add is_regular_file and is_symlink

Author: wassup05

src/stdlib_system.F90

@@ -241,6 +241,9 @@ module stdlib_system
 !! Any encountered errors are handled using `state_type`.
 !!
 public :: exists
+
+public :: is_symlink
+public :: is_regular_file
 
 ! CPU clock ticks storage
 integer, parameter, private :: TICKS = int64
@@ -1204,6 +1207,25 @@ end function stdlib_exists
     end if
 end function exists
 
+logical function is_symlink(path)
+    character(len=*), intent(in) :: path
+
+    is_symlink = exists(path) == fs_type_symlink
+end function is_symlink
+
+logical function is_regular_file(path)
+    character(len=*), intent(in) :: path
+
+    interface
+        logical(c_bool) function stdlib_is_regular_file(path) bind(C, name='stdlib_is_regular_file')
+            import c_char, c_bool
+            character(kind=c_char) :: path(:)
+        end function stdlib_is_regular_file
+    end interface
+
+    is_regular_file = logical(stdlib_is_regular_file(to_c_char(path)))
+end function is_regular_file
+
 character function path_sep()
     if (OS_TYPE() == OS_WINDOWS) then
         path_sep = '\'

src/stdlib_system.c

@@ -119,3 +119,15 @@ int stdlib_exists(const char* path, int* stat){
 #endif /* ifdef _WIN32 */
     return type;
 }
+
+// `stat` and `_stat` follow symlinks automatically.
+// so no need for winapi functions.
+bool stdlib_is_regular_file(const char* path) {
+#ifdef _WIN32
+    struct _stat buf = {0};
+    return _stat(path, &buf) == 0 && S_ISREG(buf.st_mode);
+#else
+    struct stat buf = {0};
+    return stat(path, &buf) == 0 && S_ISREG(buf.st_mode);
+#endif /* ifdef _WIN32 */
+}