add examples

Author: scivision

Examples/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.14)
+project(nc4fortranExample
+LANGUAGES C CXX Fortran)
+enable_testing()
+
+find_package(nc4fortran CONFIG)
+
+if(nc4fortran_FOUND)
+  include(${nc4fortran_DIR}/nc4fortranTargets.cmake)
+else()
+  include(FetchContent)
+  FetchContent_Declare(nc4fortran_proj
+    GIT_REPOSITORY https://github.com/geospace-code/nc4fortran.git
+    GIT_TAG v1.0.2)
+  FetchContent_MakeAvailable(nc4fortran_proj)
+endif()
+
+if(NOT NCDFOK)
+  message(FATAL_ERROR "NetCDF4 is not working on your system, so nc4fortran cannot work.")
+endif()
+
+set(CMAKE_EXPORT_COMPILE_COMMANDS on)
+
+# --- Fortran interface for examples
+add_library(fortran_interface fortran_interface.f90)
+target_link_libraries(fortran_interface PRIVATE nc4fortran::nc4fortran)
+
+# --- example 1
+add_executable(example1 example1.f90)
+target_link_libraries(example1 nc4fortran::nc4fortran)
+add_test(NAME nc4fortran:Example1 COMMAND $<TARGET_FILE:example1>
+WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
+
+# --- example 2
+add_executable(example2 example2.f90)
+target_link_libraries(example2 nc4fortran::nc4fortran)
+add_test(NAME nc4fortran:Example2 COMMAND $<TARGET_FILE:example2>
+WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})

Examples/Readme.md

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+# nc4ortran Example project
+
+It's easiest to use CMake with nc4fortran, since HDF5 consists of many library files and headers.
+From the nc4fortran/ directory, build the examples (or change to the Examples/ directory):
+
+```sh
+cmake -B Examples/build -S Examples
+cmake --build Examples/build
+```
+
+which creates examples under the Examples/build direcotry
+
+If you installed nc4fortran previously, you can use that version by:
+
+```sh
+cmake -B Examples/build -S Examples -Dnc4fortran_DIR=~/libs/nc4fortran/lib/cmake/nc4fortran
+```
+
+## Examples
+
+Example 1 and 2 show the object-oriented interface of nc4fortran, which may offer faster performance if more than one variable is being read or written.

Examples/example1.f90

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+program example1
+
+use nc4fortran, only : netcdf_file
+implicit none (type, external)
+
+type(netcdf_file) :: h
+character(:), allocatable :: filename
+integer :: i32
+
+filename = 'nc4fortran_example1.nc'
+
+call h%initialize(filename, status='replace')
+
+call h%write( 'x', 123)
+
+call h%read('x', i32)
+call h%finalize()
+
+if (i32 /= 123) error stop 'incorrect value read'
+
+print *, 'OK: example 1'
+
+end program

Examples/example2.f90

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+program example2
+
+use nc4fortran, only : netcdf_file
+implicit none (type, external)
+
+character(:), allocatable :: filename
+integer :: i32
+
+type(netcdf_file) :: h
+
+filename = 'nc4fortran_example2.nc'
+
+call h%initialize(filename, status='replace')
+call h%write('x', 123)
+call h%finalize()
+
+call h%initialize(filename, status='old', action='r')
+call h%read('x', i32)
+if (i32 /= 123) error stop 'incorrect value read'
+
+print *, 'OK: example 2'
+
+end program

Examples/fortran_interface.f90

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+module fortran_interface
+!! filename(256) and var_name(64) are arbitrary sizes.
+!! ensure calling program buffers are equally sized
+use, intrinsic :: iso_c_binding, only : C_INT32_T, C_CHAR, C_NULL_CHAR
+use nc4fortran, only : netcdf_file
+
+implicit none (type, external)
+
+contains
+
+
+subroutine write_int32(filename, var_name, i32) bind(C)
+character(kind=C_CHAR) :: filename(256)
+character(kind=C_CHAR) :: var_name(64)
+integer(C_INT32_T), intent(in) :: i32
+type(netcdf_file) :: h
+
+call h%initialize(cstr2fstr(filename), status='replace')
+call h%write(cstr2fstr(var_name), i32)
+call h%finalize()
+
+end subroutine write_int32
+
+
+subroutine read_int32(filename, var_name, i32) bind(C)
+character(kind=C_CHAR) :: filename(256)
+character(kind=C_CHAR) :: var_name(64)
+integer(C_INT32_T), intent(out) :: i32
+type(netcdf_file) :: h
+
+call h%initialize(cstr2fstr(filename), status='old', action='r')
+call h%read(cstr2fstr(var_name), i32)
+call h%finalize()
+
+end subroutine read_int32
+
+
+function cstr2fstr(c_str) result(f_str)
+
+character(kind=C_CHAR), intent(in) :: c_str(:)
+character(len=size(c_str)) :: buf
+character(:), allocatable :: f_str
+integer :: i
+
+buf = ""
+!! clean variable, will get extra garbled text otherwise, maybe blank but non-trimmable character
+
+do i = 1, size(c_str)
+  if (c_str(i) == C_NULL_CHAR) exit
+  buf(i:i) = c_str(i)
+enddo
+
+f_str = trim(buf)
+
+end function cstr2fstr
+
+end module fortran_interface