dataset:character: allow writing empty character

Co-authored-by: gtokic <gtokic@users.noreply.github.com>

Author: scivision

src/write.f90

@@ -65,8 +65,9 @@
 
 if(dtype == H5T_NATIVE_CHARACTER) then
   if(.not. present(charlen)) error stop "ERROR:h5fortran:hdf_create: character type must specify charlen"
+  if (charlen < 1) error stop "ERROR:h5fortran:attr_create: character type must specify charlen > 0"
 
-  call h5tset_size_f(dtype_id, int(charlen, SIZE_T), ier)
+  call H5Tset_size_f(dtype_id, int(charlen, SIZE_T), ier)
   call estop(ier, "create:H5Tset_size", self%filename, dname)
 endif
 

src/write_scalar.f90

@@ -27,6 +27,7 @@
 type is (character(*))
   dtype = H5T_NATIVE_CHARACTER
   charlen = len(A)  !< workaround for GCC 8.3.0 bug
+  if(charlen == 0) charlen = 1 !< empty string is OK but charlen is strictly positive.
 class default
   error stop "ERROR:h5fortran:write: unknown variable type for " // dname
 end select

src/writer.inc

@@ -24,6 +24,7 @@ type is (integer(int64))
 type is (character(*))
   dtype = H5T_NATIVE_CHARACTER
   charlen = len(A)  !< workaround for GCC 8.3.0 bug
+  if(charlen == 0) charlen = 1 !< empty string is OK but charlen is strictly positive.
 class default
   error stop "ERROR:h5fortran:writer:unknown variable type for " // dname
 end select

test/test_attributes.f90

@@ -54,6 +54,7 @@ subroutine test_write_attributes(path)
 call h%writeattr('/x', 'i6', i6)
 call h%writeattr('/x', 'i7', i7)
 
+call h%writeattr("/x", "1d_emptyp", [character(1) :: "", ""])
 call h%writeattr("/x", "c1d", [character(5) :: 'one', 'two', 'three'])
 call h%writeattr("/x", "c2d", reshape([character(5) :: 'one', 'two', 'three', 'four', 'five', 'six'], [2,3]))
 call h%writeattr("/x", "empty_char", "")

test/test_string.f90

@@ -29,11 +29,14 @@ subroutine test_write(fn)
 
 type(hdf5_file) :: h
 
-call h%open(fn, action='w')
+call h%open(fn, action='w', debug=.true.)
 
+call h%write("/empty", "")
 call h%write('/little', '42')
 call h%write('/MySentence', 'this is a little sentence.')
 call h%write('/vector_scalar', ['vector scalar'])
+
+call h%write("/1d_empty", [character(1) :: ""])
 call h%write("/1d", [character(3) :: "hi", "bye"])
 call h%write("/2d", reshape([character(5) :: "one", "two", "three", "four", "five", "six"], [2,3]))
 
@@ -55,6 +58,10 @@ subroutine test_read(fn)
 
 call h%open(fn, action='r')
 
+call h%read('/empty', value)
+if(len_trim(value) /= 0) error stop 'test_string: empty string failure: len_trim /= 0'
+if (value /= '') error stop 'test_string: empty string failure: value = ' // trim(value)
+
 call h%read('/little', value)
 
 if(len_trim(value) /= 2) then