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// Copyright 2021-2023 Colin Finck <colin@reactos.org>
// SPDX-License-Identifier: MIT OR Apache-2.0
use binrw::io;
use binrw::io::{Read, Seek, SeekFrom};
use crate::error::{NtfsError, Result};
/// Trait to read/seek in a source by the help of a temporarily passed mutable reference to the filesystem reader.
///
/// By requiring the user to pass the filesystem reader on every read, we circumvent the problems associated with permanently
/// holding a mutable reference.
/// If we held one, we could not read from two objects in alternation.
pub trait NtfsReadSeek {
/// See [`std::io::Read::read`].
fn read<T>(&mut self, fs: &mut T, buf: &mut [u8]) -> Result<usize>
where
T: Read + Seek;
/// See [`std::io::Read::read_exact`].
fn read_exact<T>(&mut self, fs: &mut T, mut buf: &mut [u8]) -> Result<()>
where
T: Read + Seek,
{
// This implementation is taken from https://github.com/rust-lang/rust/blob/5662d9343f0696efcc38a1264656737c9f22d427/library/std/src/io/mod.rs
// It handles all corner cases properly and outputs the known `io` error messages.
while !buf.is_empty() {
match self.read(fs, buf) {
Ok(0) => break,
Ok(n) => {
buf = &mut buf[n..];
}
Err(NtfsError::Io(e)) if e.kind() == io::ErrorKind::Interrupted => {}
Err(e) => return Err(e),
}
}
if !buf.is_empty() {
Err(NtfsError::Io(io::Error::new(
io::ErrorKind::UnexpectedEof,
"failed to fill whole buffer",
)))
} else {
Ok(())
}
}
/// See [`std::io::Seek::seek`].
fn seek<T>(&mut self, fs: &mut T, pos: SeekFrom) -> Result<u64>
where
T: Read + Seek;
/// See [`std::io::Seek::stream_position`].
fn stream_position(&self) -> u64;
}