Trait WriteBuf

pub unsafe trait WriteBuf {
    // Required methods
    fn as_slice(&self) -> &[u8] ;
    fn capacity(&self) -> usize;
    fn as_mut_ptr(&mut self) -> *mut u8;
    unsafe fn filled_until(&mut self, n: usize);

    // Provided method
    unsafe fn write_from<F>(&mut self, f: F) -> Result<usize, usize>
       where F: FnOnce(*mut c_void, usize) -> Result<usize, usize> { ... }
}

Describe a bytes container, like Vec<u8>.

Represents a contiguous segment of allocated memory, a prefix of which is initialized.

It allows starting from an uninitializes chunk of memory and writing to it, progressively initializing it. No re-allocation typically occur after the initial creation.

The main implementors are:

• Vec<u8> and similar structures. These hold both a length (initialized data) and a capacity (allocated memory).

  Use Vec::with_capacity to create an empty Vec with non-zero capacity, and the length field will be updated to cover the data written to it (as long as it fits in the given capacity).

• [u8] and [u8; N]. These must start already-initialized, and will not be resized. It will be up to the caller to only use the part that was written (as returned by the various writing operations).

• std::io::Cursor<T: WriteBuf>. This will ignore data before the cursor’s position, and append data after that.

Required Methods

fn as_slice(&self) -> &[u8]

Returns the valid data part of this container. Should only cover initialized data.

fn capacity(&self) -> usize

Returns the full capacity of this container. May include uninitialized data.

fn as_mut_ptr(&mut self) -> *mut u8

Returns a pointer to the start of the data.

unsafe fn filled_until(&mut self, n: usize)

Indicates that the first n bytes of the container have been written.

Safety: this should only be called if the n first bytes of this buffer have actually been initialized.

Provided Methods

unsafe fn write_from<F>(&mut self, f: F) -> Result<usize, usize>

where F: FnOnce(*mut c_void, usize) -> Result<usize, usize>,

Call the given closure using the pointer and capacity from self.

Assumes the given function returns a parseable code, which if valid, represents how many bytes were written to self.

The given closure must treat its first argument as pointing to potentially uninitialized memory, and should not read from it.

In addition, it must have written at least n bytes contiguously from this pointer, where n is the returned value.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl WriteBuf for Vec<u8>

fn as_slice(&self) -> &[u8]

fn capacity(&self) -> usize

fn as_mut_ptr(&mut self) -> *mut u8

unsafe fn filled_until(&mut self, n: usize)

impl WriteBuf for [u8]

fn as_slice(&self) -> &[u8]

fn capacity(&self) -> usize

fn as_mut_ptr(&mut self) -> *mut u8

unsafe fn filled_until(&mut self, _n: usize)

impl<'a> WriteBuf for &'a mut Vec<u8>

fn as_slice(&self) -> &[u8]

fn capacity(&self) -> usize

fn as_mut_ptr(&mut self) -> *mut u8

unsafe fn filled_until(&mut self, n: usize)

impl<T> WriteBuf for Cursor<T>

where T: WriteBuf,

fn as_slice(&self) -> &[u8]

fn capacity(&self) -> usize

fn as_mut_ptr(&mut self) -> *mut u8

unsafe fn filled_until(&mut self, n: usize)

impl<const N: usize> WriteBuf for [u8; N]

fn as_slice(&self) -> &[u8]

fn capacity(&self) -> usize

fn as_mut_ptr(&mut self) -> *mut u8

unsafe fn filled_until(&mut self, _n: usize)

Implementors