vendor/gix-hash/src/oid.rs - toolchain/rustc - Git at Google

 use std::{convert::TryInto, hash};

 use crate::{Kind, ObjectId, SIZE_OF_SHA1_DIGEST};

 /// A borrowed reference to a hash identifying objects.
 ///
 /// # Future Proofing
 ///
 /// In case we wish to support multiple hashes with the same length we cannot discriminate
 /// using the slice length anymore. To make that work, we will use the high bits of the
 /// internal `bytes` slice length (a fat pointer, pointing to data and its length in bytes)
 /// to encode additional information. Before accessing or returning the bytes, a new adjusted
 /// slice will be constructed, while the high bits will be used to help resolving the
 /// hash [`kind()`][oid::kind()].
 /// We expect to have quite a few bits available for such 'conflict resolution' as most hashes aren't longer
 /// than 64 bytes.
 #[derive(PartialEq, Eq, Ord, PartialOrd)]
 #[repr(transparent)]
 #[allow(non_camel_case_types)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct oid {
     bytes: [u8],
 }

 // False positive:
 // Using an automatic implementation of `Hash` for `oid` would lead to
 // it attempting to hash the length of the slice first. On 32 bit systems
 // this can lead to issues with the custom `gix_hashtable` `Hasher` implementation,
 // and it currently ends up being discarded there anyway.
 #[allow(clippy::derived_hash_with_manual_eq)]
 impl hash::Hash for oid {
     fn hash<H: hash::Hasher>(&self, state: &mut H) {
         state.write(self.as_bytes())
     }
 }

 /// A utility able to format itself with the given amount of characters in hex.
 #[derive(PartialEq, Eq, Hash, Ord, PartialOrd)]
 pub struct HexDisplay<'a> {
     inner: &'a oid,
     hex_len: usize,
 }

 impl<'a> std::fmt::Display for HexDisplay<'a> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let mut hex = Kind::hex_buf();
         let max_len = self.inner.hex_to_buf(hex.as_mut());
         let hex = std::str::from_utf8(&hex[..self.hex_len.min(max_len)]).expect("ascii only in hex");
         f.write_str(hex)
     }
 }

 impl std::fmt::Debug for oid {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(
             f,
             "{}({})",
             match self.kind() {
                 Kind::Sha1 => "Sha1",
             },
             self.to_hex(),
         )
     }
 }

 /// The error returned when trying to convert a byte slice to an [`oid`] or [`ObjectId`]
 #[allow(missing_docs)]
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
     #[error("Cannot instantiate git hash from a digest of length {0}")]
     InvalidByteSliceLength(usize),
 }

 /// Conversion
 impl oid {
     /// Try to create a shared object id from a slice of bytes representing a hash `digest`
     #[inline]
     pub fn try_from_bytes(digest: &[u8]) -> Result<&Self, Error> {
         match digest.len() {
             20 => Ok(
                 #[allow(unsafe_code)]
                 unsafe {
                     &*(digest as *const [u8] as *const oid)
                 },
             ),
             len => Err(Error::InvalidByteSliceLength(len)),
         }
     }

     /// Create an OID from the input `value` slice without performing any safety check.
     /// Use only once sure that `value` is a hash of valid length.
     pub fn from_bytes_unchecked(value: &[u8]) -> &Self {
         Self::from_bytes(value)
     }

     /// Only from code that statically assures correct sizes using array conversions.
     pub(crate) fn from_bytes(value: &[u8]) -> &Self {
         #[allow(unsafe_code)]
         unsafe {
             &*(value as *const [u8] as *const oid)
         }
     }
 }

 /// Access
 impl oid {
     /// The kind of hash used for this instance.
     #[inline]
     pub fn kind(&self) -> Kind {
         Kind::from_len_in_bytes(self.bytes.len())
     }

     /// The first byte of the hash, commonly used to partition a set of object ids.
     #[inline]
     pub fn first_byte(&self) -> u8 {
         self.bytes[0]
     }

     /// Interpret this object id as raw byte slice.
     #[inline]
     pub fn as_bytes(&self) -> &[u8] {
         &self.bytes
     }

     /// Return a type which can display itself in hexadecimal form with the `len` amount of characters.
     #[inline]
     pub fn to_hex_with_len(&self, len: usize) -> HexDisplay<'_> {
         HexDisplay {
             inner: self,
             hex_len: len,
         }
     }

     /// Return a type which displays this oid as hex in full.
     #[inline]
     pub fn to_hex(&self) -> HexDisplay<'_> {
         HexDisplay {
             inner: self,
             hex_len: self.bytes.len() * 2,
         }
     }

     /// 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.kind() {
             Kind::Sha1 => &self.bytes == oid::null_sha1().as_bytes(),
         }
     }
 }

