use std::{    borrow::Borrow,    hash::{Hash, Hasher},    ops::Deref,}; use crate::{Kind, borrowed::oid}; #[cfg(feature = "sha1")]use crate::{EMPTY_BLOB_SHA1, EMPTY_TREE_SHA1, SIZE_OF_SHA1_DIGEST}; #[cfg(feature = "sha256")]use crate::{EMPTY_BLOB_SHA256, EMPTY_TREE_SHA256, SIZE_OF_SHA256_DIGEST}; /// An owned hash identifying objects, most commonly `Sha1`#[derive(PartialEq, Eq, Ord, PartialOrd, Clone, Copy)]#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]#[non_exhaustive]pub enum ObjectId {    /// A SHA1 hash digest    #[cfg(feature = "sha1")]    Sha1([u8; SIZE_OF_SHA1_DIGEST]),    /// A SHA256 hash digest    #[cfg(feature = "sha256")]    Sha256([u8; SIZE_OF_SHA256_DIGEST]),} // False positive: https://github.com/rust-lang/rust-clippy/issues/2627// ignoring some fields while hashing is perfectly valid and just leads to// increased HashCollisions. One SHA1 being a prefix of another SHA256 is// extremely unlikely to begin with so it doesn't matter.// This implementation matches the `Hash` implementation for `oid`// and allows the usage of custom Hashers that only copy a truncated ShaHashimpl Hash for ObjectId {    fn hash<H: Hasher>(&self, state: &mut H) {        state.write(self.as_slice());    }} #[expect(missing_docs)]pub mod decode {    use std::str::FromStr;     use crate::object_id::ObjectId;     #[cfg(feature = "sha1")]    use crate::{SIZE_OF_SHA1_DIGEST, SIZE_OF_SHA1_HEX_DIGEST};     #[cfg(feature = "sha256")]    use crate::{SIZE_OF_SHA256_DIGEST, SIZE_OF_SHA256_HEX_DIGEST};     /// An error returned by [`ObjectId::from_hex()`][crate::ObjectId::from_hex()]    #[derive(Debug, thiserror::Error)]    #[expect(missing_docs)]    pub enum Error {        #[error("A hash sized {0} hexadecimal characters is invalid")]        InvalidHexEncodingLength(usize),        #[error("Invalid character encountered")]        Invalid,    }     /// Hash decoding    impl ObjectId {        /// Create an instance from a `buffer` of 40 bytes or 64 bytes encoded with hexadecimal        /// notation. The former will be interpreted as SHA1 while the latter will be interpreted        /// as SHA256 when it is enabled.        ///        /// Such a buffer can be obtained using [`oid::write_hex_to(buffer)`][super::oid::write_hex_to()]        pub fn from_hex(buffer: &[u8]) -> Result<ObjectId, Error> {            match buffer.len() {                #[cfg(feature = "sha1")]                SIZE_OF_SHA1_HEX_DIGEST => Ok({                    ObjectId::Sha1({                        let mut buf = [0; SIZE_OF_SHA1_DIGEST];                        faster_hex::hex_decode(buffer, &mut buf).map_err(|err| match err {                            faster_hex::Error::InvalidChar | faster_hex::Error::Overflow => Error::Invalid,                            faster_hex::Error::InvalidLength(_) => {                                unreachable!("BUG: This is already checked")                            }                        })?;                        buf                    })                }),                #[cfg(feature = "sha256")]                SIZE_OF_SHA256_HEX_DIGEST => Ok({                    ObjectId::Sha256({                        let mut buf = [0; SIZE_OF_SHA256_DIGEST];                        faster_hex::hex_decode(buffer, &mut buf).map_err(|err| match err {                            faster_hex::Error::InvalidChar | faster_hex::Error::Overflow => Error::Invalid,                            faster_hex::Error::InvalidLength(_) => {                                unreachable!