capnp_wrapper.h

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// Copyright (c) 2024-2025 Voyant Photonics, Inc.
// All rights reserved.
 
#pragma once
 
#include <capnp/message.h>
#include <capnp/serialize.h>
#include <cstring>
#include <memory>
#include <ostream>
#include <stdexcept>
#include <vector>
 
template <typename T> class CapnpWrapper
{
public:
  virtual ~CapnpWrapper() = default;
 
  virtual void fromProto(typename T::Reader reader) = 0;
 
  virtual void toProto(typename T::Builder &builder) const = 0;
 
  virtual void debugString(std::ostream &os) const = 0;
 
  void fromBuffer(const uint8_t *buffer, size_t size)
  {
    kj::ArrayPtr<const capnp::word> words(reinterpret_cast<const capnp::word *>(buffer),
                                          size / sizeof(capnp::word));
    capnp::FlatArrayMessageReader message = capnp::FlatArrayMessageReader(words);
    typename T::Reader reader = message.getRoot<T>();
    fromProto(reader);
  }
 
  size_t toBuffer(uint8_t *buffer, size_t buffer_size) const
  {
    capnp::MallocMessageBuilder message;
    {
      typename T::Builder builder = message.getRoot<T>();
      toProto(builder);
    }
    kj::Array<capnp::word> words = capnp::messageToFlatArray(message);
    size_t size = words.size() * sizeof(capnp::word);
 
    if(size > buffer_size)
    {
      throw std::runtime_error("Buffer too small");
    }
 
    std::memcpy(buffer, words.begin(), size);
    return size;
  }
 
  friend std::ostream &operator<<(std::ostream &os, const CapnpWrapper<T> &wrapper)
  {
    wrapper.debugString(os);
    return os;
  }
};