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use alloc::vec::Vec;
use core::fmt;
use memchr::memmem;
use crate::headers::{Headers, ParseResult};
/// A complete blackbox log file containing zero or more logs.
pub struct File<'data> {
offsets: Vec<usize>,
data: &'data [u8],
}
impl<'data> File<'data> {
/// Creates a new `File` from a byte slice of its contents.
///
/// This is relatively cheap, since it only scans for log start markers
/// without parsing any data.
pub fn new(data: &'data [u8]) -> Self {
let offsets = memmem::find_iter(data, crate::MARKER).collect();
Self { offsets, data }
}
/// Returns the number of log start markers in the file.
#[inline]
pub fn log_count(&self) -> usize {
self.offsets.len()
}
/// Returns an iterator over parsed [`Headers`] for each log.
///
/// Roughly equivalent to repeatedly calling [`File::parse`], but may
/// be able to eliminate bounds checks and skips the `Option`
/// wrapper.
pub fn iter(&self) -> impl Iterator<Item = ParseResult<Headers<'data>>> + '_ {
self.offsets
.iter()
.map(|&offset| Headers::parse(&self.data[offset..]))
}
/// Attempts to parse the headers of the `index`-th log. Returns `None` if
/// there is no log number `index`.
pub fn parse(&self, index: usize) -> Option<ParseResult<Headers<'data>>> {
let start = *self.offsets.get(index)?;
let data = if let Some(&next) = self.offsets.get(index + 1) {
&self.data[start..next]
} else {
&self.data[start..]
};
Some(Headers::parse(data))
}
}
impl fmt::Debug for File<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("File")
.field("offsets", &self.offsets)
.finish_non_exhaustive()
}
}