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use core::slice;
use core::convert::TryInto;
use core::convert::TryFrom;
pub struct Bytes<'a> {
slice: &'a [u8],
pos: usize
}
impl<'a> Bytes<'a> {
#[inline]
pub fn new(slice: &'a [u8]) -> Bytes<'a> {
Bytes {
slice,
pos: 0
}
}
#[inline]
pub fn pos(&self) -> usize {
self.pos
}
#[inline]
pub fn peek(&self) -> Option<u8> {
self.peek_ahead(0)
}
#[inline]
pub fn peek_ahead(&self, n: usize) -> Option<u8> {
self.slice.get(self.pos + n).copied()
}
#[inline]
pub fn peek_n<U: TryFrom<&'a[u8]>>(&self, n: usize) -> Option<U> {
self.slice.get(self.pos..self.pos + n)?.try_into().ok()
}
#[inline]
pub unsafe fn bump(&mut self) {
debug_assert!(self.pos < self.slice.len(), "overflow");
self.pos += 1;
}
#[allow(unused)]
#[inline]
pub unsafe fn advance(&mut self, n: usize) {
debug_assert!(self.pos + n <= self.slice.len(), "overflow");
self.pos += n;
}
#[inline]
pub fn len(&self) -> usize {
self.slice.len()
}
#[inline]
pub fn slice(&mut self) -> &'a [u8] {
// not moving position at all, so it's safe
unsafe {
self.slice_skip(0)
}
}
#[inline]
pub unsafe fn slice_skip(&mut self, skip: usize) -> &'a [u8] {
debug_assert!(self.pos >= skip);
let head_pos = self.pos - skip;
let ptr = self.slice.as_ptr();
let head = slice::from_raw_parts(ptr, head_pos);
let tail = slice::from_raw_parts(ptr.add(self.pos), self.slice.len() - self.pos);
self.pos = 0;
self.slice = tail;
head
}
#[inline]
pub unsafe fn advance_and_commit(&mut self, n: usize) {
debug_assert!(self.pos + n <= self.slice.len(), "overflow");
self.pos += n;
let ptr = self.slice.as_ptr();
let tail = slice::from_raw_parts(ptr.add(n), self.slice.len() - n);
self.pos = 0;
self.slice = tail;
}
}
impl<'a> AsRef<[u8]> for Bytes<'a> {
#[inline]
fn as_ref(&self) -> &[u8] {
&self.slice[self.pos..]
}
}
impl<'a> Iterator for Bytes<'a> {
type Item = u8;
#[inline]
fn next(&mut self) -> Option<u8> {
if self.slice.len() > self.pos {
let b = unsafe { *self.slice.get_unchecked(self.pos) };
self.pos += 1;
Some(b)
} else {
None
}
}
}