Struct eos_rs::api::io::Cursor

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pub struct Cursor<T> { /* private fields */ }

Expand description

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.

acid_io implements some I/O traits on various types which are commonly used as a buffer, like Cursor<Vec<u8>> and Cursor<&[u8]>.

Examples

use acid_io::{self, Read, Seek, SeekFrom, Write};

// a library function we've written
fn write_ten_bytes_at_end<W: Write + Seek>(writer: &mut W) -> acid_io::Result<()> {
    writer.seek(SeekFrom::End(-10))?;

    for i in 0..10 {
        writer.write(&[i])?;
    }

    // all went well
    Ok(())
}

// now let's write a test
#[test]
fn test_writes_bytes() {
    use acid_io::Cursor;
    let mut buf = Cursor::new(vec![0; 15]);

    write_ten_bytes_at_end(&mut buf).unwrap();

    assert_eq!(&buf.get_ref()[5..15], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
}

Implementations§

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impl<T> Cursor<T>

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

Creates a new cursor wrapping the provided underlying in-memory buffer.

The initial position of the cursor is 0 even if the underlying buffer is not empty.

Examples

use acid_io::Cursor;

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

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pub fn into_inner(self) -> T

Consumes this cursor, returning the underlying value.

Examples

use acid_io::Cursor;

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

let vec = buf.into_inner();

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

Gets a reference to the underlying value in this cursor.

Examples

use acid_io::Cursor;

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

let reference = buf.get_ref();

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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 acid_io::Cursor;

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

let reference = buf.get_mut();

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pub const fn position(&self) -> u64

Returns the current position of this cursor.

Examples

use acid_io::prelude::*;
use acid_io::{Cursor, SeekFrom};

let mut buf = Cursor::new(vec![1, 2, 3, 4, 5]);

assert_eq!(buf.position(), 0);

buf.seek(SeekFrom::Current(2)).unwrap();
assert_eq!(buf.position(), 2);

buf.seek(SeekFrom::Current(-1)).unwrap();
assert_eq!(buf.position(), 1);

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pub fn set_position(&mut self, pos: u64)

Sets the position of this cursor.

Examples

use acid_io::Cursor;

let mut buf = Cursor::new(vec![1, 2, 3, 4, 5]);

assert_eq!(buf.position(), 0);

buf.set_position(2);
assert_eq!(buf.position(), 2);

buf.set_position(4);
assert_eq!(buf.position(), 4);

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

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

Returns the remaining slice.

Examples

use acid_io::Cursor;

let mut buf = Cursor::new(vec![1, 2, 3, 4, 5]);

assert_eq!(buf.remaining_slice(), &[1, 2, 3, 4, 5]);

buf.set_position(2);
assert_eq!(buf.remaining_slice(), &[3, 4, 5]);

buf.set_position(4);
assert_eq!(buf.remaining_slice(), &[5]);

buf.set_position(6);
assert_eq!(buf.remaining_slice(), &[]);

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pub fn is_empty(&self) -> bool

Returns true if the remaining slice is empty.

Examples

use acid_io::Cursor;

let mut buf = Cursor::new(vec![1, 2, 3, 4, 5]);

buf.set_position(2);
assert!(!buf.is_empty());

buf.set_position(5);
assert!(buf.is_empty());

buf.set_position(10);
assert!(buf.is_empty());