From 6c28276dafe83bcc5cee0c0b68b5882857578c1b Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@gmail.com>
Date: Wed, 3 Feb 2016 12:58:30 -0500
Subject: [PATCH] Use RAII idiom for lock and locking mutex in Sequence

---
 src/Sequence.cpp                      |  4 +---
 src/Sequence.h                        | 15 +++++++++++++++
 src/ondemand/ODComputeSummaryTask.cpp |  3 +--
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/Sequence.cpp b/src/Sequence.cpp
index 1c23ba2e6..594e3a32e 100644
--- a/src/Sequence.cpp
+++ b/src/Sequence.cpp
@@ -1622,7 +1622,7 @@ bool Sequence::Delete(sampleCount start, sampleCount len)
    //TODO: add a ref-deref mechanism to SeqBlock/BlockArray so we don't have to make this a critical section.
    //On-demand threads iterate over the mBlocks and the GUI thread deletes them, so for now put a mutex here over
    //both functions,
-   LockDeleteUpdateMutex();
+   DeleteUpdateMutexLocker locker(*this);
 
    unsigned int numBlocks = mBlock.size();
 
@@ -1661,7 +1661,6 @@ bool Sequence::Delete(sampleCount start, sampleCount len)
       mDirManager->Deref(oldFile);
 
       mNumSamples -= len;
-      UnlockDeleteUpdateMutex();
 
       return ConsistencyCheck(wxT("Delete - branch one"));
    }
@@ -1786,7 +1785,6 @@ bool Sequence::Delete(sampleCount start, sampleCount len)
    // Update total number of samples and do a consistency check.
    mNumSamples -= len;
 
-   UnlockDeleteUpdateMutex();
    return ConsistencyCheck(wxT("Delete - branch two"));
 }
 
diff --git a/src/Sequence.h b/src/Sequence.h
index 4cee5a9af..a257869ce 100644
--- a/src/Sequence.h
+++ b/src/Sequence.h
@@ -194,6 +194,21 @@ class Sequence: public XMLTagHandler {
    void LockDeleteUpdateMutex(){mDeleteUpdateMutex.Lock();}
    void UnlockDeleteUpdateMutex(){mDeleteUpdateMutex.Unlock();}
 
+   // RAII idiom wrapping the functions above
+   struct DeleteUpdateMutexLocker {
+      DeleteUpdateMutexLocker(Sequence &sequence)
+         : mSequence(sequence)
+      {
+         mSequence.LockDeleteUpdateMutex();
+      }
+      ~DeleteUpdateMutexLocker()
+      {
+         mSequence.UnlockDeleteUpdateMutex();
+      }
+   private:
+      Sequence &mSequence;
+   };
+
  private:
 
    //
diff --git a/src/ondemand/ODComputeSummaryTask.cpp b/src/ondemand/ODComputeSummaryTask.cpp
index 0c10d99eb..1d818fb03 100644
--- a/src/ondemand/ODComputeSummaryTask.cpp
+++ b/src/ondemand/ODComputeSummaryTask.cpp
@@ -190,7 +190,7 @@ void ODComputeSummaryTask::Update()
             seq = clip->GetSequence();
             //This lock may be way too big since the whole file is one sequence.
             //TODO: test for large files and find a way to break it down.
-            seq->LockDeleteUpdateMutex();
+            Sequence::DeleteUpdateMutexLocker locker(*seq);
 
             //See Sequence::Delete() for why need this for now..
             //We don't need the mBlockFilesMutex here because it is only for the vector list.
@@ -223,7 +223,6 @@ void ODComputeSummaryTask::Update()
                   tempBlocks.insert(tempBlocks.begin() + insertCursor++, odpcmaFile);
                }
             }
-            seq->UnlockDeleteUpdateMutex();
             node = node->GetNext();
          }
       }