Add operator[] to batch in thread pipeline

benchmarks/bench_thread_pipeline.cpp

@@ -67,14 +67,14 @@ int main() {
       std::latch finish{1};
       {
         auto guard = pipeline.push(1, true);
-        *guard.batch.begin() = &finish;
+        guard.batch[0] = &finish;
       }
       finish.wait();
     });
 
     {
       auto guard = pipeline.push(1, true);
-      *guard.batch.begin() = &done;
+      guard.batch[0] = &done;
     }
 
     stage0_thread.join();
@@ -137,14 +137,14 @@ int main() {
         std::latch finish{1};
         {
           auto guard = pipeline.push(1, true);
-          *guard.batch.begin() = &finish;
+          guard.batch[0] = &finish;
         }
         finish.wait();
       });
 
       {
         auto guard = pipeline.push(1, true);
-        *guard.batch.begin() = &done;
+        guard.batch[0] = &done;
       }
 
       stage0_thread.join();
@@ -214,7 +214,7 @@ int main() {
           std::latch finish{1};
           {
             auto guard = pipeline.push(1, true);
-            *guard.batch.begin() = &finish;
+            guard.batch[0] = &finish;
           }
           finish.wait();
         });
@@ -222,8 +222,7 @@ int main() {
         // Shutdown
         {
           auto guard = pipeline.push(1, true);
-          auto it = guard.batch.begin();
-          *it = &done;
+          guard.batch[0] = &done;
         }
         stage0_thread.join();
         stage1_thread.join();

src/thread_pipeline.hpp

@@ -2,6 +2,7 @@
 
 #include <atomic>
 #include <cassert>
+#include <cstddef>
 #include <cstdint>
 #include <cstdio>
 #include <cstdlib>
@@ -161,9 +162,6 @@ struct ThreadPipeline {
         return static_cast<difference_type>(index_) -
                static_cast<difference_type>(rhs.index_);
       }
-      reference operator[](difference_type n) const {
-        return (*ring)[(index_ + n) & (ring->size() - 1)];
-      }
       friend Iterator operator+(difference_type n, const Iterator &iter) {
         return iter + n;
       }
@@ -211,6 +209,9 @@ struct ThreadPipeline {
 
     [[nodiscard]] size_t size() const { return end_ - begin_; }
     [[nodiscard]] bool empty() const { return end_ == begin_; }
+    T &operator[](uint32_t n) {
+      return (*ring)[(begin_ + n) & (ring->size() - 1)];
+    }
 
   private:
     friend struct ThreadPipeline;