esp-idf/components/fatfs/fatfs_utils/fat.py
2022-06-09 15:51:03 +02:00

73 lines
3.2 KiB
Python

# SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
# SPDX-License-Identifier: Apache-2.0
from typing import List
from .cluster import Cluster
from .exceptions import NoFreeClusterException
from .fatfs_state import BootSectorState
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 allocate_root_dir(self) -> None:
"""
The root directory is implicitly created with the FatFS,
its block is on the index 1 (second index) and is allocated implicitly.
"""
self.clusters[Cluster.ROOT_BLOCK_ID].allocate_cluster()
def __init__(self, boot_sector_state: BootSectorState, init_: bool) -> None:
self.boot_sector_state = boot_sector_state
self.clusters: List[Cluster] = [Cluster(cluster_id=i,
boot_sector_state=self.boot_sector_state,
init_=init_) for i in range(self.boot_sector_state.clusters)]
if init_:
self.allocate_root_dir()
def get_cluster_value(self, cluster_id_: int) -> int:
fat_cluster_value_: int = self.clusters[cluster_id_].get_from_fat()
return fat_cluster_value_
def is_cluster_last(self, cluster_id_: int) -> bool:
value_ = self.get_cluster_value(cluster_id_)
is_cluster_last_: bool = value_ == (1 << self.boot_sector_state.fatfs_type) - 1
return is_cluster_last_
def chain_content(self, cluster_id_: int) -> bytearray:
bin_im: bytearray = self.boot_sector_state.binary_image
if self.is_cluster_last(cluster_id_):
data_address_ = Cluster.compute_cluster_data_address(self.boot_sector_state, cluster_id_)
content_: bytearray = bin_im[data_address_: data_address_ + self.boot_sector_state.sector_size]
return content_
fat_value_: int = self.get_cluster_value(cluster_id_)
data_address_ = Cluster.compute_cluster_data_address(self.boot_sector_state, cluster_id_)
content_ = bin_im[data_address_: data_address_ + self.boot_sector_state.sector_size]
while not self.is_cluster_last(cluster_id_):
cluster_id_ = fat_value_
fat_value_ = self.get_cluster_value(cluster_id_)
data_address_ = Cluster.compute_cluster_data_address(self.boot_sector_state, cluster_id_)
content_ += bin_im[data_address_: data_address_ + self.boot_sector_state.sector_size]
return content_
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