mirror of https://github.com/encounter/nod-rs.git
156 lines
4.8 KiB
Rust
156 lines
4.8 KiB
Rust
//! Common stream types
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use std::{
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fs::File,
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io,
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io::{Read, Seek, SeekFrom},
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ops::DerefMut,
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};
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/// Creates a fixed-size array reference from a slice.
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#[macro_export]
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macro_rules! array_ref {
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($slice:expr, $offset:expr, $size:expr) => {{
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#[inline]
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fn to_array<T>(slice: &[T]) -> &[T; $size] {
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unsafe { &*(slice.as_ptr() as *const [_; $size]) }
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}
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to_array(&$slice[$offset..$offset + $size])
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}};
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}
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/// Creates a mutable fixed-size array reference from a slice.
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#[macro_export]
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macro_rules! array_ref_mut {
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($slice:expr, $offset:expr, $size:expr) => {{
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#[inline]
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fn to_array<T>(slice: &mut [T]) -> &mut [T; $size] {
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unsafe { &mut *(slice.as_ptr() as *mut [_; $size]) }
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}
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to_array(&mut $slice[$offset..$offset + $size])
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}};
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}
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pub trait ReadStream: Read + Seek {
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/// Replace with [`Read.stream_len`] when stabilized.
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///
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/// <https://github.com/rust-lang/rust/issues/59359>
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fn stable_stream_len(&mut self) -> io::Result<u64>;
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/// Creates a windowed read sub-stream with offset and size.
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///
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/// Seeks underlying stream immediately.
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fn new_window(&mut self, offset: u64, size: u64) -> io::Result<SharedWindowedReadStream>
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where Self: Sized {
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self.seek(SeekFrom::Start(offset))?;
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io::Result::Ok(SharedWindowedReadStream { base: self, begin: offset, end: offset + size })
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}
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}
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impl ReadStream for File {
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fn stable_stream_len(&mut self) -> io::Result<u64> {
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let before = self.stream_position()?;
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let result = self.seek(SeekFrom::End(0));
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// Try to restore position even if the above failed
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self.seek(SeekFrom::Start(before))?;
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result
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}
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}
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trait WindowedReadStream: ReadStream {
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fn base_stream(&mut self) -> &mut dyn ReadStream;
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fn window(&self) -> (u64, u64);
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}
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pub struct OwningWindowedReadStream<'a> {
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pub base: Box<dyn ReadStream + 'a>,
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pub begin: u64,
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pub end: u64,
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}
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/// Takes ownership of & wraps a read stream into a windowed read stream.
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pub fn wrap_windowed<'a>(
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mut base: Box<dyn ReadStream + 'a>,
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offset: u64,
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size: u64,
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) -> io::Result<OwningWindowedReadStream<'a>> {
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base.seek(SeekFrom::Start(offset))?;
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io::Result::Ok(OwningWindowedReadStream { base, begin: offset, end: offset + size })
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}
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pub struct SharedWindowedReadStream<'a> {
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pub base: &'a mut dyn ReadStream,
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pub begin: u64,
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pub end: u64,
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}
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#[inline(always)]
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fn windowed_read(stream: &mut dyn WindowedReadStream, buf: &mut [u8]) -> io::Result<usize> {
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let pos = stream.stream_position()?;
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let size = stream.stable_stream_len()?;
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stream.base_stream().read(if pos + buf.len() as u64 > size {
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&mut buf[..(size - pos) as usize]
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} else {
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buf
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})
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}
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#[inline(always)]
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fn windowed_seek(stream: &mut dyn WindowedReadStream, pos: SeekFrom) -> io::Result<u64> {
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let (begin, end) = stream.window();
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let result = stream.base_stream().seek(match pos {
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SeekFrom::Start(p) => SeekFrom::Start(begin + p),
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SeekFrom::End(p) => SeekFrom::End(end as i64 + p),
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SeekFrom::Current(_) => pos,
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})?;
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if result < begin || result > end {
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io::Result::Err(io::Error::from(io::ErrorKind::UnexpectedEof))
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} else {
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io::Result::Ok(result - begin)
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}
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}
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impl<'a> Read for OwningWindowedReadStream<'a> {
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fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { windowed_read(self, buf) }
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}
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impl<'a> Seek for OwningWindowedReadStream<'a> {
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fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { windowed_seek(self, pos) }
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fn stream_position(&mut self) -> io::Result<u64> {
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Result::Ok(self.base.stream_position()? - self.begin)
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}
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}
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impl<'a> ReadStream for OwningWindowedReadStream<'a> {
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fn stable_stream_len(&mut self) -> io::Result<u64> { Result::Ok(self.end - self.begin) }
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}
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impl<'a> WindowedReadStream for OwningWindowedReadStream<'a> {
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fn base_stream(&mut self) -> &mut dyn ReadStream { self.base.deref_mut() }
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fn window(&self) -> (u64, u64) { (self.begin, self.end) }
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}
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impl<'a> Read for SharedWindowedReadStream<'a> {
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fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { windowed_read(self, buf) }
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}
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impl<'a> Seek for SharedWindowedReadStream<'a> {
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fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> { windowed_seek(self, pos) }
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fn stream_position(&mut self) -> io::Result<u64> {
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Result::Ok(self.base.stream_position()? - self.begin)
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}
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}
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impl<'a> ReadStream for SharedWindowedReadStream<'a> {
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fn stable_stream_len(&mut self) -> io::Result<u64> { Result::Ok(self.end - self.begin) }
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}
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impl<'a> WindowedReadStream for SharedWindowedReadStream<'a> {
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fn base_stream(&mut self) -> &mut dyn ReadStream { self.base }
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fn window(&self) -> (u64, u64) { (self.begin, self.end) }
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}
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