stat-util: unify code that checks whether something is a regular file

Let's add a common implementation for regular file checks, that are
careful to return the right error code (EISDIR/EISLNK/EBADFD) when we
are encountering a wrong file node.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/basic/stat-util.c b/src/basic/stat-util.c
index 270e80fee..313ed4f2c 100644
--- a/src/basic/stat-util.c
+++ b/src/basic/stat-util.c
@@ -281,3 +281,32 @@ int path_is_temporary_fs(const char *path) {
         return fd_is_temporary_fs(fd);
 }
 #endif // 0
+
+int stat_verify_regular(const struct stat *st) {
+        assert(st);
+
+        /* Checks whether the specified stat() structure refers to a regular file. If not returns an appropriate error
+         * code. */
+
+        if (S_ISDIR(st->st_mode))
+                return -EISDIR;
+
+        if (S_ISLNK(st->st_mode))
+                return -ELOOP;
+
+        if (!S_ISREG(st->st_mode))
+                return -EBADFD;
+
+        return 0;
+}
+
+int fd_verify_regular(int fd) {
+        struct stat st;
+
+        assert(fd >= 0);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        return stat_verify_regular(&st);
+}