Word writevImpl()

in plugins/experimental/wasm/lib/src/exports.cc [671:718]

• 43 lines of code
• 10 McCabe index (conditional complexity)

Word writevImpl(Word fd, Word iovs, Word iovs_len, Word *nwritten_ptr) {
  auto *context = contextOrEffectiveContext();

  // Read syscall args.
  uint64_t log_level;
  switch (fd) {
  case 1 /* stdout */:
    log_level = 2; // LogLevel::info
    break;
  case 2 /* stderr */:
    log_level = 4; // LogLevel::error
    break;
  default:
    return 8; // __WASI_EBADF
  }

  std::string s;
  for (size_t i = 0; i < iovs_len; i++) {
    auto memslice =
        context->wasmVm()->getMemory(iovs + i * 2 * sizeof(uint32_t), 2 * sizeof(uint32_t));
    if (!memslice) {
      return 21; // __WASI_EFAULT
    }
    const auto *iovec = reinterpret_cast<const uint32_t *>(memslice.value().data());
    if (iovec[1] != 0U /* buf_len */) {
      const auto buf = wasmtoh(iovec[0], context->wasmVm()->usesWasmByteOrder());
      const auto buf_len = wasmtoh(iovec[1], context->wasmVm()->usesWasmByteOrder());
      memslice = context->wasmVm()->getMemory(buf, buf_len);
      if (!memslice) {
        return 21; // __WASI_EFAULT
      }
      s.append(memslice.value().data(), memslice.value().size());
    }
  }

  size_t written = s.size();
  if (written != 0U) {
    // Remove trailing newline from the logs, if any.
    if (s[written - 1] == '\n') {
      s.erase(written - 1);
    }
    if (context->log(log_level, s) != WasmResult::Ok) {
      return 8; // __WASI_EBADF
    }
  }
  *nwritten_ptr = Word(written);
  return 0; // __WASI_ESUCCESS
}