sql::MetaTable.next_download_id, DownloadManager::GetNextId()

chrome/browser/download/download_manager.h

Index: chrome/browser/download/download_manager.h
diff --git a/chrome/browser/download/download_manager.h b/chrome/browser/download/download_manager.h
index b1ba24b625a69e1f0f6c2c2e88c24aea955409bb..860cf396f9038ffe38930459d1e9320f309b5ecc 100644
--- a/chrome/browser/download/download_manager.h
+++ b/chrome/browser/download/download_manager.h
@@ -34,6 +34,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/hash_tables.h"
@@ -41,9 +42,11 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "base/synchronization/lock.h"
 #include "base/time.h"
 #include "chrome/browser/download/download_item.h"
 #include "chrome/browser/download/download_request_handle.h"
+#include "chrome/browser/download/download_state_info.h"
 #include "chrome/browser/download/download_status_updater_delegate.h"
 #include "content/browser/browser_thread.h"
 
@@ -112,6 +115,24 @@ class DownloadManager
   void SearchDownloads(const string16& query,
                        std::vector<DownloadItem*>* result);
 
+  // Returns the next download id in a DownloadId and increments the counter.
+  // May be called on any thread. The incremented counter is not persisted, but
+  // the base counter for this accessor is initialized from the largest id
+  // actually saved to the download history database.
+  DownloadId GetNextId();
+
+  // Instead of passing a DownloadManager* between threads and hoping users only
+  // call GetNextId(), you can pass this thunk around instead. Pass the thunk
+  // around by const ref and store it by copy per the base::Callback interface.
+  // The thunk may be copied, including between threads.  If you change
+  // GetNextIdThunkType from base::Callback, then you should think about how
+  // you're changing the ref-count of DownloadManager. Use it like:
+  //   const DownloadManager::GetNextIdThunkType& next_id_thunk =
+  //       download_manager->GetNextIdThunk();
+  //   id = next_id_thunk.Run();
+  typedef base::Callback<DownloadId(void)> GetNextIdThunkType;
+  GetNextIdThunkType GetNextIdThunk();
+
   // Returns true if initialized properly.
   bool Init(Profile* profile);
 
@@ -352,6 +373,9 @@ class DownloadManager
   // Add a DownloadItem to history_downloads_.
   void AddDownloadItemToHistory(DownloadItem* item, int64 db_handle);
 
+  // The DownloadHistory grabbed the next_id counter from the sql MetaTable.
+  void OnHistoryGetNextId(int next_id);
+
   // |downloads_| is the owning set for all downloads known to the
   // DownloadManager.  This includes downloads started by the user in
   // this session, downloads initialized from the history system, and
@@ -405,6 +429,9 @@ class DownloadManager
   // Observers that want to be notified of changes to the set of downloads.
   ObserverList<Observer> observers_;
 
+  base::Lock next_id_lock_;
+  int next_id_;
+
   // The current active profile.
   Profile* profile_;