 /// Sha1 specific methods
 impl oid {
     /// Write ourselves to the `out` in hexadecimal notation, returning the amount of written bytes.
     ///
     /// **Panics** if the buffer isn't big enough to hold twice as many bytes as the current binary size.
     #[inline]
     #[must_use]
     pub fn hex_to_buf(&self, buf: &mut [u8]) -> usize {
         let num_hex_bytes = self.bytes.len() * 2;
         faster_hex::hex_encode(&self.bytes, &mut buf[..num_hex_bytes]).expect("to count correctly");
         num_hex_bytes
     }

     /// Write ourselves to `out` in hexadecimal notation.
     #[inline]
     pub fn write_hex_to(&self, out: &mut dyn std::io::Write) -> std::io::Result<()> {
         let mut hex = Kind::hex_buf();
         let hex_len = self.hex_to_buf(&mut hex);
         out.write_all(&hex[..hex_len])
     }

     /// Returns a Sha1 digest with all bytes being initialized to zero.
     #[inline]
     pub(crate) fn null_sha1() -> &'static Self {
         oid::from_bytes([0u8; SIZE_OF_SHA1_DIGEST].as_ref())
     }
 }

 impl AsRef<oid> for &oid {
     fn as_ref(&self) -> &oid {
         self
     }
 }

 impl<'a> TryFrom<&'a [u8]> for &'a oid {
     type Error = Error;

     fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
         oid::try_from_bytes(value)
     }
 }

 impl ToOwned for oid {
     type Owned = ObjectId;

     fn to_owned(&self) -> Self::Owned {
         match self.kind() {
             Kind::Sha1 => ObjectId::Sha1(self.bytes.try_into().expect("no bug in hash detection")),
         }
     }
 }

 impl<'a> From<&'a [u8; SIZE_OF_SHA1_DIGEST]> for &'a oid {
     fn from(v: &'a [u8; SIZE_OF_SHA1_DIGEST]) -> Self {
         oid::from_bytes(v.as_ref())
     }
 }

 impl std::fmt::Display for &oid {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         for b in self.as_bytes() {
             write!(f, "{b:02x}")?;
         }
         Ok(())
     }
 }

 impl PartialEq<ObjectId> for &oid {
     fn eq(&self, other: &ObjectId) -> bool {
         *self == other.as_ref()
     }
 }

 /// Manually created from a version that uses a slice, and we forcefully try to convert it into a borrowed array of the desired size
 /// Could be improved by fitting this into serde.
 /// Unfortunately the `serde::Deserialize` derive wouldn't work for borrowed arrays.
 #[cfg(feature = "serde")]
 impl<'de: 'a, 'a> serde::Deserialize<'de> for &'a oid {
     fn deserialize<D>(deserializer: D) -> Result<Self, <D as serde::Deserializer<'de>>::Error>
     where
         D: serde::Deserializer<'de>,
     {
         struct __Visitor<'de: 'a, 'a> {
             marker: std::marker::PhantomData<&'a oid>,
             lifetime: std::marker::PhantomData<&'de ()>,
         }
         impl<'de: 'a, 'a> serde::de::Visitor<'de> for __Visitor<'de, 'a> {
             type Value = &'a oid;
             fn expecting(&self, __formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 std::fmt::Formatter::write_str(__formatter, "tuple struct Digest")
             }
             #[inline]
             fn visit_newtype_struct<__E>(self, __e: __E) -> std::result::Result<Self::Value, __E::Error>
             where
                 __E: serde::Deserializer<'de>,
             {
                 let __field0: &'a [u8] = match <&'a [u8] as serde::Deserialize>::deserialize(__e) {
                     Ok(__val) => __val,
                     Err(__err) => {
                         return Err(__err);
                     }
                 };
                 Ok(oid::try_from_bytes(__field0).expect("hash of known length"))
             }
             #[inline]
             fn visit_seq<__A>(self, mut __seq: __A) -> std::result::Result<Self::Value, __A::Error>
             where
                 __A: serde::de::SeqAccess<'de>,
             {
                 let __field0 = match match serde::de::SeqAccess::next_element::<&'a [u8]>(&mut __seq) {
                     Ok(__val) => __val,
                     Err(__err) => {
                         return Err(__err);
                     }
                 } {
                     Some(__value) => __value,
                     None => {
                         return Err(serde::de::Error::invalid_length(
                             0usize,
                             &"tuple struct Digest with 1 element",
                         ));
                     }
                 };
                 Ok(oid::try_from_bytes(__field0).expect("hash of known length"))
             }
         }
         serde::Deserializer::deserialize_newtype_struct(
             deserializer,
             "Digest",
             __Visitor {
                 marker: std::marker::PhantomData::<&'a oid>,
                 lifetime: std::marker::PhantomData,
             },
         )
     }
 }
	use std::{convert::TryInto, hash};

	use crate::{Kind, ObjectId, SIZE_OF_SHA1_DIGEST};

