M-Labs/rust-fatfs
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Do not write FSInfo sector if nothing changed.

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This commit is contained in:
Rafał Harabień 2018-05-27 23:56:38 +02:00
parent 147b31fdcd
commit 945612f042
1 changed files with 14 additions and 7 deletions
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21
src/fs.rs
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@ -207,9 +207,9 @@ impl Default for BootRecord {
#[derive(Default, Debug, Clone)]
struct FsInfoSector {
#[allow(dead_code)]
free_cluster_count: Option<u32>,
next_free_cluster: Option<u32>,
dirty: bool,
}
impl FsInfoSector {
@ -243,12 +243,11 @@ impl FsInfoSector {
return Err(Error::new(ErrorKind::Other, "invalid trail_sig in FsInfo sector"));
}
Ok(FsInfoSector {
free_cluster_count, next_free_cluster
free_cluster_count, next_free_cluster,
dirty: false,
})
}
// TODO: save modified FsInfo secton on unmount
#[allow(dead_code)]
fn serialize(&self, wrt: &mut Write) -> io::Result<()> {
wrt.write_u32::<LittleEndian>(Self::LEAD_SIG)?;
let reserved = [0u8; 480];
@ -265,8 +264,14 @@ impl FsInfoSector {
fn add_free_clusters(&mut self, free_clusters: i32) {
if let Some(n) = self.free_cluster_count {
self.free_cluster_count = Some((n as i32 + free_clusters) as u32);
self.dirty = true;
}
}
fn set_next_free_cluster(&mut self, cluster: u32) {
self.next_free_cluster = Some(cluster);
self.dirty = true;
}
}
/// FAT filesystem options.
@ -468,7 +473,7 @@ impl <'a> FileSystem<'a> {
let mut fat = self.fat_slice();
let cluster = alloc_cluster(&mut fat, self.fat_type, prev_cluster, hint, self.total_clusters)?;
let mut fs_info = self.fs_info.borrow_mut();
fs_info.next_free_cluster = Some(cluster + 1);
fs_info.set_next_free_cluster(cluster + 1);
fs_info.add_free_clusters(-1);
Ok(cluster)
}
@ -515,10 +520,12 @@ impl <'a> FileSystem<'a> {
}
fn flush_fs_info(&self) -> io::Result<()> {
if self.fat_type == FatType::Fat32 {
let mut fs_info = self.fs_info.borrow_mut();
if self.fat_type == FatType::Fat32 && fs_info.dirty {
let mut disk = self.disk.borrow_mut();
disk.seek(SeekFrom::Start(self.bpb.fs_info_sector as u64 * 512))?;
self.fs_info.borrow().serialize(&mut *disk)?;
fs_info.serialize(&mut *disk)?;
fs_info.dirty = false;
}
Ok(())
}