Added the Bu::ReadWriteMutex, which is super awesome. Also made the

Bu::RandomBase::rand functions visible in the Bu::RandomCmwc class.

1 files changed, 78 insertions, 0 deletions

diff --git a/src/unstable/readwritemutex.cpp b/src/unstable/readwritemutex.cpp
new file mode 100644
index 0000000..b0a3b77
--- /dev/null
+++ b/src/unstable/readwritemutex.cpp
@@ -0,0 +1,78 @@
+#include "bu/readwritemutex.h"
+
+Bu::ReadWriteMutex::ReadWriteMutex() :
+    iCounter( 0 ),
+    bWantWrite( false )
+{
+}
+
+Bu::ReadWriteMutex::~ReadWriteMutex()
+{
+}
+
+void Bu::ReadWriteMutex::lockRead()
+{
+    // Check to see if someone wants to write
+    cWrite.lock();
+    if( bWantWrite )
+    {
+        // If so, wait patiently for them to finish
+        cWrite.wait();
+    }
+    cWrite.unlock();
+
+    //  Now lock the read counter
+    mRead.lock();
+    iCounter++;
+    // If the lock counter is one, we just locked for the first time,
+    // so we lock the writer.
+    if( iCounter == 1 )
+        mWrite.lock();
+    mRead.unlock();
+}
+
+void Bu::ReadWriteMutex::unlockRead()
+{
+    // Lock the read counter
+    mRead.lock();
+    iCounter--;
+    // If we just decremented the counter back to zero then we can
+    // release the write lock
+    if( iCounter == 0 )
+        mWrite.unlock();
+    mRead.unlock();
+}
+
+void Bu::ReadWriteMutex::lockWrite()
+{
+    // Lock the read counter
+    mRead.lock();
+    if( iCounter > 0 )
+    {
+        // If there is an active read in progress then we set the bWantWrite
+        // flag to make sure no more readers start working.
+        cWrite.lock();
+        bWantWrite = true;
+        cWrite.unlock();
+    }
+    mRead.unlock();
+
+    // Lock the write lock
+    mWrite.lock();
+}
+
+void Bu::ReadWriteMutex::unlockWrite()
+{
+    // Just always set the bWantWrite flag to false at this point, as long
+    // as we're locked.
+    cWrite.lock();
+    bWantWrite = false;
+    cWrite.unlock();
+
+    // Release all waiting readers, they won't actually do much until we
+    // unlock the write lock though
+    cWrite.broadcast();
+
+    // Unlock the write lock
+    mWrite.unlock();
+}