1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
//! Bit level parsers
//!
pub mod complete;
pub mod streaming;
use crate::error::{ErrorKind, ParseError};
use crate::internal::{Err, IResult, Needed, Parser};
use crate::lib::std::ops::RangeFrom;
use crate::traits::{ErrorConvert, Slice};
/// Converts a byte-level input to a bit-level input, for consumption by a parser that uses bits.
///
/// Afterwards, the input is converted back to a byte-level parser, with any remaining bits thrown
/// away.
///
/// # Example
/// ```
/// use nom::bits::{bits, streaming::take};
/// use nom::error::Error;
/// use nom::sequence::tuple;
/// use nom::IResult;
///
/// fn parse(input: &[u8]) -> IResult<&[u8], (u8, u8)> {
/// bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize))))(input)
/// }
///
/// let input = &[0x12, 0x34, 0xff, 0xff];
///
/// let output = parse(input).expect("We take 1.5 bytes and the input is longer than 2 bytes");
///
/// // The first byte is consumed, the second byte is partially consumed and dropped.
/// let remaining = output.0;
/// assert_eq!(remaining, [0xff, 0xff]);
///
/// let parsed = output.1;
/// assert_eq!(parsed.0, 0x01);
/// assert_eq!(parsed.1, 0x23);
/// ```
pub fn bits<I, O, E1, E2, P>(mut parser: P) -> impl FnMut(I) -> IResult<I, O, E2>
where
E1: ParseError<(I, usize)> + ErrorConvert<E2>,
E2: ParseError<I>,
I: Slice<RangeFrom<usize>>,
P: Parser<(I, usize), O, E1>,
{
move |input: I| match parser.parse((input, 0)) {
Ok(((rest, offset), result)) => {
// If the next byte has been partially read, it will be sliced away as well.
// The parser functions might already slice away all fully read bytes.
// That's why `offset / 8` isn't necessarily needed at all times.
let remaining_bytes_index = offset / 8 + if offset % 8 == 0 { 0 } else { 1 };
Ok((rest.slice(remaining_bytes_index..), result))
}
Err(Err::Incomplete(n)) => Err(Err::Incomplete(n.map(|u| u.get() / 8 + 1))),
Err(Err::Error(e)) => Err(Err::Error(e.convert())),
Err(Err::Failure(e)) => Err(Err::Failure(e.convert())),
}
}
/// Counterpart to `bits`, `bytes` transforms its bit stream input into a byte slice for the underlying
/// parser, allowing byte-slice parsers to work on bit streams.
///
/// A partial byte remaining in the input will be ignored and the given parser will start parsing
/// at the next full byte.
///
/// ```
/// use nom::bits::{bits, bytes, streaming::take};
/// use nom::combinator::rest;
/// use nom::error::Error;
/// use nom::sequence::tuple;
/// use nom::IResult;
///
/// fn parse(input: &[u8]) -> IResult<&[u8], (u8, u8, &[u8])> {
/// bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((
/// take(4usize),
/// take(8usize),
/// bytes::<_, _, Error<&[u8]>, _, _>(rest)
/// )))(input)
/// }
///
/// let input = &[0x12, 0x34, 0xff, 0xff];
///
/// assert_eq!(parse( input ), Ok(( &[][..], (0x01, 0x23, &[0xff, 0xff][..]) )));
/// ```
pub fn bytes<I, O, E1, E2, P>(mut parser: P) -> impl FnMut((I, usize)) -> IResult<(I, usize), O, E2>
where
E1: ParseError<I> + ErrorConvert<E2>,
E2: ParseError<(I, usize)>,
I: Slice<RangeFrom<usize>> + Clone,
P: Parser<I, O, E1>,
{
move |(input, offset): (I, usize)| {
let inner = if offset % 8 != 0 {
input.slice((1 + offset / 8)..)
} else {
input.slice((offset / 8)..)
};
let i = (input, offset);
match parser.parse(inner) {
Ok((rest, res)) => Ok(((rest, 0), res)),
Err(Err::Incomplete(Needed::Unknown)) => Err(Err::Incomplete(Needed::Unknown)),
Err(Err::Incomplete(Needed::Size(sz))) => Err(match sz.get().checked_mul(8) {
Some(v) => Err::Incomplete(Needed::new(v)),
None => Err::Failure(E2::from_error_kind(i, ErrorKind::TooLarge)),
}),
Err(Err::Error(e)) => Err(Err::Error(e.convert())),
Err(Err::Failure(e)) => Err(Err::Failure(e.convert())),
}
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::bits::streaming::take;
use crate::error::Error;
use crate::sequence::tuple;
#[test]
/// Take the `bits` function and assert that remaining bytes are correctly returned, if the
/// previous bytes are fully consumed
fn test_complete_byte_consumption_bits() {
let input = &[0x12, 0x34, 0x56, 0x78];
// Take 3 bit slices with sizes [4, 8, 4].
let result: IResult<&[u8], (u8, u8, u8)> =
bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize), take(4usize))))(
input,
);
let output = result.expect("We take 2 bytes and the input is longer than 2 bytes");
let remaining = output.0;
assert_eq!(remaining, [0x56, 0x78]);
let parsed = output.1;
assert_eq!(parsed.0, 0x01);
assert_eq!(parsed.1, 0x23);
assert_eq!(parsed.2, 0x04);
}
#[test]
/// Take the `bits` function and assert that remaining bytes are correctly returned, if the
/// previous bytes are NOT fully consumed. Partially consumed bytes are supposed to be dropped.
/// I.e. if we consume 1.5 bytes of 4 bytes, 2 bytes will be returned, bits 13-16 will be
/// dropped.
fn test_partial_byte_consumption_bits() {
let input = &[0x12, 0x34, 0x56, 0x78];
// Take bit slices with sizes [4, 8].
let result: IResult<&[u8], (u8, u8)> =
bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize))))(input);
let output = result.expect("We take 1.5 bytes and the input is longer than 2 bytes");
let remaining = output.0;
assert_eq!(remaining, [0x56, 0x78]);
let parsed = output.1;
assert_eq!(parsed.0, 0x01);
assert_eq!(parsed.1, 0x23);
}
#[test]
#[cfg(feature = "std")]
/// Ensure that in Incomplete error is thrown, if too few bytes are passed for a given parser.
fn test_incomplete_bits() {
let input = &[0x12];
// Take bit slices with sizes [4, 8].
let result: IResult<&[u8], (u8, u8)> =
bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize))))(input);
assert!(result.is_err());
let error = result.err().unwrap();
assert_eq!("Parsing requires 2 bytes/chars", error.to_string());
}
}
|
