add mux capacity() methods

Author: tzcnt

include/tmc/mux_many.hpp

@@ -333,7 +333,11 @@ class mux_many : private tmc::detail::AwaitTagNoGroupCoAwaitLvalue {
 
   /// Provides a sentinel value that can be compared against the value returned
   /// from co_await.
-  inline size_t end() noexcept { return 64; }
+  inline constexpr size_t end() const noexcept { return 64; }
+
+  /// Returns the capacity of the mux, equal to the `Count` template argument.
+  /// This is the maximum number of awaitables that may be active concurrently.
+  inline constexpr size_t capacity() const noexcept { return Count; }
 
   /// Gets the ready result at the given index.
   TMC_TSAN_NO_SPECULATE inline std::add_lvalue_reference_t<Result>

include/tmc/mux_tuple.hpp

@@ -224,7 +224,11 @@ class mux_tuple : private tmc::detail::AwaitTagNoGroupCoAwaitLvalue {
 
   /// Provides a sentinel value that can be compared against the value returned
   /// from co_await.
-  inline size_t end() noexcept { return 64; }
+  inline constexpr size_t end() const noexcept { return 64; }
+
+  /// Returns the capacity of the mux, equal to the number of `Result` template arguments.
+  /// This is the maximum number of awaitables that may be active concurrently.
+  inline constexpr size_t capacity() const noexcept { return Count; }
 
   /// Gets the ready result at the given index.
   template <size_t I>

include/tmc/select.hpp

@@ -64,7 +64,7 @@ template <typename Awaitable, typename Canceller> consteval bool canceller_is_as
 /// an awaitable (an async cancel, which `select()` awaits). The canceller is
 /// stored by value and invoked only for losers, so an awaitable-returning canceller
 /// builds its awaitable only when the cancel is actually needed. Therefore, it is safe to
-/// pass a capturing coroutine lambda here — it will be stored by value and outlive the
+/// pass a capturing coroutine lambda here - it will be stored by value and outlive the
 /// awaited invocation.
 /// ```
 /// // sync cancel
@@ -130,7 +130,7 @@ template <typename Awaitable, typename Canceller> class cancellable {
   ///
   /// The canceller is stored by value and invoked only for losers, so an
   /// awaitable-returning canceller builds its awaitable only when the cancel is actually
-  /// needed. Therefore, it is safe to pass a capturing coroutine lambda here — it will be
+  /// needed. Therefore, it is safe to pass a capturing coroutine lambda here - it will be
   /// stored by value and outlive the awaited invocation.
   /// ```
   /// // sync cancel