vtkHDFUtilities: support `char` as unsigned

IO/HDF/vtkHDFUtilities.cxx

@@ -12,6 +12,7 @@
 #include "vtkLongArray.h"
 #include "vtkLongLongArray.h"
 #include "vtkShortArray.h"
+#include "vtkSignedCharArray.h"
 #include "vtkStringArray.h"
 #include "vtkUnsignedCharArray.h"
 #include "vtkUnsignedIntArray.h"
@@ -82,6 +83,10 @@ vtkDataArray* NewVtkDataArray()
   {
     return vtkCharArray::New();
   }
+  else if (std::is_same<T, signed char>::value)
+  {
+    return vtkSignedCharArray::New();
+  }
   else if (std::is_same<T, unsigned char>::value)
   {
     return vtkUnsignedCharArray::New();
@@ -227,6 +232,7 @@ using TypeReaderMap = std::map<::TypeDescription, ArrayReader*>;
   ::TypeReaderMap readerMap;
 
   readerMap[::GetTypeDescription(H5T_NATIVE_CHAR)] = &::NewArray<char>;
+  readerMap[::GetTypeDescription(H5T_NATIVE_SCHAR)] = &::NewArray<signed char>;
   readerMap[::GetTypeDescription(H5T_NATIVE_UCHAR)] = &::NewArray<unsigned char>;
   readerMap[::GetTypeDescription(H5T_NATIVE_SHORT)] = &::NewArray<short>;
   readerMap[::GetTypeDescription(H5T_NATIVE_USHORT)] = &::NewArray<unsigned short>;

IO/HDF/vtkHDFUtilities.txx

@@ -107,6 +107,10 @@ hid_t vtkHDFUtilities::TemplateTypeToHdfNativeType()
   {
     return H5T_NATIVE_CHAR;
   }
+  if (std::is_same<T, signed char>::value)
+  {
+    return H5T_NATIVE_SCHAR;
+  }
   else if (std::is_same<T, unsigned char>::value)
   {
     return H5T_NATIVE_UCHAR;

IO/HDF/vtkHDFWriterImplementation.cxx

@@ -1243,7 +1243,8 @@ hsize_t vtkHDFWriter::Implementation::GetSubfileNumberOf(
 
   std::vector<hsize_t> start{ static_cast<unsigned long>(part) }, count{ 1 }, result{ 0 };
   int dimension = 1;
-  if (this->HdfType == "PolyData" && primitive != (char)0xff)
+  constexpr char INVALID_PRIMITIVE = 0xff;
+  if (this->HdfType == "PolyData" && primitive != INVALID_PRIMITIVE)
   {
     start.emplace_back(static_cast<hsize_t>(primitive));
     count.emplace_back(1);