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use crate::serialization::SerializationSink;
use byteorder::{ByteOrder, LittleEndian};
use std::error::Error;
pub const CURRENT_FILE_FORMAT_VERSION: u32 = 3;
pub const FILE_MAGIC_EVENT_STREAM: &[u8; 4] = b"MMES";
pub const FILE_MAGIC_STRINGTABLE_DATA: &[u8; 4] = b"MMSD";
pub const FILE_MAGIC_STRINGTABLE_INDEX: &[u8; 4] = b"MMSI";
pub const FILE_HEADER_SIZE: usize = 8;
pub fn write_file_header<S: SerializationSink>(s: &S, file_magic: &[u8; 4]) {
assert_eq!(FILE_HEADER_SIZE, 8);
s.write_atomic(FILE_HEADER_SIZE, |bytes| {
bytes[0..4].copy_from_slice(file_magic);
LittleEndian::write_u32(&mut bytes[4..8], CURRENT_FILE_FORMAT_VERSION);
});
}
pub fn read_file_header(bytes: &[u8], expected_magic: &[u8; 4]) -> Result<u32, Box<dyn Error>> {
assert_eq!(FILE_HEADER_SIZE, 8);
let actual_magic = &bytes[0..4];
if actual_magic != expected_magic {
let msg = format!(
"Unexpected file magic `{:?}`. Expected `{:?}`",
actual_magic, expected_magic,
);
return Err(From::from(msg));
}
Ok(LittleEndian::read_u32(&bytes[4..8]))
}
pub fn strip_file_header(data: &[u8]) -> &[u8] {
&data[FILE_HEADER_SIZE..]
}
#[cfg(test)]
mod tests {
use super::*;
use crate::serialization::ByteVecSink;
#[test]
fn roundtrip() {
let data_sink = ByteVecSink::new();
write_file_header(&data_sink, FILE_MAGIC_EVENT_STREAM);
let data = data_sink.into_bytes();
assert_eq!(
read_file_header(&data, FILE_MAGIC_EVENT_STREAM).unwrap(),
CURRENT_FILE_FORMAT_VERSION
);
}
#[test]
fn invalid_magic() {
let data_sink = ByteVecSink::new();
write_file_header(&data_sink, FILE_MAGIC_STRINGTABLE_DATA);
let mut data = data_sink.into_bytes();
data[2] = 0;
assert!(read_file_header(&data, FILE_MAGIC_STRINGTABLE_DATA).is_err());
}
#[test]
fn other_version() {
let data_sink = ByteVecSink::new();
write_file_header(&data_sink, FILE_MAGIC_STRINGTABLE_INDEX);
let mut data = data_sink.into_bytes();
data[4] = 0xFF;
data[5] = 0xFF;
data[6] = 0xFF;
data[7] = 0xFF;
assert_eq!(
read_file_header(&data, FILE_MAGIC_STRINGTABLE_INDEX).unwrap(),
0xFFFF_FFFF
);
}
}