io: add iterative file reading helper

io.hpp

@@ -131,6 +131,24 @@ namespace cruft {
     }
 
 
+    ///------------------------------------------------------------------------
+    /// Read the number of bytes covered by the destination view from the
+    /// source descriptor.
+    template <typename SrcT>
+    decltype (auto)
+    read (SrcT &&src, cruft::view<u08*> dst)
+    {
+        auto remain = dst;
+
+        while (!remain.empty ()) {
+            auto const count = src.read (remain.begin (), remain.size () * sizeof (decltype(dst)::value_type));
+            remain = remain.consume (count);
+        }
+
+        return dst;
+    }
+
+
     ///////////////////////////////////////////////////////////////////////////
     class indenter : public std::streambuf {
     protected: