Clear ringbuffer after dumping to file

Clear the in-memory ringbuffer after writing to file.

Bug: 193007899
Test: Manually verified ringbuffers are cleared with command "adb shell
lshal debug android.hardware.wifi@1.5::IWifi"

Change-Id: Icfa08634e948d7155e231458edd394a4d699fbaa

wifi/1.5/default/ringbuffer.cpp

@@ -47,6 +47,11 @@ const std::list<std::vector<uint8_t>>& Ringbuffer::getData() const {
     return data_;
 }
 
+void Ringbuffer::clear() {
+    data_.clear();
+    size_ = 0;
+}
+
 }  // namespace implementation
 }  // namespace V1_5
 }  // namespace wifi

wifi/1.5/default/ringbuffer.h

@@ -37,6 +37,7 @@ class Ringbuffer {
     // within |maxSize_|.
     void append(const std::vector<uint8_t>& input);
     const std::list<std::vector<uint8_t>>& getData() const;
+    void clear();
 
    private:
     std::list<std::vector<uint8_t>> data_;

wifi/1.5/default/wifi_chip.cpp

@@ -1940,8 +1940,8 @@ bool WifiChip::writeRingbufferFilesInternal() {
     // write ringbuffers to file
     {
         std::unique_lock<std::mutex> lk(lock_t);
-        for (const auto& item : ringbuffer_map_) {
-            const Ringbuffer& cur_buffer = item.second;
+        for (auto& item : ringbuffer_map_) {
+            Ringbuffer& cur_buffer = item.second;
             if (cur_buffer.getData().empty()) {
                 continue;
             }
@@ -1959,6 +1959,7 @@ bool WifiChip::writeRingbufferFilesInternal() {
                     PLOG(ERROR) << "Error writing to file";
                 }
             }
+            cur_buffer.clear();
         }
         // unique_lock unlocked here
     }