gix,gix-odb,gix-pack: stream blob contents from the ODB

gix-odb/src/cache.rs

@@ -91,6 +91,22 @@ impl<S> Cache<S> {
     }
 }
 
+impl<S> Cache<crate::store::Handle<S>>
+where
+    S: Deref<Target = crate::Store> + Clone,
+{
+    /// Find an object and return its decoded bytes as a stream.
+    pub fn try_find_stream(
+        &self,
+        id: &gix_hash::oid,
+    ) -> Result<Option<(crate::find::Stream, Option<gix_pack::data::entry::Location>)>, gix_object::find::Error> {
+        match self.pack_cache.as_ref().map(RefCell::borrow_mut) {
+            Some(mut pack_cache) => self.inner.try_find_stream(id, pack_cache.deref_mut()),
+            None => self.inner.try_find_stream(id, &mut gix_pack::cache::Never),
+        }
+    }
+}
+
 impl<S> From<S> for Cache<S>
 where
     S: gix_pack::Find,

gix-odb/src/find.rs

@@ -1,3 +1,73 @@
+use std::io::{self, Cursor, Read};
+
+/// A streaming view over an object's decoded bytes.
+pub struct Stream {
+    kind: gix_object::Kind,
+    size: u64,
+    inner: StreamInner,
+}
+
+enum StreamInner {
+    InMemory(Cursor<Vec<u8>>),
+    File(std::fs::File),
+    Loose(crate::store_impls::loose::find::StreamReader),
+}
+
+impl Stream {
+    /// Return the kind of the object yielded by this stream.
+    pub fn kind(&self) -> gix_object::Kind {
+        self.kind
+    }
+
+    /// Return the decoded object size in bytes.
+    pub fn size(&self) -> u64 {
+        self.size
+    }
+
+    /// Return an empty blob stream.
+    pub fn empty_blob() -> Self {
+        Self::from_bytes(gix_object::Kind::Blob, Vec::new())
+    }
+
+    pub(crate) fn from_bytes(kind: gix_object::Kind, data: Vec<u8>) -> Self {
+        Self {
+            kind,
+            size: data.len() as u64,
+            inner: StreamInner::InMemory(Cursor::new(data)),
+        }
+    }
+
+    pub(crate) fn from_file(kind: gix_object::Kind, size: u64, file: std::fs::File) -> Self {
+        Self {
+            kind,
+            size,
+            inner: StreamInner::File(file),
+        }
+    }
+
+    pub(crate) fn from_loose(
+        kind: gix_object::Kind,
+        size: u64,
+        reader: crate::store_impls::loose::find::StreamReader,
+    ) -> Self {
+        Self {
+            kind,
+            size,
+            inner: StreamInner::Loose(reader),
+        }
+    }
+}
+
+impl Read for Stream {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        match &mut self.inner {
+            StreamInner::InMemory(cursor) => cursor.read(buf),
+            StreamInner::File(file) => file.read(buf),
+            StreamInner::Loose(reader) => reader.read(buf),
+        }
+    }
+}
+
 /// An object header informing about object properties, without it being fully decoded in the process.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub enum Header {

gix-odb/src/memory.rs

@@ -123,6 +123,26 @@ impl<T> Proxy<T> {
     }
 }
 
+impl<S> Proxy<crate::Cache<crate::store::Handle<S>>>
+where
+    S: Deref<Target = crate::Store> + Clone,
+{
+    /// Find an object and return its decoded bytes as a stream.
+    pub fn try_find_stream(
+        &self,
+        id: &gix_hash::oid,
+    ) -> Result<Option<(crate::find::Stream, Option<crate::pack::data::entry::Location>)>, gix_object::find::Error>
+    {
+        if let Some(map) = self.memory.as_ref() {
+            let map = map.borrow();
+            if let Some((kind, data)) = map.get(id) {
+                return Ok(Some((crate::find::Stream::from_bytes(*kind, data.clone()), None)));
+            }
+        }
+        self.inner.try_find_stream(id)
+    }
+}
+
 impl<T> Clone for Proxy<T>
 where
     T: Clone,

gix-odb/src/store_impls/dynamic/find.rs

@@ -85,7 +85,7 @@ impl<S> super::Handle<S>
 where
     S: Deref<Target = super::Store> + Clone,
 {
-    fn try_find_cached_inner<'a, 'b>(
+    pub(crate) fn try_find_cached_inner<'a, 'b>(
         &'b self,
         mut id: &'b gix_hash::oid,
         buffer: &'a mut Vec<u8>,

gix-odb/src/store_impls/dynamic/mod.rs

@@ -57,6 +57,7 @@ pub mod find;
 pub mod prefix;
 
 mod header;
+mod stream;
 
