Allow high precision performance.now() (denoland#1977)

cli/flags.rs

@@ -19,6 +19,7 @@ pub struct DenoFlags {
   pub allow_net: bool,
   pub allow_env: bool,
   pub allow_run: bool,
+  pub allow_high_precision: bool,
   pub no_prompts: bool,
   pub types: bool,
   pub prefetch: bool,
@@ -54,13 +55,17 @@ impl<'a> From<ArgMatches<'a>> for DenoFlags {
     if matches.is_present("allow-run") {
       flags.allow_run = true;
     }
+    if matches.is_present("allow-high-precision") {
+      flags.allow_high_precision = true;
+    }
     if matches.is_present("allow-all") {
       flags.allow_read = true;
       flags.allow_env = true;
       flags.allow_net = true;
       flags.allow_run = true;
       flags.allow_read = true;
       flags.allow_write = true;
+      flags.allow_high_precision = true;
     }
     if matches.is_present("no-prompt") {
       flags.no_prompts = true;
@@ -124,6 +129,10 @@ pub fn set_flags(
       Arg::with_name("allow-run")
         .long("allow-run")
         .help("Allow running subprocesses"),
+    ).arg(
+      Arg::with_name("allow-high-precision")
+        .long("allow-high-precision")
+        .help("Allow high precision time measurement"),
     ).arg(
       Arg::with_name("allow-all")
         .short("A")
@@ -338,6 +347,7 @@ fn test_set_flags_7() {
       allow_run: true,
       allow_read: true,
       allow_write: true,
+      allow_high_precision: true,
       ..DenoFlags::default()
     }
   )
@@ -356,3 +366,17 @@ fn test_set_flags_8() {
     }
   )
 }
+
+#[test]
+fn test_set_flags_9() {
+  let (flags, rest) =
+    set_flags(svec!["deno", "--allow-high-precision", "script.ts"]).unwrap();
+  assert_eq!(rest, svec!["deno", "script.ts"]);
+  assert_eq!(
+    flags,
+    DenoFlags {
+      allow_high_precision: true,
+      ..DenoFlags::default()
+    }
+  )
+}

cli/isolate_state.rs

@@ -17,6 +17,7 @@ use std::env;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 use std::sync::Mutex;
+use std::time::Instant;
 
 pub type WorkerSender = async_mpsc::Sender<Buf>;
 pub type WorkerReceiver = async_mpsc::Receiver<Buf>;
@@ -51,6 +52,7 @@ pub struct IsolateState {
   pub global_timer: Mutex<GlobalTimer>,
   pub workers: Mutex<UserWorkerTable>,
   pub is_worker: bool,
+  pub start_time: Instant,
 }
 
 impl IsolateState {
@@ -73,6 +75,7 @@ impl IsolateState {
       global_timer: Mutex::new(GlobalTimer::new()),
       workers: Mutex::new(UserWorkerTable::new()),
       is_worker,
+      start_time: Instant::now(),
     }
   }
 

cli/msg.fbs

@@ -281,6 +281,7 @@ table PermissionsRes {
   write: bool;
   net: bool;
   env: bool;
+  high_precision: bool;
 }
 
 // Note this represents The WHOLE header of an http message, not just the key
@@ -527,7 +528,8 @@ table RunStatusRes {
 table Now {}
 
 table NowRes {
-  time: uint64;
+  seconds: uint64;
+  subsec_nanos: uint32;
 }
 
 table IsTTY {}

cli/ops.rs

@@ -41,7 +41,7 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::process::Command;
 use std::sync::Arc;
-use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+use std::time::{Duration, Instant, UNIX_EPOCH};
 use tokio;
 use tokio::net::TcpListener;
 use tokio::net::TcpStream;
@@ -212,19 +212,35 @@ pub fn op_selector_std(inner_type: msg::Any) -> Option<OpCreator> {
   }
 }
 
+// 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.
 fn op_now(
-  _sc: &IsolateStateContainer,
+  sc: &IsolateStateContainer,
   base: &msg::Base<'_>,
   data: deno_buf,
 ) -> Box<OpWithError> {
   assert_eq!(data.len(), 0);
-  let start = SystemTime::now();
-  let since_the_epoch = start.duration_since(UNIX_EPOCH).unwrap();
-  let time = since_the_epoch.as_secs() * 1000
-    + u64::from(since_the_epoch.subsec_millis());
+  let seconds = sc.state().start_time.elapsed().as_secs();
+  let mut subsec_nanos = sc.state().start_time.elapsed().subsec_nanos();
+  let reduced_time_precision = 2000000; // 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 !sc.state().permissions.allows_high_precision() {
+    subsec_nanos -= subsec_nanos % reduced_time_precision
+  }
 
