Also support <filesystem> as well as <experimental/filesystem>

The change for <coroutine> vs. <experimental/coroutine> is
replicated for <filesystem> in this patch. In addition,
the std::experimental namespace is replaced by cppcoro:: namespace
in a few more places.

Author: andreasbuhr

Diff for: README.md

@@ -714,15 +714,15 @@ namespace cppcoro
   {
   public:
     bool await_ready() const noexcept;
-    bool await_suspend(std::experimental::coroutine_handle<> awaiter) noexcept;
+    bool await_suspend(cppcoro::coroutine_handle<> awaiter) noexcept;
     void await_resume() const noexcept;
   };
 
   class async_mutex_scoped_lock_operation
   {
   public:
     bool await_ready() const noexcept;
-    bool await_suspend(std::experimental::coroutine_handle<> awaiter) noexcept;
+    bool await_suspend(cppcoro::coroutine_handle<> awaiter) noexcept;
     [[nodiscard]] async_mutex_lock await_resume() const noexcept;
   };
 
@@ -836,7 +836,7 @@ namespace cppcoro
     async_manual_reset_event_operation(async_manual_reset_event& event) noexcept;
 
     bool await_ready() const noexcept;
-    bool await_suspend(std::experimental::coroutine_handle<> awaiter) noexcept;
+    bool await_suspend(cppcoro::coroutine_handle<> awaiter) noexcept;
     void await_resume() const noexcept;
   };
 }
@@ -904,7 +904,7 @@ namespace cppcoro
     async_auto_reset_event_operation(const async_auto_reset_event_operation& other) noexcept;
 
     bool await_ready() const noexcept;
-    bool await_suspend(std::experimental::coroutine_handle<> awaiter) noexcept;
+    bool await_suspend(cppcoro::coroutine_handle<> awaiter) noexcept;
     void await_resume() const noexcept;
 
   };
@@ -1389,7 +1389,7 @@ namespace cppcoro
       schedule_operation(static_thread_pool* tp) noexcept;
 
       bool await_ready() noexcept;
-      bool await_suspend(std::experimental::coroutine_handle<> h) noexcept;
+      bool await_suspend(cppcoro::coroutine_handle<> h) noexcept;
       bool await_resume() noexcept;
 
     private:
@@ -1546,7 +1546,7 @@ namespace cppcoro
     schedule_operation& operator=(const schedule_operation&) noexcept;
 
     bool await_ready() const noexcept;
-    void await_suspend(std::experimental::coroutine_handle<> awaiter) noexcept;
+    void await_suspend(cppcoro::coroutine_handle<> awaiter) noexcept;
     void await_resume() noexcept;
   };
 
@@ -1560,7 +1560,7 @@ namespace cppcoro
     timed_schedule_operation& operator=(timed_schedule_operation&&) = delete;
 
     bool await_ready() const noexcept;
-    void await_suspend(std::experimental::coroutine_handle<> awaiter);
+    void await_suspend(cppcoro::coroutine_handle<> awaiter);
     void await_resume();
   };
 
@@ -1591,12 +1591,12 @@ Example:
 #include <cppcoro/io_service.hpp>
 #include <cppcoro/read_only_file.hpp>
 
-#include <experimental/filesystem>
+#include <cppcoro/filesystem.hpp>
 #include <memory>
 #include <algorithm>
 #include <iostream>
 
-namespace fs = std::experimental::filesystem;
+namespace fs = cppcoro::filesystem;
 
 cppcoro::task<std::uint64_t> count_lines(cppcoro::io_service& ioService, fs::path path)
 {
@@ -1740,7 +1740,7 @@ namespace cppcoro
     file_read_operation(file_read_operation&& other) noexcept;
 
     bool await_ready() const noexcept;
-    bool await_suspend(std::experimental::coroutine_handle<> awaiter);
+    bool await_suspend(cppcoro::coroutine_handle<> awaiter);
     std::size_t await_resume();
 
   };
@@ -1752,7 +1752,7 @@ namespace cppcoro
     file_write_operation(file_write_operation&& other) noexcept;
 
     bool await_ready() const noexcept;
-    bool await_suspend(std::experimental::coroutine_handle<> awaiter);
+    bool await_suspend(cppcoro::coroutine_handle<> awaiter);
     std::size_t await_resume();
 
   };
@@ -1774,7 +1774,7 @@ namespace cppcoro
     [[nodiscard]]
     static read_only_file open(
       io_service& ioService,
-      const std::experimental::filesystem::path& path,
+      const cppcoro::filesystem::path& path,
       file_share_mode shareMode = file_share_mode::read,
       file_buffering_mode bufferingMode = file_buffering_mode::default_);
 
