Merge branch 'framework/sanitize_c_null_char' into hotfix-v6.2 (PR #161)

This merge adds code to remove C null characters from strings read by PIO.

The PIO2 library fills in unused characters of a string variable with
C null characters, and replaces C null characters with spaces when reading
strings. However, the PIO1 library does not perform these conversions.
Consequently, if a file written by the PIO2 library is read by the PIO1 library,
C null characters may be present in the resulting Fortran string.

Under the assumption that C null characters will generally not be expected
or handled in MPAS (e.g., in timestamp strings), this commit makes calls to
MPAS_sanitize_string to convert any C null characters in strings read by PIO
into spaces.

* framework/sanitize_c_null_char:
  Remove C null characters from strings read by PIO
  Add new MPAS_sanitize_string routine to mpas_c_interfacing

Author: mgduda

src/framework/mpas_c_interfacing.F

@@ -4,6 +4,37 @@ module mpas_c_interfacing
     contains
 
 
+    !-----------------------------------------------------------------------
+    !  routine mpas_sanitize_string
+    !
+    !> \brief Converts C null characters in a Fortran string to spaces
+    !> \author Michael Duda
+    !> \date   19 February 2019
+    !> \details
+    !>  Converts all C null characters in a Fortran string to spaces.
+    !>  This may be useful for strings that were provided by C code through other
+    !>  Fortran code external to MPAS.
+    !
+    !-----------------------------------------------------------------------
+    subroutine mpas_sanitize_string(str)
+    
+        use iso_c_binding, only : c_null_char
+    
+        implicit none
+    
+        character(len=*), intent(inout) :: str
+    
+        integer :: i
+    
+        do i=1,len(str)
+            if (str(i:i) == c_null_char) then
+                str(i:i) = ' '
+            end if
+        end do
+    
+    end subroutine mpas_sanitize_string
+
+
     !-----------------------------------------------------------------------
     !  routine mpas_c_to_f_string
     !

src/framework/mpas_io.F

@@ -2187,6 +2187,8 @@ end subroutine MPAS_io_get_var_real5d
 
    subroutine MPAS_io_get_var_char0d(handle, fieldname, val, ierr)
 
+      use mpas_c_interfacing, only : MPAS_sanitize_string
+
       implicit none
 
       type (MPAS_IO_Handle_type), intent(inout) :: handle
@@ -2198,23 +2200,31 @@ subroutine MPAS_io_get_var_char0d(handle, fieldname, val, ierr)
       if (present(ierr)) ierr = MPAS_IO_NOERR
 
       call MPAS_io_get_var_generic(handle, fieldname, charVal=val, ierr=ierr)
+      call MPAS_sanitize_string(val)
 
    end subroutine MPAS_io_get_var_char0d
 
 
    subroutine MPAS_io_get_var_char1d(handle, fieldname, val, ierr)
 
+      use mpas_c_interfacing, only : MPAS_sanitize_string
+
       implicit none
 
       type (MPAS_IO_Handle_type), intent(inout) :: handle
       character (len=*), intent(in) :: fieldname
       character (len=*), dimension(:), intent(out) :: val
       integer, intent(out), optional :: ierr
 
+      integer :: i
+
 !     call mpas_log_write('Called MPAS_io_get_var_char1d()')
       if (present(ierr)) ierr = MPAS_IO_NOERR
 
       call MPAS_io_get_var_generic(handle, fieldname, charArray1d=val, ierr=ierr)
+      do i=1,size(val)
+         call MPAS_sanitize_string(val(i))
+      end do
 
    end subroutine MPAS_io_get_var_char1d