	/// A borrowed reference to a hash identifying objects.
	///
	/// # Future Proofing
	///
	/// In case we wish to support multiple hashes with the same length we cannot discriminate
	/// using the slice length anymore. To make that work, we will use the high bits of the
	/// internal `bytes` slice length (a fat pointer, pointing to data and its length in bytes)
	/// to encode additional information. Before accessing or returning the bytes, a new adjusted
	/// slice will be constructed, while the high bits will be used to help resolving the
	/// hash [`kind()`][oid::kind()].
	/// We expect to have quite a few bits available for such 'conflict resolution' as most hashes aren't longer
	/// than 64 bytes.
	#[derive(PartialEq, Eq, Ord, PartialOrd)]
	#[repr(transparent)]
	#[allow(non_camel_case_types)]
	#[cfg_attr(feature = "serde", derive(serde::Serialize))]
	pub struct oid {
	bytes: [u8],
	}

	// False positive:
	// Using an automatic implementation of `Hash` for `oid` would lead to
	// it attempting to hash the length of the slice first. On 32 bit systems
	// this can lead to issues with the custom `gix_hashtable` `Hasher` implementation,
	// and it currently ends up being discarded there anyway.
	#[allow(clippy::derived_hash_with_manual_eq)]
	impl hash::Hash for oid {
	fn hash<H: hash::Hasher>(&self, state: &mut H) {
	state.write(self.as_bytes())
	}
	}

	/// A utility able to format itself with the given amount of characters in hex.
	#[derive(PartialEq, Eq, Hash, Ord, PartialOrd)]
	pub struct HexDisplay<'a> {
	inner: &'a oid,
	hex_len: usize,
	}

	impl<'a> std::fmt::Display for HexDisplay<'a> {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	let mut hex = Kind::hex_buf();
	let max_len = self.inner.hex_to_buf(hex.as_mut());
	let hex = std::str::from_utf8(&hex[..self.hex_len.min(max_len)]).expect("ascii only in hex");
	f.write_str(hex)
	}
	}

	impl std::fmt::Debug for oid {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	write!(
	f,
	"{}({})",
	match self.kind() {
	Kind::Sha1 => "Sha1",
	},
	self.to_hex(),
	)
	}
	}

	/// The error returned when trying to convert a byte slice to an [`oid`] or [`ObjectId`]
	#[allow(missing_docs)]
	#[derive(Debug, thiserror::Error)]
	pub enum Error {
	#[error("Cannot instantiate git hash from a digest of length {0}")]
	InvalidByteSliceLength(usize),
	}

	/// Conversion
	impl oid {
	/// Try to create a shared object id from a slice of bytes representing a hash `digest`
	#[inline]
	pub fn try_from_bytes(digest: &[u8]) -> Result<&Self, Error> {
	match digest.len() {
	20 => Ok(
	#[allow(unsafe_code)]
	unsafe {
	&(digest as const [u8] as *const oid)
	},
	),
	len => Err(Error::InvalidByteSliceLength(len)),
	}
	}

	/// Create an OID from the input `value` slice without performing any safety check.
	/// Use only once sure that `value` is a hash of valid length.
	pub fn from_bytes_unchecked(value: &[u8]) -> &Self {
	Self::from_bytes(value)
	}

	/// Only from code that statically assures correct sizes using array conversions.
	pub(crate) fn from_bytes(value: &[u8]) -> &Self {
	#[allow(unsafe_code)]
	unsafe {
	&(value as const [u8] as *const oid)
	}
	}
	}

	/// Access
	impl oid {
	/// The kind of hash used for this instance.
	#[inline]
	pub fn kind(&self) -> Kind {
	Kind::from_len_in_bytes(self.bytes.len())
	}

	/// The first byte of the hash, commonly used to partition a set of object ids.
	#[inline]
	pub fn first_byte(&self) -> u8 {
	self.bytes[0]
	}

	/// Interpret this object id as raw byte slice.
	#[inline]
	pub fn as_bytes(&self) -> &[u8] {
	&self.bytes
	}

	/// Return a type which can display itself in hexadecimal form with the `len` amount of characters.
	#[inline]
	pub fn to_hex_with_len(&self, len: usize) -> HexDisplay<'_> {
	HexDisplay {
	inner: self,
	hex_len: len,
	}
	}

	/// Return a type which displays this oid as hex in full.
	#[inline]
	pub fn to_hex(&self) -> HexDisplay<'_> {
	HexDisplay {
	inner: self,
	hex_len: self.bytes.len() * 2,
	}
	}

	/// 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.kind() {
	Kind::Sha1 => &self.bytes == oid::null_sha1().as_bytes(),
	}
	}
	}

