From b95dc034ca96fbb19995c54a8c75b5d46116a1e1 Mon Sep 17 00:00:00 2001
From: Yen Chi Hsuan <yan12125@gmail.com>
Date: Tue, 23 Feb 2016 12:17:02 +0800
Subject: [PATCH] [utils] Implement cache for OnDemandPagedList

---
 youtube_dl/utils.py | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 6978a10e4..8ec70f93c 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1570,9 +1570,12 @@ class PagedList(object):
 
 
 class OnDemandPagedList(PagedList):
-    def __init__(self, pagefunc, pagesize):
+    def __init__(self, pagefunc, pagesize, use_cache=False):
         self._pagefunc = pagefunc
         self._pagesize = pagesize
+        self._use_cache = use_cache
+        if use_cache:
+            self._cache = {}
 
     def getslice(self, start=0, end=None):
         res = []
@@ -1582,7 +1585,13 @@ class OnDemandPagedList(PagedList):
             if start >= nextfirstid:
                 continue
 
-            page_results = list(self._pagefunc(pagenum))
+            page_results = None
+            if self._use_cache:
+                page_results = self._cache.get(pagenum)
+            if page_results is None:
+                page_results = list(self._pagefunc(pagenum))
+            if self._use_cache:
+                self._cache[pagenum] = page_results
 
             startv = (
                 start % self._pagesize