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//! All binary files generated by measureme have a simple file header that
//! consists of a 4 byte file magic string and a 4 byte little-endian version
//! number.
use std::convert::TryInto;
use std::error::Error;
use std::path::Path;
pub const CURRENT_FILE_FORMAT_VERSION: u32 = 8;
pub const FILE_MAGIC_TOP_LEVEL: &[u8; 4] = b"MMPD";
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_EXTENSION: &str = "mm_profdata";
/// The size of the file header in bytes. Note that functions in this module
/// rely on this size to be `8`.
pub const FILE_HEADER_SIZE: usize = 8;
pub fn write_file_header(
s: &mut dyn std::io::Write,
file_magic: &[u8; 4],
) -> Result<(), Box<dyn Error + Send + Sync>> {
// The implementation here relies on FILE_HEADER_SIZE to have the value 8.
// Let's make sure this assumption cannot be violated without being noticed.
assert_eq!(FILE_HEADER_SIZE, 8);
s.write_all(file_magic).map_err(Box::new)?;
s.write_all(&CURRENT_FILE_FORMAT_VERSION.to_le_bytes())
.map_err(Box::new)?;
Ok(())
}
#[must_use]
pub fn verify_file_header(
bytes: &[u8],
expected_magic: &[u8; 4],
diagnostic_file_path: Option<&Path>,
stream_tag: &str,
) -> Result<(), Box<dyn Error + Send + Sync>> {
// The implementation here relies on FILE_HEADER_SIZE to have the value 8.
// Let's make sure this assumption cannot be violated without being noticed.
assert_eq!(FILE_HEADER_SIZE, 8);
let diagnostic_file_path = diagnostic_file_path.unwrap_or(Path::new("<in-memory>"));
if bytes.len() < FILE_HEADER_SIZE {
let msg = format!(
"Error reading {} stream in file `{}`: Expected file to contain at least `{:?}` bytes but found `{:?}` bytes",
stream_tag,
diagnostic_file_path.display(),
FILE_HEADER_SIZE,
bytes.len()
);
return Err(From::from(msg));
}
let actual_magic = &bytes[0..4];
if actual_magic != expected_magic {
let msg = format!(
"Error reading {} stream in file `{}`: Expected file magic `{:?}` but found `{:?}`",
stream_tag,
diagnostic_file_path.display(),
expected_magic,
actual_magic
);
return Err(From::from(msg));
}
let file_format_version = u32::from_le_bytes(bytes[4..8].try_into().unwrap());
if file_format_version != CURRENT_FILE_FORMAT_VERSION {
let msg = format!(
"Error reading {} stream in file `{}`: Expected file format version {} but found `{}`",
stream_tag,
diagnostic_file_path.display(),
CURRENT_FILE_FORMAT_VERSION,
file_format_version
);
return Err(From::from(msg));
}
Ok(())
}
pub fn strip_file_header(data: &[u8]) -> &[u8] {
&data[FILE_HEADER_SIZE..]
}
#[cfg(test)]
mod tests {
use super::*;
use crate::{PageTag, SerializationSinkBuilder};
#[test]
fn roundtrip() {
let data_sink = SerializationSinkBuilder::new_in_memory().new_sink(PageTag::Events);
write_file_header(&mut data_sink.as_std_write(), FILE_MAGIC_EVENT_STREAM).unwrap();
let data = data_sink.into_bytes();
verify_file_header(&data, FILE_MAGIC_EVENT_STREAM, None, "test").unwrap();
}
#[test]
fn invalid_magic() {
let data_sink = SerializationSinkBuilder::new_in_memory().new_sink(PageTag::Events);
write_file_header(&mut data_sink.as_std_write(), FILE_MAGIC_STRINGTABLE_DATA).unwrap();
let mut data = data_sink.into_bytes();
// Invalidate the filemagic
data[2] = 0;
assert!(verify_file_header(&data, FILE_MAGIC_STRINGTABLE_DATA, None, "test").is_err());
}
#[test]
fn other_version() {
let data_sink = SerializationSinkBuilder::new_in_memory().new_sink(PageTag::Events);
write_file_header(&mut data_sink.as_std_write(), FILE_MAGIC_STRINGTABLE_INDEX).unwrap();
let mut data = data_sink.into_bytes();
// Change version
data[4] = 0xFF;
data[5] = 0xFF;
data[6] = 0xFF;
data[7] = 0xFF;
assert!(verify_file_header(&data, FILE_MAGIC_STRINGTABLE_INDEX, None, "test").is_err());
}
#[test]
fn empty_file() {
let data: [u8; 0] = [];
assert!(verify_file_header(&data, FILE_MAGIC_STRINGTABLE_DATA, None, "test").is_err());
}
}
|
