maint: simplify printing of md5sum file names

* src/md5sum.c (main): Add a comment as to why we continue
to escape names that do not have '\n' but do have '\\' chars.
(print_filename): Use the predetermined boolean to decide
whether to escape or not, so that in the common case we
can output the file name directly, rather than inspecting each char.
* tests/misc/md5sum.pl: Add case to show '\\' chars cause escaping.
* tests/misc/sha1sum.pl: Likewise.

1 files changed, 22 insertions, 7 deletions

diff --git a/src/md5sum.c b/src/md5sum.c
index b43781150..bf7eb81a6 100644
--- a/src/md5sum.c
+++ b/src/md5sum.c
@@ -657,11 +657,17 @@ digest_check (const char *checkfile_name)
           && (!strict || n_improperly_formatted_lines == 0));
 }
 
+/* If ESCAPE is true, then translate each NEWLINE byte to the string, "\\n",
+   and each backslash to "\\\\".  */
 static void
-print_filename (char const *file)
+print_filename (char const *file, bool escape)
 {
-  /* Translate each NEWLINE byte to the string, "\\n",
-     and each backslash to "\\\\".  */
+  if (! escape)
+    {
+      fputs (file, stdout);
+      return;
+    }
+
   while (*file)
     {
       switch (*file)
@@ -823,14 +829,23 @@ main (int argc, char **argv)
             ok = false;
           else
             {
+              /* We don't really need to escape, and hence detect, the '\\'
+                 char, and not doing so should be both forwards and backwards
+                 compatible, since only escaped lines would have a '\\' char at
+                 the start.  However just in case users are directly comparing
+                 against old (hashed) outputs, in the presence of files
+                 containing '\\' characters, we decided to not simplify the
+                 output in this case.  */
+              bool needs_escape = strchr (file, '\\') || strchr (file, '\n');
+
               if (prefix_tag)
                 {
-                  if (strchr (file, '\n') || strchr (file, '\\'))
+                  if (needs_escape)
                     putchar ('\\');
 
                   fputs (DIGEST_TYPE_STRING, stdout);
                   fputs (" (", stdout);
-                  print_filename (file);
+                  print_filename (file, needs_escape);
                   fputs (") = ", stdout);
                 }
 
@@ -838,7 +853,7 @@ main (int argc, char **argv)
 
               /* Output a leading backslash if the file name contains
                  a newline or backslash.  */
-              if (!prefix_tag && (strchr (file, '\n') || strchr (file, '\\')))
+              if (!prefix_tag && needs_escape)
                 putchar ('\\');
 
               for (i = 0; i < (digest_hex_bytes / 2); ++i)
@@ -850,7 +865,7 @@ main (int argc, char **argv)
 
                   putchar (file_is_binary ? '*' : ' ');
 
-                  print_filename (file);
+                  print_filename (file, needs_escape);
                 }
 
               putchar ('\n');