
	*/
	template <typename Arg, typename... Args>
	int pack(Arg&& arg, Args&&... args)
	{
	int packRet =
	details::PackSingle_t<Arg>::op(*this, std::forward<Arg>(arg));
	if (packRet)
	{
	return packRet;
	}
	packRet = pack(std::forward<Args>(args)...);
	drain();
	return packRet;
	}

	/**
	* @brief Prepends another payload to this one
	*
	* Avoid using this unless absolutely required since it inserts into the
	* front of the response payload.
	*
	* @param p - The payload to prepend
	*
	* @retunr int - non-zero on prepend errors
	*/
	int prepend(const ipmi::message::Payload& p)
	{
	if (bitCount != 0 \|\| p.bitCount != 0)
	{
	return 1;
	}
	raw.reserve(raw.size() + p.raw.size());
	raw.insert(raw.begin(), p.raw.begin(), p.raw.end());
	return 0;
	}

	/******************************************************************
	* Request operations
	*****************************************************************/
	/**
	* @brief pop a series of bytes from the raw buffer
	*
	* @tparam T - the type pointer to return; must be compatible to a byte
	*
	* @param count - the number of bytes to return
	*
	* @return - a tuple of pointers (begin,begin+count)
	*/
	template <typename T>
	auto pop(size_t count)
	{
	static_assert(
	std::is_same_v<utility::TypeIdDowncast_t<T>, int8_t> \|\|
	std::is_same_v<utility::TypeIdDowncast_t<T>, uint8_t> \|\|
	std::is_same_v<utility::TypeIdDowncast_t<T>, char>,
	"T* must be signed or unsigned byte pointers");
	// this interface only allows full-byte access; skip partial bits
	if (bitCount)
	{
	// WARN on unused bits?
	discardBits();
	}
	if (count <= (raw.size() - rawIndex))
	{
	auto range = std::make_tuple(
	reinterpret_cast<T*>(raw.data() + rawIndex),
	reinterpret_cast<T*>(raw.data() + rawIndex + count));
	rawIndex += count;
	return range;
	}
	unpackError = true;
	return std::make_tuple(reinterpret_cast<T*>(NULL),
	reinterpret_cast<T*>(NULL));
	}

	/**
	* @brief fill bit stream with at least count bits for consumption
	*
	* @param count - number of bit needed
	*
	* @return - unpackError
	*/
	bool fillBits(size_t count)
	{
	// add more bits to the top end of the bitstream
	// so we consume bits least-significant first
	if (count > (details::bitStreamSize - CHAR_BIT))
	{
	unpackError = true;
	return unpackError;
	}
	while (bitCount < count)
	{
	if (rawIndex < raw.size())
	{
	fixed_uint_t<details::bitStreamSize> tmp = raw[rawIndex++];
	tmp <<= bitCount;
	bitStream \|= tmp;
	bitCount += CHAR_BIT;
	}
	else
	{
	// raw has run out of bytes to pop
	unpackError = true;
	return unpackError;
	}
	}
	return false;
	}

	/**
	* @brief consume count bits from bitstream (must call fillBits first)
	*
	* @param count - number of bit needed
	*
	* @return - count bits from stream
	*/
	uint8_t popBits(size_t count)
	{
	if (bitCount < count)
	{
	unpackError = true;
	return 0;
	}
	// consume bits low-order bits first
	auto bits = bitStream.convert_to<uint8_t>();
	bits &= ((1 << count) - 1);
	bitStream >>= count;
	bitCount -= count;
	return bits;
	}

	/**
	* @brief discard all partial bits
	*/
	void discardBits()
	{
	bitStream = 0;
	bitCount = 0;
	}

	/**
	* @brief fully reset the unpack stream
	*/
	void reset()
	{
	discardBits();
	rawIndex = 0;
	unpackError = false;
	}

	/**
	* @brief check to see if the stream has been fully unpacked
	*
	* @return bool - true if the stream has been unpacked and has no errors
	*/
	bool fullyUnpacked()
	{
	unpackCheck = true;
	return raw.size() == rawIndex && bitCount == 0 && !unpackError;
	}

	// base empty unpack
	int unpack()
	{
	return 0;
	}

	/**
	* @brief unpack arbitrary values (of any supported type) from the buffer
	*
	* @tparam Arg - the type of the first argument
	* @tparam Args - the type of the optional remaining arguments
	*
	* @param arg - the first argument to unpack
	* @param args... - the optional remaining arguments to unpack
	*
	* @return int - non-zero for unpack error
	*/
	template <typename Arg, typename... Args>
	int unpack(Arg&& arg, Args&&... args)
	{
	int unpackRet =
	details::UnpackSingle_t<Arg>::op(*this, std::forward<Arg>(arg));
	if (unpackRet)
	{
	unpackError = true;
	return unpackRet;
	}
	return unpack(std::forward<Args>(args)...);
	}

