pub struct Cursor<T> { /* fields omitted */ }
A Cursor wraps an in-memory buffer and provides it with a Seek implementation.
Cursors are used with in-memory buffers, anything implementing AsRef<[u8]>, to allow them to implement Read and/or Write, allowing these buffers to be used anywhere you might use a reader or writer that does actual I/O.
The standard library implements some I/O traits on various types which are commonly used as a buffer, like Cursor<Vec<u8>> and Cursor<&[u8]>.
We may want to write bytes to a File in our production code, but use an in-memory buffer in our tests. We can do this with Cursor:
use std::io::prelude::*;
use std::io::{self, SeekFrom};
use std::fs::File;
// a library function we've written
fn write_ten_bytes_at_end<W: Write + Seek>(writer: &mut W) -> io::Result<()> {
writer.seek(SeekFrom::End(-10))?;
for i in 0..10 {
writer.write(&[i])?;
}
// all went well
Ok(())
}
// Here's some code that uses this library function.
//
// We might want to use a BufReader here for efficiency, but let's
// keep this example focused.
let mut file = File::create("foo.txt")?;
write_ten_bytes_at_end(&mut file)?;
// now let's write a test
#[test]
fn test_writes_bytes() {
// setting up a real File is much slower than an in-memory buffer,
// let's use a cursor instead
use std::io::Cursor;
let mut buff = Cursor::new(vec![0; 15]);
write_ten_bytes_at_end(&mut buff).unwrap();
assert_eq!(&buff.get_ref()[5..15], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
}impl<T> Cursor<T>[src]
pub fn new(inner: T) -> Cursor<T>ⓘNotable traits for Cursor<T>
impl<T> Read for Cursor<T> where
T: AsRef<[u8]>,
impl<'_> Write for Cursor<&'_ mut [u8]>
impl<'_> Write for Cursor<&'_ mut Vec<u8>>
impl Write for Cursor<Vec<u8>>
impl Write for Cursor<Box<[u8]>>
[src]
Creates a new cursor wrapping the provided underlying in-memory buffer.
Cursor initial position is 0 even if underlying buffer (e.g., Vec) is not empty. So writing to cursor starts with overwriting Vec content, not with appending to it.
use std::io::Cursor; let buff = Cursor::new(Vec::new());
pub fn into_inner(self) -> T[src]
Consumes this cursor, returning the underlying value.
use std::io::Cursor; let buff = Cursor::new(Vec::new()); let vec = buff.into_inner();
pub fn get_ref(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
Gets a reference to the underlying value in this cursor.
use std::io::Cursor; let buff = Cursor::new(Vec::new()); let reference = buff.get_ref();
pub fn get_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
Gets a mutable reference to the underlying value in this cursor.
Care should be taken to avoid modifying the internal I/O state of the underlying value as it may corrupt this cursor's position.
use std::io::Cursor; let mut buff = Cursor::new(Vec::new()); let reference = buff.get_mut();
pub fn position(&self) -> u64[src]
Returns the current position of this cursor.
use std::io::Cursor; use std::io::prelude::*; use std::io::SeekFrom; let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]); assert_eq!(buff.position(), 0); buff.seek(SeekFrom::Current(2)).unwrap(); assert_eq!(buff.position(), 2); buff.seek(SeekFrom::Current(-1)).unwrap(); assert_eq!(buff.position(), 1);
pub fn set_position(&mut self, pos: u64)[src]
Sets the position of this cursor.
