paramlist.h: ParamValue as_span, as_cspan

Convenience methods that give a bounded span of the data that a PV holds.

Signed-off-by: Larry Gritz <[email protected]>

Author: lgritz

src/include/OpenImageIO/paramlist.h

@@ -215,6 +215,26 @@ class OIIO_UTIL_API ParamValue {
         b        = std::move(tmp);
     }
 
+    /// Return a `cspan<T>` pointing to the bounded data. If the type `T` is
+    /// not the actual underlying base type, return an empty span.
+    template<typename T> cspan<T> as_cspan() const noexcept
+    {
+        return BaseTypeFromC<T>::value == m_type.basetype
+                   ? make_cspan(reinterpret_cast<const T*>(data()),
+                                size_t(m_nvalues * m_type.basevalues()))
+                   : cspan<T>();
+    }
+
+    /// Return a `span<T>` pointing to the bounded data. If the type `T` is
+    /// not the actual underlying base type, return an empty span.
+    template<typename T> span<T> as_span() noexcept
+    {
+        return BaseTypeFromC<T>::value == m_type.basetype
+                   ? make_span(reinterpret_cast<T*>(const_cast<void*>(data())),
+                               size_t(m_nvalues * m_type.basevalues()))
+                   : span<T>();
+    }
+
     // Use with extreme caution! This is just doing a cast. You'd better
     // be really sure you are asking for the right type. Note that for
     // "string" data, you can get<ustring> or get<char*>, but it's not

src/libutil/paramlist.cpp

@@ -126,17 +126,13 @@ template<class T>
 static void
 parse_elements(string_view value, ParamValue& p)
 {
-    using namespace Strutil;
-    TypeDesc type = p.type();
-    int num_items = type.numelements() * type.aggregate;
-    T* data       = (T*)p.data();
-    // Erase any leading whitespace
+    auto data = p.as_span<T>();
     value.remove_prefix(value.find_first_not_of(" \t"));
-    for (int i = 0; i < num_items; ++i) {
+    for (auto&& d : data) {
         // Make a temporary copy so we for sure have a 0-terminated string.
         std::string temp = value;
         // Grab the first value from it
-        data[i] = from_string<T>(temp);
+        d = Strutil::from_string<T>(temp);
         // Skip the value (eat until we find a delimiter -- space, comma, tab)
         value.remove_prefix(value.find_first_of(" ,\t"));
         // Skip the delimiter