mirror of
https://github.com/espressif/esp-idf.git
synced 2024-10-05 20:47:46 -04:00
177 lines
8.1 KiB
Python
177 lines
8.1 KiB
Python
# SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
|
|
# SPDX-License-Identifier: Apache-2.0
|
|
|
|
from typing import Dict, Optional
|
|
|
|
from construct import Int16ul
|
|
|
|
from .fatfs_state import BootSectorState
|
|
from .utils import (EMPTY_BYTE, FAT12, FAT16, build_byte, merge_by_half_byte_12_bit_little_endian,
|
|
split_by_half_byte_12_bit_little_endian)
|
|
|
|
|
|
def get_dir_size(is_root: bool, boot_sector: BootSectorState) -> int:
|
|
dir_size_: int = boot_sector.root_dir_sectors_cnt * boot_sector.sector_size if is_root else boot_sector.sector_size
|
|
return dir_size_
|
|
|
|
|
|
class Cluster:
|
|
"""
|
|
class Cluster handles values in FAT table and allocates sectors in data region.
|
|
"""
|
|
RESERVED_BLOCK_ID: int = 0
|
|
ROOT_BLOCK_ID: int = 1
|
|
ALLOCATED_BLOCK_FAT12: int = 0xFFF
|
|
ALLOCATED_BLOCK_FAT16: int = 0xFFFF
|
|
ALLOCATED_BLOCK_SWITCH = {FAT12: ALLOCATED_BLOCK_FAT12, FAT16: ALLOCATED_BLOCK_FAT16}
|
|
INITIAL_BLOCK_SWITCH: Dict[int, int] = {FAT12: 0xFF8, FAT16: 0xFFF8}
|
|
|
|
def __init__(self,
|
|
cluster_id: int,
|
|
boot_sector_state: BootSectorState,
|
|
init_: bool) -> None:
|
|
self.id: int = cluster_id
|
|
self.boot_sector_state: BootSectorState = boot_sector_state
|
|
|
|
self._next_cluster = None # type: Optional[Cluster]
|
|
# First cluster in FAT is reserved, low 8 bits contains BPB_Media and the rest is filled with 1
|
|
# e.g. the esp32 media type is 0xF8 thus the FAT[0] = 0xFF8 for FAT12, 0xFFF8 for FAT16
|
|
if self.id == Cluster.RESERVED_BLOCK_ID and init_:
|
|
self.set_in_fat(self.INITIAL_BLOCK_SWITCH[self.boot_sector_state.fatfs_type])
|
|
return
|
|
self.cluster_data_address: int = self._compute_cluster_data_address()
|
|
assert self.cluster_data_address
|
|
|
|
@property
|
|
def next_cluster(self): # type: () -> Optional[Cluster]
|
|
return self._next_cluster
|
|
|
|
@next_cluster.setter
|
|
def next_cluster(self, value): # type: (Optional[Cluster]) -> None
|
|
self._next_cluster = value
|
|
|
|
def _cluster_id_to_logical_position_in_bits(self, _id: int) -> int:
|
|
# computes address of the cluster in fat table
|
|
logical_position_: int = self.boot_sector_state.fatfs_type * _id
|
|
return logical_position_
|
|
|
|
@staticmethod
|
|
def compute_cluster_data_address(boot_sector_state: BootSectorState, id_: int) -> int:
|
|
"""
|
|
This method translates the id of the cluster to the address in data region.
|
|
|
|
:param boot_sector_state: the class with FS shared data
|
|
:param id_: id of the cluster
|
|
:returns: integer denoting the address of the cluster in the data region
|
|
"""
|
|
data_address_: int = boot_sector_state.root_directory_start
|
|
if not id_ == Cluster.ROOT_BLOCK_ID:
|
|
# the first data cluster id is 2 (we have to subtract reserved cluster and cluster for root)
|
|
data_address_ = boot_sector_state.sector_size * (id_ - 2) + boot_sector_state.data_region_start
|
|
return data_address_
|
|
|
|
def _compute_cluster_data_address(self) -> int:
|
|
return self.compute_cluster_data_address(self.boot_sector_state, self.id)
|
|
|
|
def _set_left_half_byte(self, address: int, value: int) -> None:
|
|
self.boot_sector_state.binary_image[address] &= 0x0f
|
|
self.boot_sector_state.binary_image[address] |= value << 4
|
|
|
|
def _set_right_half_byte(self, address: int, value: int) -> None:
|
|
self.boot_sector_state.binary_image[address] &= 0xf0
|
|
self.boot_sector_state.binary_image[address] |= value
|
|
|
|
@property
|
|
def fat_cluster_address(self) -> int:
|
|
"""Determines how many bits precede the first bit of the cluster in FAT"""
|
|
return self._cluster_id_to_logical_position_in_bits(self.id)
|
|
|
|
@property
|
|
def real_cluster_address(self) -> int:
|
|
"""
|
|
The property method computes the real address of the cluster in the FAT region. Result is simply
|
|
address of the cluster in fat + fat table address.
