channel: replace dequeue by vector

bareos · Sep 22, 2023 · 1ccfc12 · 1ccfc12
1 parent 5c34195
commit 1ccfc12
Showing 1 changed file with 23 additions and 14 deletions.
diff --git a/core/src/lib/channel.h b/core/src/lib/channel.h
@@ -24,7 +24,7 @@
 
 #include <condition_variable>
 #include <optional>
-#include <deque>
+#include <vector>
 #include <utility>
 #include <variant>
 
@@ -44,7 +44,7 @@ struct channel_closed {};
 
 template <typename T> class queue {
   struct internal {
-    std::deque<T> data;
+    std::vector<T> data;
     bool in_dead;
     bool out_dead;
   };
@@ -73,7 +73,7 @@ template <typename T> class queue {
     {
     }
 
-    std::deque<T>& data() { return locked->data; }
+    std::vector<T>& data() { return locked->data; }
 
     ~handle()
     {
@@ -247,7 +247,8 @@ template <typename T> class input {
 
 template <typename T> class output {
   std::shared_ptr<queue<T>> shared;
-  std::deque<T> cache;
+  std::vector<T> cache{};
+  typename decltype(cache)::iterator cache_iter = cache.begin();
   bool did_close{false};
 
  public:
@@ -265,9 +266,8 @@ template <typename T> class output {
     if (did_close) { return std::nullopt; }
     update_cache();
 
-    if (cache.size() > 0) {
-      std::optional result = std::make_optional<T>(std::move(cache.front()));
-      cache.pop_front();
+    if (cache_iter != cache.end()) {
+      std::optional result = std::make_optional<T>(std::move(*cache_iter++));
       return result;
     } else {
       return std::nullopt;
@@ -279,9 +279,8 @@ template <typename T> class output {
     if (did_close) { return std::nullopt; }
     try_update_cache();
 
-    if (cache.size() > 0) {
-      std::optional result = std::make_optional<T>(std::move(cache.front()));
-      cache.pop_front();
+    if (cache_iter != cache.end()) {
+      std::optional result = std::make_optional<T>(std::move(*cache_iter++));
       return result;
     } else {
       return std::nullopt;
@@ -291,6 +290,8 @@ template <typename T> class output {
   void close()
   {
     if (!did_close) {
+      cache.clear();
+      cache_iter = cache.begin();
       shared->close_out();
       did_close = true;
     }
@@ -304,11 +305,18 @@ template <typename T> class output {
   }
 
  private:
+  void do_update_cache(std::vector<T>& data)
+  {
+    cache.clear();
+    std::swap(data, cache);
+    cache_iter = cache.begin();
+  }
+
   void update_cache()
   {
-    if (cache.empty()) {
+    if (cache_iter == cache.end()) {
       if (auto handle = shared->output_lock()) {
-        std::swap(handle->data(), cache);
+        do_update_cache(handle->data());
       } else {
         // this can only happen if the channel was closed.
         close();
@@ -318,14 +326,15 @@ template <typename T> class output {
 
   void try_update_cache()
   {
-    if (cache.empty()) {
+    if (cache_iter == cache.end()) {
       auto result = shared->try_output_lock();
       if (std::holds_alternative<failed_to_acquire_lock>(result)) {
         // intentionally left empty
       } else if (std::holds_alternative<channel_closed>(result)) {
         close();
       } else {
-        std::swap(std::get<typename queue<T>::handle>(result).data(), cache);
+        auto& handle = std::get<typename queue<T>::handle>(result);
+        do_update_cache(handle.data());
       }
     }
   }