os_calls: Add g_file_is_open()

common/os_calls.c

@@ -2160,6 +2160,13 @@ g_file_close(int fd)
     return 0;
 }
 
+/*****************************************************************************/
+int
+g_file_is_open(int fd)
+{
+    return (fcntl(fd, F_GETFD) >= 0);
+}
+
 /*****************************************************************************/
 /* read from file, returns the number of bytes read or -1 on error */
 int

common/os_calls.h

@@ -210,6 +210,12 @@ int      g_file_open(const char *file_name);
 int      g_file_open_ex(const char *file_name, int aread, int awrite,
                         int acreate, int atrunc);
 int      g_file_close(int fd);
+/**
+ * Returns 1 if a file is open (i.e. the file descriptor is valid)
+ * @param fd File descriptor
+ * @return 1 for file open, 0 for not open
+ */
+int      g_file_is_open(int fd);
 int      g_file_read(int fd, char *ptr, int len);
 int      g_file_write(int fd, const char *ptr, int len);
 int      g_file_seek(int fd, int offset);

tests/common/test_os_calls.c

@@ -262,6 +262,23 @@ START_TEST(test_g_file_get_open_fds)
 }
 END_TEST
 
+
+/******************************************************************************/
+START_TEST(test_g_file_is_open)
+{
+    int devzerofd = g_file_open("/dev/zero");
+    ck_assert(devzerofd >= 0);
+
+    // Check open file comes up as open
+    ck_assert_int_ne(g_file_is_open(devzerofd), 0);
+
+    g_file_close(devzerofd);
+
+    // Check the now-closed file no longer registers as open
+    ck_assert_int_eq(g_file_is_open(devzerofd), 0);
+}
+END_TEST
+
 /******************************************************************************/
 START_TEST(test_g_sck_fd_passing)
 {
@@ -448,6 +465,7 @@ make_suite_test_os_calls(void)
 #endif
     tcase_add_test(tc_os_calls, test_g_file_cloexec);
     tcase_add_test(tc_os_calls, test_g_file_get_open_fds);
+    tcase_add_test(tc_os_calls, test_g_file_is_open);
     tcase_add_test(tc_os_calls, test_g_sck_fd_passing);
     tcase_add_test(tc_os_calls, test_g_sck_fd_overflow);
     return s;