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core: Delay overflow detection on dirtab offsets until after division #57

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merged 1 commit into from
Nov 14, 2023
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core: Delay overflow detection on dirtab offsets until after division #57

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33 changes: 19 additions & 14 deletions xdvdfs-core/src/write/dirtab.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -125,11 +125,11 @@ impl DirectoryEntryTableWriter {

// Array of offsets for each entry in the table
// The offset is a partial sum of lengths of the dirent on disk
let offsets: Result<Vec<u16>, util::Error<E>> = self
let offsets: Result<Vec<u64>, util::Error<E>> = self
.table
.backing_vec()
.iter()
.map(|node| node.data().len_on_disk()?.try_into().or_unexpected())
.map(|node| node.data().len_on_disk())
.collect();
let mut offsets = offsets?;
if offsets.is_empty() {
Expand All @@ -143,21 +143,15 @@ impl DirectoryEntryTableWriter {
let final_dirent_size = offsets[0];
offsets[0] = 0;
for i in 1..offsets.len() {
offsets[i] = offsets[i]
.checked_add(offsets[i - 1])
.ok_or(util::Error::TooManyDirectoryEntries)?;
offsets[i] += offsets[i - 1];

let next_size = if i + 1 == offsets.len() {
final_dirent_size
} else {
offsets[i + 1]
};
let adj: u16 = sector_align(offsets[i] as u64, next_size as u64)
.try_into()
.or_unexpected()?;
offsets[i] = offsets[i]
.checked_add(adj)
.ok_or(util::Error::TooManyDirectoryEntries)?;
let adj = sector_align(offsets[i], next_size);
offsets[i] += adj;

assert!(offsets[i] % 4 == 0);
}
Expand All @@ -170,10 +164,21 @@ impl DirectoryEntryTableWriter {
let mut dirent = node.data().node;
dirent.filename_length = node.data().encode_name(&mut name_bytes)?;

let left_entry_offset: u16 = node
.left_idx()
.map(|idx| offsets[idx] / 4)
.unwrap_or_default()
.try_into()
.map_err(|_| util::Error::TooManyDirectoryEntries)?;
let right_entry_offset: u16 = node
.right_idx()
.map(|idx| offsets[idx] / 4)
.unwrap_or_default()
.try_into()
.map_err(|_| util::Error::TooManyDirectoryEntries)?;
let mut dirent = DirectoryEntryDiskNode {
left_entry_offset: node.left_idx().map(|idx| offsets[idx]).unwrap_or_default() / 4,
right_entry_offset: node.right_idx().map(|idx| offsets[idx]).unwrap_or_default()
/ 4,
left_entry_offset,
right_entry_offset,
dirent,
};

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