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// Copyright 2021-2023 Colin Finck <colin@reactos.org>
// SPDX-License-Identifier: MIT OR Apache-2.0
use core::cmp::Ordering;
use core::marker::PhantomData;
use alloc::vec;
use alloc::vec::Vec;
use binrw::io::{Read, Seek};
use crate::attribute::{NtfsAttributeItem, NtfsAttributeType};
use crate::error::{NtfsError, Result};
use crate::index_entry::{
IndexEntryRange, IndexNodeEntryRanges, NtfsIndexEntry, NtfsIndexEntryFlags,
};
use crate::indexes::NtfsIndexEntryType;
use crate::structured_values::{NtfsIndexAllocation, NtfsIndexRoot};
use crate::types::NtfsPosition;
/// Helper structure to iterate over all entries of an index or find a specific one.
///
/// The `E` type parameter of [`NtfsIndexEntryType`] specifies the type of the index entries.
/// The most common one is [`NtfsFileNameIndex`] for file name indexes, commonly known as "directories".
/// Check out [`NtfsFile::directory_index`] to return an [`NtfsIndex`] object for a directory without
/// any hassles.
///
/// [`NtfsFile::directory_index`]: crate::NtfsFile::directory_index
/// [`NtfsFileNameIndex`]: crate::indexes::NtfsFileNameIndex
#[derive(Clone, Debug)]
pub struct NtfsIndex<'n, 'f, E>
where
E: NtfsIndexEntryType,
{
index_record_size: u32,
index_root_entry_ranges: IndexNodeEntryRanges<E>,
index_root_position: NtfsPosition,
index_allocation_item: Option<NtfsAttributeItem<'n, 'f>>,
entry_type: PhantomData<E>,
}
impl<'n, 'f, E> NtfsIndex<'n, 'f, E>
where
E: NtfsIndexEntryType,
{
/// Creates a new [`NtfsIndex`] object from a previously looked up [`NtfsIndexRoot`] attribute
/// (contained in an [`NtfsAttributeItem`]) and, in case of a large index, a matching
/// [`NtfsIndexAllocation`] attribute (also contained in an [`NtfsAttributeItem`]).
///
/// If you just want to look up files in a directory, check out [`NtfsFile::directory_index`],
/// which looks up the correct [`NtfsIndexRoot`] and [`NtfsIndexAllocation`] attributes for you.
///
/// [`NtfsFile::directory_index`]: crate::NtfsFile::directory_index
pub fn new(
index_root_item: NtfsAttributeItem<'n, 'f>,
index_allocation_item: Option<NtfsAttributeItem<'n, 'f>>,
) -> Result<Self> {
let index_root_attribute = index_root_item.to_attribute()?;
index_root_attribute.ensure_ty(NtfsAttributeType::IndexRoot)?;
let index_root = index_root_attribute.resident_structured_value::<NtfsIndexRoot>()?;
if let Some(item) = &index_allocation_item {
let attribute = item.to_attribute()?;
attribute.ensure_ty(NtfsAttributeType::IndexAllocation)?;
} else if index_root.is_large_index() {
return Err(NtfsError::MissingIndexAllocation {
position: index_root.position(),
});
}
let index_record_size = index_root.index_record_size();
let index_root_entry_ranges = index_root.entry_ranges();
let index_root_position = index_root.position();
let entry_type = PhantomData;
Ok(Self {
index_record_size,
index_root_entry_ranges,
index_root_position,
index_allocation_item,
entry_type,
})
}
/// Returns an [`NtfsIndexEntries`] iterator to perform an in-order traversal of this index.
pub fn entries<'i>(&'i self) -> NtfsIndexEntries<'n, 'f, 'i, E> {
NtfsIndexEntries::new(self)
}
/// Returns an [`NtfsIndexFinder`] structure to efficiently find an entry in this index.
pub fn finder<'i>(&'i self) -> NtfsIndexFinder<'n, 'f, 'i, E> {
NtfsIndexFinder::new(self)
}
}
/// Iterator over
/// all index entries of an index,
/// sorted ascending by the index key,
/// returning an [`NtfsIndexEntry`] for each entry.
///
/// This iterator is returned from the [`NtfsIndex::entries`] function.
#[derive(Clone, Debug)]
pub struct NtfsIndexEntries<'n, 'f, 'i, E>
where
E: NtfsIndexEntryType,
{
index: &'i NtfsIndex<'n, 'f, E>,
inner_iterators: Vec<IndexNodeEntryRanges<E>>,
following_entries: Vec<Option<IndexEntryRange<E>>>,
}
impl<'n, 'f, 'i, E> NtfsIndexEntries<'n, 'f, 'i, E>
where
E: NtfsIndexEntryType,
{
fn new(index: &'i NtfsIndex<'n, 'f, E>) -> Self {
let inner_iterators = vec![index.index_root_entry_ranges.clone()];
let following_entries = Vec::new();
Self {
index,
inner_iterators,
following_entries,
}
}
/// See [`Iterator::next`].
pub fn next<'a, T>(&'a mut self, fs: &mut T) -> Option<Result<NtfsIndexEntry<'a, E>>>
where
T: Read + Seek,
{
// NTFS B-tree indexes are composed out of nodes, with multiple entries per node.
