[commissioner] add new API to get Provisioning URL (#2884)

include/openthread/commissioner.h

@@ -121,6 +121,19 @@ OTAPI otError OTCALL otCommissionerAddJoiner(otInstance *        aInstance,
  */
 OTAPI otError OTCALL otCommissionerRemoveJoiner(otInstance *aInstance, const otExtAddress *aEui64);
 
+/**
+ * This function gets the Provisioning URL.
+ *
+ * @param[in]    aInstance       A pointer to an OpenThread instance.
+ * @param[out]   aLength         A pointer to `uint16_t` to return the length (number of chars) in the URL string.
+ *
+ * Note that the returned URL string buffer is not necessarily null-terminated.
+ *
+ * @returns A pointer to char buffer containing the URL string, or NULL if @p aLength is NULL.
+ *
+ */
+const char *otCommissionerGetProvisioningUrl(otInstance *aInstance, uint16_t *aLength);
+
 /**
  * This function sets the Provisioning URL.
  *

src/core/api/commissioner_api.cpp

@@ -124,6 +124,25 @@ otError otCommissionerSetProvisioningUrl(otInstance *aInstance, const char *aPro
     return error;
 }
 
+const char *otCommissionerGetProvisioningUrl(otInstance *aInstance, uint16_t *aLength)
+{
+    const char *url = NULL;
+
+#if OPENTHREAD_FTD && OPENTHREAD_ENABLE_COMMISSIONER
+    Instance &instance = *static_cast<Instance *>(aInstance);
+
+    if (aLength != NULL)
+    {
+        url = instance.GetThreadNetif().GetCommissioner().GetProvisioningUrl(*aLength);
+    }
+#else
+    OT_UNUSED_VARIABLE(aInstance);
+    OT_UNUSED_VARIABLE(aLength);
+#endif
+
+    return url;
+}
+
 otError otCommissionerAnnounceBegin(otInstance *        aInstance,
                                     uint32_t            aChannelMask,
                                     uint8_t             aCount,

src/core/meshcop/commissioner.cpp

@@ -310,6 +310,15 @@ exit:
     return error;
 }
 
+const char *Commissioner::GetProvisioningUrl(uint16_t &aLength) const
+{
+    ProvisioningUrlTlv &provisioningUrl = GetNetif().GetDtls().mProvisioningUrl;
+
+    aLength = provisioningUrl.GetLength();
+
+    return provisioningUrl.GetProvisioningUrl();
+}
+
 otError Commissioner::SetProvisioningUrl(const char *aProvisioningUrl)
 {
     return GetNetif().GetDtls().mProvisioningUrl.SetProvisioningUrl(aProvisioningUrl);

src/core/meshcop/commissioner.hpp

@@ -116,6 +116,18 @@ public:
      */
     otError RemoveJoiner(const Mac::ExtAddress *aEui64, uint32_t aDelay);
 
+    /**
+     * This method gets the Provisioning URL.
+     *
+     * @param[out]   aLength     A reference to `uint16_t` to return the length (number of chars) in the URL string.
+     *
+     * Note that the returned URL string buffer is not necessarily null-terminated.
+     *
+     * @returns A pointer to char buffer containing the URL string.
+     *
+     */
+    const char *GetProvisioningUrl(uint16_t &aLength) const;
+
     /**
      * This method sets the Provisioning URL.
      *