comin_c_utils.F90

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!> @file comin_c_utils.F90
!! @brief ComIn C utilities, contains helper routines for converting data
!!        between C and Fortran.
!
!  @authors 01/2023 :: ICON Community Interface  <comin@icon-model.org>
!
!  SPDX-License-Identifier: BSD-3-Clause
!
!  See LICENSES for license information.
!  Where software is supplied by third parties, it is indicated in the
!  headers of the routines.
!
MODULE comin_c_utils
 
  use, INTRINSIC :: iso_c_binding, only: c_ptr, c_char, c_f_pointer, c_null_char, c_size_t
  IMPLICIT NONE
 
  PRIVATE
  PUBLIC :: convert_c_string, convert_f_string
 
  INTERFACE convert_c_string
    MODULE PROCEDURE convert_c_string_cptr
    MODULE PROCEDURE convert_c_string_arr
  END INTERFACE convert_c_string
 
CONTAINS
 
  !> Convert c-style character array into Fortran string.
  !
  FUNCTION convert_c_string_cptr( cptr ) RESULT (string)
    TYPE(c_ptr), intent(in) :: cptr
    CHARACTER(len=:), allocatable :: string
 
    INTEGER(c_size_t) :: len
    CHARACTER(kind=c_char), POINTER :: chars(:)
    INTEGER(c_size_t) :: i
 
    INTERFACE
      FUNCTION c_strlen(str_ptr) BIND ( C, name = "strlen" ) RESULT(len)
        IMPORT :: c_ptr, c_size_t
        TYPE(c_ptr), VALUE      :: str_ptr
        INTEGER(kind=c_size_t)  :: len
      END FUNCTION c_strlen
    END INTERFACE
 
    len = c_strlen(cptr)
 
    CALL c_f_pointer(cptr, chars, [ len ])
 
    ALLOCATE(CHARACTER(len=len) :: string)
    DO i=1,len
      string(i:i) = chars(i)
    END DO
  END FUNCTION convert_c_string_cptr
 
  FUNCTION convert_c_string_arr( arr ) RESULT (string)
    CHARACTER(kind=c_char), INTENT(IN) :: arr(:)
    CHARACTER(len=:), ALLOCATABLE :: string
    INTEGER :: i, strlen
 
    DO strlen=1,SIZE(arr)
      IF (arr(strlen) .EQ. c_null_char) EXIT
    END DO
 
    ALLOCATE(CHARACTER(len=strlen-1) :: string)
    DO i=1,strlen-1
      string(i:i) = arr(i)
    END DO
  END FUNCTION convert_c_string_arr
 
  !> Convert Fortran string into C-style character array.
  !
  subroutine convert_f_string( string, arr)
 
    CHARACTER(len=*), INTENT(IN) :: string
    CHARACTER(len=1, kind=c_char), INTENT(INOUT) :: arr(:)
    INTEGER :: i
 
    DO i=1,len_trim(string)
      arr(i) = string(i:i)
    END DO
    arr(i) = c_null_char
  end subroutine  convert_f_string
 
END MODULE comin_c_utils