--- previous/src/str.c	2018/04/24 19:25:10	1.1.1.1
+++ previous/src/str.c	2018/04/24 19:25:34	1.1.1.2
@@ -118,3 +118,72 @@ bool Str_IsHex(const char *str)
 	}
 	return true;
 }
+
+
+/**
+ * Convert potentially too long host filenames to 8.3 TOS filenames
+ * by truncating extension and part before it, replacing invalid
+ * GEMDOS file name characters with INVALID_CHAR + upcasing the result.
+ * 
+ * Matching them from the host file system should first try exact
+ * case-insensitive match, and then with a pattern that takes into
+ * account the conversion done in here.
+ */
+void Str_Filename2TOSname(const char *source, char *dst)
+{
+    char *dot, *tmp, *src;
+    int len;
+
+    src = strdup(source); /* dup so that it can be modified */
+    len = strlen(src);
+
+    /* does filename have an extension? */
+    dot = strrchr(src, '.');
+    if (dot)
+    {
+        /* limit extension to 3 chars */
+        if (src + len - dot > 3)
+            dot[4] = '\0';
+
+        /* if there are extra dots, convert them */
+        for (tmp = src; tmp < dot; tmp++)
+            if (*tmp == '.')
+                *tmp = INVALID_CHAR;
+    }
+
+    /* does name now fit to 8 (+3) chars? */
+    if (len <= 8 || (dot && len <= 12))
+        strcpy(dst, src);
+    else
+    {
+        /* name (still) too long, cut part before extension */
+        strncpy(dst, src, 8);
+        if (dot)
+            strcpy(dst+8, dot);
+        else
+            dst[8] = '\0';
+    }
+    free(src);
+
+    /* replace other invalid chars than '.' in filename */
+    for (tmp = dst; *tmp; tmp++)
+    {
+        if (*tmp < 33 || *tmp > 126)
+            *tmp = INVALID_CHAR;
+        else
+        {
+            switch (*tmp)
+            {
+                case '*':
+                case '/':
+                case ':':
+                case '?':
+                case '\\':
+                case '{':
+                case '}':
+                    *tmp = INVALID_CHAR;
+            }
+        }
+    }
+    Str_ToUpper(dst);
+}