Sebastian Thiel[pack #179] fix docs7ad7a445 years agoHistory
201 lines · 8.2 KB · Rust
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use crate::{data, find}; /// Describe how object can be located in an object store with built-in facilities to supports packs specifically.////// ## Notes////// Locate effectively needs [generic associated types][issue] to allow a trait for the returned object type./// Until then, we will have to make due with explicit types and give them the potentially added features we want.////// [issue]: https://github.com/rust-lang/rust/issues/44265pub trait Find {    /// The error returned by [`try_find()`][Find::try_find()]    type Error: std::error::Error + 'static;     /// Find an object matching `id` in the database while placing its raw, undecoded data into `buffer`.    /// A `pack_cache` can be used to speed up subsequent lookups, set it to [`crate::cache::Never`] if the    /// workload isn't suitable for caching.    ///    /// Returns `Some` object if it was present in the database, or the error that occurred during lookup or object    /// retrieval.    fn try_find<'a>(        &self,        id: impl AsRef<git_hash::oid>,        buffer: &'a mut Vec<u8>,        pack_cache: &mut impl crate::cache::DecodeEntry,    ) -> Result<Option<data::Object<'a>>, Self::Error>;     /// Find the packs location where an object with `id` can be found in the database, or `None` if there is no pack    /// holding the object.    ///    /// _Note_ that the object database may have no notion of packs and thus always returns `None`.    fn location_by_oid(&self, id: impl AsRef<git_hash::oid>, buf: &mut Vec<u8>) -> Option<crate::bundle::Location>;     /// Find the bundle matching `pack_id`, or `None` if there is no such pack.    ///    /// _Note_ that the object database may have no notion of packs and thus always returns `None`.    fn bundle_by_pack_id(&self, pack_id: u32) -> Option<&crate::Bundle>;     /// Return the [`find::Entry`] for `location` if it is backed by a pack.    ///    /// Note that this is only in the interest of avoiding duplicate work during pack generation.    /// Pack locations can be obtained from a [`data::Object`].    ///    /// # Notes    ///    /// Custom implementations might be interested in providing their own meta-data with `object`,    /// which currently isn't possible as the `Locate` trait requires GATs to work like that.    fn entry_by_location(&self, location: &crate::bundle::Location) -> Option<find::Entry<'_>>;} mod ext {    use git_object::{BlobRef, CommitRef, CommitRefIter, Kind, ObjectRef, TagRef, TagRefIter, TreeRef, TreeRefIter};     use crate::{data, find};     macro_rules! make_obj_lookup {        ($method:ident, $object_variant:path, $object_kind:path, $object_type:ty) => {            /// Like [`find(…)`][Self::find()], but flattens the `Result<Option<_>>` into a single `Result` making a non-existing object an error            /// while returning the desired object type.            fn $method<'a>(                &self,                id: impl AsRef<git_hash::oid>,                buffer: &'a mut Vec<u8>,                pack_cache: &mut impl crate::cache::DecodeEntry,            ) -> Result<$object_type, find::existing_object::Error<Self::Error>> {                let id = id.as_ref();                self.try_find(id, buffer, pack_cache)                    .map_err(find::existing_object::Error::Find)?                    .ok_or_else(|| find::existing_object::Error::NotFound {                        oid: id.as_ref().to_owned(),                    })                    .and_then(|o| o.decode().map_err(find::existing_object::Error::Decode))                    .and_then(|o| match o {                        $object_variant(o) => return Ok(o),                        _other => Err(find::existing_object::Error::ObjectKind {                            expected: $object_kind,                        }),                    })            }        };    }     macro_rules! make_iter_lookup {        ($method:ident, $object_kind:path, $object_type:ty, $into_iter:tt) => {            /// Like [`find(…)`][Self::find()], but flattens the `Result<Option<_>>` into a single `Result` making a non-existing object an error            /// while returning the desired iterator type.            fn $method<'a>(                &self,                id: impl AsRef<git_hash::oid>,                buffer: &'a mut Vec<u8>,                pack_cache: &mut impl crate::cache::DecodeEntry,            ) -> Result<$object_type, find::existing_iter::Error<Self::Error>> {                let id = id.as_ref();                self.try_find(id, buffer, pack_cache)                    .map_err(find::existing_iter::Error::Find)?                    .ok_or_else(|| find::existing_iter::Error::NotFound {                        oid: id.as_ref().to_owned(),                    })                    .and_then(|o| {                        o.$into_iter()                            .ok_or_else(|| find::existing_iter::Error::ObjectKind {                                expected: $object_kind,                            })                    })            }        };    }     /// An extension trait with convenience functions.    pub trait FindExt: super::Find {        /// Like [`try_find(…)`][super::Find::try_find()], but flattens the `Result<Option<_>>` into a single `Result` making a non-existing object an error.        fn find<'a>(            &self,            id: impl AsRef<git_hash::oid>,            buffer: &'a mut Vec<u8>,            pack_cache: &mut impl crate::cache::DecodeEntry,        ) -> Result<data::Object<'a>, find::existing::Error<Self::Error>> {            let id = id.as_ref();            self.try_find(id, buffer, pack_cache)                .map_err(find::existing::Error::Find)?                .ok_or_else(|| find::existing::Error::NotFound {                    oid: id.as_ref().to_owned(),                })        }         make_obj_lookup!(find_commit, ObjectRef::Commit, Kind::Commit, CommitRef<'a>);        make_obj_lookup!(find_tree, ObjectRef::Tree, Kind::Tree, TreeRef<'a>);        make_obj_lookup!(find_tag, ObjectRef::Tag, Kind::Tag, TagRef<'a>);        make_obj_lookup!(find_blob, ObjectRef::Blob, Kind::Blob, BlobRef<'a>);        make_iter_lookup!(find_commit_iter, Kind::Blob, CommitRefIter<'a>, into_commit_iter);        make_iter_lookup!(find_tree_iter, Kind::Tree, TreeRefIter<'a>, into_tree_iter);        make_iter_lookup!(find_tag_iter, Kind::Tag, TagRefIter<'a>, into_tag_iter);    }     impl<T: super::Find> FindExt for T {}}pub use ext::FindExt; mod find_impls {    use std::ops::Deref;     use git_hash::oid;     use crate::{bundle::Location, data::Object, find, Bundle};     impl<T> super::Find for std::sync::Arc<T>    where        T: super::Find,    {        type Error = T::Error;         fn try_find<'a>(            &self,            id: impl AsRef<oid>,            buffer: &'a mut Vec<u8>,            pack_cache: &mut impl crate::cache::DecodeEntry,        ) -> Result<Option<Object<'a>>, Self::Error> {            self.deref().try_find(id, buffer, pack_cache)        }         fn location_by_oid(&self, id: impl AsRef<oid>, buf: &mut Vec<u8>) -> Option<Location> {            self.deref().location_by_oid(id, buf)        }         fn bundle_by_pack_id(&self, pack_id: u32) -> Option<&Bundle> {            self.deref().bundle_by_pack_id(pack_id)        }         fn entry_by_location(&self, object: &crate::bundle::Location) -> Option<find::Entry<'_>> {            self.deref().entry_by_location(object)        }    }     impl<T> super::Find for Box<T>    where        T: super::Find,    {        type Error = T::Error;         fn try_find<'a>(            &self,            id: impl AsRef<oid>,            buffer: &'a mut Vec<u8>,            pack_cache: &mut impl crate::cache::DecodeEntry,        ) -> Result<Option<Object<'a>>, Self::Error> {            self.deref().try_find(id, buffer, pack_cache)        }         fn location_by_oid(&self, id: impl AsRef<oid>, buf: &mut Vec<u8>) -> Option<Location> {            self.deref().location_by_oid(id, buf)        }         fn bundle_by_pack_id(&self, pack_id: u32) -> Option<&Bundle> {            self.deref().bundle_by_pack_id(pack_id)        }         fn entry_by_location(&self, location: &crate::bundle::Location) -> Option<find::Entry<'_>> {            self.deref().entry_by_location(location)        }    }}