Supporting comms::option::FrameLayerSeekField option in comms::frame::SyncPrefixLayer class.

Author: arobenko

doxygen/page_frame.dox

@@ -391,13 +391,30 @@
 ///
 /// } // namespace my_protocol
 /// @endcode
-/// The comms::frame::SyncPrefixLayer class receives two template parameters.
+/// The comms::frame::SyncPrefixLayer class receives at least two template parameters.
+///
 /// The first one is the type of the @b field, that is responsible to read/write
 /// the synchronisation byte(s). Please note the usage of @ref comms::option::def::DefaultNumValue
 /// option when defining the @b field type. It insures that the default constructed
-/// field will have the required value. @n
+/// field will have the required value.
+///
 /// The second template parameter is the upper layer being wrapped.
 ///
+/// Starting from the third template parameter coming behaviour customization options
+/// For example passing extra @ref comms::option::def::FrameLayerSeekField will force
+/// the layer to actually seek the required prefix in the input data before continuing.
+/// @code
+/// using MySyncPrefix =
+///     comms::frame::SyncPrefixLayer<
+///         SyncField,
+///         MyChecksum<TMessage, TInputMessages, TAllocationOptions>,
+///         comms::option::def::FrameLayerSeekField
+///     >;
+/// @endcode
+/// Similar to the @ref page_frame_tutorial_checksum the @ref page_frame_tutorial_sync
+/// can process the trailing (after message payload) synchronization bytes. However, to
+/// process such bytes the @ref comms::frame::SyncSuffixLayer class needs to be used instead.
+///
 /// @section page_frame_tutorial_transport_value Extra Transport Values
 /// Some protocol may use extra values as part of the transport information. Such
 /// values may have an influence on how the message payload is read and/or on

include/comms/frame/ChecksumLayer.h

@@ -49,15 +49,15 @@ namespace frame
 ///     @ref comms::frame::checksum namespace (`comms/frame/checkum` folder).
 /// @tparam TNextLayer Next transport layer in frame.
 /// @tparam TOptions Extending functionality options. Supported options are:
+///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
+///         name of the extending class, which can be used to extend existing functionality.
+///         See also @ref page_custom_checksum_layer tutorial page.
 ///     @li @ref comms::option::def::FrameLayerVerifyBeforeRead - By default, the
 ///         @b ChecksumLayer will invoke @b read operation of inner (wrapped) layers
 ///         and only if it is successful, it will calculate and verify the
 ///         checksum value. Usage of @ref comms::option::def::FrameLayerVerifyBeforeRead
 ///         modifies the default behaviour by forcing the checksum verification
 ///         prior to invocation of @b read operation in the wrapped layer(s).
-///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
-///         name of the extending class, which can be used to extend existing functionality.
-///         See also @ref page_custom_checksum_layer tutorial page.
 /// @headerfile comms/frame/ChecksumLayer.h
 /// @extends comms::frame::FrameLayerBase
 template <typename TField, typename TCalc, typename TNextLayer, typename... TOptions>

include/comms/frame/ChecksumPrefixLayer.h

@@ -50,15 +50,15 @@ namespace frame
 ///     @ref comms::frame::checksum namespace (`comms/frame/checkum` folder).
 /// @tparam TNextLayer Next transport layer in frame.
 /// @tparam TOptions Extending functionality options. Supported options are:
+///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
+///         name of the extending class, which can be used to extend existing functionality.
+///         See also @ref page_custom_checksum_layer tutorial page.
 ///     @li @ref comms::option::def::FrameLayerVerifyBeforeRead - By default, the
 ///         @b ChecksumPrefixLayer will invoke @b read operation of inner (wrapped) layers
 ///         and only if it is successful, it will calculate and verify the
 ///         checksum value. Usage of @ref comms::option::def::FrameLayerVerifyBeforeRead
 ///         modifies the default behaviour by forcing the checksum verification
 ///         prior to invocation of @b read operation in the wrapped layer(s).
-///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
-///         name of the extending class, which can be used to extend existing functionality.
-///         See also @ref page_custom_checksum_layer tutorial page.
 /// @headerfile comms/frame/ChecksumPrefixLayer.h
 /// @extends comms::frame::FrameLayerBase
 template <typename TField, typename TCalc, typename TNextLayer, typename... TOptions>

include/comms/frame/SyncPrefixLayer.h

@@ -39,6 +39,12 @@ namespace frame
 ///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
 ///         name of the extending class, which can be used to extend existing functionality.
 ///         See also @ref page_custom_sync_prefix_layer.
+///     @li @ref comms::option::def::FrameLayerSeekField - By default, the
+///         @b SyncSuffixLayer will invoke @b read operation of inner (wrapped) layers
+///         and only if it is successful. Usage of @ref comms::option::def::FrameLayerSeekField
+///         modifies the default behaviour by forcing layer to seek the field in the
+///         buffer (until the successful read and verification)
+///         prior to invocation of @b read operation in the wrapped layer(s).
 /// @headerfile comms/frame/SyncPrefixLayer.h
 /// @extends comms::frame::FrameLayerBase
 template <typename TField, typename TNextLayer, typename... TOptions>
@@ -85,7 +91,7 @@ class SyncPrefixLayer : public comms::frame::details::SyncPrefixLayerBase<TField
     ///     the next layer is called.
     /// @tparam TMsg Type of the @b msg parameter.
     /// @tparam TIter Type of iterator used for reading.
-    /// @tparam TNextLayerReader next layer reader object type.
+    /// @tparam TNextLayerReader Next layer reader object type.
     /// @param[out] field Field object to read.
     /// @param[in, out] msg Reference to smart pointer, that already holds or
     ///     will hold allocated message object, or reference to actual message
@@ -114,26 +120,23 @@ class SyncPrefixLayer : public comms::frame::details::SyncPrefixLayerBase<TField
         TNextLayerReader&& nextLayerReader,
         TExtraValues... extraValues)
     {
-        auto& thisObj = BaseImpl::thisLayer();
-        auto* msgPtr = BaseImpl::toMsgPtr(msg);
-        auto beforeReadIter = iter;
-
-        auto es = thisObj.doReadField(msgPtr, field, iter, size);
-        if (es == comms::ErrorStatus::NotEnoughData) {
-            BaseImpl::updateMissingSize(field, size, extraValues...);
-        }
-
-        if (es != comms::ErrorStatus::Success) {
-            return es;
-        }
-
-        bool verified = thisObj.verifyFieldValue(field);
-        if (!verified) {
-            return comms::ErrorStatus::ProtocolError;
-        }
+        using SeekTag =
+            typename comms::util::LazyShallowConditional<
+                ParsedOptionsInternal::HasSeekField
+            >::template Type<
+                SeekFieldTag,
+                InstantOpTag
+            >;
 
-        auto fieldLen = static_cast<std::size_t>(std::distance(beforeReadIter, iter));
-        return nextLayerReader.read(msg, iter, size - fieldLen, extraValues...);
+        return
+            readInternal(
+                field,
+                msg,
+                iter,
+                size,
+                std::forward<TNextLayerReader>(nextLayerReader),
+                SeekTag(),
+                extraValues...);
     }
 
     /// @brief Customized write functionality, invoked by @ref comms::frame::FrameLayerBase::write() "write()".
@@ -195,6 +198,95 @@ class SyncPrefixLayer : public comms::frame::details::SyncPrefixLayerBase<TField
     {
         static_cast<void>(field);
     }
+
+private:
+    template <typename... TParams>
+    using SeekFieldTag = comms::details::tag::Tag1<>;
+
+    template <typename... TParams>
+    using InstantOpTag = comms::details::tag::Tag2<>;
+
+    template <typename TMsg, typename TIter, typename TReader, typename... TExtraValues>
+    ErrorStatus readInternal(
+        Field& field,
+        TMsg& msg,
+        TIter& iter,
+        std::size_t size,
+        TReader&& nextLayerReader,
+        SeekFieldTag<>,
+        TExtraValues... extraValues)
+    {
+        using IterType = typename std::decay<decltype(iter)>::type;
+        static_assert(std::is_same<typename std::iterator_traits<IterType>::iterator_category, std::random_access_iterator_tag>::value,
+            "The read operation is expected to use random access iterator");
+
+        auto& thisObj = BaseImpl::thisLayer();
+        auto* msgPtr = BaseImpl::toMsgPtr(msg);
+
+        auto fromIter = iter;
+        std::size_t consumed = 0U;
+        while (consumed < size) {
+            auto iterTmp = iter;
+            auto remSize = size - consumed;
+
+            auto fieldEs = thisObj.doReadField(msgPtr, field, iterTmp, remSize);
+            if (fieldEs == ErrorStatus::NotEnoughData) {
+                BaseImpl::updateMissingSize(field, remSize, extraValues...);
+                BaseImpl::resetMsg(msg);
+                return fieldEs;
+            }
+
+            if ((fieldEs == ErrorStatus::Success) &&
+                (thisObj.verifyFieldValue(field))) {
+                // Set iter to point after field
+                iter = iterTmp;
+                break;
+            }
+
+            ++iter;
+            ++consumed;
+        }
+
+        if (size <= consumed) {
+            // Field hasn't been recognized
+            return ErrorStatus::NotEnoughData;
+        }
+
+        auto remSize = size - static_cast<std::size_t>(std::distance(fromIter, iter));
+        return nextLayerReader.read(msg, iter, remSize, extraValues...);
+    }
+
+    template <typename TMsg, typename TIter, typename TReader, typename... TExtraValues>
+    ErrorStatus readInternal(
+        Field& field,
+        TMsg& msg,
+        TIter& iter,
+        std::size_t size,
+        TReader&& nextLayerReader,
+        InstantOpTag<>,
+        TExtraValues... extraValues)
+    {
+        auto& thisObj = BaseImpl::thisLayer();
+        auto* msgPtr = BaseImpl::toMsgPtr(msg);
+        auto beforeReadIter = iter;
+
+        auto es = thisObj.doReadField(msgPtr, field, iter, size);
+        if (es == comms::ErrorStatus::NotEnoughData) {
+            BaseImpl::updateMissingSize(field, size, extraValues...);
+        }
+
+        if (es != comms::ErrorStatus::Success) {
+            return es;
+        }
+
+        bool verified = thisObj.verifyFieldValue(field);
+        if (!verified) {
+            return comms::ErrorStatus::ProtocolError;
+        }
+
+        auto fieldLen = static_cast<std::size_t>(std::distance(beforeReadIter, iter));
+        return nextLayerReader.read(msg, iter, size - fieldLen, extraValues...);
+    }
 };
 
 namespace details

include/comms/frame/SyncSuffixLayer.h

@@ -39,6 +39,9 @@ namespace frame
 /// @tparam TField Type of the field that is used as to represent checksum value.
 /// @tparam TNextLayer Next transport layer in frame.
 /// @tparam TOptions Extending functionality options. Supported options are:
+///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
+///         name of the extending class, which can be used to extend existing functionality.
+///         See also @ref page_custom_checksum_layer tutorial page.
 ///     @li @ref comms::option::def::FrameLayerVerifyBeforeRead - By default, the
 ///         @b SyncSuffixLayer will invoke @b read operation of inner (wrapped) layers
 ///         and only if it is successful. Usage of @ref comms::option::def::FrameLayerVerifyBeforeRead
@@ -50,9 +53,6 @@ namespace frame
 ///         modifies the default behaviour by forcing layer to seek the field in the
 ///         buffer (until the successful read and verification)
 ///         prior to invocation of @b read operation in the wrapped layer(s).
-///     @li  @ref comms::option::ExtendingClass - Use this option to provide a class
-///         name of the extending class, which can be used to extend existing functionality.
-///         See also @ref page_custom_checksum_layer tutorial page.
 /// @headerfile comms/frame/SyncSuffixLayer.h
 /// @extends comms::frame::FrameLayerBase
 template <typename TField, typename TNextLayer, typename... TOptions>
@@ -144,13 +144,17 @@ class SyncSuffixLayer : public comms::frame::details::SyncSuffixLayerBase<TField
         TNextLayerReader&& nextLayerReader,
         TExtraValues... extraValues)
     {
+        std::cout << "!!! " << __FUNCTION__ << ": " << std::hex;
+        std::copy_n(iter, size, std::ostream_iterator<unsigned>(std::cout, " "));
+        std::cout << std::dec << std::endl;
+
         using IterType = typename std::decay<decltype(iter)>::type;
         static_assert(std::is_same<typename std::iterator_traits<IterType>::iterator_category, std::random_access_iterator_tag>::value,
             "The read operation is expected to use random access iterator");
 
         using SeekTag =
             typename comms::util::LazyShallowConditional<
-                ParsedOptionsInternal::HasVerifyBeforeRead
+                ParsedOptionsInternal::HasSeekField
             >::template Type<
                 SeekFieldTag,
                 InstantOpTag
@@ -243,6 +247,10 @@ class SyncSuffixLayer : public comms::frame::details::SyncSuffixLayerBase<TField
         TReader&& nextLayerReader,
         TExtraValues... extraValues)
     {
+        std::cout << "!!! " << __FUNCTION__ << ": " << std::hex;
+        std::copy_n(iter, size, std::ostream_iterator<unsigned>(std::cout, " "));
+        std::cout << std::dec << std::endl;
+
         auto fromIter = iter;
         auto* msgPtr = BaseImpl::toMsgPtr(msg);
         auto fieldLen = Field::minLength();
@@ -281,6 +289,10 @@ class SyncSuffixLayer : public comms::frame::details::SyncSuffixLayerBase<TField
         TReader&& nextLayerReader,
         TExtraValues... extraValues)
     {
+        std::cout << "!!! " << __FUNCTION__ << ": " << std::hex;
+        std::copy_n(iter, size, std::ostream_iterator<unsigned>(std::cout, " "));
+        std::cout << std::dec << std::endl;
+
         auto fromIter = iter;
 
         auto es = nextLayerReader.read(msg, iter, size, extraValues...);
@@ -321,6 +333,10 @@ class SyncSuffixLayer : public comms::frame::details::SyncSuffixLayerBase<TField
         TReader&& nextLayerReader,
         TExtraValues... extraValues)
     {
+        std::cout << "!!! " << __FUNCTION__ << ": " << std::hex;
+        std::copy_n(iter, size, std::ostream_iterator<unsigned>(std::cout, " "));
+        std::cout << std::dec << std::endl;
+
         auto& thisObj = BaseImpl::thisLayer();
         auto* msgPtr = BaseImpl::toMsgPtr(msg);
 

include/comms/frame/TransportValueLayer.h

@@ -44,8 +44,6 @@ namespace frame
 ///     (accessed via @ref comms::Message::transportFields()).
 /// @tparam TNextLayer Next transport layer in frame.
 /// @tparam TOptions Extending functionality options. Supported options are:
-///     @li @ref comms::option::def::PseudoValue - Mark the handled value to be "pseudo"
-///         one, i.e. the field is not getting serialised.
 ///     @li  @ref comms::option::def::ExtendingClass - Use this option to provide a class
 ///         name of the extending class, which can be used to extend existing functionality.
 ///         See also @ref page_custom_transport_value_layer tutorial page.
@@ -57,6 +55,8 @@ namespace frame
 ///         happens when the @ref comms::frame::TransportValueLayer preceeds (wraps)
 ///         @ref comms::frame::MsgIdLayer and is unable to re-assign the read field value
 ///         to the message object, because the latter hasn't been created yet.
+///     @li @ref comms::option::def::PseudoValue - Mark the handled value to be "pseudo"
+///         one, i.e. the field is not getting serialised.
 /// @headerfile comms/frame/TransportValueLayer.h
 /// @extends comms::frame::FrameLayerBase
 template <typename TField, std::size_t TIdx, typename TNextLayer, typename... TOptions>

include/comms/frame/details/SyncPrefixLayerOptionsParser.h

@@ -26,6 +26,7 @@ class SyncPrefixLayerOptionsParser<>
 {
 public:
     static constexpr bool HasExtendingClass = false;
+    static constexpr bool HasSeekField = false;
 
     using ExtendingClass = void;
 
@@ -45,6 +46,14 @@ class SyncPrefixLayerOptionsParser<comms::option::def::ExtendingClass<T>, TOptio
     using DefineExtendingClass = ExtendingClass;
 };
 
+template <typename... TOptions>
+class SyncPrefixLayerOptionsParser<comms::option::def::FrameLayerSeekField, TOptions...> :
+        public SyncPrefixLayerOptionsParser<TOptions...>
+{
+public:
+    static constexpr bool HasSeekField = true;
+};
+
 template <typename... TOptions>
 class SyncPrefixLayerOptionsParser<
     comms::option::app::EmptyOption,

include/comms/frame/details/SyncSuffixLayerOptionsParser.h

@@ -55,13 +55,6 @@ class SyncSuffixLayerOptionsParser<comms::option::def::ExtendingClass<T>, TOptio
     using DefineExtendingClass = ExtendingClass;
 };
 
-template <typename... TOptions>
-class SyncSuffixLayerOptionsParser<
-    comms::option::app::EmptyOption,
-    TOptions...> : public SyncSuffixLayerOptionsParser<TOptions...>
-{
-};
-
 template <typename... TOptions>
 class SyncSuffixLayerOptionsParser<comms::option::def::FrameLayerSeekField, TOptions...> :
         public SyncSuffixLayerOptionsParser<TOptions...>
@@ -70,6 +63,13 @@ class SyncSuffixLayerOptionsParser<comms::option::def::FrameLayerSeekField, TOpt
     static constexpr bool HasSeekField = true;
 };
 
+template <typename... TOptions>
+class SyncSuffixLayerOptionsParser<
+    comms::option::app::EmptyOption,
+    TOptions...> : public SyncSuffixLayerOptionsParser<TOptions...>
+{
+};
+
 template <typename... TBundledOptions, typename... TOptions>
 class SyncSuffixLayerOptionsParser<
     std::tuple<TBundledOptions...>,