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use core::marker::PhantomData;
use crate::allocate::Allocator;
pub struct Pending<'a> {
buf: *mut u8,
out: *mut u8,
pub(crate) pending: usize,
end: *mut u8,
_marker: PhantomData<&'a mut [u8]>,
}
impl<'a> Pending<'a> {
pub fn reset_keep(&mut self) {
// keep the buffer as it is
self.pending = 0;
}
pub fn pending(&self) -> &[u8] {
unsafe { core::slice::from_raw_parts(self.out, self.pending) }
}
pub(crate) fn remaining(&self) -> usize {
self.end as usize - self.out as usize
}
pub(crate) fn capacity(&self) -> usize {
self.end as usize - self.buf as usize
}
#[inline(always)]
#[track_caller]
pub fn advance(&mut self, n: usize) {
assert!(n <= self.remaining(), "advancing past the end");
debug_assert!(self.pending >= n);
self.out = self.out.wrapping_add(n);
self.pending -= n;
if self.pending == 0 {
self.out = self.buf;
}
}
#[inline(always)]
#[track_caller]
pub fn rewind(&mut self, n: usize) {
assert!(n <= self.pending, "rewinding past then start");
self.pending -= n;
}
#[inline(always)]
#[track_caller]
pub fn extend(&mut self, buf: &[u8]) {
assert!(
self.remaining() >= buf.len(),
"buf.len() must fit in remaining()"
);
unsafe {
core::ptr::copy_nonoverlapping(buf.as_ptr(), self.out.add(self.pending), buf.len());
}
self.pending += buf.len();
}
pub(crate) fn new_in(alloc: &Allocator<'a>, len: usize) -> Option<Self> {
let range = alloc.allocate_slice::<u8>(len)?.as_mut_ptr_range();
Some(Self {
buf: range.start as *mut u8,
out: range.start as *mut u8,
end: range.end as *mut u8,
pending: 0,
_marker: PhantomData,
})
}
pub(crate) fn clone_in(&self, alloc: &Allocator<'a>) -> Option<Self> {
let len = self.end as usize - self.buf as usize;
let mut clone = Self::new_in(alloc, len)?;
unsafe { core::ptr::copy_nonoverlapping(self.buf, clone.buf, len) };
clone.out = unsafe { clone.buf.add(self.out as usize - self.buf as usize) };
clone.pending = self.pending;
Some(clone)
}
pub(crate) unsafe fn drop_in(&self, alloc: &Allocator) {
let len = self.end as usize - self.buf as usize;
alloc.deallocate(self.buf, len);
}
}