Struct positioned_io::Cursor

pub struct Cursor<I> {
    // some fields omitted
}

Adapts a ReadAt or WriteAt into a Read or Write.

This wraps anything that read and write at offsets, turning into an object that can read or write at a file position. This allows you to use those types with all the many functions that expect a Read or Write.

Note that seeking on Cursor has limited functionality. We don't know how many bytes are available, so we can't use SeekFrom::End. See SizeCursor for another option.

Examples

use positioned_io::{ReadAt, Cursor};

struct NetworkStorage {
    // A remote disk that supports random access.
}
impl ReadAt for NetworkStorage {
    // ...
}

// Adapt our storage into a Read.
let storage = NetworkStorage::new(SOME_LOCATION);
let curs = Cursor::new_pos(storage, 1 << 30);

// Copy a segment to a file.
let mut input = curs.take(1 << 20);
let mut output = try!(File::create("segment.out"));
try!(io::copy(&mut input, &mut output));

Methods

impl<I> Cursor<I>

fn new_pos(io: I, pos: u64) -> Self

Create a new Cursor which starts reading at a specified offset.

Pass in a ReadAt or WriteAt as io.

fn new(io: I) -> Self

Create a new Cursor which starts reading at offset zero.

Pass in a ReadAt or WriteAt as io.

fn into_inner(self) -> I

Consume self and yield the inner ReadAt or WriteAt.

fn get_ref(&self) -> &I

Borrow the inner ReadAt or WriteAt.

fn get_mut(&mut self) -> &mut I

Borrow the inner ReadAt or WriteAt mutably.

fn position(&self) -> u64

Get the current read/write position.

fn set_position(&mut self, pos: u64)

Set the current read/write position.

Trait Implementations

impl<I> Seek for Cursor<I>

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

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

impl<I> Read for Cursor<I> where I: ReadAt

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_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, placing them into 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>

Unstable (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 chars.

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<I> Write for Cursor<I> where I: WriteAt

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

Write a buffer into this object, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flush this output stream, ensuring that all intermediately buffered contents reach their destination.

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

Attempts to write an entire buffer into this write.

fn write_fmt(&mut self, fmt: Arguments) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

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