is_{exe,readable,writable} 40x faster than native

Author: scivision

+stdlib/+legacy/file_attributes.m

@@ -4,11 +4,17 @@
 end
 % need arguments and stdlib.strempty for Matlab < R2020b
 
-assert(~stdlib.strempty(p), 'Path must not be empty.');
+a = struct.empty;
+
+if stdlib.strempty(p)
+  return
+end
 
 [status, s] = fileattrib(p);
 
-assert(status == 1, "'%s' is not a file or directory.", p);
+if status ~= 1
+  return
+end
 
 a = s;
 for n = ["GroupRead", "GroupWrite", "GroupExecute", "OtherRead", "OtherWrite", "OtherExecute"]

+stdlib/+legacy/is_exe.m

@@ -6,11 +6,10 @@
   return
 end
 
-if ~isfile(file)
-  return
-end
-
 a = stdlib.legacy.file_attributes(file);
-y = a.UserExecute || a.GroupExecute || a.OtherExecute;
+
+if ~isempty(a) && ~a.directory
+  y = a.UserExecute || a.GroupExecute || a.OtherExecute;
+end
 
 end

+stdlib/+legacy/is_readable.m

@@ -1,13 +1,11 @@
 function y = is_readable(file)
-arguments
-  file (1,1) string
-end
 
-if stdlib.exists(file)
-  a = stdlib.legacy.file_attributes(file);
+y = false;
+
+a = stdlib.legacy.file_attributes(file);
+
+if ~isempty(a)
   y = a.UserRead || a.GroupRead || a.OtherRead;
-else
-  y = false;
 end
 
 end

+stdlib/+legacy/is_writable.m

@@ -1,13 +1,11 @@
 function y = is_writable(file)
-arguments
-  file (1,1) string
-end
 
-if stdlib.exists(file)
-  a = stdlib.legacy.file_attributes(file);
+y = false;
+
+a = stdlib.legacy.file_attributes(file);
+
+if ~isempty(a)
   y = a.UserWrite || a.GroupWrite || a.OtherWrite;
-else
-  y = false;
 end
 
 end

+stdlib/get_permissions.m

@@ -13,20 +13,20 @@
   file (1,1) string
 end
 
-perm = '';
-b = '';
 
-if stdlib.exists(file)
-  try
-    perm = perm2char(filePermissions(file));
-    b = 'native';
-  catch e
-    if e.identifier ~= "MATLAB:UndefinedFunction"
+try
+  perm = perm2char(filePermissions(file));
+  b = 'native';
+catch e
+  switch e.identifier
+    case 'MATLAB:UndefinedFunction'
+      perm = perm2char(stdlib.legacy.file_attributes(file));
+      b = 'legacy';
+    case 'MATLAB:io:filesystem:filePermissions:CannotFindLocation'
+      perm = '';
+      b = '';
+    otherwise
       rethrow(e)
-    end
-
-    perm = perm2char(stdlib.legacy.file_attributes(file));
-    b = 'legacy';
   end
 end
 

+stdlib/is_exe.m

@@ -6,7 +6,7 @@
 %%% Outputs
 % ok: true if path is a file and has executable permissions
 %
-% the legacy backend is actually significantly faster for single files
+% the legacy backend is like 40x faster than native.
 
 function [ok, b] = is_exe(file)
 arguments

+stdlib/is_readable.m

@@ -5,7 +5,7 @@
 %%% Outputs
 % ok: true if file is readable
 %
-% the legacy backend is actually significantly faster for single files
+% the legacy backend is like 40x faster than native
 
 function [ok, b] = is_readable(file)
 arguments

+stdlib/is_writable.m

@@ -5,7 +5,7 @@
 %%% Outputs
 % * ok: true if file is writable
 %
-% the legacy backend is actually significantly faster for single files
+% the legacy backend is like 40x faster than native
 
 function [ok, b] = is_writable(file)
 arguments

+stdlib/private/perm2char.m

@@ -2,22 +2,28 @@
 
 function p = perm2char(v)
 arguments
-  v (1,1)
+  v {mustBeScalarOrEmpty}
+end
+
+if isempty(v)
+  p = '';
+  return
 end
 
 
 p = '---------';
 
-if isa(v, "matlab.io.WindowsPermissions") || isa(v, "matlab.io.UnixPermissions")
-  if v.Readable,  p(1) = 'r'; end
-  if v.Writable,  p(2) = 'w'; end
-elseif isstruct(v)
-  if v.UserRead,  p(1) = 'r'; end
-  if v.UserWrite, p(2) = 'w'; end
-else
-  % cloud / remote locations we don't handle
-  p = '';
-  return
+switch class(v)
+  case {'matlab.io.WindowsPermissions', 'matlab.io.UnixPermissions'}
+    if v.Readable,  p(1) = 'r'; end
+    if v.Writable,  p(2) = 'w'; end
+  case 'struct'
+    if v.UserRead,  p(1) = 'r'; end
+    if v.UserWrite, p(2) = 'w'; end
+  otherwise
+    % cloud / remote locations we don't handle
+    p = '';
+    return
 end
 
 if isa(v, "matlab.io.WindowsPermissions") || ispc()

example/BenchmarkIsExe.m

@@ -17,9 +17,9 @@ function bench_exist(tc, fun)
   e = e + ".exe";
 end
 
-tc.startMeasuring()
-y = fun(e);
-tc.stopMeasuring()
+while tc.keepMeasuring()
+  y = fun(e);
+end
 
 tc.verifyEqual(y, true)
 end