|
|
"""
|
|
cluster_address: int = self.boot_sector_state.fat_table_start_address + self.fat_cluster_address // 8
|
|
return cluster_address
|
|
|
|
def get_from_fat(self) -> int:
|
|
"""
|
|
Calculating the value in the FAT block, that denotes if the block is full, empty, or chained to other block.
|
|
|
|
For FAT12 is the block stored in one and half byte. If the order of the block is even the first byte and second
|
|
half of the second byte belongs to the block. First half of the second byte and the third byte belongs to
|
|
the second block.
|
|
|
|
e.g. b'\xff\x0f\x00' stores two blocks. First of them is evenly ordered (index 0) and is set to 0xfff,
|
|
that means full block that is final in chain of blocks
|
|
and second block is set to 0x000 that means empty block.
|
|
|
|
three bytes - AB XC YZ - stores two blocks - CAB YZX
|
|
"""
|
|
address_: int = self.real_cluster_address
|
|
bin_img_: bytearray = self.boot_sector_state.binary_image
|
|
if self.boot_sector_state.fatfs_type == FAT12:
|
|
if self.fat_cluster_address % 8 == 0:
|
|
# even block
|
|
return bin_img_[self.real_cluster_address] | ((bin_img_[self.real_cluster_address + 1] & 0x0F) << 8)
|
|
# odd block
|
|
return ((bin_img_[self.real_cluster_address] & 0xF0) >> 4) | (bin_img_[self.real_cluster_address + 1] << 4)
|
|
if self.boot_sector_state.fatfs_type == FAT16:
|
|
return int.from_bytes(bin_img_[address_:address_ + 2], byteorder='little')
|
|
raise NotImplementedError('Only valid fatfs types are FAT12 and FAT16.')
|
|
|
|
@property
|
|
def is_empty(self) -> bool:
|
|
"""
|
|
The property method takes a look into the binary array and checks if the bytes ordered by little endian
|
|
and relates to the current cluster are all zeros (which denotes they are empty).
|
|
"""
|
|
return self.get_from_fat() == 0x00
|
|
|
|
def set_in_fat(self, value: int) -> None:
|
|
"""
|
|
Sets cluster in FAT to certain value.
|
|
Firstly, we split the target value into 3 half bytes (max value is 0xfff).
|
|
Then we could encounter two situations:
|
|
1. if the cluster index (indexed from zero) is even, we set the full byte computed by
|
|
self.cluster_id_to_logical_position_in_bits and the second half of the consequent byte.
|
|
Order of half bytes is 2, 1, 3.
|
|
|
|
2. if the cluster index is odd, we set the first half of the computed byte and the full consequent byte.
|
|
Order of half bytes is 1, 3, 2.
|
|
"""
|
|
# value must fit into number of bits of the fat (12, 16 or 32)
|
|
assert value <= (1 << self.boot_sector_state.fatfs_type) - 1
|
|
half_bytes = split_by_half_byte_12_bit_little_endian(value)
|
|
bin_img_: bytearray = self.boot_sector_state.binary_image
|
|
|
|
if self.boot_sector_state.fatfs_type == FAT12:
|
|
assert merge_by_half_byte_12_bit_little_endian(*half_bytes) == value
|
|
if self.fat_cluster_address % 8 == 0:
|
|
# even block
|
|
bin_img_[self.real_cluster_address] = build_byte(half_bytes[1], half_bytes[0])
|
|
self._set_right_half_byte(self.real_cluster_address + 1, half_bytes[2])
|
|
elif self.fat_cluster_address % 8 != 0:
|
|
# odd block
|
|
self._set_left_half_byte(self.real_cluster_address, half_bytes[0])
|
|
bin_img_[self.real_cluster_address + 1] = build_byte(half_bytes[2], half_bytes[1])
|
|
elif self.boot_sector_state.fatfs_type == FAT16:
|
|
bin_img_[self.real_cluster_address:self.real_cluster_address + 2] = Int16ul.build(value)
|
|
assert self.get_from_fat() == value
|
|
|
|
@property
|
|
def is_root(self) -> bool:
|
|
return self.id == Cluster.ROOT_BLOCK_ID
|
|
|
|
def allocate_cluster(self) -> None:
|
|
"""
|
|
This method sets bits in FAT table to `allocated` and clean the corresponding sector(s)
|
|
"""
|
|
self.set_in_fat(self.ALLOCATED_BLOCK_SWITCH[self.boot_sector_state.fatfs_type])
|
|
|
|
cluster_start = self.cluster_data_address
|
|
dir_size = get_dir_size(self.is_root, self.boot_sector_state)
|
|
cluster_end = cluster_start + dir_size
|
|
self.boot_sector_state.binary_image[cluster_start:cluster_end] = dir_size * EMPTY_BYTE
|