   let builder = &mut FlatBufferBuilder::new();
-  let inner = msg::NowRes::create(builder, &msg::NowResArgs { time });
+  let inner = msg::NowRes::create(
+    builder,
+    &msg::NowResArgs {
+      seconds,
+      subsec_nanos,
+    },
+  );
   ok_future(serialize_response(
     base.cmd_id(),
     builder,
@@ -555,6 +571,7 @@ fn op_permissions(
       write: sc.state().permissions.allows_write(),
       net: sc.state().permissions.allows_net(),
       env: sc.state().permissions.allows_env(),
+      high_precision: sc.state().permissions.allows_high_precision(),
     },
   );
   ok_future(serialize_response(
@@ -582,6 +599,7 @@ fn op_revoke_permission(
     "write" => sc.state().permissions.revoke_write(),
     "net" => sc.state().permissions.revoke_net(),
     "env" => sc.state().permissions.revoke_env(),
+    "highPrecision" => sc.state().permissions.revoke_high_precision(),
     _ => Ok(()),
   };
   if let Err(e) = result {

cli/permissions.rs

@@ -131,6 +131,7 @@ pub struct DenoPermissions {
   pub allow_net: PermissionAccessor,
   pub allow_env: PermissionAccessor,
   pub allow_run: PermissionAccessor,
+  pub allow_high_precision: PermissionAccessor,
   pub no_prompts: AtomicBool,
 }
 
@@ -142,6 +143,9 @@ impl DenoPermissions {
       allow_env: PermissionAccessor::from(flags.allow_env),
       allow_net: PermissionAccessor::from(flags.allow_net),
       allow_run: PermissionAccessor::from(flags.allow_run),
+      allow_high_precision: PermissionAccessor::from(
+        flags.allow_high_precision,
+      ),
       no_prompts: AtomicBool::new(flags.no_prompts),
     }
   }
@@ -263,6 +267,10 @@ impl DenoPermissions {
     self.allow_env.is_allow()
   }
 
+  pub fn allows_high_precision(&self) -> bool {
+    return self.allow_high_precision.is_allow();
+  }
+
   pub fn revoke_run(&self) -> DenoResult<()> {
     self.allow_run.revoke();
     Ok(())
@@ -287,6 +295,10 @@ impl DenoPermissions {
     self.allow_env.revoke();
     Ok(())
   }
+  pub fn revoke_high_precision(&self) -> DenoResult<()> {
+    self.allow_high_precision.revoke();
+    return Ok(());
+  }
 }
 
 /// Quad-state value for representing user input on permission prompt

js/performance.ts

@@ -5,13 +5,9 @@ import * as flatbuffers from "./flatbuffers";
 import { assert } from "./util";
 
 export class Performance {
-  timeOrigin = 0;
-
-  constructor() {
-    this.timeOrigin = new Date().getTime();
-  }
-
-  /** Returns a current time from Deno's start
+  /** Returns a current time from Deno's start.
+   *  In milliseconds. Flag --allow-high-precision give
+   *  a precise measure.
    *
    *       const t = performance.now();
    *       console.log(`${t} ms since start!`);
@@ -23,6 +19,6 @@ export class Performance {
     assert(msg.Any.NowRes === baseRes.innerType());
     const res = new msg.NowRes();
     assert(baseRes.inner(res) != null);
-    return res.time().toFloat64() - this.timeOrigin;
+    return res.seconds().toFloat64() * 1e3 + res.subsecNanos() / 1e6;
   }
 }

js/performance_test.ts

@@ -1,7 +1,7 @@
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-import { test, assert } from "./test_util.ts";
+import { testPerm, assert } from "./test_util.ts";
 
-test(function now() {
+testPerm({ highPrecision: false }, function now() {
   const start = performance.now();
   setTimeout(() => {
     const end = performance.now();

js/permissions.ts

@@ -11,7 +11,7 @@ export interface Permissions {
   net: boolean;
   env: boolean;
   run: boolean;
-
+  highPrecision: boolean;
   // NOTE: Keep in sync with src/permissions.rs
 }
 
