ddk_messages/segmentation/
mod.rs

1//! Module used when working with message segmentation.
2
3use lightning::ln::msgs::DecodeError;
4use lightning::ln::wire::Type;
5use lightning::util::ser::{Readable, Writeable, Writer};
6
7/// The type of the [`SegmentStart`] message.
8pub const SEGMENT_START_TYPE: u16 = 42900;
9
10/// The type of the [`SegmentChunk`] message.
11pub const SEGMENT_CHUNK_TYPE: u16 = 42902;
12
13/// Maximum allowed size by noise protocol: <http://www.noiseprotocol.org/noise.html#message-format>
14pub const MAX_DATA_SIZE: usize = 65535;
15
16// Max data size - 2 for wrapper type - 5 for bigsize length prefix - 2 for nb segments
17const MAX_START_DATA_SIZE: usize = 65526;
18
19// Max data size - 2 for wrapper type - 5 for bigsize length prefix
20const MAX_CHUNK_SIZE: usize = 65528;
21
22const MAX_SEGMENTS: usize = 1000;
23
24pub mod segment_reader;
25
26#[cfg_attr(
27    feature = "use-serde",
28    derive(serde::Serialize, serde::Deserialize),
29    serde(rename_all = "camelCase")
30)]
31#[derive(Clone, Debug, PartialEq, Eq)]
32/// Message indicating that an incoming message has been split and needs to be
33/// reconstructed.
34pub struct SegmentStart {
35    /// The number of segments into which the large message has been split.
36    pub nb_segments: u16,
37    /// The data for the first segment.
38    pub data: Vec<u8>,
39}
40
41impl_dlc_writeable!(SegmentStart, {
42    (nb_segments, writeable),
43    (data, writeable)
44});
45
46impl Type for SegmentStart {
47    fn type_id(&self) -> u16 {
48        SEGMENT_START_TYPE
49    }
50}
51
52#[cfg_attr(
53    feature = "use-serde",
54    derive(serde::Serialize, serde::Deserialize),
55    serde(rename_all = "camelCase")
56)]
57#[derive(Clone, Debug, PartialEq, Eq)]
58/// Message providing a chunk of a split message.
59pub struct SegmentChunk {
60    /// The data to be appended to previously received chunks.
61    pub data: Vec<u8>,
62}
63
64impl_dlc_writeable!(SegmentChunk, { (data, writeable) });
65
66impl Type for SegmentChunk {
67    fn type_id(&self) -> u16 {
68        SEGMENT_CHUNK_TYPE
69    }
70}
71
72/// Split the given data into multiple segments, pre-pending the message type
73/// to enable decoding on the receiving side.
74pub fn get_segments(mut data: Vec<u8>, msg_type: u16) -> (SegmentStart, Vec<SegmentChunk>) {
75    debug_assert!(data.len() > MAX_DATA_SIZE);
76
77    let len_minus_start = data.len() - MAX_START_DATA_SIZE + 2;
78    let mut nb_segments = (len_minus_start / MAX_CHUNK_SIZE + 1) as u16;
79
80    if !len_minus_start.is_multiple_of(MAX_CHUNK_SIZE) {
81        nb_segments += 1;
82    }
83
84    debug_assert!(nb_segments > 1);
85
86    let mut start_data = Vec::with_capacity(MAX_START_DATA_SIZE);
87    msg_type
88        .write(&mut start_data)
89        .expect("to be able to write the type prefix");
90    start_data.append(&mut data.drain(..MAX_START_DATA_SIZE - 2).collect());
91
92    debug_assert_eq!(MAX_START_DATA_SIZE, start_data.len());
93
94    let segment_start = SegmentStart {
95        nb_segments,
96        data: start_data,
97    };
98
99    let mut segments = Vec::with_capacity((nb_segments as usize) - 1);
100
101    for _ in 1..(nb_segments as usize) {
102        let to_take = usize::min(data.len(), MAX_CHUNK_SIZE);
103        segments.push(SegmentChunk {
104            data: data.drain(..to_take).collect(),
105        });
106    }
107
108    (segment_start, segments)
109}
110
111#[cfg(test)]
112mod tests {
113    use super::*;
114
115    #[test]
116    fn test_get_segments() {
117        let data_size = MAX_START_DATA_SIZE + 2 * MAX_CHUNK_SIZE + 1234;
118        let mut data = Vec::new();
119        data.resize(data_size, 1);
120
121        let (segment_start, segment_chunks) = get_segments(data, 2);
122
123        assert_eq!(4, segment_start.nb_segments);
124        assert_eq!(MAX_START_DATA_SIZE, segment_start.data.len());
125        assert_eq!(3, segment_chunks.len());
126        assert_eq!(MAX_CHUNK_SIZE, segment_chunks[0].data.len());
127        assert_eq!(MAX_CHUNK_SIZE, segment_chunks[1].data.len());
128        assert_eq!(1236, segment_chunks[2].data.len());
129    }
130}
ddk_messages/segmentation/mod.rs

ddk_messages/segmentation/
mod.rs
