X-Git-Url: https://git.mdrn.pl/wolnelektury.git/blobdiff_plain/f59e7c3de6bd0f85a61a4d9481db60cd7369ae92..075fb07f19c2f20cd3b6818b973e7aebebdacc9f:/apps/catalogue/utils.py

diff --git a/apps/catalogue/utils.py b/apps/catalogue/utils.py
index acbd778cd..145511e06 100644
--- a/apps/catalogue/utils.py
+++ b/apps/catalogue/utils.py
@@ -164,3 +164,33 @@ def async_build_pdf(book_id, customizations, file_name):
     if not DefaultStorage().exists(file_name):
         book.build_pdf(customizations=customizations, file_name=file_name)
     print "done."
+
+
+class MultiQuerySet(object):
+    def __init__(self, *args, **kwargs):
+        self.querysets = args
+        self._count = None
+    
+    def count(self):
+        if not self._count:
+            self._count = sum(len(qs) for qs in self.querysets)
+        return self._count
+    
+    def __len__(self):
+        return self.count()
+        
+    def __getitem__(self, item):
+        indices = (offset, stop, step) = item.indices(self.count())
+        items = []
+        total_len = stop - offset
+        for qs in self.querysets:
+            if len(qs) < offset:
+                offset -= len(qs)
+            else:
+                items += list(qs[offset:stop])
+                if len(items) >= total_len:
+                    return items
+                else:
+                    offset = 0
+                    stop = total_len - len(items)
+                    continue
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