denoland-deno/cli/ops/performance.rs

// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
use super::dispatch_flatbuffers::serialize_response;
use super::utils::*;
use crate::msg;
use crate::state::ThreadSafeState;
use deno::*;
use flatbuffers::FlatBufferBuilder;

// Returns a milliseconds and nanoseconds subsec
// since the start time of the deno runtime.
// If the High precision flag is not set, the
// nanoseconds are rounded on 2ms.
pub fn op_now(
  state: &ThreadSafeState,
  base: &msg::Base<'_>,
  data: Option<PinnedBuf>,
) -> CliOpResult {
  assert!(data.is_none());
  let seconds = state.start_time.elapsed().as_secs();
  let mut subsec_nanos = state.start_time.elapsed().subsec_nanos();
  let reduced_time_precision = 2_000_000; // 2ms in nanoseconds

  // If the permission is not enabled
  // Round the nano result on 2 milliseconds
  // see: https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp#Reduced_time_precision
  if !state.permissions.allows_hrtime() {
    subsec_nanos -= subsec_nanos % reduced_time_precision
  }

  let builder = &mut FlatBufferBuilder::new();
  let inner = msg::NowRes::create(
    builder,
    &msg::NowResArgs {
      seconds,
      subsec_nanos,
    },
  );

  ok_buf(serialize_response(
    base.cmd_id(),
    builder,
    msg::BaseArgs {
      inner: Some(inner.as_union_value()),
      inner_type: msg::Any::NowRes,
      ..Default::default()
    },
  ))
}