use std::io::Cursor; let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]); assert_eq!(buff.position(), 0); buff.set_position(2); assert_eq!(buff.position(), 2); buff.set_position(4); assert_eq!(buff.position(), 4);
impl<T> BufRead for Cursor<T> where
T: AsRef<[u8]>, [src]
fn fill_buf(&mut self) -> Result<&[u8]>[src]
fn consume(&mut self, amt: usize)[src]
fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize>[src]
fn read_line(&mut self, buf: &mut String) -> Result<usize>[src]
fn split(self, byte: u8) -> Split<Self>ⓘNotable traits for Split<B>
impl<B: BufRead> Iterator for Split<B>
type Item = Result<Vec<u8>>;
where
Self: Sized, [src]
fn lines(self) -> Lines<Self>ⓘNotable traits for Lines<B>
impl<B: BufRead> Iterator for Lines<B>
type Item = Result<String>;
where
Self: Sized, [src]
impl<T: Clone> Clone for Cursor<T>[src]
fn clone(&self) -> Cursor<T>ⓘNotable traits for Cursor<T>
impl<T> Read for Cursor<T> where
T: AsRef<[u8]>,
impl<'_> Write for Cursor<&'_ mut [u8]>
impl<'_> Write for Cursor<&'_ mut Vec<u8>>
impl Write for Cursor<Vec<u8>>
impl Write for Cursor<Box<[u8]>>
[src]
fn clone_from(&mut self, source: &Self)[src]
impl<T: Debug> Debug for Cursor<T>[src]
impl<T: Default> Default for Cursor<T>[src]
fn default() -> Cursor<T>ⓘNotable traits for Cursor<T>
impl<T> Read for Cursor<T> where
T: AsRef<[u8]>,
impl<'_> Write for Cursor<&'_ mut [u8]>
impl<'_> Write for Cursor<&'_ mut Vec<u8>>
impl Write for Cursor<Vec<u8>>
impl Write for Cursor<Box<[u8]>>
[src]
impl<T: Eq> Eq for Cursor<T>[src]
impl<T: PartialEq> PartialEq<Cursor<T>> for Cursor<T>[src]
impl<T> Read for Cursor<T> where
T: AsRef<[u8]>, [src]
fn read(&mut self, buf: &mut [u8]) -> Result<usize>[src]
fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize>[src]
fn is_read_vectored(&self) -> bool[src]
fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>[src]
unsafe fn initializer(&self) -> Initializer[src]
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize>[src]
fn read_to_string(&mut self, buf: &mut String) -> Result<usize>[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
where
Self: Sized, [src]
fn bytes(self) -> Bytes<Self>ⓘNotable traits for Bytes<R>
impl<R: Read> Iterator for Bytes<R>
type Item = Result<u8>;
where
Self: Sized, [src]
fn chain<R: Read>(self, next: R) -> Chain<Self, R>ⓘNotable traits for Chain<T, U>
impl<T: Read, U: Read> Read for Chain<T, U>
where
Self: Sized, [src]
fn take(self, limit: u64) -> Take<Self>ⓘNotable traits for Take<T>
impl<T: Read> Read for Take<T>
where
Self: Sized, [src]
impl<T> Seek for Cursor<T> where
T: AsRef<[u8]>, [src]
fn seek(&mut self, style: SeekFrom) -> Result<u64>[src]
fn stream_len(&mut self) -> Result<u64>[src]
fn stream_position(&mut self) -> Result<u64>[src]
impl<T> StructuralEq for Cursor<T>[src]
impl<T> StructuralPartialEq for Cursor<T>[src]
impl<'_> Write for Cursor<&'_ mut [u8]>[src]
fn write(&mut self, buf: &[u8]) -> Result<usize>[src]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>[src]
fn is_write_vectored(&self) -> bool[src]
fn flush(&mut self) -> Result<()>[src]
fn write_all(&mut self, buf: &[u8]) -> Result<()>[src]
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()>[src]
fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<()>[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
where
Self: Sized, [src]
impl<'_> Write for Cursor<&'_ mut Vec<u8>>[src]1.25.0
fn write(&mut self, buf: &[u8]) -> Result<usize>[src]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>[src]
fn is_write_vectored(&self) -> bool[src]
fn flush(&mut self) -> Result<()>[src]
fn write_all(&mut self, buf: &[u8]) -> Result<()>[src]
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()>[src]
fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<()>[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
where
Self: Sized, [src]
impl Write for Cursor<Vec<u8>>[src]
fn write(&mut self, buf: &[u8]) -> Result<usize>[src]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>[src]
fn is_write_vectored(&self) -> bool[src]
fn flush(&mut self) -> Result<()>[src]
fn write_all(&mut self, buf: &[u8]) -> Result<()>[src]
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()>[src]
fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<()>[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
where
Self: Sized, [src]
impl Write for Cursor<Box<[u8]>>[src]1.5.0
fn write(&mut self, buf: &[u8]) -> Result<usize>[src]
fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize>[src]
fn is_write_vectored(&self) -> bool[src]
fn flush(&mut self) -> Result<()>[src]
fn write_all(&mut self, buf: &[u8]) -> Result<()>[src]
fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<()>[src]
fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<()>[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
where
Self: Sized, [src]
impl<T> RefUnwindSafe for Cursor<T> where
T: RefUnwindSafe, impl<T> Send for Cursor<T> where
T: Send, impl<T> Sync for Cursor<T> where
T: Sync, impl<T> Unpin for Cursor<T> where
T: Unpin, impl<T> UnwindSafe for Cursor<T> where
T: UnwindSafe, impl<T> Any for T where
T: 'static + ?Sized, [src]
impl<T> Borrow<T> for T where
T: ?Sized, [src]
fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> BorrowMut<T> for T where
T: ?Sized, [src]
fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> From<T> for T[src]
impl<T, U> Into<U> for T where
U: From<T>, [src]
impl<T> ToOwned for T where
T: Clone, [src]
type Owned = TThe resulting type after obtaining ownership.
fn to_owned(&self) -> T[src]
fn clone_into(&self, target: &mut T)[src]
impl<T, U> TryFrom<U> for T where
U: Into<T>, [src]
type Error = InfallibleThe type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>[src]
impl<T, U> TryInto<U> for T where
U: TryFrom<T>, [src]
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/io/struct.Cursor.html