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

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# SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
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# SPDX-License-Identifier: Apache-2.0
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from typing import List
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from .cluster import Cluster
from .exceptions import NoFreeClusterException
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from .fatfs_state import BootSectorState
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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.
"""
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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_
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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