sqlite_encoder/
wal.rs

1use sqlite_types::{checksum, Wal, WalFrame, WalFrameHeader, WalHeader, MAGIC_NUMBER_2};
2
3type BoxError = Box<dyn std::error::Error>;
4
5pub fn encode(wal: Wal) -> Result<Vec<u8>, BoxError> {
6    let mut buff = Vec::new();
7
8    let (checksum_1, checksum_2) = wal.header.checksum();
9
10    write_wal_header(&mut buff, &wal.header, checksum_1, checksum_2)
11        .map_err(|err| format!("failed to encode header: {}", err))?;
12
13    let mut checksum_1 = checksum_1;
14    let mut checksum_2 = checksum_2;
15
16    for frame in &wal.frames {
17        (checksum_1, checksum_2) = frame.header.checksum(checksum_1, checksum_2);
18        (checksum_1, checksum_2) = checksum_bytes(&frame.data, checksum_1, checksum_2);
19
20        write_wal_frame(&mut buff, frame, checksum_1, checksum_2).map_err(|err| {
21            format!(
22                "failed to write WAL frame #{}: {}",
23                frame.header.page_number, err
24            )
25        })?;
26    }
27
28    Ok(buff)
29}
30
31fn write_u32(writer: &mut Vec<u8>, value: u32) {
32    writer.extend(value.to_be_bytes());
33}
34
35pub fn write_wal_header(
36    writer: &mut Vec<u8>,
37    header: &WalHeader,
38    checksum_1: u32,
39    checksum_2: u32,
40) -> Result<(), BoxError> {
41    // MAGIC_NUMBER_2 uses big-endian, which we'll assume for now.
42    write_u32(writer, MAGIC_NUMBER_2);
43    write_u32(writer, header.file_format);
44    write_u32(writer, header.page_size);
45    write_u32(writer, header.checkpoint_seq);
46    write_u32(writer, header.salt_1);
47    write_u32(writer, header.salt_2);
48
49    write_u32(writer, checksum_1);
50    write_u32(writer, checksum_2);
51    Ok(())
52}
53
54pub fn write_wal_frame(
55    writer: &mut Vec<u8>,
56    frame: &WalFrame,
57    checksum_1: u32,
58    checksum_2: u32,
59) -> Result<(), BoxError> {
60    write_wal_frame_header(writer, &frame.header, checksum_1, checksum_2)?;
61    writer.extend(&frame.data);
62    Ok(())
63}
64
65pub fn write_wal_frame_header(
66    writer: &mut Vec<u8>,
67    header: &WalFrameHeader,
68    checksum_1: u32,
69    checksum_2: u32,
70) -> Result<(), BoxError> {
71    write_u32(writer, header.page_number);
72    write_u32(writer, header.db_size_after_commit);
73    write_u32(writer, header.salt_1);
74    write_u32(writer, header.salt_2);
75    write_u32(writer, checksum_1);
76    write_u32(writer, checksum_2);
77    Ok(())
78}
79
80fn checksum_bytes(bytes: &[u8], checksum_1: u32, checksum_2: u32) -> (u32, u32) {
81    let mut out = Vec::with_capacity(bytes.len() / 4);
82
83    for i in (0..bytes.len()).step_by(4) {
84        let v = u32::from_be_bytes([bytes[i], bytes[i + 1], bytes[i + 2], bytes[i + 3]]);
85        out.push(v);
86    }
87
88    checksum(&out, Some(checksum_1), Some(checksum_2))
89}
90
91#[cfg(test)]
92mod tests {
93    use super::*;
94
95    // #[test]
96    // fn test_calc_checksum_wal_frame() {
97    //     let header = WalHeader {
98    //         magic_number: MAGIC_NUMBER_2,
99    //         file_format: SUPPORTED_FILE_FORMAT,
100    //         page_size: 4096,
101    //         checkpoint_seq: 0,
102    //         salt_1: 1,
103    //         salt_2: 2,
104    //         checksum_1: 3,
105    //         checksum_2: 4,
106    //     };
107    //     let (s0, s1) = header.checksum();
108    //     println!("s0 {} s1 {}", s0, s1);
109    //     panic!()
110    // }
111}
sqlite_encoder/wal.rs

sqlite_encoder/
wal.rs
