file_checksum: use missing

Author: scivision

+stdlib/+dotnet/file_checksum.m

@@ -23,7 +23,7 @@
   hash = sprintf('%.2x', uint8(inst.Hash));
 catch e
   dotnetException(e)
-  hash = '';
+  hash = missing;
 end
 
 fclose(fid);

+stdlib/+java/file_checksum.m

@@ -4,13 +4,13 @@
 function hash = file_checksum(file, hash_method)
 
 if strcmpi(hash_method, 'sha256')
-  hash_method = "SHA-256";
+  hash_method = 'SHA-256';
 end
 
 file_chunk = 10e6;  % arbitrary (bytes) didn't seem to be very sensitive for speed
 
 fid = fopen(file, 'r');
-assert(fid > 1, "could not open file %s", file)
+assert(fid > 1, 'could not open file %s', file)
 
 try
 
@@ -27,7 +27,7 @@
 
 catch e
   javaException(e)
-  hash = '';
+  hash = missing;
 end
 
 fclose(fid);

+stdlib/+shell/file_checksum.m

@@ -2,15 +2,15 @@
 function [hash, cmd] = file_checksum(file, hash_method)
 
 switch lower(hash_method)
-  case {"sha-256", "sha256"}
+  case {'sha-256', 'sha256'}
     if ismac()
       cmd = sprintf('shasum --algorithm 256 --binary "%s"', file);
     elseif ispc()
       cmd = sprintf('CertUtil -hashfile "%s" SHA256', file);
     else
       cmd = sprintf('sha256sum --binary "%s"', file);
     end
-  case "md5"
+  case 'md5'
     if ismac()
       cmd = sprintf('md5 -r "%s"', file);
     elseif ispc()
@@ -25,13 +25,13 @@
 
 if s == 0
   switch lower(hash_method)
-  case {"sha-256", "sha256"}
+  case {'sha-256', 'sha256'}
     hash = regexp(m, '^\w{64}','match','once','lineanchors');
-  case "md5"
+  case 'md5'
     hash = regexp(m, '^\w{32}','match','once','lineanchors');
   end
 else
-  hash = '';
+  hash = missing;
 end
 
 end

+stdlib/file_checksum.m

@@ -19,7 +19,7 @@
   backend (1,:) string = ["java", "dotnet", "shell"]
 end
 
-r = '';
+r = missing;
 
 for b = backend
   switch b
@@ -33,7 +33,7 @@
       error('stdlib:file_checksum:ValueError', 'Unknown backend: %s', b)
   end
 
-  if ~isempty(r)
+  if ~ismissing(r)
     return
   end
 end

test/TestHash.m

@@ -41,29 +41,29 @@ function test_hash_text(tc, Ph, backend)
 
 [r, b] = stdlib.file_checksum(tc.file, Ph{1}, backend);
 tc.assertMatches(b, backend)
-tc.verifyClass(r, 'char')
 
 if ismember(backend, stdlib.Backend().select('file_checksum'))
+  tc.verifyClass(r, 'char')
   tc.verifyEqual(r, Ph{2})
 else
-  tc.assertEmpty(r)
+  tc.assertEqual(r, missing)
 end
 end
 
 
 function test_hash_empty(tc, Pe, backend)
 
 r = stdlib.file_checksum(tc.empty, Pe{1}, backend);
-tc.verifyClass(r, 'char')
 
 if ismember(backend, stdlib.Backend().select('file_checksum'))
   if ispc() && strcmp(backend, 'shell')
-    tc.verifyEmpty(r)
+    tc.verifyEqual(r, missing)
   else
+    tc.verifyClass(r, 'char')
     tc.verifyEqual(r, Pe{2})
   end
 else
-  tc.assertEmpty(r)
+  tc.assertEqual(r, missing)
 end
 end