//! Low-level access to reading and writing chunk file based formats.//!//! See the [git documentation](https://github.com/git/git/blob/seen/Documentation/technical/chunk-format.txt) for details.#![deny(unsafe_code)]#![deny(rust_2018_idioms, missing_docs)] /// An identifier to describe the kind of chunk, unique within a chunk file, typically in ASCIIpub type Id = [u8; 4]; /// A special value denoting the end of the chunk file table of contents.pub const SENTINEL: Id = [0u8; 4]; ///pub mod range {    use std::{convert::TryInto, ops::Range};     use crate::file;     /// Turn a u64 Range into a usize range safely, to make chunk ranges useful in memory mapped files.    pub fn into_usize(Range { start, end }: Range<file::Offset>) -> Option<Range<usize>> {        let start = start.try_into().ok()?;        let end = end.try_into().ok()?;        Some(Range { start, end })    }     /// Similar to [`into_usize()`], but panics assuming that the memory map couldn't be created if offsets    /// stored are too high.    ///    /// This is only true for correctly formed files, as it's entirely possible to provide out of bounds offsets    /// which are checked for separately - we wouldn't be here if that was the case.    pub fn into_usize_or_panic(range: Range<file::Offset>) -> Range<usize> {        into_usize(range).expect("memory maps can't be created if files are too large")    }} ///pub mod file;