Merge pull request #7669

679d055 Remove payload copy in all outgoing p2p messages (Lee Clagett)

7 files changed, 164 insertions, 135 deletions

diff --git a/contrib/epee/include/net/levin_base.h b/contrib/epee/include/net/levin_base.h
index fce6d4b7e..df59a6c44 100644
--- a/contrib/epee/include/net/levin_base.h
+++ b/contrib/epee/include/net/levin_base.h
@@ -31,6 +31,7 @@
 
 #include <cstdint>
 
+#include "byte_stream.h"
 #include "net_utils_base.h"
 #include "span.h"
 
@@ -83,11 +84,12 @@ namespace levin
 
 #define LEVIN_PROTOCOL_VER_0         0
 #define LEVIN_PROTOCOL_VER_1         1
+
  
   template<class t_connection_context = net_utils::connection_context_base>
   struct levin_commands_handler
   {
-    virtual int invoke(int command, const epee::span<const uint8_t> in_buff, byte_slice& buff_out, t_connection_context& context)=0;
+    virtual int invoke(int command, const epee::span<const uint8_t> in_buff, byte_stream& buff_out, t_connection_context& context)=0;
     virtual int notify(int command, const epee::span<const uint8_t> in_buff, t_connection_context& context)=0;
     virtual void callback(t_connection_context& context){};
 
@@ -125,12 +127,41 @@ namespace levin
     }
   }
 
+  //! Provides space for levin (p2p) header, so that payload can be sent without copy
+  class message_writer
+  {
+    byte_slice finalize(uint32_t command, uint32_t flags, uint32_t return_code, bool expect_response);
+  public:
+    using header = bucket_head2;
+
+    explicit message_writer(std::size_t reserve = 8192);
+
+    message_writer(const message_writer&) = delete;
+    message_writer(message_writer&&) = default;
+    ~message_writer() = default;
+    message_writer& operator=(const message_writer&) = delete;
+    message_writer& operator=(message_writer&&) = default;
+
+    //! \return Size of payload (excludes header size).
+    std::size_t payload_size() const noexcept
+    {
+      return buffer.size() < sizeof(header) ? 0 : buffer.size() - sizeof(header);
+    }
+
+    byte_slice finalize_invoke(uint32_t command) { return finalize(command, LEVIN_PACKET_REQUEST, 0, true); }
+    byte_slice finalize_notify(uint32_t command) { return finalize(command, LEVIN_PACKET_REQUEST, 0, false); }
+    byte_slice finalize_response(uint32_t command, uint32_t return_code)
+    {
+      return finalize(command, LEVIN_PACKET_RESPONSE, return_code, false);
+    }
+
+    //! Has space for levin header until a finalize method is used
+    byte_stream buffer;
+  };
+
   //! \return Intialized levin header.
   bucket_head2 make_header(uint32_t command, uint64_t msg_size, uint32_t flags, bool expect_response) noexcept;
 
-  //! \return A levin notification message.
-  byte_slice make_notify(int command, epee::span<const std::uint8_t> payload);
-
   /*! Generate a dummy levin message.
 
       \param noise_bytes Total size of the returned `byte_slice`.
@@ -140,12 +171,11 @@ namespace levin
 
   /*! Generate 1+ levin messages that are identical to the noise message size.
 
-   \param noise Each levin message will be identical to the size of this
-      message. The bytes from this message will be used for padding.
+   \param noise_size Each levin message will be identical to this value.
    \return `nullptr` if `noise.size()` is less than the levin header size.
       Otherwise, a levin notification message OR 2+ levin fragment messages.
       Each message is `noise.size()` in length. */
-  byte_slice make_fragmented_notify(const byte_slice& noise, int command, epee::span<const std::uint8_t> payload);
+  byte_slice make_fragmented_notify(const std::size_t noise_size, int command, message_writer message);
 }
 }
 
diff --git a/contrib/epee/include/net/levin_protocol_handler_async.h b/contrib/epee/include/net/levin_protocol_handler_async.h
index d062fa877..a6816cafc 100644
--- a/contrib/epee/include/net/levin_protocol_handler_async.h
+++ b/contrib/epee/include/net/levin_protocol_handler_async.h
@@ -51,6 +51,21 @@
 #define MIN_BYTES_WANTED	512
 #endif
 