("BUG: This is already checked")                            }                        })?;                        buf                    })                }),                len => Err(Error::InvalidHexEncodingLength(len)),            }        }    }     impl FromStr for ObjectId {        type Err = Error;         fn from_str(s: &str) -> Result<Self, Self::Err> {            Self::from_hex(s.as_bytes())        }    }} /// Access and conversionimpl ObjectId {    /// Returns the kind of hash used in this instance.    #[inline]    pub fn kind(&self) -> Kind {        match self {            #[cfg(feature = "sha1")]            ObjectId::Sha1(_) => Kind::Sha1,            #[cfg(feature = "sha256")]            ObjectId::Sha256(_) => Kind::Sha256,        }    }    /// Return the raw byte slice representing this hash.    #[inline]    pub fn as_slice(&self) -> &[u8] {        match self {            #[cfg(feature = "sha1")]            Self::Sha1(b) => b.as_ref(),            #[cfg(feature = "sha256")]            Self::Sha256(b) => b.as_ref(),        }    }    /// Return the raw mutable byte slice representing this hash.    #[inline]    pub fn as_mut_slice(&mut self) -> &mut [u8] {        match self {            #[cfg(feature = "sha1")]            Self::Sha1(b) => b.as_mut(),            #[cfg(feature = "sha256")]            Self::Sha256(b) => b.as_mut(),        }    }     /// The hash of an empty blob.    #[inline]    pub const fn empty_blob(hash: Kind) -> ObjectId {        match hash {            #[cfg(feature = "sha1")]            Kind::Sha1 => ObjectId::Sha1(*EMPTY_BLOB_SHA1),            #[cfg(feature = "sha256")]            Kind::Sha256 => ObjectId::Sha256(*EMPTY_BLOB_SHA256),        }    }     /// The hash of an empty tree.    #[inline]    pub const fn empty_tree(hash: Kind) -> ObjectId {        match hash {            #[cfg(feature = "sha1")]            Kind::Sha1 => ObjectId::Sha1(*EMPTY_TREE_SHA1),            #[cfg(feature = "sha256")]            Kind::Sha256 => ObjectId::Sha256(*EMPTY_TREE_SHA256),        }    }     /// Returns an instances whose bytes are all zero.    #[inline]    #[doc(alias = "zero", alias = "git2")]    pub const fn null(kind: Kind) -> ObjectId {        match kind {            #[cfg(feature = "sha1")]            Kind::Sha1 => Self::null_sha1(),            #[cfg(feature = "sha256")]            Kind::Sha256 => Self::null_sha256(),        }    }     /// Returns `true` if this hash consists of all null bytes.    #[inline]    #[doc(alias = "is_zero", alias = "git2")]    pub fn is_null(&self) -> bool {        match self {            #[cfg(feature = "sha1")]            ObjectId::Sha1(digest) => &digest[..] == oid::null_sha1().as_bytes(),            #[cfg(feature = "sha256")]            ObjectId::Sha256(digest) => &digest[..] == oid::null_sha256().as_bytes(),        }    }     /// Returns `true` if this hash is equal to an empty blob.    #[inline]    pub fn is_empty_blob(&self) -> bool {        self == &Self::empty_blob(self.kind())    }     /// Returns `true` if this hash is equal to an empty tree.    #[inline]    pub fn is_empty_tree(&self) -> bool {        self == &Self::empty_tree(self.kind())    }} /// Lifecycleimpl ObjectId {    /// Convert `bytes` into an owned object Id or panic if the slice length doesn't indicate a supported hash.    ///    /// Use `Self::try_from(bytes)` for a fallible version.    pub fn from_bytes_or_panic(bytes: &[u8]) -> Self {        match bytes.len() {            #[cfg(feature = "sha1")]            SIZE_OF_SHA1_DIGEST => Self::Sha1(bytes.try_into().expect("prior length validation")),            #[cfg(feature = "sha256")]            SIZE_OF_SHA256_DIGEST => Self::Sha256(bytes.try_into().expect("prior length validation")),            other => panic!