Enum Fat 

pub enum Fat {
    Fat12(Fat12),
    Fat16(Fat16),
    Fat32(Fat32),
}

Allocation-table implementation selected for a mounted FAT volume.

Variants

Fat12(Fat12)

FAT12 allocation table.

Fat16(Fat16)

FAT16 allocation table.

Fat32(Fat32)

FAT32 allocation table.

Implementations

impl Fat

pub fn next_cluster<T: Read + Seek>( &self, reader: &mut T, cluster: usize, ) -> Result<Option<u32>>

Returns the next cluster in a chain, or None at end-of-chain.

pub fn fat_type(&self) -> FatType

Get the FAT type for informational purposes

pub fn max_cluster(&self) -> u32

Highest valid cluster number on this volume (inclusive). Clusters 0 and 1 are reserved, so the chain-loop ceiling is max_cluster - 1 distinct clusters; one extra step lets the walker observe the end-of-chain marker before declaring a loop.

pub fn walk_chain<T, F>( &self, reader: &mut T, start: u32, max_steps: u32, visit: F, ) -> Result<u32>

where T: Read + Seek, F: FnMut(u32),

Walk a cluster chain starting at start, calling visit for each cluster (including start) until the chain ends. Returns the last cluster visited.

Aborts with Error::ClusterLoop if more than max_steps clusters are walked. The natural upper bound is Self::max_cluster — any chain longer than that must repeat a cluster and is therefore corrupt.

pub fn truncate_chain<T: Read + Write + Seek>( &self, rw: &mut T, cluster: usize, ) -> Result<u32>

Truncate a cluster chain after the specified cluster.

The specified cluster becomes the end of chain (marked with end-of-chain marker). All clusters following it are freed.

Returns the number of clusters freed.

pub fn free_chain<T: Read + Write + Seek>( &self, rw: &mut T, cluster: usize, ) -> Result<u32>

Free a cluster chain starting at start, returns count of freed clusters.

pub fn mark_bad<T: Read + Write + Seek>( &self, rw: &mut T, cluster: usize, ) -> Result<()>

Mark a cluster as bad in the FAT.

Writes the appropriate bad-cluster marker (0xFF7 / 0xFFF7 / 0x0FFFFFF7) to the FAT entry for the given cluster. This prevents the cluster from being allocated in the future.

pub fn read_status_flags<T: Read + Seek>( &self, reader: &mut T, ) -> Result<(bool, bool)>

Read the FAT-resident status bits from FAT[1].

The FAT spec stores two volume-level status bits in the high bits of the FAT entry for cluster 1:

• “clean shutdown” (set = clean, cleared = dirty)
• “no I/O errors” (set = ok, cleared = errors during last use) FAT12 has no spare bits in its packed 12-bit entries, so it returns (false, false) (treat as “clean, no errors”) — matches the spec’s “FAT12 has no status word” reading.

Returns (dirty, io_errors) — both true means trouble.

pub fn fat_copy_count(&self) -> usize

Returns the number of FAT copies on disk (typically 1 or 2).

pub fn compare_entry<T: Read + Seek>( &self, reader: &mut T, cluster: usize, ) -> Result<bool>

Compare a FAT entry between the primary (index 0) and backup (index 1) copies.

Returns Ok(true) if both copies match, Ok(false) if they differ. Returns an error if there is only one FAT copy or on I/O failure.

pub fn next_cluster_with_fallback<T: Read + Seek>( &self, reader: &mut T, cluster: usize, ) -> Result<Option<u32>>

Read the next cluster, falling back to the backup FAT copy on error.

Tries the primary FAT first. If reading fails and a backup FAT exists, reads from the backup copy instead.