+template<typename context_t>
+void on_levin_traffic(const context_t &context, bool initiator, bool sent, bool error, size_t bytes, const char* category)
+{
+  MCINFO("net.p2p.traffic", context << bytes << " bytes " << (sent ? "sent" : "received") << (error ? "/corrupt" : "")
+      << " for category " << category << " initiated by " << (initiator ? "us" : "peer"));
+}
+
+template<typename context_t>
+void on_levin_traffic(const context_t &context, bool initiator, bool sent, bool error, size_t bytes, int command)
+{
+  char buf[32];
+  snprintf(buf, sizeof(buf),  "command-%u", command);
+  on_levin_traffic(context, initiator, sent, error, bytes, buf);
+}
+
 namespace epee
 {
 namespace levin
@@ -88,11 +103,10 @@ public:
   uint64_t m_max_packet_size;
   uint64_t m_invoke_timeout;
 
-  int invoke(int command, const epee::span<const uint8_t> in_buff, std::string& buff_out, boost::uuids::uuid connection_id);
+  int invoke(int command, message_writer in_msg, std::string& buff_out, boost::uuids::uuid connection_id);
   template<class callback_t>
-  int invoke_async(int command, const epee::span<const uint8_t> in_buff, boost::uuids::uuid connection_id, const callback_t &cb, size_t timeout = LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED);
+  int invoke_async(int command, message_writer in_msg, boost::uuids::uuid connection_id, const callback_t &cb, size_t timeout = LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED);
 
-  int notify(int command, const epee::span<const uint8_t> in_buff, boost::uuids::uuid connection_id);
   int send(epee::byte_slice message, const boost::uuids::uuid& connection_id);
   bool close(boost::uuids::uuid connection_id);
   bool update_connection_context(const t_connection_context& contxt);
@@ -122,12 +136,17 @@ class async_protocol_handler
 {
   std::string m_fragment_buffer;
 
-  bool send_message(uint32_t command, epee::span<const uint8_t> in_buff, uint32_t flags, bool expect_response)
+  bool send_message(byte_slice message)
   {
-    const bucket_head2 head = make_header(command, in_buff.size(), flags, expect_response);
-    if(!m_pservice_endpoint->do_send(byte_slice{as_byte_span(head), in_buff}))
+    if (message.size() < sizeof(message_writer::header))
+      return false;
+
+    message_writer::header head;
+    std::memcpy(std::addressof(head), message.data(), sizeof(head));
+    if(!m_pservice_endpoint->do_send(std::move(message)))
       return false;
 
+    on_levin_traffic(m_connection_context, true, true, false, head.m_cb, head.m_command);
     MDEBUG(m_connection_context << "LEVIN_PACKET_SENT. [len=" << head.m_cb
         << ", flags" << head.m_flags
         << ", r?=" << head.m_have_to_return_data
@@ -523,26 +542,17 @@ public:
           {
             if(m_current_head.m_have_to_return_data)
             {
-              byte_slice return_buff;
+              levin::message_writer return_message{32 * 1024};
               const uint32_t return_code = m_config.m_pcommands_handler->invoke(
-                m_current_head.m_command, buff_to_invoke, return_buff, m_connection_context
+                m_current_head.m_command, buff_to_invoke, return_message.buffer, m_connection_context
               );
 
               // peer_id remains unset if dropped
               if (m_current_head.m_command == m_connection_context.handshake_command() && m_connection_context.handshake_complete())
                 m_max_packet_size = m_config.m_max_packet_size;
 
-              bucket_head2 head = make_header(m_current_head.m_command, return_buff.size(), LEVIN_PACKET_RESPONSE, false);
-              head.m_return_code = SWAP32LE(return_code);
-
-              if(!m_pservice_endpoint->do_send(byte_slice{{epee::as_byte_span(head), epee::to_span(return_buff)}}))
+              if(!send_message(return_message.finalize_response(m_current_head.m_command, return_code)))
                 return false;
-
-              MDEBUG(m_connection_context << "LEVIN_PACKET_SENT. [len=" << head.m_cb
-                << ", flags" << head.m_flags
-                << ", r?=" << head.m_have_to_return_data
-                <<", cmd = " << head.m_command
-                << ", ver=" << head.m_protocol_version);
             }
             else
               m_config.m_pcommands_handler->notify(m_current_head.m_command, buff_to_invoke, m_connection_context);
@@ -619,7 +629,7 @@ public:
   }
 
   template<class callback_t>
-  bool async_invoke(int command, const epee::span<const uint8_t> in_buff, const callback_t &cb, size_t timeout = LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED)
+  bool async_invoke(int command, message_writer in_msg, const callback_t &cb, size_t timeout = LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED)
   {
     misc_utils::auto_scope_leave_caller scope_exit_handler = misc_utils::create_scope_leave_handler(
       boost::bind(&async_protocol_handler::finish_outer_call, this));
@@ -638,7 +648,7 @@ public:
       if (command == m_connection_context.handshake_command())
         m_max_packet_size = m_config.m_max_packet_size;
 
-      if(!send_message(command, in_buff, LEVIN_PACKET_REQUEST, true))
+      if(!send_message(in_msg.finalize_invoke(command)))
       {
         LOG_ERROR_CC(m_connection_context, "Failed to do_send");
         err_code = LEVIN_ERROR_CONNECTION;
@@ -664,7 +674,7 @@ public:
     return true;
   }
 
-  int invoke(int command, const epee::span<const uint8_t> in_buff, std::string& buff_out)
+  int invoke(int command, message_writer in_msg, std::string& buff_out)
   {
     misc_utils::auto_scope_leave_caller scope_exit_handler = misc_utils::create_scope_leave_handler(
                                       boost::bind(&async_protocol_handler::finish_outer_call, this));
@@ -676,7 +686,7 @@ public:
     if (command == m_connection_context.handshake_command())
       m_max_packet_size = m_config.m_max_packet_size;
 
-    if (!send_message(command, in_buff, LEVIN_PACKET_REQUEST, true))
+    if (!send_message(in_msg.finalize_invoke(command)))
     {
       LOG_ERROR_CC(m_connection_context, "Failed to send request");
       return LEVIN_ERROR_CONNECTION;
@@ -713,25 +723,9 @@ public:
     return m_invoke_result_code;
   }
 
-  int notify(int command, const epee::span<const uint8_t> in_buff)
-  {
-    misc_utils::auto_scope_leave_caller scope_exit_handler = misc_utils::create_scope_leave_handler(
-                          boost::bind(&async_protocol_handler::finish_outer_call, this));
-
-    CRITICAL_REGION_LOCAL(m_call_lock);
-
-    if (!send_message(command, in_buff, LEVIN_PACKET_REQUEST, false))
-    {
-      LOG_ERROR_CC(m_connection_context, "Failed to send notify message");
-      return -1;
-    }
-
-    return 1;
-  }
-
-  /*! Sends `message` without adding a levin header. The message must have
-      been created with `make_notify`, `make_noise_notify` or
-      `make_fragmented_notify`. See additional instructions for
+  /*! Sends `message` without adding a levin header. The message must have been
+      created with `make_noise_notify`, `make_fragmented_notify`, or
+      `message_writer::finalize_notify`. See additional instructions for
       `make_fragmented_notify`.
 
       \return 1 on success */
@@ -741,14 +735,11 @@ public:
       boost::bind(&async_protocol_handler::finish_outer_call, this)
     );
 
-    const std::size_t length = message.size();
-    if (!m_pservice_endpoint->do_send(std::move(message)))
+    if (!send_message(std::move(message)))
     {
       LOG_ERROR_CC(m_connection_context, "Failed to send message, dropping it");
       return -1;
     }
-
-    MDEBUG(m_connection_context << "LEVIN_PACKET_SENT. [len=" << (length - sizeof(bucket_head2)) << ", r?=0]");
     return 1;
   }
   //------------------------------------------------------------------------------------------
@@ -838,19 +829,19 @@ int async_protocol_handler_config<t_connection_context>::find_and_lock_connectio
 }
 //------------------------------------------------------------------------------------------
 template<class t_connection_context>
-int async_protocol_handler_config<t_connection_context>::invoke(int command, const epee::span<const uint8_t> in_buff, std::string& buff_out, boost::uuids::uuid connection_id)
+int async_protocol_handler_config<t_connection_context>::invoke(int command, message_writer in_msg, std::string& buff_out, boost::uuids::uuid connection_id)
 {
   async_protocol_handler<t_connection_context>* aph;
   int r = find_and_lock_connection(connection_id, aph);
-  return LEVIN_OK == r ? aph->invoke(command, in_buff, buff_out) : r;
+  return LEVIN_OK == r ? aph->invoke(command, std::move(in_msg), buff_out) : r;
 }
 //------------------------------------------------------------------------------------------
 template<class t_connection_context> template<class callback_t>
-int async_protocol_handler_config<t_connection_context>::invoke_async(int command, const epee::span<const uint8_t> in_buff, boost::uuids::uuid connection_id, const callback_t &cb, size_t timeout)
+int async_protocol_handler_config<t_connection_context>::invoke_async(int command, message_writer in_msg, boost::uuids::uuid connection_id, const callback_t &cb, size_t timeout)
 {
   async_protocol_handler<t_connection_context>* aph;
   int r = find_and_lock_connection(connection_id, aph);
-  return LEVIN_OK == r ? aph->async_invoke(command, in_buff, cb, timeout) : r;
+  return LEVIN_OK == r ? aph->async_invoke(command, std::move(in_msg), cb, timeout) : r;
 }
 //------------------------------------------------------------------------------------------
 template<class t_connection_context> template<class callback_t>
@@ -929,14 +920,6 @@ void async_protocol_handler_config<t_connection_context>::set_handler(levin_comm
 }
 //------------------------------------------------------------------------------------------
 template<class t_connection_context>
-int async_protocol_handler_config<t_connection_context>::notify(int command, const epee::span<const uint8_t> in_buff, boost::uuids::uuid connection_id)
-{
-  async_protocol_handler<t_connection_context>* aph;
-  int r = find_and_lock_connection(connection_id, aph);
-  return LEVIN_OK == r ? aph->notify(command, in_buff) : r;
-}
-//------------------------------------------------------------------------------------------
-template<class t_connection_context>
 int async_protocol_handler_config<t_connection_context>::send(byte_slice message, const boost::uuids::uuid& connection_id)
 {
   async_protocol_handler<t_connection_context>* aph;
diff --git a/contrib/epee/include/storages/levin_abstract_invoke2.h b/contrib/epee/include/storages/levin_abstract_invoke2.h
index 802e16c1b..383d67cc2 100644
--- a/contrib/epee/include/storages/levin_abstract_invoke2.h
+++ b/contrib/epee/include/storages/levin_abstract_invoke2.h
@@ -37,21 +37,14 @@
 #undef MONERO_DEFAULT_LOG_CATEGORY
 #define MONERO_DEFAULT_LOG_CATEGORY "net"
 
+template<typename context_t>
+void on_levin_traffic(const context_t &context, bool initiator, bool sent, bool error, size_t bytes, const char *category);
+
+template<typename context_t>
+void on_levin_traffic(const context_t &context, bool initiator, bool sent, bool error, size_t bytes, int command);
+
 namespace
 {
-  template<typename context_t>
-  void on_levin_traffic(const context_t &context, bool initiator, bool sent, bool error, size_t bytes, const char *category)
-  {
-    MCINFO("net.p2p.traffic", context << bytes << " bytes " << (sent ? "sent" : "received") << (error ? "/corrupt" : "")
-        << " for category " << category << " initiated by " << (initiator ? "us" : "peer"));
-  }
-  template<typename context_t>
-  void on_levin_traffic(const context_t &context, bool initiator, bool sent, bool error, size_t bytes, int command)
-  {
-    char buf[32];
-    snprintf(buf, sizeof(buf),  "command-%u", command);
-    return on_levin_traffic(context, initiator, sent, error, bytes, buf);
-  }
   static const constexpr epee::serialization::portable_storage::limits_t default_levin_limits = {
     8192, // objects
     16384, // fields
@@ -117,12 +110,11 @@ namespace epee
       const boost::uuids::uuid &conn_id = context.m_connection_id;
       typename serialization::portable_storage stg;
       out_struct.store(stg);
-      byte_slice buff_to_send;
+      levin::message_writer to_send{16 * 1024};
       std::string buff_to_recv;
-      stg.store_to_binary(buff_to_send, 16 * 1024);
+      stg.store_to_binary(to_send.buffer);
 
-      on_levin_traffic(context, true, true, false, buff_to_send.size(), command);
-      int res = transport.invoke(command, boost::string_ref{reinterpret_cast<const char*>(buff_to_send.data()), buff_to_send.size()}, buff_to_recv, conn_id);
+      int res = transport.invoke(command, std::move(to_send), buff_to_recv, conn_id);
       if( res <=0 )
       {
         LOG_PRINT_L1("Failed to invoke command " << command << " return code " << res);
@@ -145,10 +137,9 @@ namespace epee
       const boost::uuids::uuid &conn_id = context.m_connection_id;
       typename serialization::portable_storage stg;
       const_cast<t_arg&>(out_struct).store(stg);//TODO: add true const support to searilzation
-      byte_slice buff_to_send;
-      stg.store_to_binary(buff_to_send, 16 * 1024);
-      on_levin_traffic(context, true, true, false, buff_to_send.size(), command);
-      int res = transport.invoke_async(command, epee::to_span(buff_to_send), conn_id, [cb, command](int code, const epee::span<const uint8_t> buff, typename t_transport::connection_context& context)->bool
+      levin::message_writer to_send{16 * 1024};
+      stg.store_to_binary(to_send.buffer);
+      int res = transport.invoke_async(command, std::move(to_send), conn_id, [cb, command](int code, const epee::span<const uint8_t> buff, typename t_transport::connection_context& context)->bool
       {
         t_result result_struct = AUTO_VAL_INIT(result_struct);
         if( code <=0 )
@@ -192,11 +183,10 @@ namespace epee
       const boost::uuids::uuid &conn_id = context.m_connection_id;
       serialization::portable_storage stg;
       out_struct.store(stg);
-      byte_slice buff_to_send;
-      stg.store_to_binary(buff_to_send);
+      levin::message_writer to_send;
+      stg.store_to_binary(to_send.buffer);
 
-      on_levin_traffic(context, true, true, false, buff_to_send.size(), command);
-      int res = transport.notify(command, epee::to_span(buff_to_send), conn_id);
+      int res = transport.send(to_send.finalize_notify(command), conn_id);
       if(res <=0 )
       {
         MERROR("Failed to notify command " << command << " return code " << res);
@@ -207,7 +197,7 @@ namespace epee
     //----------------------------------------------------------------------------------------------------
     //----------------------------------------------------------------------------------------------------
     template<class t_owner, class t_in_type, class t_out_type, class t_context, class callback_t>
-    int buff_to_t_adapter(int command, const epee::span<const uint8_t> in_buff, byte_slice& buff_out, callback_t cb, t_context& context )
+    int buff_to_t_adapter(int command, const epee::span<const uint8_t> in_buff, byte_stream& buff_out, callback_t cb, t_context& context )
     {
       serialization::portable_storage strg;
       if(!strg.load_from_binary(in_buff, &default_levin_limits))
@@ -230,12 +220,11 @@ namespace epee
       serialization::portable_storage strg_out;
       static_cast<t_out_type&>(out_struct).store(strg_out);
 
-      if(!strg_out.store_to_binary(buff_out, 32 * 1024))
+      if(!strg_out.store_to_binary(buff_out))
       {
         LOG_ERROR("Failed to store_to_binary in command" << command);
         return -1;
       }
-      on_levin_traffic(context, false, true, false, buff_out.size(), command);
 
       return res;
     }
@@ -262,7 +251,7 @@ namespace epee
     }
 
 #define CHAIN_LEVIN_INVOKE_MAP2(context_type) \
-  int invoke(int command, const epee::span<const uint8_t> in_buff, epee::byte_slice& buff_out, context_type& context) \
+  int invoke(int command, const epee::span<const uint8_t> in_buff, epee::byte_stream& buff_out, context_type& context) \
   { \
   bool handled = false; \
   return handle_invoke_map(false, command, in_buff, buff_out, context, handled); \
@@ -271,13 +260,13 @@ namespace epee
 #define CHAIN_LEVIN_NOTIFY_MAP2(context_type) \
   int notify(int command, const epee::span<const uint8_t> in_buff, context_type& context) \
   { \
-  bool handled = false; epee::byte_slice fake_str; \
-  return handle_invoke_map(true, command, in_buff, fake_str, context, handled); \
+    bool handled = false; epee::byte_stream fake_str; \
+    return handle_invoke_map(true, command, in_buff, fake_str, context, handled); \
   } 
 
 
 #define CHAIN_LEVIN_INVOKE_MAP() \
-  int invoke(int command, const epee::span<const uint8_t> in_buff, epee::byte_slice& buff_out, epee::net_utils::connection_context_base& context) \
+  int invoke(int command, const epee::span<const uint8_t> in_buff, epee::byte_stream& buff_out, epee::net_utils::connection_context_base& context) \
   { \
   bool handled = false; \
   return handle_invoke_map(false, command, in_buff, buff_out, context, handled); \
@@ -297,7 +286,7 @@ namespace epee
   } 
 
 #define BEGIN_INVOKE_MAP2(owner_type) \
-  template <class t_context> int handle_invoke_map(bool is_notify, int command, const epee::span<const uint8_t> in_buff, epee::byte_slice& buff_out, t_context& context, bool& handled) \
+  template <class t_context> int handle_invoke_map(bool is_notify, int command, const epee::span<const uint8_t> in_buff, epee::byte_stream& buff_out, t_context& context, bool& handled) \
   { \
   try { \
   typedef owner_type internal_owner_type_name;
diff --git a/contrib/epee/include/storages/portable_storage.h b/contrib/epee/include/storages/portable_storage.h
index c5d0c48ee..655a2eb12 100644
--- a/contrib/epee/include/storages/portable_storage.h
+++ b/contrib/epee/include/storages/portable_storage.h
@@ -34,6 +34,7 @@
 namespace epee
 {
   class byte_slice;
+  class byte_stream;
   namespace serialization
   {
     /************************************************************************/
@@ -83,8 +84,13 @@ namespace epee
 
       //-------------------------------------------------------------------------------
       bool		store_to_binary(byte_slice& target, std::size_t initial_buffer_size = 8192);
-      bool		load_from_binary(const epee::span<const uint8_t> target, const limits_t *limits = NULL);
-      bool		load_from_binary(const std::string& target, const limits_t *limits = NULL);
+      bool		store_to_binary(byte_stream& ss);
+      bool		load_from_binary(const epee::span<const uint8_t> target, const limits_t *limits = nullptr);
+      bool		load_from_binary(const std::string& target, const limits_t *limits = nullptr)
+      {
+        return load_from_binary(epee::strspan<uint8_t>(target), limits);
+      }
+
       template<class trace_policy>
       bool		  dump_as_xml(std::string& targetObj, const std::string& root_name = "");
       bool		  dump_as_json(std::string& targetObj, size_t indent = 0, bool insert_newlines = true);
diff --git a/contrib/epee/include/storages/portable_storage_template_helper.h b/contrib/epee/include/storages/portable_storage_template_helper.h
index 00ad15e9d..7f6596f36 100644
--- a/contrib/epee/include/storages/portable_storage_template_helper.h
+++ b/contrib/epee/include/storages/portable_storage_template_helper.h
@@ -36,6 +36,8 @@
 
 namespace epee
 {
+  class byte_stream;
+
   namespace serialization
   {
     //-----------------------------------------------------------------------------------------------------------
@@ -127,5 +129,14 @@ namespace epee
       store_t_to_binary(str_in, binary_buff, initial_buffer_size);
       return binary_buff;
     }
+    //-----------------------------------------------------------------------------------------------------------
+    template<class t_struct>
+    bool store_t_to_binary(t_struct& str_in, byte_stream& binary_buff)
+    {
+      portable_storage ps;
+      str_in.store(ps);
+      return ps.store_to_binary(binary_buff);
+    }
+
   }
 }
diff --git a/contrib/epee/src/levin_base.cpp b/contrib/epee/src/levin_base.cpp
index 5ec86b3d6..7c5cd5a78 100644
--- a/contrib/epee/src/levin_base.cpp
+++ b/contrib/epee/src/levin_base.cpp
@@ -34,6 +34,25 @@ namespace epee
 {
 namespace levin
 {
+  message_writer::message_writer(const std::size_t reserve)
+    : buffer()
+  {
+    buffer.reserve(reserve);
+    buffer.put_n(0, sizeof(header));
+  }
+
+  byte_slice message_writer::finalize(const uint32_t command, const uint32_t flags, const uint32_t return_code, const bool expect_response)
+  {
+    if (buffer.size() < sizeof(header))
+      throw std::runtime_error{"levin_writer::finalize already called"};
+
+    header head = make_header(command, payload_size(), flags, expect_response);
+    head.m_return_code = SWAP32LE(return_code);
+
+    std::memcpy(buffer.tellp() - buffer.size(), std::addressof(head), sizeof(head));
+    return byte_slice{std::move(buffer)};
+  }
+
   bucket_head2 make_header(uint32_t command, uint64_t msg_size, uint32_t flags, bool expect_response) noexcept
   {
     bucket_head2 head = {0};
@@ -47,12 +66,6 @@ namespace levin
     return head;
   }
 
-  byte_slice make_notify(int command, epee::span<const std::uint8_t> payload)
-  {
-    const bucket_head2 head = make_header(command, payload.size(), LEVIN_PACKET_REQUEST, false);
-    return byte_slice{epee::as_byte_span(head), payload};
-  }
-
   byte_slice make_noise_notify(const std::size_t noise_bytes)
   {
     static constexpr const std::uint32_t flags =
@@ -68,46 +81,40 @@ namespace levin
     return byte_slice{std::move(buffer)};
   }
 
-  byte_slice make_fragmented_notify(const byte_slice& noise_message, int command, epee::span<const std::uint8_t> payload)
+  byte_slice make_fragmented_notify(const std::size_t noise_size, const int command, message_writer message)
   {
-    const size_t noise_size = noise_message.size();
     if (noise_size < sizeof(bucket_head2) * 2)
       return nullptr;
 
-    if (payload.size() <= noise_size - sizeof(bucket_head2))
+    if (message.buffer.size() <= noise_size)
     {
       /* The entire message can be sent at once, and the levin binary parser
          will ignore extra bytes. So just pad with zeroes and otherwise send
          a "normal", not fragmented message. */
-      const size_t padding = noise_size - sizeof(bucket_head2) - payload.size();
-      const span<const uint8_t> padding_bytes{noise_message.end() - padding, padding};
 
-      const bucket_head2 head = make_header(command, noise_size - sizeof(bucket_head2), LEVIN_PACKET_REQUEST, false);
-      return byte_slice{as_byte_span(head), payload, padding_bytes};
+      message.buffer.put_n(0, noise_size - message.buffer.size());
+      return message.finalize_notify(command);
     }
 
     // fragment message
+    const byte_slice payload_bytes = message.finalize_notify(command);
+    span<const std::uint8_t> payload = to_span(payload_bytes);
+
     const size_t payload_space = noise_size - sizeof(bucket_head2);
     const size_t expected_fragments = ((payload.size() - 2) / payload_space) + 1;
 
-    std::string buffer{};
-    buffer.reserve((expected_fragments + 1) * noise_size); // +1 here overselects for internal bucket_head2 value
+    byte_stream buffer{};
+    buffer.reserve(expected_fragments * noise_size);
 
-    bucket_head2 head = make_header(0, noise_size - sizeof(bucket_head2), LEVIN_PACKET_BEGIN, false);
-    buffer.append(reinterpret_cast<const char*>(&head), sizeof(head));
+    bucket_head2 head = make_header(0, payload_space, LEVIN_PACKET_BEGIN, false);
+    buffer.write(as_byte_span(head));
 
-    head.m_command = command;
-    head.m_flags = LEVIN_PACKET_REQUEST;
-    head.m_cb = payload.size();
-    buffer.append(reinterpret_cast<const char*>(&head), sizeof(head));
+    // internal levin header is in payload already
 
-    size_t copy_size = payload.remove_prefix(payload_space - sizeof(bucket_head2));
-    buffer.append(reinterpret_cast<const char*>(payload.data()) - copy_size, copy_size);
+    size_t copy_size = payload.remove_prefix(payload_space);
+    buffer.write(payload.data() - copy_size, copy_size);
 
-    head.m_command = 0;
     head.m_flags = 0;
-    head.m_cb = noise_size - sizeof(bucket_head2);
-
     while (!payload.empty())
     {
       copy_size = payload.remove_prefix(payload_space);
@@ -115,12 +122,12 @@ namespace levin
       if (payload.empty())
         head.m_flags = LEVIN_PACKET_END;
 
-      buffer.append(reinterpret_cast<const char*>(&head), sizeof(head));
-      buffer.append(reinterpret_cast<const char*>(payload.data()) - copy_size, copy_size);
+      buffer.write(as_byte_span(head));
+      buffer.write(payload.data() - copy_size, copy_size);
     }
 
     const size_t padding = noise_size - copy_size - sizeof(bucket_head2);
-    buffer.append(reinterpret_cast<const char*>(noise_message.end()) - padding, padding);
+    buffer.put_n(0, padding);
 
     return byte_slice{std::move(buffer)};
   }
diff --git a/contrib/epee/src/portable_storage.cpp b/contrib/epee/src/portable_storage.cpp
index c3c9ccc02..b922cc9e3 100644
--- a/contrib/epee/src/portable_storage.cpp
+++ b/contrib/epee/src/portable_storage.cpp
@@ -48,15 +48,23 @@ namespace serialization
     TRY_ENTRY();
     byte_stream ss;
     ss.reserve(initial_buffer_size);
+    store_to_binary(ss);
+    target = epee::byte_slice{std::move(ss)};
+    return true;
+    CATCH_ENTRY("portable_storage::store_to_binary", false);
+  }
+
+  bool portable_storage::store_to_binary(byte_stream& ss)
+  {
+    TRY_ENTRY();
     storage_block_header sbh{};
     sbh.m_signature_a = SWAP32LE(PORTABLE_STORAGE_SIGNATUREA);
     sbh.m_signature_b = SWAP32LE(PORTABLE_STORAGE_SIGNATUREB);
     sbh.m_ver = PORTABLE_STORAGE_FORMAT_VER;
     ss.write(epee::as_byte_span(sbh));
     pack_entry_to_buff(ss, m_root);
-    target = epee::byte_slice{std::move(ss)};
     return true;
-    CATCH_ENTRY("portable_storage::store_to_binary", false)
+    CATCH_ENTRY("portable_storage::store_to_binary", false);
   }
 
     bool portable_storage::dump_as_json(std::string& buff, size_t indent, bool insert_newlines)
@@ -76,11 +84,6 @@ namespace serialization
       CATCH_ENTRY("portable_storage::load_from_json", false)
     }
 
-    bool portable_storage::load_from_binary(const std::string& target, const limits_t *limits)
-    {
-         return load_from_binary(epee::strspan<uint8_t>(target), limits);
-    }
-
     bool portable_storage::load_from_binary(const epee::span<const uint8_t> source, const limits_t *limits)
     {
       m_root.m_entries.clear();