("BUG: unsupported hash len: {other}"),        }    }} /// Methods related to SHA1 and SHA256impl ObjectId {    /// Instantiate an `ObjectId` from a 20 bytes SHA1 digest.    #[inline]    #[cfg(feature = "sha1")]    fn new_sha1(id: [u8; SIZE_OF_SHA1_DIGEST]) -> Self {        ObjectId::Sha1(id)    }     /// Instantiate an `ObjectId` from a 32 bytes SHA256 digest.    #[inline]    #[cfg(feature = "sha256")]    fn new_sha256(id: [u8; SIZE_OF_SHA256_DIGEST]) -> Self {        ObjectId::Sha256(id)    }     /// Instantiate an `ObjectId` from a borrowed 20 bytes SHA1 digest.    ///    /// Panics if the slice doesn't have a length of 20.    #[inline]    #[cfg(feature = "sha1")]    pub(crate) fn from_20_bytes(b: &[u8]) -> ObjectId {        let mut id = [0; SIZE_OF_SHA1_DIGEST];        id.copy_from_slice(b);        ObjectId::Sha1(id)    }     /// Instantiate an `ObjectId` from a borrowed 32 bytes SHA256 digest.    ///    /// Panics if the slice doesn't have a length of 32.    #[inline]    #[cfg(feature = "sha256")]    pub(crate) fn from_32_bytes(b: &[u8]) -> ObjectId {        let mut id = [0; SIZE_OF_SHA256_DIGEST];        id.copy_from_slice(b);        ObjectId::Sha256(id)    }     /// Returns an `ObjectId` representing a SHA1 whose memory is zeroed.    #[inline]    #[cfg(feature = "sha1")]    pub(crate) const fn null_sha1() -> ObjectId {        ObjectId::Sha1([0u8; SIZE_OF_SHA1_DIGEST])    }     /// Returns an `ObjectId` representing a SHA256 whose memory is zeroed.    #[inline]    #[cfg(feature = "sha256")]    pub(crate) const fn null_sha256() -> ObjectId {        ObjectId::Sha256([0u8; SIZE_OF_SHA256_DIGEST])    }} impl std::fmt::Debug for ObjectId {    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {        match self {            #[cfg(feature = "sha1")]            ObjectId::Sha1(_hash) => f.write_str("Sha1(")?,            #[cfg(feature = "sha256")]            ObjectId::Sha256(_) => f.write_str("Sha256(")?,        }        for b in self.as_bytes() {            write!(f, "{b:02x}")?;        }        f.write_str(")")    }} #[cfg(feature = "sha1")]impl From<[u8; SIZE_OF_SHA1_DIGEST]> for ObjectId {    fn from(v: [u8; SIZE_OF_SHA1_DIGEST]) -> Self {        Self::new_sha1(v)    }} #[cfg(feature = "sha256")]impl From<[u8; SIZE_OF_SHA256_DIGEST]> for ObjectId {    fn from(v: [u8; SIZE_OF_SHA256_DIGEST]) -> Self {        Self::new_sha256(v)    }} impl From<&oid> for ObjectId {    fn from(v: &oid) -> Self {        match v.kind() {            #[cfg(feature = "sha1")]            Kind::Sha1 => ObjectId::from_20_bytes(v.as_bytes()),            #[cfg(feature = "sha256")]            Kind::Sha256 => ObjectId::from_32_bytes(v.as_bytes()),        }    }} impl TryFrom<&[u8]> for ObjectId {    type Error = crate::Error;     fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {        Ok(oid::try_from_bytes(bytes)?.into())    }} impl Deref for ObjectId {    type Target = oid;     fn deref(&self) -> &Self::Target {        self.as_ref()    }} impl AsRef<oid> for ObjectId {    fn as_ref(&self) -> &oid {        oid::from_bytes_unchecked(self.as_slice())    }} impl Borrow<oid> for ObjectId {    fn borrow(&self) -> &oid {        self.as_ref()    }} impl std::fmt::Display for ObjectId {    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {        write!(f, "{}", self.to_hex())    }} impl PartialEq<&oid> for ObjectId {    fn eq(&self, other: &&oid) -> bool {        self.as_ref() == *other    }}