Struct otter_api_tests::io::Cursor

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]>.

Examples

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]);
}

Implementations

impl<T> Cursor<T>

pub const fn new(inner: T) -> Cursor<T>

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.

Examples

use std::io::Cursor;

let buff = Cursor::new(Vec::new());

pub fn into_inner(self) -> T

Consumes this cursor, returning the underlying value.

Examples

use std::io::Cursor;

let buff = Cursor::new(Vec::new());

let vec = buff.into_inner();

pub const fn get_ref(&self) -> &T

Gets a reference to the underlying value in this cursor.

Examples

use std::io::Cursor;

let buff = Cursor::new(Vec::new());

let reference = buff.get_ref();

pub fn get_mut(&mut self) -> &mut T

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.

Examples

use std::io::Cursor;

let mut buff = Cursor::new(Vec::new());

let reference = buff.get_mut();

pub const fn position(&self) -> u64

Returns the current position of this cursor.

Examples

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)

Sets the position of this cursor.

Examples

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);

Trait Implementations

impl<T> AsyncBufRead for Cursor<T> where
    T: AsRef<[u8]> + Unpin, 

pub fn poll_fill_buf(
    self: Pin<&mut Cursor<T>>,
    _cx: &mut Context<'_>
) -> Poll<Result<&[u8], Error>>

Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

pub fn consume(self: Pin<&mut Cursor<T>>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read.

impl<T> AsyncRead for Cursor<T> where
    T: AsRef<[u8]> + Unpin, 

pub fn poll_read(
    self: Pin<&mut Cursor<T>>,
    _cx: &mut Context<'_>,
    buf: &mut ReadBuf<'_>
) -> Poll<Result<(), Error>>

Attempts to read from the AsyncRead into buf.

impl<T> AsyncSeek for Cursor<T> where
    T: AsRef<[u8]> + Unpin, 

pub fn start_seek(self: Pin<&mut Cursor<T>>, pos: SeekFrom) -> Result<(), Error>

Attempts to seek to an offset, in bytes, in a stream.

pub fn poll_complete(
    self: Pin<&mut Cursor<T>>,
    &mut Context<'_>
) -> Poll<Result<u64, Error>>

Waits for a seek operation to complete.

impl<'_> AsyncWrite for Cursor<&'_ mut Vec<u8, Global>>

pub fn poll_write(
    self: Pin<&mut Cursor<&'_ mut Vec<u8, Global>>>,
    &mut Context<'_>,
    buf: &[u8]
) -> Poll<Result<usize, Error>>

Attempt to write bytes from buf into the object.

pub fn poll_write_vectored(
    self: Pin<&mut Cursor<&'_ mut Vec<u8, Global>>>,
    &mut Context<'_>,
    bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>

Like poll_write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

pub fn poll_flush(
    self: Pin<&mut Cursor<&'_ mut Vec<u8, Global>>>,
    &mut Context<'_>
) -> Poll<Result<(), Error>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

pub fn poll_shutdown(
    self: Pin<&mut Cursor<&'_ mut Vec<u8, Global>>>,
    cx: &mut Context<'_>
) -> Poll<Result<(), Error>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

impl AsyncWrite for Cursor<Vec<u8, Global>>

pub fn poll_write(
    self: Pin<&mut Cursor<Vec<u8, Global>>>,
    &mut Context<'_>,
    buf: &[u8]
) -> Poll<Result<usize, Error>>

Attempt to write bytes from buf into the object.

pub fn poll_write_vectored(
    self: Pin<&mut Cursor<Vec<u8, Global>>>,
    &mut Context<'_>,
    bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>

Like poll_write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

pub fn poll_flush(
    self: Pin<&mut Cursor<Vec<u8, Global>>>,
    &mut Context<'_>
) -> Poll<Result<(), Error>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

pub fn poll_shutdown(
    self: Pin<&mut Cursor<Vec<u8, Global>>>,
    cx: &mut Context<'_>
) -> Poll<Result<(), Error>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

impl<'_> AsyncWrite for Cursor<&'_ mut [u8]>

pub fn poll_write(
    self: Pin<&mut Cursor<&'_ mut [u8]>>,
    &mut Context<'_>,
    buf: &[u8]
) -> Poll<Result<usize, Error>>