	/// Sha1 specific methods
	impl oid {
	/// Write ourselves to the `out` in hexadecimal notation, returning the amount of written bytes.
	///
	/// Panics if the buffer isn't big enough to hold twice as many bytes as the current binary size.
	#[inline]
	#[must_use]
	pub fn hex_to_buf(&self, buf: &mut [u8]) -> usize {
	let num_hex_bytes = self.bytes.len() * 2;
	faster_hex::hex_encode(&self.bytes, &mut buf[..num_hex_bytes]).expect("to count correctly");
	num_hex_bytes
	}

	/// Write ourselves to `out` in hexadecimal notation.
	#[inline]
	pub fn write_hex_to(&self, out: &mut dyn std::io::Write) -> std::io::Result<()> {
	let mut hex = Kind::hex_buf();
	let hex_len = self.hex_to_buf(&mut hex);
	out.write_all(&hex[..hex_len])
	}

	/// Returns a Sha1 digest with all bytes being initialized to zero.
	#[inline]
	pub(crate) fn null_sha1() -> &'static Self {
	oid::from_bytes([0u8; SIZE_OF_SHA1_DIGEST].as_ref())
	}
	}

	impl AsRef<oid> for &oid {
	fn as_ref(&self) -> &oid {
	self
	}
	}

	impl<'a> TryFrom<&'a [u8]> for &'a oid {
	type Error = Error;

	fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
	oid::try_from_bytes(value)
	}
	}

	impl ToOwned for oid {
	type Owned = ObjectId;

	fn to_owned(&self) -> Self::Owned {
	match self.kind() {
	Kind::Sha1 => ObjectId::Sha1(self.bytes.try_into().expect("no bug in hash detection")),
	}
	}
	}

	impl<'a> From<&'a [u8; SIZE_OF_SHA1_DIGEST]> for &'a oid {
	fn from(v: &'a [u8; SIZE_OF_SHA1_DIGEST]) -> Self {
	oid::from_bytes(v.as_ref())
	}
	}

	impl std::fmt::Display for &oid {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	for b in self.as_bytes() {
	write!(f, "{b:02x}")?;
	}
	Ok(())
	}
	}

	impl PartialEq<ObjectId> for &oid {
	fn eq(&self, other: &ObjectId) -> bool {
	*self == other.as_ref()
	}
	}

	/// Manually created from a version that uses a slice, and we forcefully try to convert it into a borrowed array of the desired size
	/// Could be improved by fitting this into serde.
	/// Unfortunately the `serde::Deserialize` derive wouldn't work for borrowed arrays.
	#[cfg(feature = "serde")]
	impl<'de: 'a, 'a> serde::Deserialize<'de> for &'a oid {
	fn deserialize<D>(deserializer: D) -> Result<Self, <D as serde::Deserializer<'de>>::Error>
	where
	D: serde::Deserializer<'de>,
	{
	struct __Visitor<'de: 'a, 'a> {
	marker: std::marker::PhantomData<&'a oid>,
	lifetime: std::marker::PhantomData<&'de ()>,
	}
	impl<'de: 'a, 'a> serde::de::Visitor<'de> for __Visitor<'de, 'a> {
	type Value = &'a oid;
	fn expecting(&self, __formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	std::fmt::Formatter::write_str(__formatter, "tuple struct Digest")
	}
	#[inline]
	fn visit_newtype_struct<__E>(self, __e: __E) -> std::result::Result<Self::Value, __E::Error>
	where
	__E: serde::Deserializer<'de>,
	{
	let __field0: &'a [u8] = match <&'a [u8] as serde::Deserialize>::deserialize(__e) {
	Ok(__val) => __val,
	Err(__err) => {
	return Err(__err);
	}
	};
	Ok(oid::try_from_bytes(__field0).expect("hash of known length"))
	}
	#[inline]
	fn visit_seq<__A>(self, mut __seq: __A) -> std::result::Result<Self::Value, __A::Error>
	where
	__A: serde::de::SeqAccess<'de>,
	{
	let __field0 = match match serde::de::SeqAccess::next_element::<&'a [u8]>(&mut __seq) {
	Ok(__val) => __val,
	Err(__err) => {
	return Err(__err);
	}
	} {
	Some(__value) => __value,
	None => {
	return Err(serde::de::Error::invalid_length(
	0usize,
	&"tuple struct Digest with 1 element",
	));
	}
	};
	Ok(oid::try_from_bytes(__field0).expect("hash of known length"))
	}
	}
	serde::Deserializer::deserialize_newtype_struct(
	deserializer,
	"Digest",
	__Visitor {
	marker: std::marker::PhantomData::<&'a oid>,
	lifetime: std::marker::PhantomData,
	},
	)
	}
	}