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

use crate::*;
use core::slice::from_raw_parts;

///A slice containing an udp header of a network package. Struct allows the selective read of fields in the header.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct UdpHeaderSlice<'a> {
    pub(crate) slice: &'a [u8],
}

impl<'a> UdpHeaderSlice<'a> {
    /// Creates a slice containing an udp header.
    #[inline]
    pub fn from_slice(slice: &'a [u8]) -> Result<UdpHeaderSlice<'a>, err::LenError> {
        //check length
        if slice.len() < UdpHeader::LEN {
            return Err(err::LenError {
                required_len: UdpHeader::LEN,
                len: slice.len(),
                len_source: LenSource::Slice,
                layer: err::Layer::UdpHeader,
                layer_start_offset: 0,
            });
        }

        //done
        Ok(UdpHeaderSlice {
            // SAFETY:
            // Safe as slice length is checked to be at least
            // UdpHeader::LEN (8) before this.
            slice: unsafe { from_raw_parts(slice.as_ptr(), UdpHeader::LEN) },
        })
    }

    /// Returns the slice containing the udp header
    #[inline]
    pub fn slice(&self) -> &'a [u8] {
        self.slice
    }

    /// Reads the "udp source port" from the slice.
    #[inline]
    pub fn source_port(&self) -> u16 {
        // SAFETY:
        // Safe as the contructor checks that the slice has
        // at least the length of UdpHeader::LEN (8).
        unsafe { get_unchecked_be_u16(self.slice.as_ptr()) }
    }

    /// Reads the "udp destination port" from the slice.
    #[inline]
    pub fn destination_port(&self) -> u16 {
        // SAFETY:
        // Safe as the contructor checks that the slice has
        // at least the length of UdpHeader::LEN (8).
        unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(2)) }
    }

    /// Reads the "length" from the slice.
    #[inline]
    pub fn length(&self) -> u16 {
        // SAFETY:
        // Safe as the contructor checks that the slice has
        // at least the length of UdpHeader::LEN (8).
        unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(4)) }
    }

    /// Reads the "checksum" from the slice.
    #[inline]
    pub fn checksum(&self) -> u16 {
        // SAFETY:
        // Safe as the contructor checks that the slice has
        // at least the length of UdpHeader::LEN (8).
        unsafe { get_unchecked_be_u16(self.slice.as_ptr().add(6)) }
    }

    /// Decode all the fields and copy the results to a UdpHeader struct
    #[inline]
    pub fn to_header(&self) -> UdpHeader {
        UdpHeader {
            source_port: self.source_port(),
            destination_port: self.destination_port(),
            length: self.length(),
            checksum: self.checksum(),
        }
    }
}

#[cfg(test)]
mod test {
    use crate::{test_gens::*, *};
    use alloc::{format, vec::Vec};
    use proptest::prelude::*;

    proptest! {
        #[test]
        fn from_slice(
            input in udp_any(),
            dummy_data in proptest::collection::vec(any::<u8>(), 0..20)
        ) {
            // serialize
            let mut buffer: Vec<u8> = Vec::with_capacity(8 + dummy_data.len());
            input.write(&mut buffer).unwrap();
            buffer.extend(&dummy_data[..]);

            // calls with a valid result
            {
                let result = UdpHeaderSlice::from_slice(&buffer[..]).unwrap();
                assert_eq!(&buffer[..8], result.slice());
            }

            // call with not enough data in the slice
            for len in 0..8 {
                assert_eq!(
                    UdpHeaderSlice::from_slice(&buffer[0..len]).unwrap_err(),
                    err::LenError{
                        required_len: UdpHeader::LEN,
                        len: len,
                        len_source: LenSource::Slice,
                        layer: err::Layer::UdpHeader,
                        layer_start_offset: 0,
                    }
                );
            }
        }
    }

    proptest! {
        #[test]
        fn getters(input in udp_any()) {
            let bytes = input.to_bytes();
            let slice = UdpHeaderSlice::from_slice(&bytes).unwrap();

            assert_eq!(slice.source_port(), input.source_port);
            assert_eq!(slice.destination_port(), input.destination_port);
            assert_eq!(slice.length(), input.length);
            assert_eq!(slice.checksum(), input.checksum);
        }
    }

    proptest! {
        #[test]
        fn to_header(input in udp_any()) {
            let bytes = input.to_bytes();
            let slice = UdpHeaderSlice::from_slice(&bytes).unwrap();
            assert_eq!(input, slice.to_header());
        }
    }

    proptest! {
        #[test]
        fn clone_eq(input in udp_any()) {
            let bytes = input.to_bytes();
            let slice = UdpHeaderSlice::from_slice(&bytes).unwrap();
            assert_eq!(slice, slice.clone());
        }
    }

    proptest! {
        #[test]
        fn dbg(input in udp_any()) {
            let bytes = input.to_bytes();
            let slice = UdpHeaderSlice::from_slice(&bytes).unwrap();
            assert_eq!(
                &format!(
                    "UdpHeaderSlice {{ slice: {:?} }}",
                    slice.slice()
                ),
                &format!("{:?}", slice)
            );
        }
    }
}