L2CAP/GATT: Replace State with dedicated atomic<bool> isConnected and hasIOError, allowing atomic compare_exchange_strong w/o mutex

Using an atomic threshold via compare_exchange_strong allows us to avoid using a mutex and ease complexity.

The State had been reduced to a tri-state earlier, hence the atomic<bool> tuple is sufficient.

2 files changed, 18 insertions, 18 deletions

diff --git a/api/direct_bt/GATTHandler.hpp b/api/direct_bt/GATTHandler.hpp
index 67c932fd..253077d0 100644
--- a/api/direct_bt/GATTHandler.hpp
+++ b/api/direct_bt/GATTHandler.hpp
@@ -89,7 +89,8 @@ namespace direct_bt {
 
             L2CAPComm l2cap;
             const int replyTimeoutMS;
-            std::atomic<L2CAPComm::State> state;
+            std::atomic<bool> isConnected; // reflects state
+            std::atomic<bool> hasIOError;  // reflects state
 
             LFRingbuffer<std::shared_ptr<const AttPDUMsg>, nullptr> attPDURing;
             std::atomic<pthread_t> l2capReaderThreadId;
@@ -107,7 +108,7 @@ namespace direct_bt {
             uint16_t usedMTU;
             std::vector<GATTServiceRef> services;
 
-            L2CAPComm::State validateState();
+            bool validateConnected();
 
             void l2capReaderThreadImpl();
 
@@ -127,8 +128,9 @@ namespace direct_bt {
 
             ~GATTHandler();
 
-            L2CAPComm::State getState() const { return state; }
-            std::string getStateString() const { return L2CAPComm::getStateString(state); }
+            bool getIsConnected() const { return isConnected; }
+            bool getHasIOError() const { return hasIOError; }
+            std::string getStateString() const { return L2CAPComm::getStateString(isConnected, hasIOError); }
 
             /**
              * After successful l2cap connection, the MTU will be exchanged.
@@ -144,7 +146,7 @@ namespace direct_bt {
              */
             bool disconnect(const bool disconnectDevice, const bool ioErrorCause);
 
-            bool isOpen() const { return L2CAPComm::State::Disconnected < state && l2cap.isOpen(); }
+            bool isOpen() const { return isConnected && l2cap.isOpen(); }
 
             uint16_t getServerMTU() const { return serverMTU; }
             uint16_t getUsedMTU()  const { return usedMTU; }
diff --git a/api/direct_bt/L2CAPComm.hpp b/api/direct_bt/L2CAPComm.hpp
index b8dd1fcc..8e79085f 100644
--- a/api/direct_bt/L2CAPComm.hpp
+++ b/api/direct_bt/L2CAPComm.hpp
@@ -51,19 +51,15 @@ namespace direct_bt {
 
     class L2CAPComm {
         public:
-            enum class State : int {
-                Error        = -1,
-                Disconnected =  0,
-                Connected    =  1,
-            };
-
-            static std::string getStateString(const State state);
-
             enum class Defaults : int {
                 L2CAP_CONNECT_MAX_RETRY = 3
             };
             static inline int number(const Defaults d) { return static_cast<int>(d); }
 
+            static std::string getStateString(bool isConnected, bool hasIOError) {
+                return "State[connected "+std::to_string(isConnected)+", ioError "+std::to_string(hasIOError)+"]";
+            }
+
         private:
             static int l2cap_open_dev(const EUI48 & adapterAddress, const uint16_t psm, const uint16_t cid, const bool pubaddr);
             static int l2cap_close_dev(int dd);
@@ -72,24 +68,26 @@ namespace direct_bt {
             const uint16_t psm;
             const uint16_t cid;
             const bool pubaddr;
-            std::atomic<State> state;
             std::atomic<int> _dd; // the l2cap socket
+            std::atomic<bool> isConnected; // reflects state
+            std::atomic<bool> hasIOError;  // reflects state
             std::atomic<bool> interruptFlag; // for forced disconnect
             std::atomic<pthread_t> tid_connect;
 
         public:
             L2CAPComm(std::shared_ptr<DBTDevice> device, const uint16_t psm, const uint16_t cid, const bool pubaddr=true)
             : device(device), psm(psm), cid(cid), pubaddr(pubaddr),
-              state(State::Disconnected), _dd(-1), interruptFlag(false), tid_connect(0) {}
+              _dd(-1), isConnected(false), hasIOError(false), interruptFlag(false), tid_connect(0) {}
             ~L2CAPComm() { disconnect(); }
 
             std::shared_ptr<DBTDevice> getDevice() { return device; }
 
-            State getState() const { return state; }
-            std::string getStateString() const { return getStateString(state); }
+            bool getIsConnected() const { return isConnected; }
+            bool getHasIOError() const { return hasIOError; }
+            std::string getStateString() const { return getStateString(isConnected, hasIOError); }
 
             /** BT Core Spec v5.2: Vol 3, Part A: L2CAP_CONNECTION_REQ */
-            State connect();
+            bool connect();
 
             bool disconnect();