1 //! Buffer management for same-process client<->server communication.
3 use std::io::{self, Write};
5 use std::ops::{Deref, DerefMut};
14 unsafe impl<'a, T: Sync> Sync for Slice<'a, T> {}
15 unsafe impl<'a, T: Sync> Send for Slice<'a, T> {}
17 impl<T> Copy for Slice<'a, T> {}
18 impl<T> Clone for Slice<'a, T> {
19 fn clone(&self) -> Self {
24 impl<T> From<&'a [T]> for Slice<'a, T> {
25 fn from(xs: &'a [T]) -> Self {
26 Slice { data: unsafe { &*(xs.as_ptr() as *const [T; 0]) }, len: xs.len() }
30 impl<T> Deref for Slice<'a, T> {
32 fn deref(&self) -> &[T] {
33 unsafe { slice::from_raw_parts(self.data.as_ptr(), self.len) }
38 pub struct Buffer<T: Copy> {
42 extend_from_slice: extern "C" fn(Buffer<T>, Slice<'_, T>) -> Buffer<T>,
43 drop: extern "C" fn(Buffer<T>),
46 unsafe impl<T: Copy + Sync> Sync for Buffer<T> {}
47 unsafe impl<T: Copy + Send> Send for Buffer<T> {}
49 impl<T: Copy> Default for Buffer<T> {
50 fn default() -> Self {
55 impl<T: Copy> Deref for Buffer<T> {
57 fn deref(&self) -> &[T] {
58 unsafe { slice::from_raw_parts(self.data as *const T, self.len) }
62 impl<T: Copy> DerefMut for Buffer<T> {
63 fn deref_mut(&mut self) -> &mut [T] {
64 unsafe { slice::from_raw_parts_mut(self.data, self.len) }
68 impl<T: Copy> Buffer<T> {
69 pub(super) fn new() -> Self {
73 pub(super) fn clear(&mut self) {
77 pub(super) fn take(&mut self) -> Self {
81 pub(super) fn extend_from_slice(&mut self, xs: &[T]) {
82 // Fast path to avoid going through an FFI call.
83 if let Some(final_len) = self.len.checked_add(xs.len()) {
84 if final_len <= self.capacity {
85 let dst = unsafe { slice::from_raw_parts_mut(self.data, self.capacity) };
86 dst[self.len..][..xs.len()].copy_from_slice(xs);
92 *self = (b.extend_from_slice)(b, Slice::from(xs));
96 impl Write for Buffer<u8> {
97 fn write(&mut self, xs: &[u8]) -> io::Result<usize> {
98 self.extend_from_slice(xs);
102 fn write_all(&mut self, xs: &[u8]) -> io::Result<()> {
103 self.extend_from_slice(xs);
107 fn flush(&mut self) -> io::Result<()> {
112 impl<T: Copy> Drop for Buffer<T> {
119 impl<T: Copy> From<Vec<T>> for Buffer<T> {
120 fn from(mut v: Vec<T>) -> Self {
121 let (data, len, capacity) = (v.as_mut_ptr(), v.len(), v.capacity());
124 // This utility function is nested in here because it can *only*
125 // be safely called on `Buffer`s created by *this* `proc_macro`.
126 fn to_vec<T: Copy>(b: Buffer<T>) -> Vec<T> {
128 let Buffer { data, len, capacity, .. } = b;
130 Vec::from_raw_parts(data, len, capacity)
134 extern "C" fn extend_from_slice<T: Copy>(b: Buffer<T>, xs: Slice<'_, T>) -> Buffer<T> {
135 let mut v = to_vec(b);
136 v.extend_from_slice(&xs);
140 extern "C" fn drop<T: Copy>(b: Buffer<T>) {
141 mem::drop(to_vec(b));
144 Buffer { data, len, capacity, extend_from_slice, drop }