@@ -1787,7 +1787,7 @@ namespace cppcoro
     [[nodiscard]]
     static write_only_file open(
       io_service& ioService,
-      const std::experimental::filesystem::path& path,
+      const cppcoro::filesystem::path& path,
       file_open_mode openMode = file_open_mode::create_or_open,
       file_share_mode shareMode = file_share_mode::none,
       file_buffering_mode bufferingMode = file_buffering_mode::default_);
@@ -1801,7 +1801,7 @@ namespace cppcoro
     [[nodiscard]]
     static read_write_file open(
       io_service& ioService,
-      const std::experimental::filesystem::path& path,
+      const cppcoro::filesystem::path& path,
       file_open_mode openMode = file_open_mode::create_or_open,
       file_share_mode shareMode = file_share_mode::none,
       file_buffering_mode bufferingMode = file_buffering_mode::default_);
@@ -2794,7 +2794,7 @@ coroutine.
 
 A type that satisfies `Awaiter<T>` must have, for an instance of the type, `awaiter`:
 - `awaiter.await_ready()` -> `bool`
-- `awaiter.await_suspend(std::experimental::coroutine_handle<void>{})` -> `void` or `bool` or `std::experimental::coroutine_handle<P>` for some `P`.
+- `awaiter.await_suspend(cppcoro::coroutine_handle<void>{})` -> `void` or `bool` or `cppcoro::coroutine_handle<P>` for some `P`.
 - `awaiter.await_resume()` -> `T`
 
 Any type that implements the `Awaiter<T>` concept also implements the `Awaitable<T>` concept.

Diff for: include/cppcoro/coroutine.hpp

@@ -11,6 +11,7 @@ namespace cppcoro {
 
   using suspend_always = std::suspend_always;
   using suspend_never = std::suspend_never;
+  static inline auto noop_coroutine() { return std::noop_coroutine(); }
 }
 
 #elif __has_include(<experimental/coroutine>)
@@ -23,6 +24,7 @@ namespace cppcoro {
 
   using suspend_always = std::experimental::suspend_always;
   using suspend_never = std::experimental::suspend_never;
+  static inline auto noop_coroutine() { return std::experimental::noop_coroutine(); }
 }
 
 #else

Diff for: include/cppcoro/file.hpp

@@ -15,7 +15,7 @@
 # include <cppcoro/detail/win32.hpp>
 #endif
 
-#include <experimental/filesystem>
+#include <cppcoro/filesystem.hpp>
 
 namespace cppcoro
 {

Diff for: include/cppcoro/filesystem.hpp

@@ -0,0 +1,24 @@
+#ifndef CPPCORO_FILESYSTEM_HPP_INCLUDED
+#define CPPCORO_FILESYSTEM_HPP_INCLUDED
+
+#if __has_include(<filesystem>)
+
+#include <filesystem>
+
+namespace cppcoro {
+    namespace filesystem = std::filesystem;
+}
+
+#elif __has_include(<experimental/filesystem>)
+
+#include <experimental/filesystem>
+
+namespace cppcoro {
+    namespace filesystem = std::experimental::filesystem;
+}
+
+#else
+#error Cppcoro requires a C++20 compiler with filesystem support
+#endif
+
+#endif

Diff for: include/cppcoro/net/socket_accept_operation.hpp

@@ -15,7 +15,7 @@
 
 # include <atomic>
 # include <optional>
-# include <experimental/coroutine>
+# include <cppcoro/coroutine.hpp>
 
 namespace cppcoro
 {

Diff for: include/cppcoro/read_only_file.hpp

@@ -9,7 +9,7 @@
 #include <cppcoro/file_share_mode.hpp>
 #include <cppcoro/file_buffering_mode.hpp>
 
-#include <experimental/filesystem>
+#include <cppcoro/filesystem.hpp>
 
 namespace cppcoro
 {

Diff for: include/cppcoro/read_write_file.hpp

@@ -11,7 +11,7 @@
 #include <cppcoro/file_buffering_mode.hpp>
 #include <cppcoro/file_open_mode.hpp>
 
-#include <experimental/filesystem>
+#include <cppcoro/filesystem.hpp>
 
 namespace cppcoro
 {

Diff for: include/cppcoro/write_only_file.hpp

@@ -10,7 +10,7 @@
 #include <cppcoro/file_buffering_mode.hpp>
 #include <cppcoro/file_open_mode.hpp>
 
-#include <experimental/filesystem>
+#include <cppcoro/filesystem.hpp>
 
 namespace cppcoro
 {