// Each entry may have a reference to a subnode.
// If that is the case, the subnode entries comes before the parent entry lexicographically.
//
// An example for an unbalanced, but otherwise valid and sorted tree:
//
// -------------
// INDEX ROOT NODE: | 4 | 5 | 6 |
// -------------
// |
// ---------
// INDEX ALLOCATION SUBNODE: | 1 | 3 |
// ---------
// |
// -----
// INDEX ALLOCATION SUBNODE: | 2 |
// -----
//
let entry_range = loop {
// Get the iterator from the current node level, if any.
let iter = self.inner_iterators.last_mut()?;
// Get the next `IndexEntryRange` from it.
if let Some(entry_range) = iter.next() {
let entry_range = iter_try!(entry_range);
// Convert that `IndexEntryRange` to a (lifetime-bound) `NtfsIndexEntry`.
let entry = iter_try!(entry_range.to_entry(iter.data()));
let is_last_entry = entry.flags().contains(NtfsIndexEntryFlags::LAST_ENTRY);
// Does this entry have a subnode that needs to be iterated first?
if let Some(subnode_vcn) = entry.subnode_vcn() {
let subnode_vcn = iter_try!(subnode_vcn);
// Read the subnode from the filesystem and get an iterator for it.
let index_allocation_item =
iter_try!(self.index.index_allocation_item.as_ref().ok_or(
NtfsError::MissingIndexAllocation {
position: self.index.index_root_position,
}
));
let index_allocation_attribute =
iter_try!(index_allocation_item.to_attribute());
let index_allocation =
iter_try!(index_allocation_attribute
.structured_value::<_, NtfsIndexAllocation>(fs));
let subnode = iter_try!(index_allocation.record_from_vcn(
fs,
self.index.index_record_size,
subnode_vcn
));
let subnode_iter = subnode.into_entry_ranges();
let following_entry = if !is_last_entry {
// This entry comes after the subnode lexicographically, so save it.
// We'll pick it up again after the subnode iterator has been fully iterated.
Some(entry_range)
} else {
None
};
// Save this subnode's iterator and any following entry.
// We'll pick up the iterator through `self.inner_iterators.last_mut()` in the next loop iteration.
self.inner_iterators.push(subnode_iter);
self.following_entries.push(following_entry);
} else if !is_last_entry {
// There is no subnode, and this is not the empty "last entry",
// so our entry comes next lexicographically.
break entry_range;
}
} else {
// The iterator for this subnode level has been fully iterated.
// Drop it.
self.inner_iterators.pop();
// The entry, whose subnode we just fully iterated, may have been saved in `following_entries`.
// This depends on its `is_last_entry` flag:
// * If it was not the last entry, it contains an entry that comes next lexicographically,
// and has therefore been saved in `following_entries`.
// * If it was the last entry, it contains no further information.
// `None` has been saved in `following_entries`, so that `following_entries.len()` always
// matches `inner_iterators.len() - 1`.
//
// If we just finished iterating the root-level node, `following_entries` is empty and we are done.
// Otherwise, we can be sure that `inner_iterators.last()` is the matching iterator for converting
// `IndexEntryRange` to a (lifetime-bound) `NtfsIndexEntry`.
if let Some(entry_range) = self.following_entries.pop()? {
break entry_range;
}
}
};
let iter = self.inner_iterators.last().unwrap();
let entry = iter_try!(entry_range.to_entry(iter.data()));
Some(Ok(entry))
}
}
/// Helper structure to efficiently find an entry in an index, created by [`NtfsIndex::finder`].
///
/// This helper is required, because the returned entry borrows from the iterator it was created from.
/// The idea is that you copy the field(s) you need from the returned entry and then drop the entry and the finder.
pub struct NtfsIndexFinder<'n, 'f, 'i, E>
where
E: NtfsIndexEntryType,
{
index: &'i NtfsIndex<'n, 'f, E>,
inner_iterator: IndexNodeEntryRanges<E>,
}
impl<'n, 'f, 'i, E> NtfsIndexFinder<'n, 'f, 'i, E>
where
E: NtfsIndexEntryType,
{
fn new(index: &'i NtfsIndex<'n, 'f, E>) -> Self {
// This is superfluous and done again in `find`, but doesn't justify using an `Option` here.
let inner_iterator = index.index_root_entry_ranges.clone();
Self {
index,
inner_iterator,
}
}
/// Finds an entry in this index using the given comparison function and returns an [`NtfsIndexEntry`]
/// (if there is one).
pub fn find<'a, T, F>(&'a mut self, fs: &mut T, cmp: F) -> Option<Result<NtfsIndexEntry<'a, E>>>
where
T: Read + Seek,
F: Fn(&E::KeyType) -> Ordering,
{
// Always (re)start by iterating through the Index Root entry ranges.
self.inner_iterator = self.index.index_root_entry_ranges.clone();
loop {
// Get the next entry.
