cursor

import std::io::cursor; · source

Cursor#

type struct Cursor {
    buffer: Array<u8>;
    pos:    u64;

    static new(buffer: Array<u8>) -> Cursor;
    static empty() -> Cursor;
    position(&this) -> u64;
    set_position(mut &this, pos: u64) -> void;
    len(&this) -> u64;
    as_bytes(&this) -> Slice<u8>;
    into_inner(mut &this) -> Array<u8>;
}

An in-memory byte buffer that is Read, Write, and Seek. This is how you run code written against the I/O traits against memory instead of a file or socket — the standard way to unit-test a reader or writer, or to build up a payload before handing it to a real sink.

import std::io::cursor;

mut c: Cursor = Cursor::empty();
c.write(header);
c.write(body);
mut bytes: Array<u8> = c.into_inner();

new(buffer) takes ownership of an existing buffer with the cursor at 0; empty() starts fresh. into_inner() moves the buffer out and leaves the cursor holding a fresh empty one.

Reads copy forward and return 0 at the end. Writes overwrite the bytes under the cursor and extend past the end; a write starting beyond the current end zero-fills the gap first, matching the sparse region a File seek-past-end leaves. Reads never error, and writes fail only on allocation failure, surfaced as WriteZero.

Trait implementations#

implement trait Read for struct Cursor

implement trait Write for struct Cursor

implement trait Seek for struct Cursor

implement trait Drop for struct Cursor