net/adc_netproto.h: add AdcStartStopSeqSessionProto class

net/adc_netproto.h

@@ -21,6 +21,7 @@ concept adc_netproto_c = adc_range_of_view_char_range<R> && requires(T t, const
 namespace constants
 {
 
+static constexpr char ADC_DEFAULT_NETPROTO_STARTSEQ[] = "\v";
 static constexpr char ADC_DEFAULT_NETPROTO_STOPSEQ[] = "\n";
 
 static constexpr char ADC_DEFAULT_NETPROTO_STARTMARK[] = "\n\t\r\v\r\t\n";
@@ -39,7 +40,10 @@ struct AdcStopSeqSessionProto {
 
     typedef std::string proto_ident_t;
 
-    proto_ident_t ident() const { return "STOP SEQUENCE PROTO"; }
+    proto_ident_t ident() const
+    {
+        return "STOP SEQUENCE PROTO";
+    }
 
     // template <traits::adc_input_char_range R>
     // auto search(const R& r)
@@ -142,6 +146,105 @@ struct AdcStopSeqSessionProto {
 };
 
 
+template <const char* STARTSEQ = constants::ADC_DEFAULT_NETPROTO_STARTSEQ,
+          const char* STOPSEQ = constants::ADC_DEFAULT_NETPROTO_STOPSEQ>
+struct AdcStartStopSeqSessionProto {
+    static constexpr std::string_view START_SEQ{STARTSEQ};
+    static constexpr size_t START_SEQ_SIZE = START_SEQ.size();
+    static constexpr std::string_view STOP_SEQ{STOPSEQ};
+    static constexpr size_t STOP_SEQ_SIZE = STOP_SEQ.size();
+
+    static_assert(START_SEQ_SIZE, "START BYTE SEQUENCE MUST NOT BE AN EMPTY ONE!!!");
+    static_assert(STOP_SEQ_SIZE, "STOP BYTE SEQUENCE MUST NOT BE AN EMPTY ONE!!!");
+
+    typedef std::string proto_ident_t;
+
+    proto_ident_t ident() const
+    {
+        return "STOP SEQUENCE PROTO";
+    }
+
+    template <traits::adc_input_char_range R>
+    auto search(const R& r)
+    {
+        auto func = [&r](auto& result) {
+            if (std::ranges::size(r) < (START_SEQ_SIZE + STOP_SEQ_SIZE)) {
+                return;
+            }
+
+            auto found_start = std::ranges::search(r, START_SEQ);
+            if (found_start.empty()) {
+                return;
+            }
+
+            auto found_stop = std::ranges::search(r, STOP_SEQ);
+            if (found_stop.empty()) {
+                return;
+            }
+
+            if (found_start.begin() > found_stop.begin()) {
+                return;
+            }
+
+            if constexpr (std::ranges::viewable_range<R>) {
+                result = std::span(found_start.begin(), found_stop.end());
+            } else {
+                std::ranges::copy(found_start.begin(), found_stop.end(), std::back_inserter(result));
+            }
+        };
+
+        if constexpr (std::ranges::viewable_range<R>) {
+            auto res = std::span(r.begin(), r.begin());  // empty std::span
+            func(res);
+            return res;
+        } else {
+            auto res = std::vector<char>();
+            func(res);
+            return res;
+        }
+    }
+
+
+    template <traits::adc_input_char_range R>
+    auto toProto(const R& r)
+    {
+        // return 3-element array with the first element - a view of the start sequence, the second one - as a view of
+        // the input range and the third one - a view of the stop sequence
+
+        if constexpr (std::ranges::viewable_range<R>) {
+            auto res = std::array{std::span(std::span(START_SEQ.begin(), START_SEQ.end()), r.begin(), r.end()),
+                                  std::span(STOP_SEQ.begin(), STOP_SEQ.end())};
+
+            return res;
+        } else {  // return a copy of input range with added to the fron start sequence and appended stop sequence
+            std::decay_t<decltype(r)> res;
+            std::ranges::copy(START_SEQ, std::back_inserter(res));
+            std::ranges::copy(r, std::back_inserter(res));
+            std::ranges::copy(STOP_SEQ, std::back_inserter(res));
+            return res;
+        }
+    }
+
+    template <traits::adc_input_char_range R>
+    auto fromProto(const R& r)
+    {
+        size_t N = std::distance(r.begin(), r.end());
+
+        if (N < (START_SEQ_SIZE + STOP_SEQ_SIZE)) {  // one must ensure for input range size correctness
+            return std::span(r.begin(), r.begin());
+        }
+
+        if constexpr (std::ranges::viewable_range<R>) {
+            return std::span(r.begin() + START_SEQ_SIZE, r.end() - STOP_SEQ_SIZE);
+        } else {
+            R res;
+            std::ranges::copy(r | std::views::drop(START_SEQ_SIZE) | std::views::take(N - STOP_SEQ_SIZE),
+                              std::back_inserter(res));
+            return res;
+        }
+    }
+};
+
 // session protocol for datagram-kind message (e.g. UDP, seqpacket)
 // The protocol does not contain any special characters, so to/fromProto methods
 // return just a copy/one-element-array-of-vew/view of input byte
@@ -149,7 +252,10 @@ struct AdcStopSeqSessionProto {
 struct AdcDatagramSessionProto {
     typedef std::string proto_ident_t;
 
-    proto_ident_t ident() const { return "DATAGRAM PROTO"; }
+    proto_ident_t ident() const
+    {
+        return "DATAGRAM PROTO";
+    }
 
     template <traits::adc_input_char_range R>
     auto search(const R& r)
@@ -201,7 +307,10 @@ struct AdcBinaryBlobSessionProto {
 
     typedef std::string proto_ident_t;
 
-    proto_ident_t ident() const { return "BINARY BLOB PROTO"; }
+    proto_ident_t ident() const
+    {
+        return "BINARY BLOB PROTO";
+    }
 
     template <traits::adc_input_char_range R>
     auto search(const R& r)