use crate::encoder::Encoder;
#[derive(Debug, Eq, PartialEq, PartialOrd, Ord)]
pub struct EncoderBuffer<'a> {
bytes: &'a mut [u8],
position: usize,
}
impl<'a> EncoderBuffer<'a> {
#[inline]
pub fn new(bytes: &'a mut [u8]) -> Self {
Self { bytes, position: 0 }
}
#[inline]
pub fn set_position(&mut self, position: usize) {
debug_assert!(
position <= self.capacity(),
"position {position} exceeded capacity of {}",
self.capacity()
);
self.position = position;
}
#[inline]
pub fn advance_position(&mut self, offset: usize) {
let position = self.position + offset;
self.set_position(position)
}
#[inline]
pub fn split_off(self) -> (&'a mut [u8], &'a mut [u8]) {
self.bytes.split_at_mut(self.position)
}
#[inline]
pub fn split_mut(&mut self) -> (&mut [u8], &mut [u8]) {
self.bytes.split_at_mut(self.position)
}
#[inline]
pub fn as_mut_slice(&mut self) -> &mut [u8] {
unsafe { self.bytes.get_unchecked_mut(..self.position) }
}
#[inline]
pub(crate) fn assert_capacity(&self, len: usize) {
debug_assert!(
len <= self.remaining_capacity(),
"not enough buffer capacity. wanted: {}, available: {}",
len,
self.remaining_capacity()
);
}
}
impl<'a> Encoder for EncoderBuffer<'a> {
#[inline]
fn write_sized<F: FnOnce(&mut [u8])>(&mut self, len: usize, write: F) {
self.assert_capacity(len);
let end = self.position + len;
let bytes = unsafe {
self.bytes.get_unchecked_mut(self.position..end)
};
write(bytes);
self.position = end;
}
#[inline]
fn write_slice(&mut self, slice: &[u8]) {
self.write_sized(slice.len(), |dest| dest.copy_from_slice(slice));
}
#[inline]
fn write_repeated(&mut self, count: usize, value: u8) {
self.write_sized(count, |dest| {
for byte in dest {
*byte = value;
}
})
}
#[inline]
fn write_zerocopy<
T: zerocopy::AsBytes + zerocopy::FromBytes + zerocopy::Unaligned,
F: FnOnce(&mut T),
>(
&mut self,
write: F,
) {
let len = core::mem::size_of::<T>();
self.write_sized(len, |bytes| {
let value = unsafe {
&mut *(bytes as *mut _ as *mut T)
};
write(value)
})
}
#[inline]
fn capacity(&self) -> usize {
self.bytes.len()
}
#[inline]
fn len(&self) -> usize {
self.position
}
}