TerraSync: validate local dirs incrementally

Add a process() method to HTTPRepository, and use this to
incrementally validate subdirs after the .dirIndex is received. This 
avoids large pauses of the TerraSync thread, when all of Airports/
is validated at once.

simgear/io/HTTPRepository.cxx

@@ -274,7 +274,7 @@ public:
           if (c.type == HTTPRepository::DirectoryType) {
             // If it's a directory,perform a recursive check.
             HTTPDirectory *childDir = childDirectory(c.name);
-            childDir->updateChildrenBasedOnHash();
+            _repository->scheduleUpdateOfChildren(childDir);
           }
         }
       } // of repository-defined (well, .dirIndex) children iteration
@@ -654,6 +654,33 @@ bool HTTPRepository::isDoingSync() const
     return _d->isUpdating;
 }
 
+void HTTPRepository::process()
+{
+    int processedCount = 0;
+    const int maxToProcess = 16;
+
+    while (processedCount < maxToProcess) {
+        if (_d->pendingUpdateOfChildren.empty()) {
+            break;
+        }
+
+        auto dirToUpdate = _d->pendingUpdateOfChildren.front();
+        _d->pendingUpdateOfChildren.pop_front();
+        dirToUpdate->updateChildrenBasedOnHash();
+        ++processedCount;
+    }
+
+    _d->checkForComplete();
+}
+
+void HTTPRepoPrivate::checkForComplete()
+{
+    if (pendingUpdateOfChildren.empty() && activeRequests.empty() && queuedRequests.empty()) {
+        isUpdating = false;
+        writeHashCache();
+    }
+}
+
 size_t HTTPRepository::bytesToDownload() const
 {
     size_t result = 0;
@@ -1208,10 +1235,7 @@ HTTPRepository::failure() const
         writeHashCache();
       }
 
-      if (activeRequests.empty() && queuedRequests.empty()) {
-        isUpdating = false;
-        writeHashCache();
-      }
+      checkForComplete();
     }
 
     void HTTPRepoPrivate::failedToGetRootIndex(HTTPRepository::ResultCode st)
@@ -1272,4 +1296,14 @@ HTTPRepository::failure() const
           failures.end());
     }
 
+    void HTTPRepoPrivate::scheduleUpdateOfChildren(HTTPDirectory* dir)
+    {
+        auto it = std::find(pendingUpdateOfChildren.begin(), pendingUpdateOfChildren.end(), dir);
+        if (it != pendingUpdateOfChildren.end()) {
+            return; // duplicate add, skip
+        }
+
+        pendingUpdateOfChildren.push_back(dir);
+    }
+
 } // of namespace simgear

simgear/io/HTTPRepository.hxx

@@ -62,6 +62,11 @@ public:
 
   virtual bool isDoingSync() const;
 
+  /**
+        @brief call this periodically to progress non-network tasks
+     */
+  void process();
+
   virtual ResultCode failure() const;
 
   virtual size_t bytesToDownload() const;

simgear/io/HTTPRepository_private.hxx

@@ -19,6 +19,7 @@
 
 #pragma once
 
+#include <deque>
 #include <memory>
 #include <string>
 #include <unordered_map>
@@ -102,6 +103,8 @@ public:
 
   void updatedChildSuccessfully(const SGPath &relativePath);
 
+  void checkForComplete();
+
   typedef std::vector<RepoRequestPtr> RequestVector;
   RequestVector queuedRequests, activeRequests;
 
@@ -114,9 +117,16 @@ public:
   HTTPDirectory *getOrCreateDirectory(const std::string &path);
   bool deleteDirectory(const std::string &relPath, const SGPath &absPath);
 
+  void scheduleUpdateOfChildren(HTTPDirectory* dir);
+
   typedef std::vector<HTTPDirectory_ptr> DirectoryVector;
   DirectoryVector directories;
 
+  // list of directories to be locally processed
+  // this is used to avoid deep recursion when receiving the .dirIndex;
+  // we don't want to recurse over a large repo in a single call
+  std::deque<HTTPDirectory*> pendingUpdateOfChildren;
+
   SGPath installedCopyPath;
 };
 

simgear/io/test_repository.cxx

@@ -409,6 +409,7 @@ void waitForUpdateComplete(HTTP::Client* cl, HTTPRepository* repo)
         cl->update();
         testServer.poll();
 
+        repo->process();
         if (!repo->isDoingSync()) {
             return;
         }
@@ -423,6 +424,7 @@ void runForTime(HTTP::Client *cl, HTTPRepository *repo, int msec = 15) {
   while (start.elapsedMSec() < msec) {
     cl->update();
     testServer.poll();
+    repo->process();
     SGTimeStamp::sleepForMSec(1);
   }
 }

simgear/scene/tsync/terrasync.cxx

@@ -547,6 +547,7 @@ void SGTerraSync::WorkerThread::run()
 void SGTerraSync::WorkerThread::updateSyncSlot(SyncSlot &slot)
 {
     if (slot.repository.get()) {
+        slot.repository->process();
         if (slot.repository->isDoingSync()) {
 #if 1
             if (slot.stamp.elapsedMSec() > (int)slot.nextWarnTimeout) {