diff rust/hg-core/src/revlog/mod.rs @ 49937:750409505286

rust-clippy: merge "revlog" module definition and struct implementation

Module inception is confusing when looking for code and almost never
the right choice.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-core/src/revlog/mod.rs	Tue Jan 10 11:20:54 2023 +0100
@@ -0,0 +1,710 @@
+// Copyright 2018-2023 Georges Racinet <[e-mail]>
+//           and Mercurial contributors
+//
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2 or any later version.
+//! Mercurial concepts for handling revision history
+
+pub mod node;
+pub mod nodemap;
+mod nodemap_docket;
+pub mod path_encode;
+pub use node::{FromHexError, Node, NodePrefix};
+pub mod changelog;
+pub mod filelog;
+pub mod index;
+pub mod manifest;
+pub mod patch;
+
+use std::borrow::Cow;
+use std::io::Read;
+use std::ops::Deref;
+use std::path::Path;
+
+use flate2::read::ZlibDecoder;
+use sha1::{Digest, Sha1};
+use zstd;
+
+use self::node::{NODE_BYTES_LENGTH, NULL_NODE};
+use self::nodemap_docket::NodeMapDocket;
+use super::index::Index;
+use super::nodemap::{NodeMap, NodeMapError};
+use crate::errors::HgError;
+use crate::vfs::Vfs;
+
+/// Mercurial revision numbers
+///
+/// As noted in revlog.c, revision numbers are actually encoded in
+/// 4 bytes, and are liberally converted to ints, whence the i32
+pub type Revision = i32;
+
+/// Marker expressing the absence of a parent
+///
+/// Independently of the actual representation, `NULL_REVISION` is guaranteed
+/// to be smaller than all existing revisions.
+pub const NULL_REVISION: Revision = -1;
+
+/// Same as `mercurial.node.wdirrev`
+///
+/// This is also equal to `i32::max_value()`, but it's better to spell
+/// it out explicitely, same as in `mercurial.node`
+#[allow(clippy::unreadable_literal)]
+pub const WORKING_DIRECTORY_REVISION: Revision = 0x7fffffff;
+
+pub const WORKING_DIRECTORY_HEX: &str =
+    "ffffffffffffffffffffffffffffffffffffffff";
+
+/// The simplest expression of what we need of Mercurial DAGs.
+pub trait Graph {
+    /// Return the two parents of the given `Revision`.
+    ///
+    /// Each of the parents can be independently `NULL_REVISION`
+    fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError>;
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum GraphError {
+    ParentOutOfRange(Revision),
+    WorkingDirectoryUnsupported,
+}
+
+/// The Mercurial Revlog Index
+///
+/// This is currently limited to the minimal interface that is needed for
+/// the [`nodemap`](nodemap/index.html) module
+pub trait RevlogIndex {
+    /// Total number of Revisions referenced in this index
+    fn len(&self) -> usize;
+
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Return a reference to the Node or `None` if rev is out of bounds
+    ///
+    /// `NULL_REVISION` is not considered to be out of bounds.
