| //! 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)] |
| pub struct Buffer { |
| data: *mut u8, |
| len: usize, |
| capacity: usize, |
| reserve: extern "C" fn(Buffer, usize) -> Buffer, |
| drop: extern "C" fn(Buffer), |
| } |
| |
| unsafe impl Sync for Buffer {} |
| unsafe impl Send for Buffer {} |
| |
| impl Default for Buffer { |
| #[inline] |
| fn default() -> Self { |
| Self::from(vec![]) |
| } |
| } |
| |
| impl Deref for Buffer { |
| type Target = [u8]; |
| #[inline] |
| fn deref(&self) -> &[u8] { |
| unsafe { slice::from_raw_parts(self.data as *const u8, self.len) } |
| } |
| } |
| |
| impl DerefMut for Buffer { |
| #[inline] |
| fn deref_mut(&mut self) -> &mut [u8] { |
| unsafe { slice::from_raw_parts_mut(self.data, self.len) } |
| } |
| } |
| |
| impl Buffer { |
| #[inline] |
| pub(super) fn new() -> Self { |
| Self::default() |
| } |
| |
| #[inline] |
| pub(super) fn clear(&mut self) { |
| self.len = 0; |
| } |
| |
| #[inline] |
| pub(super) fn take(&mut self) -> Self { |
| mem::take(self) |
| } |
| |
| // We have the array method separate from extending from a slice. This is |
| // because in the case of small arrays, codegen can be more efficient |
| // (avoiding a memmove call). With extend_from_slice, LLVM at least |
| // currently is not able to make that optimization. |
| #[inline] |
| pub(super) fn extend_from_array<const N: usize>(&mut self, xs: &[u8; N]) { |
| if xs.len() > (self.capacity - self.len) { |
| let b = self.take(); |
| *self = (b.reserve)(b, xs.len()); |
| } |
| unsafe { |
| xs.as_ptr().copy_to_nonoverlapping(self.data.add(self.len), xs.len()); |
| self.len += xs.len(); |
| } |
| } |
| |
| #[inline] |
| pub(super) fn extend_from_slice(&mut self, xs: &[u8]) { |
| if xs.len() > (self.capacity - self.len) { |
| let b = self.take(); |
| *self = (b.reserve)(b, xs.len()); |
| } |
| unsafe { |
| xs.as_ptr().copy_to_nonoverlapping(self.data.add(self.len), xs.len()); |
| self.len += xs.len(); |
| } |
| } |
| |
| #[inline] |
| pub(super) fn push(&mut self, v: u8) { |
| // The code here is taken from Vec::push, and we know that reserve() |
| // will panic if we're exceeding isize::MAX bytes and so there's no need |
| // to check for overflow. |
| if self.len == self.capacity { |
| let b = self.take(); |
| *self = (b.reserve)(b, 1); |
| } |
| unsafe { |
| *self.data.add(self.len) = v; |
| self.len += 1; |
| } |
| } |
| } |
| |
| impl Write for Buffer { |
| #[inline] |
| fn write(&mut self, xs: &[u8]) -> io::Result<usize> { |
| self.extend_from_slice(xs); |
| Ok(xs.len()) |
| } |
| |
| #[inline] |
| fn write_all(&mut self, xs: &[u8]) -> io::Result<()> { |
| self.extend_from_slice(xs); |
| Ok(()) |
| } |
| |
| #[inline] |
| fn flush(&mut self) -> io::Result<()> { |
| Ok(()) |
| } |
| } |
| |
| impl Drop for Buffer { |
| #[inline] |
| fn drop(&mut self) { |
| let b = self.take(); |
| (b.drop)(b); |
| } |
| } |
| |
| impl From<Vec<u8>> for Buffer { |
| fn from(mut v: Vec<u8>) -> 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(b: Buffer) -> Vec<u8> { |
| unsafe { |
| let Buffer { data, len, capacity, .. } = b; |
| mem::forget(b); |
| Vec::from_raw_parts(data, len, capacity) |
| } |
| } |
| |
| extern "C" fn reserve(b: Buffer, additional: usize) -> Buffer { |
| let mut v = to_vec(b); |
| v.reserve(additional); |
| Buffer::from(v) |
| } |
| |
| extern "C" fn drop(b: Buffer) { |
| mem::drop(to_vec(b)); |
| } |
| |
| Buffer { data, len, capacity, reserve, drop } |
| } |
| } |