//
// A textbook B-tree search algorithm would get the middle entry and perform binary search.
// But we can't do that here, as we are dealing with variable-length entries.
let entry_range = iter_try!(self.inner_iterator.next()?);
let entry = iter_try!(entry_range.to_entry(self.inner_iterator.data()));
// Check if this entry has a key.
if let Some(key) = entry.key() {
// The entry has a key, so compare it using the given function.
let key = iter_try!(key);
match cmp(&key) {
Ordering::Equal => {
// We found what we were looking for!
// Recreate `entry` from the last `self.inner_iterator` to please the borrow checker.
let entry = iter_try!(entry_range.to_entry(self.inner_iterator.data()));
return Some(Ok(entry));
}
Ordering::Less => {
// What we are looking for comes BEFORE this entry.
// Hence, it must be in a subnode of this entry and we continue below.
}
Ordering::Greater => {
// What we are looking for comes AFTER this entry.
// Keep searching on the same subnode level.
continue;
}
}
}
// Either this entry has no key (= is the last one on this subnode level) or
// it comes lexicographically AFTER what we're looking for.
// In both cases, we have to continue iterating in the subnode of this entry (if there is any).
let subnode_vcn = iter_try!(entry.subnode_vcn()?);
let index_allocation_item = iter_try!(self.index.index_allocation_item.as_ref().ok_or(
NtfsError::MissingIndexAllocation {
position: self.index.index_root_position,
}
));
let index_allocation_attribute = iter_try!(index_allocation_item.to_attribute());
let index_allocation = iter_try!(
index_allocation_attribute.structured_value::<_, NtfsIndexAllocation>(fs)
);
let subnode = iter_try!(index_allocation.record_from_vcn(
fs,
self.index.index_record_size,
subnode_vcn
));
self.inner_iterator = subnode.into_entry_ranges();
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::indexes::NtfsFileNameIndex;
use crate::ntfs::Ntfs;
#[test]
fn test_index_find() {
let mut testfs1 = crate::helpers::tests::testfs1();
let mut ntfs = Ntfs::new(&mut testfs1).unwrap();
ntfs.read_upcase_table(&mut testfs1).unwrap();
let root_dir = ntfs.root_directory(&mut testfs1).unwrap();
// Find the "many_subdirs" subdirectory.
let root_dir_index = root_dir.directory_index(&mut testfs1).unwrap();
let mut root_dir_finder = root_dir_index.finder();
let entry =
NtfsFileNameIndex::find(&mut root_dir_finder, &ntfs, &mut testfs1, "many_subdirs")
.unwrap()
.unwrap();
let subdir = entry.to_file(&ntfs, &mut testfs1).unwrap();
// Prove that we can find all 512 indexed subdirectories.
let subdir_index = subdir.directory_index(&mut testfs1).unwrap();
let mut subdir_finder = subdir_index.finder();
for i in 1..=512 {
let dir_name = format!("{i}");
let entry = NtfsFileNameIndex::find(&mut subdir_finder, &ntfs, &mut testfs1, &dir_name)
.unwrap()
.unwrap();
let entry_name = entry.key().unwrap().unwrap();
assert_eq!(entry_name.name(), dir_name.as_str());
}
}
#[test]
fn test_index_iter() {
let mut testfs1 = crate::helpers::tests::testfs1();
let mut ntfs = Ntfs::new(&mut testfs1).unwrap();
ntfs.read_upcase_table(&mut testfs1).unwrap();
let root_dir = ntfs.root_directory(&mut testfs1).unwrap();
// Find the "many_subdirs" subdirectory.
let root_dir_index = root_dir.directory_index(&mut testfs1).unwrap();
let mut root_dir_finder = root_dir_index.finder();
let entry =
NtfsFileNameIndex::find(&mut root_dir_finder, &ntfs, &mut testfs1, "many_subdirs")
.unwrap()
.unwrap();
let subdir = entry.to_file(&ntfs, &mut testfs1).unwrap();
// Prove that we can iterate through all 512 indexed subdirectories in order.
// Keep in mind that subdirectories are ordered like "1", "10", "100", "101", ...
// We can create the same order by adding them to a vector and sorting that vector.
let mut dir_names = Vec::with_capacity(512);
for i in 1..=512 {
dir_names.push(format!("{i}"));
}
dir_names.sort_unstable();
let subdir_index = subdir.directory_index(&mut testfs1).unwrap();
let mut subdir_iter = subdir_index.entries();
for dir_name in dir_names {
let entry = subdir_iter.next(&mut testfs1).unwrap().unwrap();
let entry_name = entry.key().unwrap().unwrap();
assert_eq!(entry_name.name(), dir_name.as_str());
}
assert!(subdir_iter.next(&mut testfs1).is_none());
}
}