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//! Utility functions that are not specific to X11.
//!
//! # CSlice
//!
//! [`CSlice`] is a wrapper around some bytes in memory. It is unsafe to construct, but takes
//! ownership of the bytes and allows accessing them as a `[u8]`. When dropped, the underlying
//! memory is freed via [`libc::free`].
//!
//! `CSlice` is only available when the `allow-unsafe-code` feature is enabled.
pub use x11rb_protocol::RawFdContainer;
#[cfg(feature = "allow-unsafe-code")]
mod unsafe_code {
use std::mem::forget;
use std::ops::{Deref, Index};
use std::ptr::NonNull;
use std::slice::{from_raw_parts, SliceIndex};
use libc::free;
/// Wrapper around a slice that was allocated in C code.
///
/// `CSlice` is only available when the `allow-unsafe-code` feature is enabled.
pub struct CSlice {
ptr: NonNull<[u8]>,
}
// `CSlice` is `Send` and `Sync` because, once created, it is
// completely immutable (it does not have interior mutability),
// so it can be safely accessed from different threads simultaneously.
unsafe impl Send for CSlice {}
unsafe impl Sync for CSlice {}
impl CSlice {
/// Constructs a new `CSlice` from the given parts. `libc::free` will be called on the given
/// pointer when the slice is dropped.
///
/// # Safety
///
/// The same rules as for `std::slice::from_raw_parts` apply. Additionally, the given pointer
/// must be safe to free with `libc::free`.
pub unsafe fn new(ptr: *const u8, len: usize) -> CSlice {
CSlice {
ptr: NonNull::from(from_raw_parts(ptr, len)),
}
}
/// Convert `self` into a raw part.
///
/// Ownership of the returned pointer is given to the caller. Specifically, `libc::free` will
/// not be called on it by `CSlice`.
pub fn into_ptr(self) -> *const u8 {
let ptr = self.ptr.as_ptr() as *const u8;
forget(self);
ptr
}
}
impl Drop for CSlice {
fn drop(&mut self) {
unsafe { free(self.ptr.as_ptr() as _) }
}
}
impl Deref for CSlice {
type Target = [u8];
fn deref(&self) -> &[u8] {
unsafe { self.ptr.as_ref() }
}
}
impl AsRef<[u8]> for CSlice {
fn as_ref(&self) -> &[u8] {
self
}
}
impl<I> Index<I> for CSlice
where
I: SliceIndex<[u8]>,
{
type Output = I::Output;
fn index(&self, index: I) -> &I::Output {
(**self).index(index)
}
}
impl std::fmt::Debug for CSlice {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
std::fmt::Debug::fmt(&**self, f)
}
}
}
#[cfg(feature = "allow-unsafe-code")]
pub use unsafe_code::CSlice;