Struct olio::fs::ReadPos

pub struct ReadPos<P>where
    P: PosRead,{ /* private fields */ }

Re-implements Read and Seek over PosRead using only positioned reads, and by maintaining an instance independent position.

PosRead is implemented for any Borrow<File> so this can own via ReadPos<File> or use a shared reference, as in ReadPos<&File> or ReadPos<Arc<File>>.

A fixed length is passed on construction and used solely to interpret SeekFrom::End. Reads are not constrained by this length. The length is neither checked against nor updated from the inner PosRead (for example via file metadata) and could deviate if concurrent writes or truncation is possible. Reads beyond the end of the inner PosRead will return 0 length. Seeking past the end is allowed by the platforms for File, and is also allowed for ReadPos.

Implementations

impl<P> ReadPos<P>where
    P: PosRead,

pub fn new(pos_read: P, length: u64) -> Self

New instance for PosRead and fixed length. The initial position is the start (index 0).

pub fn len(&self) -> u64

Return the length as provided on construction. This may differ from the inner PosRead length.

pub fn is_empty(&self) -> bool

Return true if length is 0.

pub fn tell(&self) -> u64

Return the current instance position. This is a convenience shorthand for seek(SeekFrom::Current(0)), is infallable, and does not require a mutable reference.

impl<P> ReadPos<P>where
    P: PosRead + Clone,

pub fn subslice(&self, start: u64, end: u64) -> ReadSlice<P>

Return a new and independent ReadSlice by clone of the inner PosRead, for the range of byte offsets start..end, and positoned at start. This implementation panics if start is greater than end. Note that the end parameter is not checked against the length of self as passed on construction.

Trait Implementations

impl<P> Clone for ReadPos<P>where
    P: PosRead + Clone,

fn clone(&self) -> Self

Return a new, independent ReadPos by clone of the inner PosRead, with the same length as self, and at position 0.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<P: Debug> Debug for ReadPos<P>where
    P: PosRead,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<P> PosRead for ReadPos<P>where
    P: PosRead,

fn pread(&self, buf: &mut [u8], offset: u64) -> Result<usize>

Read bytes, starting at the specified offset, into the specified buffer and return the number of bytes read. The offset is from the start of the underlying file or file range. Reads beyond the end of available bytes will return 0 length. The position of the underlying file pointer (aka cursor) is not used. It is platform dependent whether the underlying file pointer is modified by this operation.

impl<P> Read for ReadPos<P>where
    P: PosRead,

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8, Global>) -> Result<usize, Error>

Read all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Read all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Read the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Read the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Selfwhere
    Self: Sized,

Creates a “by reference” adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>where
    Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>where
    R: Read,
    Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>where
    Self: Sized,

Creates an adapter which will read at most limit bytes from it.

impl<P> Seek for ReadPos<P>where
    P: PosRead,

fn seek(&mut self, from: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.