buffer: use slightly faster NaN check

PR-URL: #12286 Reviewed-By: Timothy Gu <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

Author: mscdex

benchmark/buffers/buffer-indexof-number.js

@@ -0,0 +1,23 @@
+'use strict';
+constcommon=require('../common.js');
+constfs=require('fs');
+constpath=require('path');
+
+constbench=common.createBenchmark(main,{
+value: ['@'.charCodeAt(0)],
+n: [1e7]
+});
+
+functionmain(conf){
+constn=+conf.n;
+constsearch=+conf.value;
+constaliceBuffer=fs.readFileSync(
+path.resolve(__dirname,'../fixtures/alice.html')
+);
+
+bench.start();
+for(vari=0;i<n;i++){
+aliceBuffer.indexOf(search,0,undefined);
+}
+bench.end(n);
+}

lib/buffer.js

@@ -602,7 +602,8 @@ function bidirectionalIndexOf(buffer, val, byteOffset, encoding, dir){
 // Coerce to Number. Values like null and [] become 0.
 byteOffset=+byteOffset;
 // If the offset is undefined, "foo",{}, coerces to NaN, search whole buffer.
-if(Number.isNaN(byteOffset)){
+// `x !== x`-style conditionals are a faster form of `isNaN(x)`
+if(byteOffset!==byteOffset){
 byteOffset=dir ? 0 : (buffer.length-1);
 }
 dir=!!dir;// Cast to bool.
@@ -824,7 +825,8 @@ function adjustOffset(offset, length){
 // Use Math.trunc() to convert offset to an integer value that can be larger
 // than an Int32. Hence, don't use offset | 0 or similar techniques.
 offset=Math.trunc(offset);
-if(offset===0||Number.isNaN(offset)){
+// `x !== x`-style conditionals are a faster form of `isNaN(x)`
+if(offset===0||offset!==offset){
 return0;
 }elseif(offset<0){
 offset+=length;