Allow multiple substitute mappings for music tracks.

For the Hexen substitute mapping configuration file, it's desirable
to be able to include two mappings for each music lump: a straight
high quality recording of that lump, and the recording that was
included on the Hexen CD audio tracks. So allow multiple mappings
so that we can fall back to try other filenames if the first choice
file doesn't appear to exist.

1 files changed, 17 insertions, 2 deletions

diff --git a/src/i_sdlmusic.c b/src/i_sdlmusic.c
index cf4a6b8b..cca41322 100644
--- a/src/i_sdlmusic.c
+++ b/src/i_sdlmusic.c
@@ -414,6 +414,7 @@ static char *GetSubstituteMusicFile(void *data, size_t data_len)
 {
     sha1_context_t context;
     sha1_digest_t hash;
+    char *filename;
     int i;
 
     // Don't bother doing a hash if we're never going to find anything.
@@ -427,16 +428,30 @@ static char *GetSubstituteMusicFile(void *data, size_t data_len)
     SHA1_Final(hash, &context);
 
     // Look for a hash that matches.
+    // The substitute mapping list can (intentionally) contain multiple
+    // filename mappings for the same hash. This allows us to try
+    // different files and fall back if our first choice isn't found.
+
+    filename = NULL;
 
     for (i = 0; i < subst_music_len; ++i)
     {
         if (memcmp(hash, subst_music[i].hash, sizeof(hash)) == 0)
         {
-            return subst_music[i].filename;
+            filename = subst_music[i].filename;
+
+            // If the file exists, then use this file in preference to
+            // any fallbacks. But we always return a filename if it's
+            // in the list, even if it's just so we can print an error
+            // message to the user saying it doesn't exist.
+            if (M_FileExists(filename))
+            {
+                break;
+            }
         }
     }
 
-    return NULL;
+    return filename;
 }
 
 // Add a substitute music file to the lookup list.