+    fn node(&self, rev: Revision) -> Option<&Node>;
+}
+
+const REVISION_FLAG_CENSORED: u16 = 1 << 15;
+const REVISION_FLAG_ELLIPSIS: u16 = 1 << 14;
+const REVISION_FLAG_EXTSTORED: u16 = 1 << 13;
+const REVISION_FLAG_HASCOPIESINFO: u16 = 1 << 12;
+
+// Keep this in sync with REVIDX_KNOWN_FLAGS in
+// mercurial/revlogutils/flagutil.py
+const REVIDX_KNOWN_FLAGS: u16 = REVISION_FLAG_CENSORED
+    | REVISION_FLAG_ELLIPSIS
+    | REVISION_FLAG_EXTSTORED
+    | REVISION_FLAG_HASCOPIESINFO;
+
+const NULL_REVLOG_ENTRY_FLAGS: u16 = 0;
+
+#[derive(Debug, derive_more::From)]
+pub enum RevlogError {
+    InvalidRevision,
+    /// Working directory is not supported
+    WDirUnsupported,
+    /// Found more than one entry whose ID match the requested prefix
+    AmbiguousPrefix,
+    #[from]
+    Other(HgError),
+}
+
+impl From<NodeMapError> for RevlogError {
+    fn from(error: NodeMapError) -> Self {
+        match error {
+            NodeMapError::MultipleResults => RevlogError::AmbiguousPrefix,
+            NodeMapError::RevisionNotInIndex(rev) => RevlogError::corrupted(
+                format!("nodemap point to revision {} not in index", rev),
+            ),
+        }
+    }
+}
+
+fn corrupted<S: AsRef<str>>(context: S) -> HgError {
+    HgError::corrupted(format!("corrupted revlog, {}", context.as_ref()))
+}
+
+impl RevlogError {
+    fn corrupted<S: AsRef<str>>(context: S) -> Self {
+        RevlogError::Other(corrupted(context))
+    }
+}
+
+/// Read only implementation of revlog.
+pub struct Revlog {
+    /// When index and data are not interleaved: bytes of the revlog index.
+    /// When index and data are interleaved: bytes of the revlog index and
+    /// data.
+    index: Index,
+    /// When index and data are not interleaved: bytes of the revlog data
+    data_bytes: Option<Box<dyn Deref<Target = [u8]> + Send>>,
+    /// When present on disk: the persistent nodemap for this revlog
+    nodemap: Option<nodemap::NodeTree>,
+}
+
+impl Revlog {
+    /// Open a revlog index file.
+    ///
+    /// It will also open the associated data file if index and data are not
+    /// interleaved.
+    pub fn open(
+        store_vfs: &Vfs,
+        index_path: impl AsRef<Path>,
+        data_path: Option<&Path>,
+        use_nodemap: bool,
+    ) -> Result<Self, HgError> {
+        let index_path = index_path.as_ref();
+        let index = {
+            match store_vfs.mmap_open_opt(&index_path)? {
+                None => Index::new(Box::new(vec![])),
+                Some(index_mmap) => {
+                    let index = Index::new(Box::new(index_mmap))?;
+                    Ok(index)
+                }
+            }
+        }?;
+
+        let default_data_path = index_path.with_extension("d");
+
+        // type annotation required
+        // won't recognize Mmap as Deref<Target = [u8]>
+        let data_bytes: Option<Box<dyn Deref<Target = [u8]> + Send>> =
+            if index.is_inline() {
+                None
+            } else {
+                let data_path = data_path.unwrap_or(&default_data_path);
+                let data_mmap = store_vfs.mmap_open(data_path)?;
+                Some(Box::new(data_mmap))
+            };
+
+        let nodemap = if index.is_inline() || !use_nodemap {
+            None
+        } else {
+            NodeMapDocket::read_from_file(store_vfs, index_path)?.map(
+                |(docket, data)| {
+                    nodemap::NodeTree::load_bytes(
+                        Box::new(data),
+                        docket.data_length,
+                    )
+                },
+            )
+        };
+
+        Ok(Revlog {
+            index,
+            data_bytes,
+            nodemap,
+        })
+    }
+
+    /// Return number of entries of the `Revlog`.
+    pub fn len(&self) -> usize {
+        self.index.len()
+    }
+
+    /// Returns `true` if the `Revlog` has zero `entries`.
