//! Hash functions and hash utilities//!//! With the `fast-sha1` feature, the `Sha1` hash type will use a more elaborate implementation utilizing hardware support//! in case it is available. Otherwise the `sha1` feature should be set. `fast-sha1` will take precedence.//! Otherwise, a minimal yet performant implementation is used instead for a decent trade-off between compile times and run-time performance.#[cfg(all(feature = "rustsha1", not(feature = "fast-sha1")))]mod _impl {    use super::Sha1Digest;     /// A implementation of the Sha1 hash, which can be used once.    #[derive(Default, Clone)]    pub struct Sha1(rustsha1::Sha1);     impl Sha1 {        /// Digest the given `bytes`.        pub fn update(&mut self, bytes: &[u8]) {            self.0.update(bytes)        }        /// Finalize the hash and produce a digest.        pub fn digest(self) -> Sha1Digest {            self.0.digest().bytes()        }    }} /// A 20 bytes digest produced by a [`Sha1`] hash implementation.#[cfg(any(feature = "fast-sha1", feature = "rustsha1"))]pub type Sha1Digest = [u8; 20]; #[cfg(feature = "fast-sha1")]mod _impl {    use super::Sha1Digest;    use sha1::Digest;     /// A implementation of the Sha1 hash, which can be used once.    #[derive(Default, Clone)]    pub struct Sha1(sha1::Sha1);     impl Sha1 {        /// Digest the given `bytes`.        pub fn update(&mut self, bytes: &[u8]) {            self.0.update(bytes)        }        /// Finalize the hash and produce a digest.        pub fn digest(self) -> Sha1Digest {            self.0.finalize().into()        }    }} #[cfg(any(feature = "rustsha1", feature = "fast-sha1"))]pub use _impl::Sha1; /// Compute a CRC32 hash from the given `bytes`, returning the CRC32 hash.////// When calling this function for the first time, `previous_value` should be `0`. Otherwise it/// should be the previous return value of this function to provide a hash of multiple sequential/// chunks of `bytes`.#[cfg(feature = "crc32")]pub fn crc32_update(previous_value: u32, bytes: &[u8]) -> u32 {    let mut h = crc32fast::Hasher::new_with_initial(previous_value);    h.update(bytes);    h.finalize()} /// Compute a CRC32 value of the given input `bytes`.////// In case multiple chunkes of `bytes` are present, one should use [`crc32_update()`] instead.#[cfg(feature = "crc32")]pub fn crc32(bytes: &[u8]) -> u32 {    let mut h = crc32fast::Hasher::new();    h.update(bytes);    h.finalize()} /// Produce a hasher suitable for the given kind of hash.#[cfg(any(feature = "rustsha1", feature = "fast-sha1"))]pub fn hasher(kind: git_hash::Kind) -> Sha1 {    match kind {        git_hash::Kind::Sha1 => Sha1::default(),    }} /// Compute the hash of `kind` for the bytes in the file at `path`, hashing only the first `num_bytes_from_start`/// while initializing and calling `progress`.////// `num_bytes_from_start` is useful to avoid reading trailing hashes, which are never part of the hash itself,/// denoting the amount of bytes to hash starting from the beginning of the file.////// # Note////// * Only available with the `git-object` feature enabled due to usage of the [`git_hash::Kind`] enum and the///   [`git_hash::ObjectId`] return value./// * [Interrupts][crate::interrupt] are supported.#[cfg(all(feature = "progress", any(feature = "rustsha1", feature = "fast-sha1")))]pub fn bytes_of_file(    path: impl AsRef<std::path::Path>,    num_bytes_from_start: usize,    kind: git_hash::Kind,    progress: &mut impl crate::progress::Progress,    should_interrupt: &std::sync::atomic::AtomicBool,) -> std::io::Result<git_hash::ObjectId> {    bytes(        std::fs::File::open(path)?,        num_bytes_from_start,        kind,        progress,        should_interrupt,    )} /// Similar to [`bytes_of_file`], but operates on an already open file.#[cfg(all(feature = "progress", any(feature = "rustsha1", feature = "fast-sha1")))]pub fn bytes(    mut read: impl std::io::Read,    num_bytes_from_start: usize,    kind: git_hash::Kind,    progress: &mut impl crate::progress::Progress,    should_interrupt: &std::sync::atomic::AtomicBool,) -> std::io::Result<git_hash::ObjectId> {    let mut hasher = hasher(kind);    let start = std::time::Instant::now();    // init progress before the possibility for failure, as convenience in case people want to recover    progress.init(Some(num_bytes_from_start), crate::progress::bytes());     const BUF_SIZE: usize = u16::MAX as usize;    let mut buf = [0u8; BUF_SIZE];    let mut bytes_left = num_bytes_from_start;     while bytes_left > 0 {        let out = &mut buf[..BUF_SIZE.min(bytes_left)];        read.read_exact(out)?;        bytes_left -= out.len();        progress.inc_by(out.len());        hasher.update(out);        if should_interrupt.load(std::sync::atomic::Ordering::SeqCst) {            return Err(std::io::ErrorKind::Interrupted.into());        }    }     let id = git_hash::ObjectId::new_sha1(hasher.digest());    progress.show_throughput(start);    Ok(id)} #[cfg(any(feature = "rustsha1", feature = "fast-sha1"))]mod write {    use crate::hash::Sha1;     /// A utility to automatically generate a hash while writing into an inner writer.    pub struct Write<T> {        /// The hash implementation.        pub hash: Sha1,        /// The inner writer.        pub inner: T,    }     impl<T> std::io::Write for Write<T>    where        T: std::io::Write,    {        fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {            let written = self.inner.write(buf)?;            self.hash.update(&buf[..written]);            Ok(written)        }         fn flush(&mut self) -> std::io::Result<()> {            self.inner.flush()        }    }     impl<T> Write<T>    where        T: std::io::Write,    {        /// Create a new hash writer which hashes all bytes written to `inner` with a hash of `kind`.        pub fn new(inner: T, kind: git_hash::Kind) -> Self {            match kind {                git_hash::Kind::Sha1 => Write {                    inner,                    hash: Sha1::default(),                },            }        }    }}#[cfg(any(feature = "rustsha1", feature = "fast-sha1"))]pub use write::Write;