Disk cache: move eviction code to a separate file....

net/disk_cache/rankings.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/rankings.h"
 
 #include "base/histogram.h"
 #include "net/disk_cache/backend_impl.h"
 #include "net/disk_cache/entry_impl.h"
 #include "net/disk_cache/errors.h"
@@ skipping 477 matching lines @@
     if (!my_head.is_initialized())
       return NULL;
     next.reset(new CacheRankingsBlock(backend_->File(my_head), my_head));
   } else {
     Addr& my_tail = tails_[list];
     if (!my_tail.is_initialized())
       return NULL;
     if (my_tail.value() == node->address().value())
       return NULL;
     Addr address(node->Data()->next);
+    if (address.value() == node->address().value())
+      return NULL;  // Another tail? fail it.
     next.reset(new CacheRankingsBlock(backend_->File(address), address));
   }
 
   TrackRankingsBlock(next.get(), true);
 
   if (!GetRanking(next.get()))
     return NULL;
 
   if (node && !CheckSingleLink(node, next.get()))
     return NULL;
 
   return next.release();
 }
 
 CacheRankingsBlock* Rankings::GetPrev(CacheRankingsBlock* node, List list) {
   ScopedRankingsBlock prev(this);
   if (!node) {
     Addr& my_tail = tails_[list];
     if (!my_tail.is_initialized())
       return NULL;
     prev.reset(new CacheRankingsBlock(backend_->File(my_tail), my_tail));
   } else {
     Addr& my_head = heads_[list];
     if (!my_head.is_initialized())
       return NULL;
     if (my_head.value() == node->address().value())
       return NULL;
     Addr address(node->Data()->prev);
+    if (address.value() == node->address().value())
+      return NULL;  // Another head? fail it.
     prev.reset(new CacheRankingsBlock(backend_->File(address), address));
   }
 
   TrackRankingsBlock(prev.get(), true);
 
   if (!GetRanking(prev.get()))
     return NULL;
 
   if (node && !CheckSingleLink(prev.get(), node))
     return NULL;
@@ skipping 180 matching lines @@
        ++it) {
     if (it->first == address) {
       CacheRankingsBlock* other = it->second;
       other->Data()->next = node->Data()->next;
       other->Data()->prev = node->Data()->prev;
     }
   }
 }
 
 }  // namespace disk_cache