+    pub fn is_empty(&self) -> bool {
+        self.index.is_empty()
+    }
+
+    /// Returns the node ID for the given revision number, if it exists in this
+    /// revlog
+    pub fn node_from_rev(&self, rev: Revision) -> Option<&Node> {
+        if rev == NULL_REVISION {
+            return Some(&NULL_NODE);
+        }
+        Some(self.index.get_entry(rev)?.hash())
+    }
+
+    /// Return the revision number for the given node ID, if it exists in this
+    /// revlog
+    pub fn rev_from_node(
+        &self,
+        node: NodePrefix,
+    ) -> Result<Revision, RevlogError> {
+        if node.is_prefix_of(&NULL_NODE) {
+            return Ok(NULL_REVISION);
+        }
+
+        if let Some(nodemap) = &self.nodemap {
+            return nodemap
+                .find_bin(&self.index, node)?
+                .ok_or(RevlogError::InvalidRevision);
+        }
+
+        // Fallback to linear scan when a persistent nodemap is not present.
+        // This happens when the persistent-nodemap experimental feature is not
+        // enabled, or for small revlogs.
+        //
+        // TODO: consider building a non-persistent nodemap in memory to
+        // optimize these cases.
+        let mut found_by_prefix = None;
+        for rev in (0..self.len() as Revision).rev() {
+            let index_entry = self.index.get_entry(rev).ok_or_else(|| {
+                HgError::corrupted(
+                    "revlog references a revision not in the index",
+                )
+            })?;
+            if node == *index_entry.hash() {
+                return Ok(rev);
+            }
+            if node.is_prefix_of(index_entry.hash()) {
+                if found_by_prefix.is_some() {
+                    return Err(RevlogError::AmbiguousPrefix);
+                }
+                found_by_prefix = Some(rev)
+            }
+        }
+        found_by_prefix.ok_or(RevlogError::InvalidRevision)
+    }
+
+    /// Returns whether the given revision exists in this revlog.
+    pub fn has_rev(&self, rev: Revision) -> bool {
+        self.index.get_entry(rev).is_some()
+    }
+
+    /// Return the full data associated to a revision.
+    ///
+    /// All entries required to build the final data out of deltas will be
+    /// retrieved as needed, and the deltas will be applied to the inital
+    /// snapshot to rebuild the final data.
+    pub fn get_rev_data(
+        &self,
+        rev: Revision,
+    ) -> Result<Cow<[u8]>, RevlogError> {
+        if rev == NULL_REVISION {
+            return Ok(Cow::Borrowed(&[]));
+        };
+        Ok(self.get_entry(rev)?.data()?)
+    }
+
+    /// Check the hash of some given data against the recorded hash.
+    pub fn check_hash(
+        &self,
+        p1: Revision,
+        p2: Revision,
+        expected: &[u8],
+        data: &[u8],
+    ) -> bool {
+        let e1 = self.index.get_entry(p1);
+        let h1 = match e1 {
+            Some(ref entry) => entry.hash(),
+            None => &NULL_NODE,
+        };
+        let e2 = self.index.get_entry(p2);
+        let h2 = match e2 {
+            Some(ref entry) => entry.hash(),
+            None => &NULL_NODE,
+        };
+
+        hash(data, h1.as_bytes(), h2.as_bytes()) == expected
+    }
+
+    /// Build the full data of a revision out its snapshot
+    /// and its deltas.
+    fn build_data_from_deltas(
+        snapshot: RevlogEntry,
+        deltas: &[RevlogEntry],
+    ) -> Result<Vec<u8>, HgError> {
+        let snapshot = snapshot.data_chunk()?;
+        let deltas = deltas
+            .iter()
+            .rev()
+            .map(RevlogEntry::data_chunk)
+            .collect::<Result<Vec<_>, _>>()?;
+        let patches: Vec<_> =
+            deltas.iter().map(|d| patch::PatchList::new(d)).collect();
+        let patch = patch::fold_patch_lists(&patches);
+        Ok(patch.apply(&snapshot))
+    }
+
+    /// Return the revlog data.
