brec 0.4.0

A flexible binary format for storing and streaming structured data as packets with CRC protection and recoverability from corruption. Built for extensibility and robustness.
Documentation 
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

use crate::*;

/// Serializes a `Slot` into a contiguous byte buffer.
///
/// The buffer layout includes:
/// - [8 bytes] signature (`STORAGE_SLOT_SIG`)
/// - [8 bytes] capacity
/// - [N × 8 bytes] lengths (each as `u64`, where N = `capacity`)
/// - [4 bytes] CRC
fn get_buffer(slot: &Slot) -> Vec<u8> {
    let mut buffer = vec![0u8; slot.size() as usize];
    let mut offset = 0;
    buffer[offset..offset + 8usize].copy_from_slice(&STORAGE_SLOT_SIG);
    offset += 8usize;
    buffer[offset..offset + 8usize].copy_from_slice(&slot.capacity.to_le_bytes());
    offset += 8usize;
    for lenght in slot.lenghts.iter() {
        buffer[offset..offset + 8usize].copy_from_slice(&lenght.to_le_bytes());
        offset += 8usize;
    }
    buffer[offset..offset + 4usize].copy_from_slice(&slot.crc);
    buffer
}

impl WriteTo for Slot {
    /// Writes the serialized `Slot` to the given writer. May write partially.
    fn write<T: std::io::Write>(&self, buf: &mut T) -> std::io::Result<usize> {
        buf.write(&get_buffer(self))
    }

    /// Writes the entire serialized `Slot` to the writer. Will retry until complete.
    fn write_all<T: std::io::Write>(&self, buf: &mut T) -> std::io::Result<()> {
        buf.write_all(&get_buffer(self))
    }
}

#[cfg(test)]
mod tests {
    use crate::{STORAGE_SLOT_SIG, Size, Slot, WriteTo};

    #[test]
    fn slot_write_and_write_all_emit_identical_serialization() {
        let mut slot = Slot::new(vec![9, 8, 7], 3, [0; 4]);
        slot.overwrite_crc();

        let mut partial = Vec::new();
        let written = slot.write(&mut partial).expect("write");
        assert_eq!(written, slot.size() as usize);
        assert_eq!(partial.len(), slot.size() as usize);
        assert_eq!(&partial[..STORAGE_SLOT_SIG.len()], &STORAGE_SLOT_SIG);

        let mut full = Vec::new();
        slot.write_all(&mut full).expect("write_all");
        assert_eq!(full.len(), slot.size() as usize);
        assert_eq!(partial, full);
    }
}