 ///
 pub mod iter;

gix-odb/src/store_impls/dynamic/stream.rs

@@ -0,0 +1,230 @@
+use std::{io::Seek, ops::Deref};
+
+use gix_features::zlib;
+use gix_hash::oid;
+use gix_pack::cache::DecodeEntry;
+
+use super::find::Error;
+use crate::store::{find::error::DeltaBaseRecursion, handle, load_index};
+
+impl<S> super::Handle<S>
+where
+    S: Deref<Target = super::Store> + Clone,
+{
+    pub(crate) fn try_find_stream_inner<'b>(
+        &'b self,
+        mut id: &'b gix_hash::oid,
+        inflate: &mut zlib::Inflate,
+        pack_cache: &mut dyn DecodeEntry,
+        snapshot: &mut load_index::Snapshot,
+        recursion: Option<DeltaBaseRecursion<'_>>,
+    ) -> Result<Option<(crate::find::Stream, Option<gix_pack::data::entry::Location>)>, Error> {
+        if let Some(r) = recursion {
+            if r.depth >= self.max_recursion_depth {
+                return Err(Error::DeltaBaseRecursionLimit {
+                    max_depth: self.max_recursion_depth,
+                    id: r.original_id.to_owned(),
+                });
+            }
+        } else if !self.ignore_replacements {
+            if let Ok(pos) = self
+                .store
+                .replacements
+                .binary_search_by(|(map_this, _)| map_this.as_ref().cmp(id))
+            {
+                id = self.store.replacements[pos].1.as_ref();
+            }
+        }
+
+        'outer: loop {
+            {
+                let marker = snapshot.marker;
+                for (idx, index) in snapshot.indices.iter_mut().enumerate() {
+                    if let Some(handle::index_lookup::Outcome {
+                        object_index: handle::IndexForObjectInPack { pack_id, pack_offset },
+                        index_file,
+                        pack: possibly_pack,
+                    }) = index.lookup(id)
+                    {
+                        let pack = match possibly_pack {
+                            Some(pack) => pack,
+                            None => match self.store.load_pack(pack_id, marker)? {
+                                Some(pack) => {
+                                    *possibly_pack = Some(pack);
+                                    possibly_pack.as_deref().expect("just put it in")
+                                }
+                                None => match self.store.load_one_index(self.refresh, snapshot.marker)? {
+                                    Some(new_snapshot) => {
+                                        *snapshot = new_snapshot;
+                                        self.clear_cache();
+                                        continue 'outer;
+                                    }
+                                    None => return Ok(None),
+                                },
+                            },
+                        };
+                        let resolved_pack_id = pack.id;
+                        let entry = pack.entry(pack_offset)?;
+                        let header_size = entry.header_size();
+                        let result = {
+                            let mut scratch = Vec::new();
+                            let mut temp = tempfile::tempfile()?;
+                            let result = match pack.decode_entry_to_write(
+                                entry,
+                                &mut scratch,
+                                inflate,
+                                &mut temp,
+                                &|id, _out| {
+                                    index_file.pack_offset_by_id(id).and_then(|pack_offset| {
+                                        pack.entry(pack_offset)
+                                            .ok()
+                                            .map(gix_pack::data::decode::entry::ResolvedBase::InPack)
+                                    })
+                                },
+                                pack_cache,
+                            ) {
+                                Ok(outcome) => Ok((outcome, temp)),
+                                Err(gix_pack::data::decode::Error::DeltaBaseUnresolved(base_id)) => {
+                                    let mut buf = Vec::new();
+                                    let obj_kind = self
+                                        .try_find_cached_inner(
+                                            &base_id,
+                                            &mut buf,
+                                            inflate,
+                                            pack_cache,
+                                            snapshot,
+                                            recursion
+                                                .map(DeltaBaseRecursion::inc_depth)
+                                                .or_else(|| DeltaBaseRecursion::new(id).into()),
+                                        )
+                                        .map_err(|err| Error::DeltaBaseLookup {
+                                            err: Box::new(err),
+                                            base_id,
+                                            id: id.to_owned(),
+                                        })?
+                                        .ok_or_else(|| Error::DeltaBaseMissing {
+                                            base_id,
+                                            id: id.to_owned(),
+                                        })?
+                                        .0
+                                        .kind;
+                                    let handle::index_lookup::Outcome {
+                                        object_index:
+                                            handle::IndexForObjectInPack {
+                                                pack_id: _,
+                                                pack_offset,