+    fn data(&self) -> &[u8] {
+        match &self.data_bytes {
+            Some(data_bytes) => data_bytes,
+            None => panic!(
+                "forgot to load the data or trying to access inline data"
+            ),
+        }
+    }
+
+    pub fn make_null_entry(&self) -> RevlogEntry {
+        RevlogEntry {
+            revlog: self,
+            rev: NULL_REVISION,
+            bytes: b"",
+            compressed_len: 0,
+            uncompressed_len: 0,
+            base_rev_or_base_of_delta_chain: None,
+            p1: NULL_REVISION,
+            p2: NULL_REVISION,
+            flags: NULL_REVLOG_ENTRY_FLAGS,
+            hash: NULL_NODE,
+        }
+    }
+
+    /// Get an entry of the revlog.
+    pub fn get_entry(
+        &self,
+        rev: Revision,
+    ) -> Result<RevlogEntry, RevlogError> {
+        if rev == NULL_REVISION {
+            return Ok(self.make_null_entry());
+        }
+        let index_entry = self
+            .index
+            .get_entry(rev)
+            .ok_or(RevlogError::InvalidRevision)?;
+        let start = index_entry.offset();
+        let end = start + index_entry.compressed_len() as usize;
+        let data = if self.index.is_inline() {
+            self.index.data(start, end)
+        } else {
+            &self.data()[start..end]
+        };
+        let entry = RevlogEntry {
+            revlog: self,
+            rev,
+            bytes: data,
+            compressed_len: index_entry.compressed_len(),
+            uncompressed_len: index_entry.uncompressed_len(),
+            base_rev_or_base_of_delta_chain: if index_entry
+                .base_revision_or_base_of_delta_chain()
+                == rev
+            {
+                None
+            } else {
+                Some(index_entry.base_revision_or_base_of_delta_chain())
+            },
+            p1: index_entry.p1(),
+            p2: index_entry.p2(),
+            flags: index_entry.flags(),
+            hash: *index_entry.hash(),
+        };
+        Ok(entry)
+    }
+
+    /// when resolving internal references within revlog, any errors
+    /// should be reported as corruption, instead of e.g. "invalid revision"
+    fn get_entry_internal(
+        &self,
+        rev: Revision,
+    ) -> Result<RevlogEntry, HgError> {
+        self.get_entry(rev)
+            .map_err(|_| corrupted(format!("revision {} out of range", rev)))
+    }
+}
+
+/// The revlog entry's bytes and the necessary informations to extract
+/// the entry's data.
+#[derive(Clone)]
+pub struct RevlogEntry<'a> {
+    revlog: &'a Revlog,
+    rev: Revision,
+    bytes: &'a [u8],
+    compressed_len: u32,
+    uncompressed_len: i32,
+    base_rev_or_base_of_delta_chain: Option<Revision>,
+    p1: Revision,
+    p2: Revision,
+    flags: u16,
+    hash: Node,
+}
+
+impl<'a> RevlogEntry<'a> {
+    pub fn revision(&self) -> Revision {
+        self.rev
+    }
+
+    pub fn node(&self) -> &Node {
+        &self.hash
+    }
+
+    pub fn uncompressed_len(&self) -> Option<u32> {
+        u32::try_from(self.uncompressed_len).ok()
+    }
+
+    pub fn has_p1(&self) -> bool {
+        self.p1 != NULL_REVISION
+    }
+
+    pub fn p1_entry(&self) -> Result<Option<RevlogEntry>, RevlogError> {
+        if self.p1 == NULL_REVISION {
+            Ok(None)
+        } else {
+            Ok(Some(self.revlog.get_entry(self.p1)?))
+        }
+    }
+
+    pub fn p2_entry(&self) -> Result<Option<RevlogEntry>, RevlogError> {
+        if self.p2 == NULL_REVISION {
+            Ok(None)
+        } else {
+            Ok(Some(self.revlog.get_entry(self.p2)?))
