use sqlite_types::{checksum, Wal, WalFrame, WalFrameHeader, WalHeader, MAGIC_NUMBER_2};
type BoxError = Box<dyn std::error::Error>;
pub fn encode(wal: Wal) -> Result<Vec<u8>, BoxError> {
let mut buff = Vec::new();
let (checksum_1, checksum_2) = wal.header.checksum();
write_wal_header(&mut buff, &wal.header, checksum_1, checksum_2)
.map_err(|err| format!("failed to encode header: {}", err))?;
let mut checksum_1 = checksum_1;
let mut checksum_2 = checksum_2;
for frame in &wal.frames {
(checksum_1, checksum_2) = frame.header.checksum(checksum_1, checksum_2);
(checksum_1, checksum_2) = checksum_bytes(&frame.data, checksum_1, checksum_2);
write_wal_frame(&mut buff, frame, checksum_1, checksum_2).map_err(|err| {
format!(
"failed to write WAL frame #{}: {}",
frame.header.page_number, err
)
})?;
}
Ok(buff)
}
fn write_u32(writer: &mut Vec<u8>, value: u32) {
writer.extend(value.to_be_bytes());
}
pub fn write_wal_header(
writer: &mut Vec<u8>,
header: &WalHeader,
checksum_1: u32,
checksum_2: u32,
) -> Result<(), BoxError> {
write_u32(writer, MAGIC_NUMBER_2);
write_u32(writer, header.file_format);
write_u32(writer, header.page_size);
write_u32(writer, header.checkpoint_seq);
write_u32(writer, header.salt_1);
write_u32(writer, header.salt_2);
write_u32(writer, checksum_1);
write_u32(writer, checksum_2);
Ok(())
}
pub fn write_wal_frame(
writer: &mut Vec<u8>,
frame: &WalFrame,
checksum_1: u32,
checksum_2: u32,
) -> Result<(), BoxError> {
write_wal_frame_header(writer, &frame.header, checksum_1, checksum_2)?;
writer.extend(&frame.data);
Ok(())
}
pub fn write_wal_frame_header(
writer: &mut Vec<u8>,
header: &WalFrameHeader,
checksum_1: u32,
checksum_2: u32,
) -> Result<(), BoxError> {
write_u32(writer, header.page_number);
write_u32(writer, header.db_size_after_commit);
write_u32(writer, header.salt_1);
write_u32(writer, header.salt_2);
write_u32(writer, checksum_1);
write_u32(writer, checksum_2);
Ok(())
}
fn checksum_bytes(bytes: &[u8], checksum_1: u32, checksum_2: u32) -> (u32, u32) {
let mut out = Vec::with_capacity(bytes.len() / 4);
for i in (0..bytes.len()).step_by(4) {
let v = u32::from_be_bytes([bytes[i], bytes[i + 1], bytes[i + 2], bytes[i + 3]]);
out.push(v);
}
checksum(&out, Some(checksum_1), Some(checksum_2))
}
#[cfg(test)]
mod tests {
use super::*;
}