+                                            },
+                                        index_file,
+                                        pack: possibly_pack,
+                                    } = match snapshot.indices[idx].lookup(id) {
+                                        Some(res) => res,
+                                        None => {
+                                            let mut out = None;
+                                            for index in &mut snapshot.indices {
+                                                out = index.lookup(id);
+                                                if out.is_some() {
+                                                    break;
+                                                }
+                                            }
+
+                                            out.unwrap_or_else(|| {
+                                                panic!(
+                                                    "could not find object {id} in any index after looking up one of its base objects {base_id}"
+                                                )
+                                            })
+                                        }
+                                    };
+                                    let pack = possibly_pack
+                                        .as_ref()
+                                        .expect("pack to still be available like just now");
+                                    let entry = pack.entry(pack_offset)?;
+                                    let mut scratch = Vec::new();
+                                    let mut temp = tempfile::tempfile()?;
+                                    pack.decode_entry_to_write(
+                                        entry,
+                                        &mut scratch,
+                                        inflate,
+                                        &mut temp,
+                                        &|id, out| {
+                                            index_file
+                                                .pack_offset_by_id(id)
+                                                .and_then(|pack_offset| {
+                                                    pack.entry(pack_offset)
+                                                        .ok()
+                                                        .map(gix_pack::data::decode::entry::ResolvedBase::InPack)
+                                                })
+                                                .or_else(|| {
+                                                    (id == base_id).then(|| {
+                                                        out.resize(buf.len(), 0);
+                                                        out.copy_from_slice(buf.as_slice());
+                                                        gix_pack::data::decode::entry::ResolvedBase::OutOfPack {
+                                                            kind: obj_kind,
+                                                            end: out.len(),
+                                                        }
+                                                    })
+                                                })
+                                        },
+                                        pack_cache,
+                                    )
+                                    .map(|outcome| (outcome, temp))
+                                }
+                                Err(err) => Err(err),
+                            }?;
+                            result
+                        };
+                        let (outcome, mut temp) = result;
+                        temp.rewind()?;
+                        let res = (
+                            crate::find::Stream::from_file(outcome.kind, outcome.object_size, temp),
+                            Some(gix_pack::data::entry::Location {
+                                pack_id: resolved_pack_id,
+                                pack_offset,
+                                entry_size: outcome.compressed_size + header_size,
+                            }),
+                        );
+
+                        if idx != 0 {
+                            snapshot.indices.swap(0, idx);
+                        }
+                        return Ok(Some(res));
+                    }
+                }
+            }
+
+            for lodb in snapshot.loose_dbs.iter() {
+                if lodb.contains(id) {
+                    return lodb
+                        .try_find_stream(id)
+                        .map(|obj| obj.map(|obj| (obj, None)))
+                        .map_err(Into::into);
+                }
+            }
+
+            match self.store.load_one_index(self.refresh, snapshot.marker)? {
+                Some(new_snapshot) => {
+                    *snapshot = new_snapshot;
+                    self.clear_cache();
+                }
+                None => return Ok(None),
+            }
+        }
+    }
+}
+
+impl<S> super::Handle<S>
+where
+    S: Deref<Target = super::Store> + Clone,
+{
+    /// Try to find the object identified by `id` in any backing store and return it as a readable stream,
+    /// along with its pack location if it came from a pack.
+    pub fn try_find_stream(
+        &self,
+        id: &oid,
+        pack_cache: &mut dyn DecodeEntry,
+    ) -> Result<Option<(crate::find::Stream, Option<gix_pack::data::entry::Location>)>, gix_object::find::Error> {
+        let mut snapshot = self.snapshot.borrow_mut();
+        let mut inflate = self.inflate.borrow_mut();
+        self.try_find_stream_inner(id, &mut inflate, pack_cache, &mut snapshot, None)
+            .map_err(|err| Box::new(err) as _)
+    }
+}