//! 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.//!//! ## Examples//!//! ```//! # fn main() -> Result<(), Box<dyn std::error::Error>> {//! use std::io::Write;//!//! let mut index = gix_chunk::file::Index::for_writing();//! index.plan_chunk(*b"OIDF", 4);//! index.plan_chunk(*b"DATA", 3);//!//! let mut out = index.into_write(Vec::new(), 0)?;//! while let Some(kind) = out.next_chunk() {//!     match kind {//!         [b'O', b'I', b'D', b'F'] => out.write_all(b"abcd")?,//!         [b'D', b'A', b'T', b'A'] => out.write_all(b"xyz")?,//!         _ => unreachable!("planned chunks are known"),//!     }//! }//!//! let data = out.into_inner();//! let decoded = gix_chunk::file::Index::from_bytes(&data, 0, 2)?;//! assert_eq!(decoded.data_by_id(&data, *b"OIDF")?, b"abcd");//! assert_eq!(decoded.data_by_id(&data, *b"DATA")?, b"xyz");//! # Ok(()) }//! ```#![deny(missing_docs, unsafe_code)] /// 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::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;