fatfsgen.py: Support for detection of minimal partition size

components/fatfs/fatfs_utils/utils.py

@@ -14,6 +14,7 @@ from construct import BitsInteger, BitStruct, Int16ul
 # the regex pattern defines symbols that are allowed by long file names but not by short file names
 INVALID_SFN_CHARS_PATTERN = re.compile(r'[.+,;=\[\]]')
 
+FATFS_MIN_ALLOC_UNIT: int = 128
 FAT12_MAX_CLUSTERS: int = 4085
 FAT16_MAX_CLUSTERS: int = 65525
 RESERVED_CLUSTERS_COUNT: int = 2
@@ -174,7 +175,9 @@ def get_args_for_partition_generator(desc: str, wl: bool) -> argparse.Namespace:
                         help='Filename of the generated fatfs image')
     parser.add_argument('--partition_size',
                         default=FATDefaults.SIZE,
-                        help='Size of the partition in bytes')
+                        help='Size of the partition in bytes.' +
+                             ('' if wl else ' Use `--partition_size detect` for detecting the minimal partition size.')
+                        )
     parser.add_argument('--sector_size',
                         default=FATDefaults.SECTOR_SIZE,
                         type=int,
@@ -207,6 +210,8 @@ def get_args_for_partition_generator(desc: str, wl: bool) -> argparse.Namespace:
     args = parser.parse_args()
     if args.fat_type == 0:
         args.fat_type = None
+    if args.partition_size == 'detect' and not wl:
+        args.partition_size = -1
     args.partition_size = int(str(args.partition_size), 0)
     if not os.path.isdir(args.input_directory):
         raise NotADirectoryError(f'The target directory `{args.input_directory}` does not exist!')

components/fatfs/fatfsgen.py

@@ -7,11 +7,15 @@ from datetime import datetime
 from typing import Any, List, Optional
 
 from fatfs_utils.boot_sector import BootSector
+from fatfs_utils.exceptions import NoFreeClusterException
 from fatfs_utils.fat import FAT
 from fatfs_utils.fatfs_state import FATFSState
 from fatfs_utils.fs_object import Directory
-from fatfs_utils.utils import (BYTES_PER_DIRECTORY_ENTRY, FATFS_INCEPTION, FATDefaults,
+from fatfs_utils.long_filename_utils import get_required_lfn_entries_count
-                               get_args_for_partition_generator, read_filesystem)
+from fatfs_utils.utils import (BYTES_PER_DIRECTORY_ENTRY, FATFS_INCEPTION, FATFS_MIN_ALLOC_UNIT,
+                               RESERVED_CLUSTERS_COUNT, FATDefaults, get_args_for_partition_generator,
+                               get_fat_sectors_count, get_non_data_sectors_cnt, read_filesystem,
+                               required_clusters_count)
 
 
 class FATFS:
@@ -184,8 +188,47 @@ class FATFS:
         self._generate_partition_from_folder(folder_name, folder_path=path_to_folder, is_dir=True)
 
 
+def calculate_min_space(path: List[str],
+                        fs_entity: str,
+                        sector_size: int = 0x1000,
+                        long_file_names: bool = False,
+                        is_root: bool = False) -> int:
+    if os.path.isfile(os.path.join(*path, fs_entity)):
+        with open(os.path.join(*path, fs_entity), 'rb') as file_:
+            content = file_.read()
+        res: int = required_clusters_count(sector_size, content)
+        return res
+    buff: int = 0
+    dir_size = 2 * FATDefaults.ENTRY_SIZE  # record for symlinks "." and ".."
+    for file in sorted(os.listdir(os.path.join(*path, fs_entity))):
+        if long_file_names and True:
+            # LFN entries + one short entry
+            dir_size += (get_required_lfn_entries_count(fs_entity) + 1) * FATDefaults.ENTRY_SIZE
+        else:
+            dir_size += FATDefaults.ENTRY_SIZE
+        buff += calculate_min_space(path + [fs_entity], file, sector_size, long_file_names, is_root=False)
+    if is_root and dir_size // FATDefaults.ENTRY_SIZE > FATDefaults.ROOT_ENTRIES_COUNT:
+        raise NoFreeClusterException('Not enough space in root!')
+
+    # roundup sectors, at least one is required
+    buff += (dir_size + sector_size - 1) // sector_size
+    return buff
+
+
 def main() -> None:
     args = get_args_for_partition_generator('Create a FAT filesystem and populate it with directory content', wl=False)
+
+    if args.partition_size == -1:
+        clusters = calculate_min_space([], args.input_directory, args.sector_size, long_file_names=True, is_root=True)
+        fats = get_fat_sectors_count(clusters, args.sector_size)
+        root_dir_sectors = (FATDefaults.ROOT_ENTRIES_COUNT * FATDefaults.ENTRY_SIZE) // args.sector_size
+        args.partition_size = max(FATFS_MIN_ALLOC_UNIT * args.sector_size,
+                                  (clusters + fats + get_non_data_sectors_cnt(RESERVED_CLUSTERS_COUNT,
+                                                                              fats,
+                                                                              root_dir_sectors)
+                                   ) * args.sector_size
+                                  )
+
     fatfs = FATFS(sector_size=args.sector_size,
                   sectors_per_cluster=args.sectors_per_cluster,
                   size=args.partition_size,