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// Copyright 2021 Colin Finck <colin@reactos.org>
// SPDX-License-Identifier: GPL-2.0-or-later
//
//! Supplementary helper types.
use crate::error::{NtfsError, Result};
use crate::ntfs::Ntfs;
use binread::BinRead;
use derive_more::{Binary, Display, From, LowerHex, Octal, UpperHex};
/// A Logical Cluster Number (LCN).
///
/// NTFS divides a filesystem into clusters of a given size (power of two), see [`Ntfs::cluster_size`].
/// The LCN is an absolute cluster index into the filesystem.
#[derive(
Binary,
BinRead,
Clone,
Copy,
Debug,
Display,
Eq,
From,
LowerHex,
Octal,
Ord,
PartialEq,
PartialOrd,
UpperHex,
)]
pub struct Lcn(u64);
impl Lcn {
/// Performs a checked addition of the given Virtual Cluster Number (VCN), returning a new LCN.
pub fn checked_add(&self, vcn: Vcn) -> Option<Lcn> {
if vcn.0 >= 0 {
self.0.checked_add(vcn.0 as u64).map(Into::into)
} else {
self.0
.checked_sub(vcn.0.wrapping_neg() as u64)
.map(Into::into)
}
}
/// Returns the absolute byte position of this LCN within the filesystem.
pub fn position(&self, ntfs: &Ntfs) -> Result<u64> {
self.0
.checked_mul(ntfs.cluster_size() as u64)
.ok_or(NtfsError::LcnTooBig { lcn: *self })
}
}
/// A Virtual Cluster Number (VCN).
///
/// NTFS divides a filesystem into clusters of a given size (power of two), see [`Ntfs::cluster_size`].
/// The VCN is a cluster index into the filesystem that is relative to a Logical Cluster Number (LCN)
/// or relative to the start of an attribute value.
#[derive(
Binary,
BinRead,
Clone,
Copy,
Debug,
Display,
Eq,
From,
LowerHex,
Octal,
Ord,
PartialEq,
PartialOrd,
UpperHex,
)]
pub struct Vcn(i64);
impl Vcn {
/// Converts this VCN into a byte offset (with respect to the cluster size of the provided [`Ntfs`] filesystem).
pub fn offset(&self, ntfs: &Ntfs) -> Result<i64> {
self.0
.checked_mul(ntfs.cluster_size() as i64)
.ok_or(NtfsError::VcnTooBig { vcn: *self })
}
}
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