Attempt to write bytes from buf into the object.

pub fn poll_write_vectored(
    self: Pin<&mut Cursor<&'_ mut [u8]>>,
    &mut Context<'_>,
    bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>

Like poll_write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

pub fn poll_flush(
    self: Pin<&mut Cursor<&'_ mut [u8]>>,
    &mut Context<'_>
) -> Poll<Result<(), Error>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

pub fn poll_shutdown(
    self: Pin<&mut Cursor<&'_ mut [u8]>>,
    cx: &mut Context<'_>
) -> Poll<Result<(), Error>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

impl AsyncWrite for Cursor<Box<[u8], Global>>

pub fn poll_write(
    self: Pin<&mut Cursor<Box<[u8], Global>>>,
    &mut Context<'_>,
    buf: &[u8]
) -> Poll<Result<usize, Error>>

Attempt to write bytes from buf into the object.

pub fn poll_write_vectored(
    self: Pin<&mut Cursor<Box<[u8], Global>>>,
    &mut Context<'_>,
    bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>

Like poll_write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

pub fn poll_flush(
    self: Pin<&mut Cursor<Box<[u8], Global>>>,
    &mut Context<'_>
) -> Poll<Result<(), Error>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

pub fn poll_shutdown(
    self: Pin<&mut Cursor<Box<[u8], Global>>>,
    cx: &mut Context<'_>
) -> Poll<Result<(), Error>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

impl<T> Buf for Cursor<T> where
    T: AsRef<[u8]>, 

pub fn remaining(&self) -> usize

Returns the number of bytes between the current position and the end of the buffer.

pub fn chunk(&self) -> &[u8]

Returns a slice starting at the current position and of length between 0 and Buf::remaining(). Note that this can return shorter slice (this allows non-continuous internal representation).

pub fn advance(&mut self, cnt: usize)

Advance the internal cursor of the Buf

fn chunks_vectored(&'a self, dst: &mut [IoSlice<'a>]) -> usize

Fills dst with potentially multiple slices starting at self’s current position.

fn has_remaining(&self) -> bool

Returns true if there are any more bytes to consume

fn copy_to_slice(&mut self, dst: &mut [u8])

Copies bytes from self into dst.

fn get_u8(&mut self) -> u8

Gets an unsigned 8 bit integer from self.

fn get_i8(&mut self) -> i8

Gets a signed 8 bit integer from self.

fn get_u16(&mut self) -> u16

Gets an unsigned 16 bit integer from self in big-endian byte order.

fn get_u16_le(&mut self) -> u16

Gets an unsigned 16 bit integer from self in little-endian byte order.

fn get_i16(&mut self) -> i16

Gets a signed 16 bit integer from self in big-endian byte order.

fn get_i16_le(&mut self) -> i16

Gets a signed 16 bit integer from self in little-endian byte order.

fn get_u32(&mut self) -> u32

Gets an unsigned 32 bit integer from self in the big-endian byte order.

fn get_u32_le(&mut self) -> u32

Gets an unsigned 32 bit integer from self in the little-endian byte order.

fn get_i32(&mut self) -> i32

Gets a signed 32 bit integer from self in big-endian byte order.

fn get_i32_le(&mut self) -> i32

Gets a signed 32 bit integer from self in little-endian byte order.

fn get_u64(&mut self) -> u64

Gets an unsigned 64 bit integer from self in big-endian byte order.

fn get_u64_le(&mut self) -> u64

Gets an unsigned 64 bit integer from self in little-endian byte order.

fn get_i64(&mut self) -> i64

Gets a signed 64 bit integer from self in big-endian byte order.

fn get_i64_le(&mut self) -> i64

Gets a signed 64 bit integer from self in little-endian byte order.

fn get_u128(&mut self) -> u128

Gets an unsigned 128 bit integer from self in big-endian byte order.

fn get_u128_le(&mut self) -> u128

Gets an unsigned 128 bit integer from self in little-endian byte order.

fn get_i128(&mut self) -> i128

Gets a signed 128 bit integer from self in big-endian byte order.

