Fix writing metadata to RTF files with no info block

src/libprs500/ebooks/metadata/rtf.py

@@ -69,7 +69,7 @@ def get_metadata(stream):
     stream.seek(0)
     if stream.read(5) != r'{\rtf':
         raise Exception('Not a valid RTF file')
-    block, pos = get_document_info(stream)
+    block = get_document_info(stream)[0]
     if not block:
         return MetaInformation(None, None)
     title, author, comment, category = None, None, None, None
@@ -90,6 +90,29 @@ def get_metadata(stream):
     mi.category = category
     return mi
     
+
+def create_metadata(stream, options):
+    md = r'{\info'
+    if options.title:
+        title = options.title.encode('ascii', 'replace')
+        md += r'{\title %s}'%(title,)
+    if options.authors:
+        author = options.authors.encode('ascii', 'replace')
+        md += r'{\author %s}'%(author,)
+    if options.category:
+        category = options.category.encode('ascii', 'replace')
+        md += r'{\category %s}'%(category,)
+    if options.comment:
+        comment = options.comment.encode('ascii', 'replace')
+        md += r'{\subject %s}'%(comment,)
+    if len(md) > 6:
+        md += '}'
+        stream.seek(0)
+        src   = stream.read()
+        ans = src[:6] + md + src[6:]
+        stream.seek(0)
+        stream.write(ans)
+
 def set_metadata(stream, options):
     '''
     Modify/add RTF metadata in stream
@@ -99,7 +122,11 @@ def set_metadata(stream, options):
         index = src.rindex('}')
         return src[:index] + r'{\ '[:-1] + name + ' ' + val + '}}'
     src, pos = get_document_info(stream)
+    if not src:
+        create_metadata(stream, options)
+    else:
         olen = len(src)
+         
         base_pat = r'\{\\name(.*?)(?<!\\)\}'
         title = options.title
         if title != None: