Add UTF-8 and byte strings (#142)

Closes #51

See OpenCyphal/pydsdl#97

---------

Co-authored-by: Copilot <[email protected]>

Author: pavel-kirienko

specification/dsdl/grammar.parsimonious

@@ -47,18 +47,22 @@ type_scalar = type_versioned
 type_versioned         = identifier ("." identifier)* "." type_version_specifier
 type_version_specifier = literal_integer_decimal "." literal_integer_decimal
 
-type_primitive = type_primitive_truncated
+type_primitive = type_primitive_boolean
+               / type_primitive_byte
+               / type_primitive_utf8
+               / type_primitive_truncated
                / type_primitive_saturated
 
+type_primitive_boolean   = "bool"
+type_primitive_byte      = "byte"
+type_primitive_utf8      = "utf8"
 type_primitive_truncated =  "truncated" _   type_primitive_name
 type_primitive_saturated = ("saturated" _)? type_primitive_name     # Defaults to this.
 
-type_primitive_name = type_primitive_name_boolean
-                    / type_primitive_name_unsigned_integer
+type_primitive_name = type_primitive_name_unsigned_integer
                     / type_primitive_name_signed_integer
                     / type_primitive_name_floating_point
 
-type_primitive_name_boolean          = "bool"
 type_primitive_name_unsigned_integer = "uint"  type_bit_length_suffix
 type_primitive_name_signed_integer   = "int"   type_bit_length_suffix
 type_primitive_name_floating_point   = "float" type_bit_length_suffix

specification/dsdl/grammar.tex

@@ -227,7 +227,9 @@ \subsection{Reserved identifiers}\label{sec:dsdl_reserved_identifiers}
     \texttt{saturated}                                 &                    & Cast mode specifier \\
     \texttt{true}                                      &                    & Boolean literal \\
     \texttt{false}                                     &                    & Boolean literal \\
-    \texttt{bool}                                      &                    & Primitive type category \\
+    \texttt{bool}                                      &                    & Primitive type  \\
+    \texttt{utf8}                                      &                    & Primitive type  \\
+    \texttt{byte}                                      &                    & Primitive type  \\
     \texttt{u?int\textbackslash{}d*}                   & \texttt{uint8}     & Primitive type category \\
     \texttt{float\textbackslash{}d*}                   & \texttt{float}     & Primitive type category \\
     \texttt{u?q\textbackslash{}d+\_\textbackslash{}d+} & \texttt{q16\_8}    & Primitive type category (future) \\

specification/dsdl/serializable_types.tex

@@ -80,6 +80,17 @@ \subsubsection{Hierarchy}
             The corresponding DSDL data type name pattern is ``\verb|uint[1-9]\d*|'',
             where the trailing integer represents the length of the
             serialized representation of the value, in bits, ranging from 1 to 64, inclusive.
+            \begin{itemize}
+                \item \textbf{UTF-8 octet.} This type is used as an element type of variable-length
+                arrays (section \ref{sec:dsdl_array_types}) containing UTF-8 encoded strings.
+                The DSDL name is ``\verb|utf8|''.
+                The only valid use of this type is as an element type of a variable-length array.
+
+                \item \textbf{Byte.} This type is used as an element type of fixed-length or variable-length
+                arrays (section \ref{sec:dsdl_array_types}) containing an arbitrary sequence of bytes.
+                The DSDL name is ``\verb|byte|''.
+                The only valid use of this type is as an element type of an array.
+            \end{itemize}
         \end{itemize}
 
         \item \textbf{Floating point types} are used to approximately represent real values.
@@ -138,10 +149,6 @@ \subsubsection{Cast mode}
     Type category & Truncated mode & Saturated mode (default)
     \label{table:dsdl_cast_mode} \\
 
-    Boolean &
-    Illegal: boolean type with truncated cast mode is not allowed. &
-    Falsity if the value is zero or false, truth otherwise. \\
-
     Signed integer &
     Illegal: signed integer types with truncated cast mode are not allowed. &
     Nearest reachable value. \\
@@ -189,7 +196,7 @@ \subsubsection{Reference list}
 \immediate\write18{../render_list_of_void_and_primitive_types.py > ../latex.tmp}
 \immediate\input{../latex.tmp}
 
-\subsection{Array types}
+\subsection{Array types}\label{sec:dsdl_array_types}
 
 An array type represents an ordered collection of values.
 All values in the collection share the same type, which is referred to as \emph{array element type}.

specification/introduction/introduction.tex

@@ -240,6 +240,8 @@ \subsection{v1.0 -- work in progress}
     \item The constraint on DSDL namespaces being defined in a single folder was removed. Namespaces can be hosted
     across multiple repositories and code can be generated from a union of said folders.
 
+    \item Support for UTF-8 strings and byte strings has been added.
+
     \item Cyphal/UDP and Cyphal/serial transport specifications have been introduced.
 
     \item Minor adjustments of the transport layer definitions.