Removed SCardCancelTransaction completely; Added neesting counter; refs #8

src/pcsc.hxx

@@ -143,6 +143,13 @@ namespace pcsc {
       runtime_error(const std::string& reason, const std::string& data) throw():
           exception("runtime error,\n"+reason+":\n"+crypto::hex(data)) {}
   };
+  //----------------------------------------------------------------------------
+  class neesting_error: public exception {
+    public:
+      neesting_error() throw():
+          exception("neesting error: more endTransaction than beginTransaction")
+      {}
+  };
   //@}
 
   //! @addtogroup pcsclib
@@ -165,25 +172,26 @@ namespace pcsc {
           friend class Transaction;
           //! Scoped transaction.
           /*! This is a scoped transaction. That means, the
-              transaction is started in the constructor and cancelled
-              in the destructor, unless it is committed before. That
-              means: If you commit the transaction, it is executed. If
-              you leave the code block unexpectedly, i.e. through an
-              exception, the transaction is cancelled.
+              transaction is started in the constructor and ended in
+              the destructor, unless it is already ended before.  In
+              case of an exception or leaving the block, the
+              transaction is always cleaned up.
+
+              There's a neesting counter to make sure, transaction is
+              started only once and ended only once, even though the
+              locking can be neested.
 
               @code
               pcsc::Connection c;
               {
               Transaction t(c.reader("name"));
               [...] // do some stuff, possible exceptions thrown
-              if (problem) return; // automatically cancelled
+              if (problem) return; // automatically ended
               [...]
-              t.commit(); // commit if we reach this line
-              } // cancelled, unless commit reaced
-              @endcode
-
-              @note Micro$oft QinSCard does not know cancel, therefore
-              on Windoze cancel is replaced by commit. */
+              t.end(); // ended if we reach this line
+              [...]
+              } // also ended, unless commit reaced
+              @endcode */
           class Transaction {
             public:
               //! Begins a transaction.
@@ -195,18 +203,13 @@ namespace pcsc {
               }
               //! Cancels the transaction if not yet finished.
               ~Transaction() try {
-                cancel();
+                end();
               } catch (...) {
                 if (!std::uncaught_exception()) throw;
               }
-              //! Ends (commits) the running transaction.
-              void commit() {
-                if (_running) _reader.commitTransaction();
-                _running = false;
-              }
-              //! Cancels the running transaction.
-              void cancel() {
-                if (_running) _reader.cancelTransaction();
+              //! Ends the running transaction.
+              void end() {
+                if (_running) _reader.endTransaction();
                 _running = false;
               }
             private:
@@ -348,25 +351,26 @@ namespace pcsc {
         private:
 
           //! Use scoped transactions with @ref Transaction
+          /*! Calls @c SCardBeginTransaction unless it's already inside
+              a transaction. */
           void beginTransaction() {
-            check(SCardBeginTransaction(_id), "smartcard begin transaction");
+            if (++_neesting==1)
+              check(SCardBeginTransaction(_id), "smartcard begin transaction");
           }
 
           //! Use scoped transactions with @ref Transaction
-          void commitTransaction() {
-            check(SCardEndTransaction(_id, SCARD_LEAVE_CARD),
-                  "smartcard end transaction");
-          }
-
-          //! Use scoped transactions with @ref Transaction
-          /*! @note Micro$oft QinSCard does not know cancel, therefore
-              on Windoze cancel is replaced by commit. */
-          void cancelTransaction() {
-#ifndef WIN32
-            check(SCardCancelTransaction(_id), "smartcard cancel transaction");
-#endif
-            check(SCardEndTransaction(_id, SCARD_LEAVE_CARD),
-                  "smartcard end transaction");
+          /*! Calls @c SCardEndTransaction if it's inside a transaction.
+              
+              @throws neesting_error if there are more calls to @c
+              endTransaction than to @c beginTransaction. */
+          void endTransaction() {
+            if (--_neesting==0)
+              check(SCardEndTransaction(_id, SCARD_LEAVE_CARD),
+                    "smartcard end transaction");
+            else if (_neesting<0) {
+              _neesting = 0;
+              throw neesting_error();
+            }
           }
 
           /*! @throw not_implemented if _protocol is unknown. */
@@ -414,6 +418,7 @@ namespace pcsc {
           SCARDHANDLE _id;
           DWORD _state;
           DWORD _protocol;
+          static int _neesting;
       
       };
       //------------------------------------------------------------------Reader