1 | use core::slice; |
2 | use core::convert::TryInto; |
3 | use core::convert::TryFrom; |
4 | |
5 | pub struct Bytes<'a> { |
6 | slice: &'a [u8], |
7 | pos: usize |
8 | } |
9 | |
10 | impl<'a> Bytes<'a> { |
11 | #[inline ] |
12 | pub fn new(slice: &'a [u8]) -> Bytes<'a> { |
13 | Bytes { |
14 | slice, |
15 | pos: 0 |
16 | } |
17 | } |
18 | |
19 | #[inline ] |
20 | pub fn pos(&self) -> usize { |
21 | self.pos |
22 | } |
23 | |
24 | #[inline ] |
25 | pub fn peek(&self) -> Option<u8> { |
26 | self.peek_ahead(0) |
27 | } |
28 | |
29 | #[inline ] |
30 | pub fn peek_ahead(&self, n: usize) -> Option<u8> { |
31 | self.slice.get(self.pos + n).copied() |
32 | } |
33 | |
34 | #[inline ] |
35 | pub fn peek_n<U: TryFrom<&'a[u8]>>(&self, n: usize) -> Option<U> { |
36 | self.slice.get(self.pos..self.pos + n)?.try_into().ok() |
37 | } |
38 | |
39 | #[inline ] |
40 | pub unsafe fn bump(&mut self) { |
41 | debug_assert!(self.pos < self.slice.len(), "overflow" ); |
42 | self.pos += 1; |
43 | } |
44 | |
45 | #[allow (unused)] |
46 | #[inline ] |
47 | pub unsafe fn advance(&mut self, n: usize) { |
48 | debug_assert!(self.pos + n <= self.slice.len(), "overflow" ); |
49 | self.pos += n; |
50 | } |
51 | |
52 | #[inline ] |
53 | pub fn len(&self) -> usize { |
54 | self.slice.len() |
55 | } |
56 | |
57 | #[inline ] |
58 | pub fn slice(&mut self) -> &'a [u8] { |
59 | // not moving position at all, so it's safe |
60 | unsafe { |
61 | self.slice_skip(0) |
62 | } |
63 | } |
64 | |
65 | #[inline ] |
66 | pub unsafe fn slice_skip(&mut self, skip: usize) -> &'a [u8] { |
67 | debug_assert!(self.pos >= skip); |
68 | let head_pos = self.pos - skip; |
69 | let ptr = self.slice.as_ptr(); |
70 | let head = slice::from_raw_parts(ptr, head_pos); |
71 | let tail = slice::from_raw_parts(ptr.add(self.pos), self.slice.len() - self.pos); |
72 | self.pos = 0; |
73 | self.slice = tail; |
74 | head |
75 | } |
76 | |
77 | #[inline ] |
78 | pub unsafe fn advance_and_commit(&mut self, n: usize) { |
79 | debug_assert!(self.pos + n <= self.slice.len(), "overflow" ); |
80 | self.pos += n; |
81 | let ptr = self.slice.as_ptr(); |
82 | let tail = slice::from_raw_parts(ptr.add(n), self.slice.len() - n); |
83 | self.pos = 0; |
84 | self.slice = tail; |
85 | } |
86 | } |
87 | |
88 | impl<'a> AsRef<[u8]> for Bytes<'a> { |
89 | #[inline ] |
90 | fn as_ref(&self) -> &[u8] { |
91 | &self.slice[self.pos..] |
92 | } |
93 | } |
94 | |
95 | impl<'a> Iterator for Bytes<'a> { |
96 | type Item = u8; |
97 | |
98 | #[inline ] |
99 | fn next(&mut self) -> Option<u8> { |
100 | if self.slice.len() > self.pos { |
101 | let b: u8 = unsafe { *self.slice.get_unchecked(self.pos) }; |
102 | self.pos += 1; |
103 | Some(b) |
104 | } else { |
105 | None |
106 | } |
107 | } |
108 | } |
109 | |