path: remove unnecessary string copies

tniessen · tniessen · commit 2ac0aff2839a · 2017-07-26T13:49:25.000+02:00
As the length of `path` is known at this point, there is no point in making an exact copy using `slice`. PR-URL: nodejs#14438 Reviewed-By: Refael Ackermann <refack@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Timothy Gu <timothygu99@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Khaidi Chu <i@2333.moe>
diff --git a/lib/path.js b/lib/path.js
@@ -788,7 +788,9 @@ const win32 = {
         }
       }
     } else if (code === 47/*/*/ || code === 92/*\*/) {
-      return path[0];
+      // `path` contains just a path separator, exit early to avoid
+      // unnecessary work
+      return path;
     }
 
     for (var i = len - 1; i >= offset; --i) {
@@ -1040,7 +1042,7 @@ const win32 = {
               if (len === 3) {
                 // `path` contains just a drive root, exit early to avoid
                 // unnecessary work
-                ret.root = ret.dir = path.slice(0, 3);
+                ret.root = ret.dir = path;
                 return ret;
               }
               isAbsolute = true;
@@ -1049,15 +1051,15 @@ const win32 = {
           } else {
             // `path` contains just a drive root, exit early to avoid
             // unnecessary work
-            ret.root = ret.dir = path.slice(0, 2);
+            ret.root = ret.dir = path;
             return ret;
           }
         }
       }
     } else if (code === 47/*/*/ || code === 92/*\*/) {
       // `path` contains just a path separator, exit early to avoid
       // unnecessary work
-      ret.root = ret.dir = path[0];
+      ret.root = ret.dir = path;
       return ret;
     }
 

Original file line number	Diff line number	Diff line change
`@@ -788,7 +788,9 @@ const win32 = {`
`788`	`788`	`}`
`789`	`789`	`}`
`790`	`790`	`} else if (code === 47/// \|\| code === 92/\/) {`
`791`		`- return path[0];`
	`791`	+ // `path` contains just a path separator, exit early to avoid
	`792`	`+ // unnecessary work`
	`793`	`+ return path;`
`792`	`794`	`}`
`793`	`795`
`794`	`796`	`for (var i = len - 1; i >= offset; --i) {`
`@@ -1040,7 +1042,7 @@ const win32 = {`
`1040`	`1042`	`if (len === 3) {`
`1041`	`1043`	// `path` contains just a drive root, exit early to avoid
`1042`	`1044`	`// unnecessary work`
`1043`		`- ret.root = ret.dir = path.slice(0, 3);`
	`1045`	`+ ret.root = ret.dir = path;`
`1044`	`1046`	`return ret;`
`1045`	`1047`	`}`
`1046`	`1048`	`isAbsolute = true;`
`@@ -1049,15 +1051,15 @@ const win32 = {`
`1049`	`1051`	`} else {`
`1050`	`1052`	// `path` contains just a drive root, exit early to avoid
`1051`	`1053`	`// unnecessary work`
`1052`		`- ret.root = ret.dir = path.slice(0, 2);`
	`1054`	`+ ret.root = ret.dir = path;`
`1053`	`1055`	`return ret;`
`1054`	`1056`	`}`
`1055`	`1057`	`}`
`1056`	`1058`	`}`
`1057`	`1059`	`} else if (code === 47/// \|\| code === 92/\/) {`
`1058`	`1060`	// `path` contains just a path separator, exit early to avoid
`1059`	`1061`	`// unnecessary work`
`1060`		`- ret.root = ret.dir = path[0];`
	`1062`	`+ ret.root = ret.dir = path;`
`1061`	`1063`	`return ret;`
`1062`	`1064`	`}`
`1063`	`1065`