Optimize Path#drive, #root, and #anchor

src/path.cr

@@ -1122,7 +1122,10 @@ struct Path
   #
   # NOTE: Drives are only available for Windows paths. It can either be a drive letter (`C:`) or a UNC share (`\\host\share`).
   def drive : Path?
-    if drive = drive_and_root[0]
+    drive_end, _ = drive_and_root_indices
+
+    if drive_end
+      drive = @name.byte_slice(0, drive_end)
       new_instance drive
     end
   end
@@ -1138,7 +1141,11 @@ struct Path
   # Path.windows("\\\\host\\share\\folder").root # => Path.windows("\\")
   # ```
   def root : Path?
-    if root = drive_and_root[1]
+    drive_end, root_end = drive_and_root_indices
+
+    if root_end
+      root_start = drive_end || 0
+      root = @name.byte_slice(root_start, root_end - root_start)
       new_instance root
     end
   end
@@ -1152,47 +1159,49 @@ struct Path
   # Path.windows("\\\\host\\share\\folder").anchor # => Path.windows("\\\\host\\share\\")
   # ```
   def anchor : Path?
-    drive, root = drive_and_root
+    drive_end, root_end = drive_and_root_indices
+    anchor_end = root_end || drive_end
 
-    if root
-      if drive
-        new_instance({drive, root}.join)
-      else
-        new_instance(root)
-      end
-    elsif drive
-      new_instance drive
+    if anchor_end
+      new_instance(@name.byte_slice(0, anchor_end))
     end
   end
 
   # Returns a tuple of `#drive` and `#root` as strings.
   def drive_and_root : {String?, String?}
+    drive_end, root_end = drive_and_root_indices
+
+    if drive_end
+      drive = @name.byte_slice(0, drive_end)
+    end
+
+    if root_end
+      root_start = drive_end || 0
+      root = @name.byte_slice(root_start, root_end - root_start)
+    end
+
+    {drive, root}
+  end
+
+  private def drive_and_root_indices : {Int32?, Int32?}
     if windows?
       if windows_drive?
-        drive = @name.byte_slice(0, 2)
         if separators.includes?(@name.byte_at?(2).try(&.chr))
-          return drive, @name.byte_slice(2, 1)
+          {2, 3}
         else
-          return drive, nil
+          {2, nil}
         end
       elsif unc_share = unc_share?
-        share_end, root_end = unc_share
-        if share_end == root_end
-          root = nil
-        else
-          root = @name.byte_slice(share_end, root_end - share_end)
-        end
-
-        return @name.byte_slice(0, share_end), root
+        unc_share
       elsif starts_with_separator?
-        return nil, @name.byte_slice(0, 1)
+        {nil, 1}
       else
-        return nil, nil
+        {nil, nil}
       end
     elsif absolute? # posix
-      return nil, "/"
+      {nil, 1}
     else
-      return nil, nil
+      {nil, nil}
     end
   end
 
@@ -1261,7 +1270,11 @@ struct Path
       break unless separators.includes?(char)
     end
 
-    return share_end, reader.pos
+    unless reader.pos == share_end
+      root_end = reader.pos
+    end
+
+    return share_end, root_end
   end
 
   # Returns `true` if this path is absolute.