+        }
+    }
+
+    pub fn p1(&self) -> Option<Revision> {
+        if self.p1 == NULL_REVISION {
+            None
+        } else {
+            Some(self.p1)
+        }
+    }
+
+    pub fn p2(&self) -> Option<Revision> {
+        if self.p2 == NULL_REVISION {
+            None
+        } else {
+            Some(self.p2)
+        }
+    }
+
+    pub fn is_censored(&self) -> bool {
+        (self.flags & REVISION_FLAG_CENSORED) != 0
+    }
+
+    pub fn has_length_affecting_flag_processor(&self) -> bool {
+        // Relevant Python code: revlog.size()
+        // note: ELLIPSIS is known to not change the content
+        (self.flags & (REVIDX_KNOWN_FLAGS ^ REVISION_FLAG_ELLIPSIS)) != 0
+    }
+
+    /// The data for this entry, after resolving deltas if any.
+    pub fn rawdata(&self) -> Result<Cow<'a, [u8]>, HgError> {
+        let mut entry = self.clone();
+        let mut delta_chain = vec![];
+
+        // The meaning of `base_rev_or_base_of_delta_chain` depends on
+        // generaldelta. See the doc on `ENTRY_DELTA_BASE` in
+        // `mercurial/revlogutils/constants.py` and the code in
+        // [_chaininfo] and in [index_deltachain].
+        let uses_generaldelta = self.revlog.index.uses_generaldelta();
+        while let Some(base_rev) = entry.base_rev_or_base_of_delta_chain {
+            let base_rev = if uses_generaldelta {
+                base_rev
+            } else {
+                entry.rev - 1
+            };
+            delta_chain.push(entry);
+            entry = self.revlog.get_entry_internal(base_rev)?;
+        }
+
+        let data = if delta_chain.is_empty() {
+            entry.data_chunk()?
+        } else {
+            Revlog::build_data_from_deltas(entry, &delta_chain)?.into()
+        };
+
+        Ok(data)
+    }
+
+    fn check_data(
+        &self,
+        data: Cow<'a, [u8]>,
+    ) -> Result<Cow<'a, [u8]>, HgError> {
+        if self.revlog.check_hash(
+            self.p1,
+            self.p2,
+            self.hash.as_bytes(),
+            &data,
+        ) {
+            Ok(data)
+        } else {
+            if (self.flags & REVISION_FLAG_ELLIPSIS) != 0 {
+                return Err(HgError::unsupported(
+                    "ellipsis revisions are not supported by rhg",
+                ));
+            }
+            Err(corrupted(format!(
+                "hash check failed for revision {}",
+                self.rev
+            )))
+        }
+    }
+
+    pub fn data(&self) -> Result<Cow<'a, [u8]>, HgError> {
+        let data = self.rawdata()?;
+        if self.is_censored() {
+            return Err(HgError::CensoredNodeError);
+        }
+        self.check_data(data)
+    }
+
+    /// Extract the data contained in the entry.
+    /// This may be a delta. (See `is_delta`.)
+    fn data_chunk(&self) -> Result<Cow<'a, [u8]>, HgError> {
+        if self.bytes.is_empty() {
+            return Ok(Cow::Borrowed(&[]));
+        }
+        match self.bytes[0] {
+            // Revision data is the entirety of the entry, including this
+            // header.
+            b'\0' => Ok(Cow::Borrowed(self.bytes)),
+            // Raw revision data follows.
+            b'u' => Ok(Cow::Borrowed(&self.bytes[1..])),
+            // zlib (RFC 1950) data.
+            b'x' => Ok(Cow::Owned(self.uncompressed_zlib_data()?)),
+            // zstd data.
+            b'\x28' => Ok(Cow::Owned(self.uncompressed_zstd_data()?)),
+            // A proper new format should have had a repo/store requirement.
