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// Copyright 2021 Colin Finck <colin@reactos.org>
// SPDX-License-Identifier: GPL-2.0-or-later
use crate::ntfs::Ntfs;
use alloc::string::String;
use core::char;
use core::cmp::Ordering;
use core::convert::{identity, TryInto};
use core::fmt;
/// Zero-copy representation of a string stored in an NTFS filesystem structure.
#[derive(Clone, Debug, Eq)]
pub struct NtfsString<'a>(pub &'a [u8]);
impl<'a> NtfsString<'a> {
fn cmp_iter<TI, OI, F>(mut this_iter: TI, mut other_iter: OI, code_unit_fn: F) -> Ordering
where
TI: Iterator<Item = u16>,
OI: Iterator<Item = u16>,
F: Fn(u16) -> u16,
{
loop {
match (this_iter.next(), other_iter.next()) {
(Some(this_code_unit), Some(other_code_unit)) => {
// We have two UTF-16 code units to compare.
let this_upper = code_unit_fn(this_code_unit);
let other_upper = code_unit_fn(other_code_unit);
if this_upper != other_upper {
return this_upper.cmp(&other_upper);
}
}
(Some(_), None) => {
// `this_iter` is longer than `other_iter` but otherwise equal.
return Ordering::Greater;
}
(None, Some(_)) => {
// `other_iter` is longer than `this_iter` but otherwise equal.
return Ordering::Less;
}
(None, None) => {
// We made it to the end of both strings, so they must be equal.
return Ordering::Equal;
}
}
}
}
fn u16_iter(&'a self) -> impl Iterator<Item = u16> + 'a {
self.0
.chunks_exact(2)
.map(|two_bytes| u16::from_le_bytes(two_bytes.try_into().unwrap()))
}
/// Returns `true` if `self` has a length of zero bytes.
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
/// Returns the length of `self`.
///
/// This length is in bytes, not characters! In other words,
/// it may not be what a human considers the length of the string.
pub const fn len(&self) -> usize {
self.0.len()
}
/// Attempts to convert `self` to an owned `String`.
/// Returns `Some(String)` if all characters could be converted successfully or `None` if a decoding error occurred.
pub fn to_string_checked(&self) -> Option<String> {
char::decode_utf16(self.u16_iter())
.map(|x| x.ok())
.collect::<Option<String>>()
}
/// Converts `self` to an owned `String`, replacing invalid data with the replacement character (U+FFFD).
pub fn to_string_lossy(&self) -> String {
char::decode_utf16(self.u16_iter())
.map(|x| x.unwrap_or(char::REPLACEMENT_CHARACTER))
.collect()
}
}
impl<'a> fmt::Display for NtfsString<'a> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let utf16_iter =
char::decode_utf16(self.u16_iter()).map(|x| x.unwrap_or(char::REPLACEMENT_CHARACTER));
for single_char in utf16_iter {
single_char.fmt(f)?;
}
Ok(())
}
}
impl<'a> Ord for NtfsString<'a> {
fn cmp(&self, other: &Self) -> Ordering {
NtfsString::cmp_iter(self.u16_iter(), other.u16_iter(), identity)
}
}
impl<'a> PartialEq for NtfsString<'a> {
/// Checks that two strings are a (case-sensitive!) match.
fn eq(&self, other: &Self) -> bool {
self.cmp(other) == Ordering::Equal
}
}
impl<'a> PartialEq<str> for NtfsString<'a> {
fn eq(&self, other: &str) -> bool {
NtfsString::cmp_iter(self.u16_iter(), other.encode_utf16(), identity) == Ordering::Equal
}
}
impl<'a> PartialEq<NtfsString<'a>> for str {
fn eq(&self, other: &NtfsString<'a>) -> bool {
NtfsString::cmp_iter(self.encode_utf16(), other.u16_iter(), identity) == Ordering::Equal
}
}
impl<'a> PartialEq<&str> for NtfsString<'a> {
fn eq(&self, other: &&str) -> bool {
NtfsString::cmp_iter(self.u16_iter(), other.encode_utf16(), identity) == Ordering::Equal
}
}
impl<'a> PartialEq<NtfsString<'a>> for &str {
fn eq(&self, other: &NtfsString<'a>) -> bool {
NtfsString::cmp_iter(self.encode_utf16(), other.u16_iter(), identity) == Ordering::Equal
}
}
impl<'a> PartialOrd for NtfsString<'a> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl<'a> PartialOrd<str> for NtfsString<'a> {
fn partial_cmp(&self, other: &str) -> Option<Ordering> {
Some(NtfsString::cmp_iter(
self.u16_iter(),
other.encode_utf16(),
identity,
))
}
}
impl<'a> PartialOrd<NtfsString<'a>> for str {
fn partial_cmp(&self, other: &NtfsString<'a>) -> Option<Ordering> {
Some(NtfsString::cmp_iter(
self.encode_utf16(),
other.u16_iter(),
identity,
))
}
}
impl<'a> PartialOrd<&str> for NtfsString<'a> {
fn partial_cmp(&self, other: &&str) -> Option<Ordering> {
Some(NtfsString::cmp_iter(
self.u16_iter(),
other.encode_utf16(),
identity,
))
}
}
impl<'a> PartialOrd<NtfsString<'a>> for &str {
fn partial_cmp(&self, other: &NtfsString<'a>) -> Option<Ordering> {
Some(NtfsString::cmp_iter(
self.encode_utf16(),
other.u16_iter(),
identity,
))
}
}
/// Trait for a case-insensitive ordering with respect to the $UpCase table read from the filesystem.
pub trait UpcaseOrd<Rhs> {
/// Performs a case-insensitive ordering based on the $UpCase table read from the filesystem.
///
/// # Panics
///
/// Panics if [`read_upcase_table`][Ntfs::read_upcase_table] had not been called on the passed [`Ntfs`] object.
fn upcase_cmp(&self, ntfs: &Ntfs, other: &Rhs) -> Ordering;
}
impl<'a> UpcaseOrd<NtfsString<'a>> for NtfsString<'a> {
fn upcase_cmp(&self, ntfs: &Ntfs, other: &NtfsString<'a>) -> Ordering {
let upcase_fn = |x| ntfs.upcase_table().u16_to_uppercase(x);
NtfsString::cmp_iter(self.u16_iter(), other.u16_iter(), upcase_fn)
}
}
impl<'a> UpcaseOrd<&str> for NtfsString<'a> {
fn upcase_cmp(&self, ntfs: &Ntfs, other: &&str) -> Ordering {
let upcase_fn = |x| ntfs.upcase_table().u16_to_uppercase(x);
NtfsString::cmp_iter(self.u16_iter(), other.encode_utf16(), upcase_fn)
}
}
impl<'a> UpcaseOrd<NtfsString<'a>> for &str {
fn upcase_cmp(&self, ntfs: &Ntfs, other: &NtfsString<'a>) -> Ordering {
let upcase_fn = |x| ntfs.upcase_table().u16_to_uppercase(x);
NtfsString::cmp_iter(self.encode_utf16(), other.u16_iter(), upcase_fn)
}
}
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