Update FFI to be more portable and direct. (#25)

* Update FFI to be more portable and direct.

* Update CHANGELOG

Author: natefaubion

CHANGELOG.md

@@ -11,6 +11,7 @@ New features:
 Bugfixes:
 
 Other improvements:
+- Update FFI to use a more direct and portable convention (#25 by @natefaubion)
 
 ## [v4.0.0](https://github.com/purescript/purescript-minibench/releases/tag/v4.0.0) - 2022-04-27
 

src/Performance/Minibench.js

@@ -1,4 +1,9 @@
-export const hrTime = process.hrtime;
+export function timeNs(k) {
+  const t1 = process.hrtime();
+  k();
+  const t2 = process.hrtime(t1);
+  return t2[0] * 1.0e9 + t2[1];
+}
 
 export function gc() {
   global.gc && global.gc();

src/Performance/Minibench.purs

@@ -20,21 +20,16 @@ import Effect.Console (log)
 import Effect.Ref as Ref
 import Effect.Uncurried (EffectFn1, runEffectFn1)
 import Data.Number (infinity, max, min, sqrt)
-import Partial.Unsafe (unsafeCrashWith)
 
--- | A wrapper around the Node `process.hrtime()` function.
-foreign import hrTime :: EffectFn1 (Array Int) (Array Int)
+-- | Returns the number of nanoseconds it takes to evaluate the given closure.
+foreign import timeNs :: forall a. EffectFn1 (Unit -> a) Number
 
 -- | Force garbage collection.
 -- | Requires node to be run with the --force-gc flag.
 foreign import gc :: Effect Unit
 
 foreign import toFixed :: Number -> String
 
-fromHrTime :: Array Int -> Number
-fromHrTime [s, ns] = toNumber s * 1.0e9 + toNumber ns
-fromHrTime _ = unsafeCrashWith "fromHrTime: unexpected result from process.hrtime()"
-
 withUnits :: Number -> String
 withUnits t
   | t < 1.0e3 = toFixed t <> " ns"
@@ -79,10 +74,8 @@ benchWith' n f = do
   maxRef <- Ref.new 0.0
   gc
   forE 0 n \_ -> do
-    t1 <- runEffectFn1 hrTime [0, 0]
-    t2 <- const (runEffectFn1 hrTime t1) (f unit)
-    let ns     = fromHrTime t2
-        square = ns * ns
+    ns <- runEffectFn1 timeNs f
+    let square = ns * ns
     _ <- Ref.modify (_ + ns) sumRef
     _ <- Ref.modify (_ + square) sum2Ref
     _ <- Ref.modify (_ `min` ns) minRef