new cyclic writer

tty_protocol_writer.h

@@ -1,34 +1,41 @@
 #pragma once
 
+#include <cstddef>
 #include <cstdint>
+#include <memory>
 #include <string>
 
 class TtyProtocolWriter {
 public:
-    explicit TtyProtocolWriter(std::string path);
+    struct StatsSnapshot {
+        std::uint64_t frames_written = 0;
+        std::uint64_t frames_dropped = 0;
+        std::uint64_t ring_overflows = 0;
+    };
+
+    TtyProtocolWriter(std::string path, std::size_t ring_capacity_bytes);
     ~TtyProtocolWriter();
 
     TtyProtocolWriter(const TtyProtocolWriter&) = delete;
     TtyProtocolWriter& operator=(const TtyProtocolWriter&) = delete;
-    TtyProtocolWriter(TtyProtocolWriter&& other) noexcept;
-    TtyProtocolWriter& operator=(TtyProtocolWriter&& other) noexcept;
+    TtyProtocolWriter(TtyProtocolWriter&& other) noexcept = delete;
+    TtyProtocolWriter& operator=(TtyProtocolWriter&& other) noexcept = delete;
 
-    void emit_packet_start() const;
-    void emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg) const;
+    void emit_packet_start();
+    void emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg);
+    void enqueue_encoded_frames(const uint16_t* words, std::size_t frame_count);
+    StatsSnapshot stats() const;
 
     const std::string& path() const;
+    void throw_if_failed() const;
+    void shutdown();
 
 private:
-    void write_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3) const;
-    void close_fd() noexcept;
-    void close_slave_fd() noexcept;
-    void remove_owned_link() noexcept;
+    void enqueue_frame(uint16_t word0, uint16_t word1, uint16_t word2, uint16_t word3);
+    void worker_loop();
 
     std::string path_;
-#ifndef _WIN32
-    int fd_ = -1;
-    int slave_fd_ = -1;
-    std::string slave_path_;
-    bool owns_link_ = false;
-#endif
+
+    struct Impl;
+    std::unique_ptr<Impl> impl_;
 };