esp-idf/components/fatfs/fatfsgen_utils/fat.py

43 wiersze
1.6 KiB
Python

# SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
# SPDX-License-Identifier: Apache-2.0
from .cluster import Cluster
from .exceptions import NoFreeClusterException
from .fatfs_state import FATFSState
class FAT:
"""
The FAT represents the FAT region in file system. It is responsible for storing clusters
and chaining them in case we need to extend file or directory to more clusters.
"""
def __init__(self,
fatfs_state: FATFSState,
reserved_sectors_cnt: int) -> None:
self.fatfs_state = fatfs_state
self.reserved_sectors_cnt = reserved_sectors_cnt
self.clusters = [Cluster(cluster_id=i, fatfs_state=self.fatfs_state) for i in
range(1, self.fatfs_state.max_clusters)]
# update root directory record
self.clusters[0].allocate_cluster()
# add first reserved cluster
self.clusters = [Cluster(cluster_id=Cluster.RESERVED_BLOCK_ID, fatfs_state=self.fatfs_state)] + self.clusters
def find_free_cluster(self) -> Cluster:
# finds first empty cluster and allocates it
for cluster in self.clusters:
if cluster.is_empty:
cluster.allocate_cluster()
return cluster
raise NoFreeClusterException('No free cluster available!')
def allocate_chain(self, first_cluster: Cluster, size: int) -> None:
current = first_cluster
for _ in range(size - 1):
free_cluster = self.find_free_cluster()
current.next_cluster = free_cluster
current.set_in_fat(free_cluster.id)
current = free_cluster