fn get_i128_le(&mut self) -> i128

Gets a signed 128 bit integer from self in little-endian byte order.

fn get_uint(&mut self, nbytes: usize) -> u64

Gets an unsigned n-byte integer from self in big-endian byte order.

fn get_uint_le(&mut self, nbytes: usize) -> u64

Gets an unsigned n-byte integer from self in little-endian byte order.

fn get_int(&mut self, nbytes: usize) -> i64

Gets a signed n-byte integer from self in big-endian byte order.

fn get_int_le(&mut self, nbytes: usize) -> i64

Gets a signed n-byte integer from self in little-endian byte order.

fn get_f32(&mut self) -> f32

Gets an IEEE754 single-precision (4 bytes) floating point number from self in big-endian byte order.

fn get_f32_le(&mut self) -> f32

Gets an IEEE754 single-precision (4 bytes) floating point number from self in little-endian byte order.

fn get_f64(&mut self) -> f64

Gets an IEEE754 double-precision (8 bytes) floating point number from self in big-endian byte order.

fn get_f64_le(&mut self) -> f64

Gets an IEEE754 double-precision (8 bytes) floating point number from self in little-endian byte order.

fn copy_to_bytes(&mut self, len: usize) -> Bytes

Consumes len bytes inside self and returns new instance of Bytes with this data.

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

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

fn chain<U>(self, next: U) -> Chain<Self, U> where
    U: Buf, 

Creates an adaptor which will chain this buffer with another.

fn reader(self) -> Reader<Self>

Creates an adaptor which implements the Read trait for self.

impl<T> BufRead for Cursor<T> where
    T: AsRef<[u8]>, 

pub fn fill_buf(&mut self) -> Result<&[u8], Error>

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

pub fn consume(&mut self, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read.

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

Read all bytes into buf until the delimiter byte or EOF is reached.

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

Read all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer.

fn split(self, byte: u8) -> Split<Self>

Returns an iterator over the contents of this reader split on the byte byte.

fn lines(self) -> Lines<Self>

Returns an iterator over the lines of this reader.

impl<T> Clone for Cursor<T> where
    T: Clone, 

pub fn clone(&self) -> Cursor<T>

Returns a copy of the value.

pub fn clone_from(&mut self, other: &Cursor<T>)

Performs copy-assignment from source.

impl<T> Debug for Cursor<T> where
    T: Debug, 

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

Formats the value using the given formatter.

impl<T> Default for Cursor<T> where
    T: Default, 

pub fn default() -> Cursor<T>

Returns the “default value” for a type.

impl<T> PartialEq<Cursor<T>> for Cursor<T> where
    T: PartialEq<T>, 

pub fn eq(&self, other: &Cursor<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

pub fn ne(&self, other: &Cursor<T>) -> bool

This method tests for !=.

impl<T> Read for Cursor<T> where
    T: AsRef<[u8]>, 

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

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

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

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

pub 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.

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

Read the exact number of bytes required to fill buf.

pub 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, 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 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 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<T> Seek for Cursor<T> where
    T: AsRef<[u8]>, 

pub fn seek(&mut self, style: SeekFrom) -> Result<u64, Error>

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

pub 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).

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

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

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

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

Rewind to the beginning of a stream.

impl Write for Cursor<Box<[u8], Global>>

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

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

pub fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

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

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 writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

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

Attempts to write multiple buffers into this writer.

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.

impl<'_> Write for Cursor<&'_ mut Vec<u8, Global>>

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

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

pub fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

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

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 writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

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

Attempts to write multiple buffers into this writer.

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.

impl<'_> Write for Cursor<&'_ mut [u8]>

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

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

pub fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

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

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 writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

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

Attempts to write multiple buffers into this writer.

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.

impl Write for Cursor<Vec<u8, Global>>

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

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

pub fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

pub fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

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

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 writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

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

Attempts to write multiple buffers into this writer.

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.

impl<T> Eq for Cursor<T> where
    T: Eq, 

impl<T> StructuralEq for Cursor<T>

impl<T> StructuralPartialEq for Cursor<T>