file_checksum: streamline, output char

This is for efficiency

Author: scivision

+stdlib/file_checksum.m

@@ -13,14 +13,8 @@
 
 function hash = file_checksum(file, method)
 arguments
-  file (1,1) string
-  method (1,1) string
-end
-
-try
-  hash = string.empty;
-catch
-  hash = [];
+  file {mustBeFile}
+  method {mustBeTextScalar}
 end
 
 if strcmp(method, "sha256") || strcmp(method, "SHA256")
@@ -36,10 +30,7 @@
 end
 
 fid = fopen(file, 'r');
-if fid < 1
-  warning("stdlib:file_checksum:ioerror", strcat("could not open ", file))
-  return
-end
+assert(fid > 1, "could not open file %s", file)
 
 while ~feof(fid)
   % https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/security/MessageDigest.html#update(byte)
@@ -52,10 +43,6 @@
 
 hash = sprintf('%.2x', hash);
 
-try %#ok<TRYNC>
-  hash = string(hash);
-end
-
 end
 
 %!assert(!isempty(file_checksum('file_checksum.m', "sha256")))

+stdlib/md5sum.m

@@ -2,7 +2,7 @@
 % requires: java
 function hash = md5sum(file)
 arguments
-  file (1,1) string
+  file {mustBeScalarText}
 end
 
 hash = stdlib.file_checksum(file, "md5");

+stdlib/sha256sum.m

@@ -3,7 +3,7 @@
 
 function hash = sha256sum(file)
 arguments
-  file (1,1) string
+  file {mustBeScalarText}
 end
 
 hash = stdlib.file_checksum(file, "SHA-256");

test/TestHash.m

@@ -1,8 +1,8 @@
 classdef TestHash < matlab.unittest.TestCase
 
 properties (TestParameter)
-Ph = {{"md5", "5d41402abc4b2a76b9719d911017c592"}, {"sha-256", "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"}}
-Pe = {"", "/"}
+Ph = {{'md5', '5d41402abc4b2a76b9719d911017c592'}, ...
+      {'sha-256', '2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824'}}
 end
 
 methods(TestClassSetup)
@@ -34,12 +34,6 @@ function test_hash_text(tc, Ph)
 end
 
 
-function test_hash_empty(tc, Pe)
-tc.applyFixture(matlab.unittest.fixtures.SuppressedWarningsFixture("stdlib:file_checksum:ioerror"))
-
-tc.verifyEmpty(stdlib.file_checksum(Pe, "sha256"))
-end
-
 end
 
 end