hbtree ensure only one transaction active at any time

Disable support for concurrent read and write transactions since they
dont make sense with current implementations

Change-Id: I57125d94b71af3cba6322b428bcb0cde297443cc
Reviewed-by: Denis Dzyubenko <denis.dzyubenko@nokia.com>

2 files changed, 17 insertions, 1 deletions

diff --git a/src/hbtree/hbtree.cpp b/src/hbtree/hbtree.cpp
index 5e8f0810..46b3585c 100644
--- a/src/hbtree/hbtree.cpp
+++ b/src/hbtree/hbtree.cpp
@@ -91,7 +91,7 @@ const quint32 HBtreePrivate::PageInfo::INVALID_PAGE = 0xFFFFFFFF;
 HBtreePrivate::HBtreePrivate(HBtree *q, const QString &name)
     : q_ptr(q), fileName_(name), fd_(-1), openMode_(HBtree::ReadOnly), size_(0), lastSyncedId_(0), cacheSize_(20),
       compareFunction_(0),
-      writeTransaction_(0), lastPage_(PageInfo::INVALID_PAGE), cursorDisrupted_(false)
+      writeTransaction_(0), readTransaction_(0), lastPage_(PageInfo::INVALID_PAGE), cursorDisrupted_(false)
 {
 }
 
@@ -209,6 +209,8 @@ bool HBtreePrivate::open(int fd)
 
 void HBtreePrivate::close(bool doSync)
 {
+    HBTREE_ASSERT(!readTransaction_ && !writeTransaction_);
+
     if (fd_ != -1) {
         HBTREE_DEBUG("closing btree with fd:" << fd_);
         if (doSync)
@@ -931,9 +933,13 @@ void HBtreePrivate::abort(HBtreeTransaction *transaction)
     }
     dirtyPages_.clear();
     if (transaction->isReadWrite()) {
+        HBTREE_ASSERT(transaction == writeTransaction_);
         if (::flock(fd_, LOCK_UN) != 0)
             HBTREE_ERROR("failed to unlock file with transaction @" << transaction);
         writeTransaction_ = 0;
+    } else {
+        HBTREE_ASSERT(transaction == readTransaction_);
+        readTransaction_ = 0;
     }
     delete transaction;
     cachePrune();
@@ -998,6 +1004,13 @@ HBtreeTransaction *HBtreePrivate::beginTransaction(HBtreeTransaction::Type type)
 {
     Q_Q(HBtree);
 
+    HBTREE_ASSERT(!writeTransaction_ && !readTransaction_);
+
+    if (writeTransaction_ || readTransaction_) {
+        HBTREE_ERROR("Only one transaction type supported at a time");
+        return 0;
+    }
+
     if (type == HBtreeTransaction::ReadWrite && writeTransaction_) {
         HBTREE_ERROR("cannot open write transaction when one in progress");
         return 0;
@@ -1031,6 +1044,8 @@ HBtreeTransaction *HBtreePrivate::beginTransaction(HBtreeTransaction::Type type)
     transaction->revision_ = marker_.meta.revision;
     if (type == HBtreeTransaction::ReadWrite)
         writeTransaction_ = transaction;
+    else
+        readTransaction_ = transaction;
     HBTREE_DEBUG("began" << (transaction->isReadOnly() ? "read" : "write")
                  << "transaction @" << transaction
                  << "[root:" << transaction->rootPage_
diff --git a/src/hbtree/hbtree_p.h b/src/hbtree/hbtree_p.h
index ab529797..8575db31 100644
--- a/src/hbtree/hbtree_p.h
+++ b/src/hbtree/hbtree_p.h
@@ -388,6 +388,7 @@ public:
     PageMap dirtyPages_;
     HBtree::CompareFunction compareFunction_;
     HBtreeTransaction *writeTransaction_;
+    HBtreeTransaction *readTransaction_;
     QSet<quint32> collectiblePages_;
     PageMap cache_;
     quint32 lastPage_;