@@ -29,7 +29,8 @@ function createPermissions(inner: msg.PermissionsRes): Permissions {
     write: inner.write(),
     net: inner.net(),
     env: inner.env(),
-    run: inner.run()
+    run: inner.run(),
+    highPrecision: inner.highPrecision()
   };
 }
 

js/permissions_test.ts

@@ -6,7 +6,8 @@ const knownPermissions: Deno.Permission[] = [
   "read",
   "write",
   "net",
-  "env"
+  "env",
+  "highPrecision"
 ];
 
 for (let grant of knownPermissions) {

js/test_util.ts

@@ -26,6 +26,7 @@ interface DenoPermissions {
   net?: boolean;
   env?: boolean;
   run?: boolean;
+  highPrecision?: boolean;
 }
 
 function permToString(perms: DenoPermissions): string {
@@ -34,11 +35,12 @@ function permToString(perms: DenoPermissions): string {
   const n = perms.net ? 1 : 0;
   const e = perms.env ? 1 : 0;
   const u = perms.run ? 1 : 0;
-  return `permR${r}W${w}N${n}E${e}U${u}`;
+  const h = perms.highPrecision ? 1 : 0;
+  return `permR${r}W${w}N${n}E${e}U${u}H${h}`;
 }
 
 function permFromString(s: string): DenoPermissions {
-  const re = /^permR([01])W([01])N([01])E([01])U([01])$/;
+  const re = /^permR([01])W([01])N([01])E([01])U([01])H([01])$/;
   const found = s.match(re);
   if (!found) {
     throw Error("Not a permission string");
@@ -48,7 +50,8 @@ function permFromString(s: string): DenoPermissions {
     write: Boolean(Number(found[2])),
     net: Boolean(Number(found[3])),
     env: Boolean(Number(found[4])),
-    run: Boolean(Number(found[5]))
+    run: Boolean(Number(found[5])),
+    highPrecision: Boolean(Number(found[6]))
   };
 }
 
@@ -62,7 +65,14 @@ export function testPerm(
 
 export function test(fn: testing.TestFunction): void {
   testPerm(
-    { read: false, write: false, net: false, env: false, run: false },
+    {
+      read: false,
+      write: false,
+      net: false,
+      env: false,
+      run: false,
+      highPrecision: false
+    },
     fn
   );
 }
@@ -73,8 +83,17 @@ test(function permSerialization() {
       for (const env of [true, false]) {
         for (const run of [true, false]) {
           for (const read of [true, false]) {
-            const perms: DenoPermissions = { write, net, env, run, read };
-            assertEquals(perms, permFromString(permToString(perms)));
+            for (const highPrecision of [true, false]) {
+              const perms: DenoPermissions = {
+                write,
+                net,
+                env,
+                run,
+                read,
+                highPrecision
+              };
+              assertEquals(perms, permFromString(permToString(perms)));
+            }
           }
         }
       }

tests/025_high_precision.test

@@ -0,0 +1,2 @@
+args: --allow-high-precision --reload tests/025_high_precision.ts
+output: tests/025_high_precision.ts.out

tests/025_high_precision.ts

@@ -0,0 +1,3 @@
+console.log(performance.now() % 2 !== 0);
+Deno.revokePermission("highPrecision");
+console.log(performance.now() % 2 === 0);

tests/025_high_precision.ts.out

@@ -0,0 +1,2 @@
+true
+true

tools/unit_tests.py

@@ -45,14 +45,16 @@ def run_unit_test(deno_exe, permStr, flags=None):
 # tests by the special string. permW0N0 means allow-write but not allow-net.
 # See js/test_util.ts for more details.
 def unit_tests(deno_exe):
-    run_unit_test(deno_exe, "permR0W0N0E0U0", ["--reload"])
-    run_unit_test(deno_exe, "permR1W0N0E0U0", ["--allow-read"])
-    run_unit_test(deno_exe, "permR0W1N0E0U0", ["--allow-write"])
-    run_unit_test(deno_exe, "permR1W1N0E0U0",
+    run_unit_test(deno_exe, "permR0W0N0E0U0H0", ["--reload"])
+    run_unit_test(deno_exe, "permR1W0N0E0U0H0", ["--allow-read"])
+    run_unit_test(deno_exe, "permR0W1N0E0U0H0", ["--allow-write"])
+    run_unit_test(deno_exe, "permR1W1N0E0U0H0",
                   ["--allow-read", "--allow-write"])
-    run_unit_test(deno_exe, "permR0W0N0E1U0", ["--allow-env"])
-    run_unit_test(deno_exe, "permR0W0N0E0U1", ["--allow-run"])
-    run_unit_test(deno_exe, "permR0W1N0E0U1", ["--allow-run", "--allow-write"])
+    run_unit_test(deno_exe, "permR0W0N0E1U0H0", ["--allow-env"])
+    run_unit_test(deno_exe, "permR0W0N0E0U0H1", ["--allow-high-precision"])
+    run_unit_test(deno_exe, "permR0W0N0E0U1H0", ["--allow-run"])
+    run_unit_test(deno_exe, "permR0W1N0E0U1H0",
+                  ["--allow-run", "--allow-write"])
     # TODO We might accidentally miss some. We should be smarter about which we
     # run. Maybe we can use the "filtered out" number to check this.