Future LengthFieldPrepender::write()

in wangle/codec/LengthFieldPrepender.cpp [39:101]
59 lines of code
13 McCabe index (conditional complexity)

Future<Unit> LengthFieldPrepender::write(
    Context* ctx,
    std::unique_ptr<IOBuf> buf) {
  size_t length = lengthAdjustment_ + buf->computeChainDataLength();
  if (lengthIncludesLengthField_) {
    length += lengthFieldLength_;
  }

  if (length < 0) {
    throw std::runtime_error("Length field < 0");
  }

  auto len = IOBuf::create(lengthFieldLength_);
  len->append(lengthFieldLength_);
  folly::io::RWPrivateCursor c(len.get());

  switch (lengthFieldLength_) {
    case 1: {
      if (length >= 256) {
        throw std::runtime_error("length does not fit byte");
      }
      if (networkByteOrder_) {
        c.writeBE((uint8_t)length);
      } else {
        c.writeLE((uint8_t)length);
      }
      break;
    }
    case 2: {
      if (length >= 65536) {
        throw std::runtime_error("length does not fit byte");
      }
      if (networkByteOrder_) {
        c.writeBE((uint16_t)length);
      } else {
        c.writeLE((uint16_t)length);
      }
      break;
    }
    case 4: {
      if (networkByteOrder_) {
        c.writeBE((uint32_t)length);
      } else {
        c.writeLE((uint32_t)length);
      }
      break;
    }
    case 8: {
      if (networkByteOrder_) {
        c.writeBE((uint64_t)length);
      } else {
        c.writeLE((uint64_t)length);
      }
      break;
    }
    default: {
      throw std::runtime_error("Invalid lengthFieldLength");
    }
  }

  len->prependChain(std::move(buf));
  return ctx->fireWrite(std::move(len));
}