{is,read}_symlink: speedup

Author: scivision

+stdlib/+dotnet/read_symlink.m

@@ -7,12 +7,9 @@
   h = System.IO.FileInfo(file);
   r = string(h.LinkTarget);
   % on Unix, this can be empty if the file is not a symlink
-  if isempty(r)
-    r = "";
-  end
 catch e
   dotnetException(e)
-  r = "";
+  r = string.empty;
 end
 
 end

+stdlib/+java/is_symlink.m

@@ -1,5 +1,9 @@
 function ok = is_symlink(file)
 
-ok = java.nio.file.Files.isSymbolicLink(javaAbsolutePath(file));
+try
+  ok = java.nio.file.Files.isSymbolicLink(javaAbsolutePath(file));
+catch e
+  javaException(e)
+end
 
 end

+stdlib/+java/read_symlink.m

@@ -10,7 +10,7 @@
   r = string(java.nio.file.Files.readSymbolicLink(javaAbsolutePath(file)));
 catch e
   javaException(e)
-  r = "";
+  r = string.empty;
 end
 
 end

+stdlib/+legacy/canonical.m

@@ -6,7 +6,9 @@
 
 c = "";
 
-if stdlib.strempty(file), return, end
+if stdlib.strempty(file)
+  return
+end
 
 [s, r] = fileattrib(file);
 

+stdlib/+native/is_symlink.m

@@ -0,0 +1,12 @@
+function i = is_symlink(file)
+
+try
+  i = isSymbolicLink(file);
+catch e
+  if e.identifier ~= "MATLAB:UndefinedFunction"
+    rethrow(e)
+  end
+  i = logical.empty;
+end
+
+end

+stdlib/+native/read_symlink.m

@@ -0,0 +1,15 @@
+function r = read_symlink(file)
+
+try
+  [ok, r] = isSymbolicLink(file);
+  if ~ok
+    r = string.empty;
+  end
+catch e
+  if e.identifier ~= "MATLAB:UndefinedFunction"
+    rethrow(e)
+  end
+  r = string.empty;
+end
+
+end

+stdlib/+python/read_symlink.m

@@ -1,9 +1,11 @@
 function r = read_symlink(file)
 
-r = "";
+r = string.empty;
 
 p = py.pathlib.Path(file);
-if ~p.is_symlink(), return, end
+if ~p.is_symlink()
+  return
+end
 
 % https://docs.python.org/3/library/pathlib.html#pathlib.Path.readlink
 try

+stdlib/+sys/read_symlink.m

@@ -3,7 +3,7 @@
   file (1,1) string
 end
 
-r = "";
+r = string.empty;
 
 if isunix()
   cmd = sprintf('readlink -fn "%s"', file);
@@ -14,7 +14,7 @@
   % worried if searching for "Tag value: Symbolic Link" might be locale dependent
 end
 
-if stdlib.is_symlink(file)
+if stdlib.sys.is_symlink(file)
   [s, m] = system(cmd);
   if s == 0
     m = strip(string(m));

+stdlib/Backend.m

@@ -102,6 +102,18 @@
           pyv = stdlib.python_version();
           if any(pyv(1:2) < [3, 12]), continue, end
       end
+    case 'native'
+
+      switch functionName
+        case 'create_symlink'
+          % Some Windows R2025a give error 'MATLAB:io:filesystem:symlink:NeedsAdminPerms'
+          % 25.1.0.2973910 (R2025a) Update 1 gave this error for example.
+          if stdlib.matlabOlderThan('R2024b') || ispc()
+            continue
+          end
+        case {'is_symlink', 'read_symlink'}
+          if stdlib.matlabOlderThan('R2024b'), continue, end
+      end
   end
 
   if ~isempty(which(sprintf('%s.%s.%s', self.namespace, m, functionName)))

+stdlib/is_symlink.m

@@ -4,31 +4,37 @@
 % * file: path to check
 % * backend: backend to use
 %%% Outputs
-% * ok: true if path is a symbolic link
+% * i: true if path is a symbolic link
 % * b: backend used
 
-function [ok, b] = is_symlink(file, backend)
+function [i, b] = is_symlink(file, backend)
 arguments
-  file string
+  file (1,1) string
   backend (1,:) string = ["native", "java", "python", "dotnet", "sys"]
 end
 
-if ismember('native', backend) || stdlib.strempty(backend)
-  try
-    ok = isSymbolicLink(file);
-    b = "native";
-    return
-  catch e
-    if e.identifier ~= "MATLAB:UndefinedFunction"
-      rethrow(e)
-    end
+i = logical.empty;
+
+for b = backend
+  switch b
+    case "java"
+      i = stdlib.java.is_symlink(file);
+    case "native"
+      i = stdlib.native.is_symlink(file);
+    case "dotnet"
+      i = stdlib.dotnet.is_symlink(file);
+    case "python"
+      if stdlib.matlabOlderThan('R2022a'), continue, end
+      i = stdlib.python.is_symlink(file);
+    case "sys"
+      i = stdlib.sys.is_symlink(file);
+    otherwise
+      error("stdlib:is_symlink:ValueError", "Unknown backend: %s", b)
   end
 
-  backend(ismember(backend, 'native')) = [];
+  if ~isempty(i)
+    return
+  end
 end
 
-o = stdlib.Backend(mfilename(), backend);
-b = o.backend;
-ok = o.func(file);
-
 end