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use core::fmt;
use crate::allocate::Allocator;
use crate::weak_slice::WeakSliceMut;
pub struct ReadBuf<'a> {
buf: WeakSliceMut<'a, u8>,
filled: usize,
}
impl<'a> ReadBuf<'a> {
/// Pointer to the start of the `ReadBuf`
#[inline]
pub fn as_mut_ptr(&mut self) -> *mut u8 {
self.buf.as_mut_ptr()
}
/// Returns the total capacity of the buffer.
#[inline]
pub fn capacity(&self) -> usize {
self.buf.len()
}
/// Returns the length of the filled part of the buffer
#[inline]
pub fn len(&self) -> usize {
self.filled
}
/// Returns true if there are no bytes in this ReadBuf
#[inline]
pub fn is_empty(&self) -> bool {
self.filled == 0
}
/// Returns a shared reference to the filled portion of the buffer.
#[inline]
pub fn filled(&self) -> &[u8] {
&self.buf.as_slice()[..self.filled]
}
/// Clears the buffer, resetting the filled region to empty.
///
/// The number of initialized bytes is not changed, and the contents of the buffer are not modified.
#[inline]
pub fn clear(&mut self) {
self.buf.as_mut_slice().fill(0);
self.filled = 0;
}
#[inline(always)]
pub fn push_lit(&mut self, byte: u8) {
// NOTE: we rely on the buffer being zeroed here!
self.buf.as_mut_slice()[self.filled + 2] = byte;
self.filled += 3;
}
#[inline(always)]
pub fn push_dist(&mut self, dist: u16, len: u8) {
let buf = &mut self.buf.as_mut_slice()[self.filled..][..3];
let [dist1, dist2] = dist.to_le_bytes();
buf[0] = dist1;
buf[1] = dist2;
buf[2] = len;
self.filled += 3;
}
pub(crate) fn new_in(alloc: &Allocator<'a>, len: usize) -> Option<Self> {
let ptr = alloc.allocate_zeroed(len)?;
// safety: all elements are now initialized
let buf = unsafe { WeakSliceMut::from_raw_parts_mut(ptr.as_ptr(), len) };
Some(Self { buf, filled: 0 })
}
pub(crate) fn clone_in(&self, alloc: &Allocator<'a>) -> Option<Self> {
let mut clone = Self::new_in(alloc, self.buf.len())?;
clone
.buf
.as_mut_slice()
.copy_from_slice(self.buf.as_slice());
clone.filled = self.filled;
Some(clone)
}
pub(crate) unsafe fn drop_in(&mut self, alloc: &Allocator<'a>) {
if !self.buf.is_empty() {
let mut buf = core::mem::replace(&mut self.buf, WeakSliceMut::empty());
alloc.deallocate(buf.as_mut_ptr(), buf.len());
}
}
}
impl fmt::Debug for ReadBuf<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ReadBuf")
.field("filled", &self.filled)
.field("capacity", &self.capacity())
.finish()
}
}