Better approach to finding an algorithm

1 files changed, 18 insertions, 16 deletions

diff --git a/checkem b/checkem
index 7afcdbb..1df8fb6 100755
--- a/checkem
+++ b/checkem
@@ -42,23 +42,25 @@ my %STATS = (
     size => 7,
 );
 
-# Create a digest object, trying to safely detect ancient Perl (5.6)
-# installations, or others that are bereft of Digest::SHA, in order
-# to pick the algorithm. It can be foced with the CHECKEM_ALG environment
-# variable.
-my $dig = do {
-    my $alg;
-    if ( exists $ENV{CHECKEM_ALG} ) {
-        $alg = $ENV{CHECKEM_ALG};
-    }
-    elsif ( eval { require Digest::SHA; } ) {
-        $alg = 'SHA-1';
-    }
-    else {
-        $alg = 'MD5';
+# We need to pick and create a Digest object
+my $dig;
+
+# We were told which algorithm to use
+if ( exists $ENV{CHECKEM_ALG} ) {
+    $dig = Digest->new( $ENV{CHECKEM_ALG} );
+}
+
+# Try worse and worse algorithms until we get a digest object
+else {
+  ALG: for my $alg (qw(SHA-256 SHA-1 MD5)) {
+        next ALG if not eval { $dig = Digest->new($alg); };
     }
-    Digest->new($alg);
-};
+}
+
+# Still no digest object, give up
+if ( !defined $dig ) {
+    croak 'Could not create a useable Digest object';
+}
 
 # Start a hash of filesizes to file names/stats...
 my %sizes;