Struct olio::fs::rc::ReadSlice

pub struct ReadSlice { /* fields omitted */ }

Re-implements Read and Seek over a shared File reference using only positioned reads, and by maintaining instance independent start, end, and position.

As compared with ReadPos, ReadSlice adds a general start offset, and limits access to the start..end range. Seeks are relative, so a seek to SeekFrom::Start(0) is always the first byte of the slice.

Fixed start and end offsets are passed on construction and used to constrain reads and interpret SeekFrom::Start and SeekFrom::End. These offsets are neither checked nor updated via file metadata, and the end offset could deviate from the underlying file length if concurrent writes or truncation is possible. Reads beyond end or the end of the underlying File will return 0 length. Seeking past the end is allowed by the platforms for File, and is also allowed for ReadSlice.

Methods

impl ReadSlice

Important traits for ReadSlice

impl Read for ReadSlice

pub fn new(file: Arc<File>, start: u64, end: u64) -> ReadSlice

New instance by File reference, fixed start and end offsets. The initial position is at the start (relative offset 0).

pub fn len(&self) -> u64

Return the total size of the slice in bytes. This is based on the start and end offsets as constructed and can differ from the underlying file length.

pub fn is_empty(&self) -> bool

Return true if length is 0.

pub fn mem_map(&self) -> Result<Mmap, Error>

Return a new read-only memory map handle Mmap for the complete region of the underlying file, from start to end.

Important traits for ReadSlice

impl Read for ReadSlice

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

Return a new and independent ReadSlice on the same file, for the range of byte offsets start..end which are relative to, and must be fully contained by self. Checks for and panics on overflow, if start..end is not fully contained, or if start is greater-than end.

pub fn tell(&self) -> u64

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

Trait Implementations

impl Debug for ReadSlice

fn fmt(&self, __arg_0: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Clone for ReadSlice

Important traits for ReadSlice

impl Read for ReadSlice

fn clone(&self) -> ReadSlice

Return a new, independent ReadSlice with the same start, end and file reference as self, and positioned at start (ignores the current position of self).

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

Performs copy-assignment from source.

impl PosRead for ReadSlice

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

Read some 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. 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 Read for ReadSlice

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.

unsafe fn initializer(&self) -> Initializer

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

Determines if this Reader can work with buffers of uninitialized memory.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> 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 by_ref(&mut self) -> &mut Self

Creates a "by reference" adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>

Transforms this Read instance to an [Iterator] over its bytes.

fn chars(self) -> Chars<Self>

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

the semantics of a partial read/write of where errors happen is currently unclear and may change

Transforms this Read instance to an [Iterator] over [char]s.

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

Creates an adaptor which will chain this stream with another.

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

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

impl Seek for ReadSlice

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

Seek to an offset, in bytes, in a stream. In this implementation, seeks are relative to the fixed starting offset to underlying File, so a seek to SeekFrom::Start(0) is always the first byte of the slice.