Merge pull request #15293 from chrysn-pull-requests/vfs-generic-stat

vfs: Provide generic stat implementation (and use in fatfs)

pkg/fatfs/fatfs_vfs/fatfs_vfs.c

@@ -445,6 +445,7 @@ static const vfs_file_system_ops_t fatfs_fs_ops = {
     .unlink = _unlink,
     .mkdir = _mkdir,
     .rmdir = _rmdir,
+    .stat = vfs_sysop_stat_from_fstat,
 };
 
 static const vfs_file_ops_t fatfs_file_ops = {

sys/include/vfs.h

@@ -969,6 +969,20 @@ const vfs_mount_t *vfs_iterate_mounts(const vfs_mount_t *cur);
  */
 const vfs_file_t *vfs_file_get(int fd);
 
+/** @brief  Implementation of `stat` using `fstat`
+ *
+ * This helper can be used by file system drivers that do not have any more
+ * efficient implementation of `fs_op::stat` than opening the file and running
+ * `f_op::fstat` on it.
+ *
+ * It can be set as `fs_op::stat` by a file system driver, provided it
+ * implements `f_op::open` and `f_op::fstat` and `f_op::close`, and its `open`
+ * accepts `NULL` in the `abs_path` position.
+ */
+int vfs_sysop_stat_from_fstat(vfs_mount_t *mountp,
+        const char *restrict path,
+        struct stat *restrict buf);
+
 #ifdef __cplusplus
 }
 #endif

sys/vfs/vfs.c

@@ -1000,4 +1000,23 @@ static inline int _fd_is_valid(int fd)
     return 0;
 }
 
+int vfs_sysop_stat_from_fstat(vfs_mount_t *mountp, const char *restrict path, struct stat *restrict buf)
+{
+    const vfs_file_ops_t * f_op = mountp->fs->f_op;
+    vfs_file_t opened = {
+        .mp = mountp,
+        /* As per definition of the `vfsfile_ops::open` field */
+        .f_op = f_op,
+        .private_data = { .ptr = NULL },
+        .pos = 0,
+    };
+    int err = f_op->open(&opened, path, 0, 0, NULL);
+    if (err < 0) {
+        return err;
+    }
+    err = f_op->fstat(&opened, buf);
+    f_op->close(&opened);
+    return err;
+}
+
 /** @} */

tests/pkg_fatfs_vfs/main.c

@@ -318,6 +318,8 @@ static void test_fstat(void)
             vfs_write(fd, test_txt, sizeof(test_txt)) == sizeof(test_txt));
     print_test_result("test_stat__close", vfs_close(fd) == 0);
 
+    print_test_result("test_stat__direct", vfs_stat(FULL_FNAME1, &stat_buf) == 0);
+
     fd = vfs_open(FULL_FNAME1, O_RDONLY, 0);
     print_test_result("test_stat__open", fd >= 0);
     print_test_result("test_stat__stat", vfs_fstat(fd, &stat_buf) == 0);