fatfsparse.py: add cluster chaining support to enable reading longer-than-sector files

Closes IDF-4975

components/fatfs/fatfs_utils/fat.py

@@ -0,0 +1,55 @@
+# 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 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