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