	/**
	* @brief unpack a tuple of values (of any supported type) from the buffer
	*
	* This will unpack the elements of the tuple as if each one was passed in
	* individually, as if passed into the above variadic function.
	*
	* @tparam Types - the implicitly declared list of the tuple element types
	*
	* @param t - the tuple of values to unpack
	*
	* @return int - non-zero on unpack error
	*/
	template <typename... Types>
	int unpack(std::tuple<Types...>& t)
	{
	// roll back checkpoint so that unpacking a tuple is atomic
	size_t priorBitCount = bitCount;
	size_t priorIndex = rawIndex;
	fixed_uint_t<details::bitStreamSize> priorBits = bitStream;

	int ret =
	std::apply([this](Types&... args) { return unpack(args...); }, t);
	if (ret)
	{
	bitCount = priorBitCount;
	bitStream = priorBits;
	rawIndex = priorIndex;
	}

	return ret;
	}

	// partial bytes in the form of bits
	fixed_uint_t<details::bitStreamSize> bitStream;
	size_t bitCount = 0;
	std::vector<uint8_t> raw;
	size_t rawIndex = 0;
	bool trailingOk = true;
	bool unpackCheck = false;
	bool unpackError = false;
	};

	/**
	* @brief high-level interface to an IPMI response
	*
	* Make it easy to just pack in the response args from the callback into a
	* buffer that goes back to the requester.
	*/
	struct Response
	{
	/* Define all of the basic class operations:
	* Not allowed:
	* - Default constructor to avoid nullptrs.
	* Allowed:
	* - Copy operations.
	* - Move operations.
	* - Destructor.
	*/
	Response() = delete;
	Response(const Response&) = default;
	Response& operator=(const Response&) = default;
	Response(Response&&) = default;
	Response& operator=(Response&&) = default;
	~Response() = default;

	using ptr = std::shared_ptr<Response>;

	explicit Response(Context::ptr& context) :
	payload(), ctx(context), cc(ccSuccess)
	{
	}

	/**
	* @brief pack arbitrary values (of any supported type) into the payload
	*
	* @tparam Args - the type of the optional arguments
	*
	* @param args... - the optional arguments to pack
	*
	* @return int - non-zero on pack errors
	*/
	template <typename... Args>
	int pack(Args&&... args)
	{
	return payload.pack(std::forward<Args>(args)...);
	}

	/**
	* @brief pack a tuple of values (of any supported type) into the payload
	*
	* This will pack the elements of the tuple as if each one was passed in
	* individually, as if passed into the above variadic function.
	*
	* @tparam Types - the implicitly declared list of the tuple element types
	*
	* @param t - the tuple of values to pack
	*
	* @return int - non-zero on pack errors
	*/
	template <typename... Types>
	int pack(std::tuple<Types...>& t)
	{
	return payload.pack(t);
	}

	/**
	* @brief Prepends another payload to this one
	*
	* Avoid using this unless absolutely required since it inserts into the
	* front of the response payload.
	*
	* @param p - The payload to prepend
	*
	* @retunr int - non-zero on prepend errors
	*/
	int prepend(const ipmi::message::Payload& p)
	{
	return payload.prepend(p);
	}

	Payload payload;
	Context::ptr ctx;
	Cc cc;
	};

	/**
	* @brief high-level interface to an IPMI request
	*
	* Make it easy to unpack the buffer into the request args for the callback.
	*/
	struct Request
	{
	/* Define all of the basic class operations:
	* Not allowed:
	* - Default constructor to avoid nullptrs.
	* Allowed:
	* - Copy operations.
	* - Move operations.
	* - Destructor.
	*/
	Request() = delete;
	Request(const Request&) = default;
	Request& operator=(const Request&) = default;
	Request(Request&&) = default;
	Request& operator=(Request&&) = default;
	~Request() = default;

	using ptr = std::shared_ptr<Request>;

	explicit Request(Context::ptr context, std::vector<uint8_t>&& d) :
	payload(std::forward<std::vector<uint8_t>>(d)), ctx(context)
	{
	}

	/**
	* @brief unpack arbitrary values (of any supported type) from the payload
	*
	* @tparam Args - the type of the optional arguments
	*
	* @param args... - the optional arguments to unpack
	*
	* @return int - non-zero for unpack error
	*/
	template <typename... Args>
	int unpack(Args&&... args)
	{
	int unpackRet = payload.unpack(std::forward<Args>(args)...);
	if (unpackRet == ipmi::ccSuccess)
	{
	if (!payload.trailingOk)
	{
	if (!payload.fullyUnpacked())
	{
	// not all bits were consumed by requested parameters
	return ipmi::ccReqDataLenInvalid;
	}
	}
	}
	return unpackRet;
	}

	/**
	* @brief unpack a tuple of values (of any supported type) from the payload
	*
	* This will unpack the elements of the tuple as if each one was passed in
	* individually, as if passed into the above variadic function.
	*
	* @tparam Types - the implicitly declared list of the tuple element types
	*
	* @param t - the tuple of values to unpack
	*
	* @return int - non-zero on unpack error
	*/
	template <typename... Types>
	int unpack(std::tuple<Types...>& t)
	{
	return std::apply([this](Types&... args) { return unpack(args...); },
	t);
	}

	/** @brief Create a response message that corresponds to this request
	*
	* @return A shared_ptr to the response message created
	*/
	Response::ptr makeResponse()
	{
	return std::make_shared<Response>(ctx);
	}

	Payload payload;
	Context::ptr ctx;
	};

	} // namespace message

	} // namespace ipmi

	// include packing and unpacking of types
	#include <ipmid/message/pack.hpp>
	#include <ipmid/message/unpack.hpp>