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//! exFAT Directory iteration.
//!
//! Provides directory traversal for exFAT filesystems.
use alloc::vec::Vec;
use core::mem::size_of;
use crate::error::{FatError, Result};
use crate::io::{Read, Seek};
use super::entry::{ExFatFileEntry, RawDirectoryEntry, entry_type, parse_entry_set};
use super::fs::ExFatFs;
/// A directory in an exFAT filesystem.
pub struct ExFatDir<'a, DATA: Read + Seek> {
/// Reference to the filesystem
pub(crate) fs: &'a ExFatFs<DATA>,
/// First cluster of the directory
pub(crate) first_cluster: u32,
/// Whether the directory is stored contiguously
pub(crate) is_contiguous: bool,
/// Size of the directory in bytes (for contiguous dirs)
pub(crate) size: u64,
}
impl<'a, DATA: Read + Seek> ExFatDir<'a, DATA> {
/// Create an iterator over directory entries.
pub fn entries(&self) -> ExFatDirIter<'a, DATA> {
ExFatDirIter {
fs: self.fs,
first_cluster: self.first_cluster,
is_contiguous: self.is_contiguous,
dir_size: self.size,
current_cluster: self.first_cluster,
cluster_offset: 0,
dir_offset: 0,
}
}
/// Find an entry by name.
///
/// Performs case-insensitive comparison using the up-case table.
pub fn find(&self, name: &str) -> Result<Option<ExFatFileEntry>> {
for entry in self.entries() {
let entry = entry?;
// Perform case-insensitive comparison
if self.fs.names_equal(&entry.name, name)? {
return Ok(Some(entry));
}
}
Ok(None)
}
/// Open a subdirectory by name.
pub fn open_dir(&self, name: &str) -> Result<ExFatDir<'a, DATA>> {
let entry = self.find(name)?.ok_or(FatError::EntryNotFound)?;
if !entry.is_directory() {
return Err(FatError::NotADirectory);
}
Ok(ExFatDir {
fs: self.fs,
first_cluster: entry.first_cluster,
is_contiguous: entry.no_fat_chain,
size: entry.data_length,
})
}
}
/// Iterator over exFAT directory entries.
pub struct ExFatDirIter<'a, DATA: Read + Seek> {
/// Reference to the filesystem
fs: &'a ExFatFs<DATA>,
/// First cluster of the directory
first_cluster: u32,
/// Whether the directory is stored contiguously
is_contiguous: bool,
/// Total directory size (for contiguous dirs, or 0 for unknown)
dir_size: u64,
/// Current cluster being read
current_cluster: u32,
/// Byte offset within current cluster
cluster_offset: usize,
/// Total byte offset from start of directory
dir_offset: u64,
}
impl<DATA: Read + Seek> Iterator for ExFatDirIter<'_, DATA> {
type Item = Result<ExFatFileEntry>;
fn next(&mut self) -> Option<Self::Item> {
loop {
// Try to read the next entry
match self.read_next_entry() {
Ok(Some(entry)) => return Some(Ok(entry)),
Ok(None) => return None, // End of directory
Err(e) => return Some(Err(e)),
}
}
}
}
impl<DATA: Read + Seek> ExFatDirIter<'_, DATA> {
/// Read the next file entry from the directory.
fn read_next_entry(&mut self) -> Result<Option<ExFatFileEntry>> {
let info = self.fs.info();
let entry_size = size_of::<RawDirectoryEntry>();
let cluster_size = info.bytes_per_cluster;
loop {
// Check if we've reached a size limit (for contiguous directories)
if self.dir_size > 0 && self.dir_offset >= self.dir_size {
return Ok(None);
}
// Check if we need to move to the next cluster
if self.cluster_offset >= cluster_size {
if self.is_contiguous {
// Contiguous: just increment cluster
self.current_cluster += 1;
if !info.is_valid_cluster(self.current_cluster) {
return Ok(None);
}
} else {
// Follow FAT chain
match self.fs.next_cluster(self.current_cluster)? {
Some(next) => self.current_cluster = next,
None => return Ok(None),
}
}
self.cluster_offset = 0;
}
// Read a single entry
let offset = info.cluster_to_offset(self.current_cluster) + self.cluster_offset as u64;
let raw_entry = self.fs.read_entry_at(offset)?;
let entry_type = unsafe { raw_entry.entry_type };
// Check for end of directory
if entry_type == entry_type::END_OF_DIRECTORY {
return Ok(None);
}
self.cluster_offset += entry_size;
self.dir_offset += entry_size as u64;
// Skip deleted entries and non-file entries
if entry_type == entry_type::DELETED_FILE {
continue;
}
// Skip critical system entries (bitmap, upcase, volume label)
if entry_type == entry_type::ALLOCATION_BITMAP
|| entry_type == entry_type::UPCASE_TABLE
|| entry_type == entry_type::VOLUME_LABEL
|| entry_type == entry_type::VOLUME_GUID
|| entry_type == entry_type::TEXFAT_PADDING
|| entry_type == entry_type::ACCESS_CONTROL
{
continue;
}
// File directory entry - need to read the complete entry set
if entry_type == entry_type::FILE_DIRECTORY {
let entry_offset = self.dir_offset - entry_size as u64;
return self.read_entry_set(raw_entry, entry_offset);
}
// Skip any other entry types
}
}
/// Read a complete file entry set starting from a File Directory Entry.
fn read_entry_set(
&mut self,
primary: RawDirectoryEntry,
entry_offset: u64,
) -> Result<Option<ExFatFileEntry>> {
let info = self.fs.info();
let entry_size = size_of::<RawDirectoryEntry>();
let cluster_size = info.bytes_per_cluster;
let primary_entry = unsafe { &primary.file };
let secondary_count = primary_entry.secondary_count as usize;
if secondary_count < 2 || secondary_count > 18 {
// Invalid entry, skip
return Ok(None);
}
// Read all entries in the set
let mut entries = Vec::with_capacity(1 + secondary_count);
entries.push(primary);
for _ in 0..secondary_count {
// Check if we've reached the directory size limit
if self.dir_size > 0 && self.dir_offset >= self.dir_size {
return Ok(None);
}
// Check if we need to move to the next cluster
if self.cluster_offset >= cluster_size {
if self.is_contiguous {
self.current_cluster += 1;
if !info.is_valid_cluster(self.current_cluster) {
return Ok(None);
}
} else {
match self.fs.next_cluster(self.current_cluster)? {
Some(next) => self.current_cluster = next,
None => return Ok(None),
}
}
self.cluster_offset = 0;
}
let offset = info.cluster_to_offset(self.current_cluster) + self.cluster_offset as u64;
let entry = self.fs.read_entry_at(offset)?;
entries.push(entry);
self.cluster_offset += entry_size;
self.dir_offset += entry_size as u64;
}
// Parse the entry set
if let Some((mut file_entry, _)) = parse_entry_set(&entries) {
file_entry.parent_cluster = self.first_cluster;
file_entry.entry_offset = entry_offset;
Ok(Some(file_entry))
} else {
// Failed to parse, skip
Ok(None)
}
}
}