msg.cpp

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/* Flow-IPC: Structured Transport
 * Copyright (c) 2023 Akamai Technologies, Inc.; and other contributors.
 * Each commit is copyright by its respective author or author's employer.
 *
 * Licensed under the MIT License:
 *
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/// @file
 
#include "ipc/transport/struc/msg.hpp"
#include "ipc/transport/struc/error.hpp"
#include <flow/error/error.hpp>
#include <cassert>
#include <cstdint>
#include <cstring>
 
namespace ipc::transport::struc
{
 
// Capped_sz_capnp_message_*der implementations.
 
Capped_sz_capnp_message_builder::Capped_sz_capnp_message_builder(const util::Blob_mutable& seg, bool zero_it_please) :
  m_seg(seg.data(),
        (seg.size() / sizeof(::capnp::word)) * sizeof(::capnp::word)), // Round down to nearest word.
  m_returned_seg(false)
{
  if (zero_it_please)
  {
    std::memset(m_seg.data(), 0, m_seg.size());
  }
  assert(m_seg.size() != 0);
  assert(((reinterpret_cast<uintptr_t>(m_seg.data()) % alignof(::capnp::word)) == 0)
         && "capnp requires word-aligned segments; beware, e.g., a stack byte-array sans alignas.");
}
 
kj::ArrayPtr<::capnp::word> Capped_sz_capnp_message_builder::allocateSegment([[maybe_unused]] unsigned int min_sz_words)
  // Virtual.
{
  using flow::error::Runtime_error;
  using Word = capnp::word;
  using Capnp_word_buf = kj::ArrayPtr<Word>;
 
  if (m_returned_seg)
  {
    // Segment 1 was not enough to store the needed data; so seg.size() (size cap) was insufficient.
    throw Runtime_error{error::Code::S_INVALID_ARGUMENT,
                        "Capped_sz_capnp_message_builder::allocateSegment()[bad size cap]"};
  }
  m_returned_seg = true;
 
  assert(((min_sz_words * sizeof(Word)) <= m_seg.size())
         && "Should not be possible: First allocateSegment() always takes `1`; second would have thrown above.");
 
  return Capnp_word_buf{reinterpret_cast<Word*>(m_seg.data()),
                        reinterpret_cast<Word*>(static_cast<uint8_t*>(m_seg.data()) + m_seg.size())};
}
 
Capped_sz_capnp_message_reader::Capped_sz_capnp_message_reader(const util::Blob_const& seg) :
  // Init this private base (glorified data member) first.  See class doc header Impl section for brief explanation.
  Word_array_ptr_base(static_cast<const ::capnp::word*>(seg.data()),
                      seg.size() / sizeof(::capnp::word)),
  Seg_array_msg_reader_base
    (kj::ArrayPtr<const Word_array_ptr_base>
       {static_cast<const Word_array_ptr_base*>(this), 1})
{
  assert(((reinterpret_cast<uintptr_t>(seg.data()) % alignof(::capnp::word)) == 0)
         && "capnp requires word-aligned segments; beware, e.g., a stack byte-array sans alignas.");
}
 
} // namespace ipc::transport::struc