| //! Buffer management for same-process client<->server communication. |
| |
| use std::io::{self, Write}; |
| use std::mem; |
| use std::ops::{Deref, DerefMut}; |
| use std::slice; |
| |
| #[repr(C)] |
| struct Slice<'a, T> { |
| data: &'a [T; 0], |
| len: usize, |
| } |
| |
| unsafe impl<'a, T: Sync> Sync for Slice<'a, T> {} |
| unsafe impl<'a, T: Sync> Send for Slice<'a, T> {} |
| |
| impl<T> Copy for Slice<'a, T> {} |
| impl<T> Clone for Slice<'a, T> { |
| fn clone(&self) -> Self { |
| *self |
| } |
| } |
| |
| impl<T> From<&'a [T]> for Slice<'a, T> { |
| fn from(xs: &'a [T]) -> Self { |
| Slice { |
| data: unsafe { &*(xs.as_ptr() as *const [T; 0]) }, |
| len: xs.len(), |
| } |
| } |
| } |
| |
| impl<T> Deref for Slice<'a, T> { |
| type Target = [T]; |
| fn deref(&self) -> &[T] { |
| unsafe { slice::from_raw_parts(self.data.as_ptr(), self.len) } |
| } |
| } |
| |
| #[repr(C)] |
| pub struct Buffer<T: Copy> { |
| data: *mut T, |
| len: usize, |
| capacity: usize, |
| extend_from_slice: extern "C" fn(Buffer<T>, Slice<'_, T>) -> Buffer<T>, |
| drop: extern "C" fn(Buffer<T>), |
| } |
| |
| unsafe impl<T: Copy + Sync> Sync for Buffer<T> {} |
| unsafe impl<T: Copy + Send> Send for Buffer<T> {} |
| |
| impl<T: Copy> Default for Buffer<T> { |
| fn default() -> Self { |
| Self::from(vec![]) |
| } |
| } |
| |
| impl<T: Copy> Deref for Buffer<T> { |
| type Target = [T]; |
| fn deref(&self) -> &[T] { |
| unsafe { slice::from_raw_parts(self.data as *const T, self.len) } |
| } |
| } |
| |
| impl<T: Copy> DerefMut for Buffer<T> { |
| fn deref_mut(&mut self) -> &mut [T] { |
| unsafe { slice::from_raw_parts_mut(self.data, self.len) } |
| } |
| } |
| |
| impl<T: Copy> Buffer<T> { |
| pub(super) fn new() -> Self { |
| Self::default() |
| } |
| |
| pub(super) fn clear(&mut self) { |
| self.len = 0; |
| } |
| |
| pub(super) fn take(&mut self) -> Self { |
| mem::take(self) |
| } |
| |
| pub(super) fn extend_from_slice(&mut self, xs: &[T]) { |
| // Fast path to avoid going through an FFI call. |
| if let Some(final_len) = self.len.checked_add(xs.len()) { |
| if final_len <= self.capacity { |
| let dst = unsafe { slice::from_raw_parts_mut(self.data, self.capacity) }; |
| dst[self.len..][..xs.len()].copy_from_slice(xs); |
| self.len = final_len; |
| return; |
| } |
| } |
| let b = self.take(); |
| *self = (b.extend_from_slice)(b, Slice::from(xs)); |
| } |
| } |
| |
| impl Write for Buffer<u8> { |
| fn write(&mut self, xs: &[u8]) -> io::Result<usize> { |
| self.extend_from_slice(xs); |
| Ok(xs.len()) |
| } |
| |
| fn write_all(&mut self, xs: &[u8]) -> io::Result<()> { |
| self.extend_from_slice(xs); |
| Ok(()) |
| } |
| |
| fn flush(&mut self) -> io::Result<()> { |
| Ok(()) |
| } |
| } |
| |
| impl<T: Copy> Drop for Buffer<T> { |
| fn drop(&mut self) { |
| let b = self.take(); |
| (b.drop)(b); |
| } |
| } |
| |
| impl<T: Copy> From<Vec<T>> for Buffer<T> { |
| fn from(mut v: Vec<T>) -> Self { |
| let (data, len, capacity) = (v.as_mut_ptr(), v.len(), v.capacity()); |
| mem::forget(v); |
| |
| // This utility function is nested in here because it can *only* |
| // be safely called on `Buffer`s created by *this* `proc_macro`. |
| fn to_vec<T: Copy>(b: Buffer<T>) -> Vec<T> { |
| unsafe { |
| let Buffer { |
| data, |
| len, |
| capacity, |
| .. |
| } = b; |
| mem::forget(b); |
| Vec::from_raw_parts(data, len, capacity) |
| } |
| } |
| |
| extern "C" fn extend_from_slice<T: Copy>(b: Buffer<T>, xs: Slice<'_, T>) -> Buffer<T> { |
| let mut v = to_vec(b); |
| v.extend_from_slice(&xs); |
| Buffer::from(v) |
| } |
| |
| extern "C" fn drop<T: Copy>(b: Buffer<T>) { |
| mem::drop(to_vec(b)); |
| } |
| |
| Buffer { |
| data, |
| len, |
| capacity, |
| extend_from_slice, |
| drop, |
| } |
| } |
| } |