1 //! lib-proc-macro Buffer management for same-process client<->server communication.
3 //! Copy from <https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/buffer.rs>
4 //! augmented with removing unstable features
6 use std::io::{self, Write};
8 use std::ops::{Deref, DerefMut};
17 unsafe impl<'a, T: Sync> Sync for Slice<'a, T> {}
18 unsafe impl<'a, T: Sync> Send for Slice<'a, T> {}
20 impl<'a, T> Copy for Slice<'a, T> {}
21 impl<'a, T> Clone for Slice<'a, T> {
22 fn clone(&self) -> Self {
27 impl<'a, T> From<&'a [T]> for Slice<'a, T> {
28 fn from(xs: &'a [T]) -> Self {
29 Slice { data: unsafe { &*(xs.as_ptr() as *const [T; 0]) }, len: xs.len() }
33 impl<'a, T> Deref for Slice<'a, T> {
35 fn deref(&self) -> &[T] {
36 unsafe { slice::from_raw_parts(self.data.as_ptr(), self.len) }
41 pub struct Buffer<T: Copy> {
45 extend_from_slice: extern "C" fn(Buffer<T>, Slice<'_, T>) -> Buffer<T>,
46 drop: extern "C" fn(Buffer<T>),
49 unsafe impl<T: Copy + Sync> Sync for Buffer<T> {}
50 unsafe impl<T: Copy + Send> Send for Buffer<T> {}
52 impl<T: Copy> Default for Buffer<T> {
53 fn default() -> Self {
58 impl<T: Copy> Deref for Buffer<T> {
60 fn deref(&self) -> &[T] {
61 unsafe { slice::from_raw_parts(self.data as *const T, self.len) }
65 impl<T: Copy> DerefMut for Buffer<T> {
66 fn deref_mut(&mut self) -> &mut [T] {
67 unsafe { slice::from_raw_parts_mut(self.data, self.len) }
71 impl<T: Copy> Buffer<T> {
72 pub(super) fn new() -> Self {
76 pub(super) fn clear(&mut self) {
80 pub(super) fn take(&mut self) -> Self {
84 pub(super) fn extend_from_slice(&mut self, xs: &[T]) {
85 // Fast path to avoid going through an FFI call.
86 if let Some(final_len) = self.len.checked_add(xs.len()) {
87 if final_len <= self.capacity {
88 let dst = unsafe { slice::from_raw_parts_mut(self.data, self.capacity) };
89 dst[self.len..][..xs.len()].copy_from_slice(xs);
95 *self = (b.extend_from_slice)(b, Slice::from(xs));
99 impl Write for Buffer<u8> {
100 fn write(&mut self, xs: &[u8]) -> io::Result<usize> {
101 self.extend_from_slice(xs);
105 fn write_all(&mut self, xs: &[u8]) -> io::Result<()> {
106 self.extend_from_slice(xs);
110 fn flush(&mut self) -> io::Result<()> {
115 impl<T: Copy> Drop for Buffer<T> {
122 impl<T: Copy> From<Vec<T>> for Buffer<T> {
123 fn from(mut v: Vec<T>) -> Self {
124 let (data, len, capacity) = (v.as_mut_ptr(), v.len(), v.capacity());
127 // This utility function is nested in here because it can *only*
128 // be safely called on `Buffer`s created by *this* `proc_macro`.
129 fn to_vec<T: Copy>(b: Buffer<T>) -> Vec<T> {
131 let Buffer { data, len, capacity, .. } = b;
133 Vec::from_raw_parts(data, len, capacity)
137 extern "C" fn extend_from_slice<T: Copy>(b: Buffer<T>, xs: Slice<'_, T>) -> Buffer<T> {
138 let mut v = to_vec(b);
139 v.extend_from_slice(&xs);
143 extern "C" fn drop<T: Copy>(b: Buffer<T>) {
144 mem::drop(to_vec(b));
147 Buffer { data, len, capacity, extend_from_slice, drop }