+            format_type => Err(corrupted(format!(
+                "unknown compression header '{}'",
+                format_type
+            ))),
+        }
+    }
+
+    fn uncompressed_zlib_data(&self) -> Result<Vec<u8>, HgError> {
+        let mut decoder = ZlibDecoder::new(self.bytes);
+        if self.is_delta() {
+            let mut buf = Vec::with_capacity(self.compressed_len as usize);
+            decoder
+                .read_to_end(&mut buf)
+                .map_err(|e| corrupted(e.to_string()))?;
+            Ok(buf)
+        } else {
+            let cap = self.uncompressed_len.max(0) as usize;
+            let mut buf = vec![0; cap];
+            decoder
+                .read_exact(&mut buf)
+                .map_err(|e| corrupted(e.to_string()))?;
+            Ok(buf)
+        }
+    }
+
+    fn uncompressed_zstd_data(&self) -> Result<Vec<u8>, HgError> {
+        if self.is_delta() {
+            let mut buf = Vec::with_capacity(self.compressed_len as usize);
+            zstd::stream::copy_decode(self.bytes, &mut buf)
+                .map_err(|e| corrupted(e.to_string()))?;
+            Ok(buf)
+        } else {
+            let cap = self.uncompressed_len.max(0) as usize;
+            let mut buf = vec![0; cap];
+            let len = zstd::bulk::decompress_to_buffer(self.bytes, &mut buf)
+                .map_err(|e| corrupted(e.to_string()))?;
+            if len != self.uncompressed_len as usize {
+                Err(corrupted("uncompressed length does not match"))
+            } else {
+                Ok(buf)
+            }
+        }
+    }
+
+    /// Tell if the entry is a snapshot or a delta
+    /// (influences on decompression).
+    fn is_delta(&self) -> bool {
+        self.base_rev_or_base_of_delta_chain.is_some()
+    }
+}
+
+/// Calculate the hash of a revision given its data and its parents.
+fn hash(
+    data: &[u8],
+    p1_hash: &[u8],
+    p2_hash: &[u8],
+) -> [u8; NODE_BYTES_LENGTH] {
+    let mut hasher = Sha1::new();
+    let (a, b) = (p1_hash, p2_hash);
+    if a > b {
+        hasher.update(b);
+        hasher.update(a);
+    } else {
+        hasher.update(a);
+        hasher.update(b);
+    }
+    hasher.update(data);
+    *hasher.finalize().as_ref()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::index::{IndexEntryBuilder, INDEX_ENTRY_SIZE};
+    use itertools::Itertools;
+
+    #[test]
+    fn test_empty() {
+        let temp = tempfile::tempdir().unwrap();
+        let vfs = Vfs { base: temp.path() };
+        std::fs::write(temp.path().join("foo.i"), b"").unwrap();
+        let revlog = Revlog::open(&vfs, "foo.i", None, false).unwrap();
+        assert!(revlog.is_empty());
+        assert_eq!(revlog.len(), 0);
+        assert!(revlog.get_entry(0).is_err());
+        assert!(!revlog.has_rev(0));
+    }
+
+    #[test]
+    fn test_inline() {
+        let temp = tempfile::tempdir().unwrap();
+        let vfs = Vfs { base: temp.path() };
+        let node0 = Node::from_hex("2ed2a3912a0b24502043eae84ee4b279c18b90dd")
+            .unwrap();
+        let node1 = Node::from_hex("b004912a8510032a0350a74daa2803dadfb00e12")
+            .unwrap();
+        let node2 = Node::from_hex("dd6ad206e907be60927b5a3117b97dffb2590582")
+            .unwrap();
+        let entry0_bytes = IndexEntryBuilder::new()
+            .is_first(true)
+            .with_version(1)
+            .with_inline(true)
+            .with_offset(INDEX_ENTRY_SIZE)
+            .with_node(node0)
+            .build();
+        let entry1_bytes = IndexEntryBuilder::new()
+            .with_offset(INDEX_ENTRY_SIZE)
+            .with_node(node1)
+            .build();
+        let entry2_bytes = IndexEntryBuilder::new()
+            .with_offset(INDEX_ENTRY_SIZE)
+            .with_p1(0)
+            .with_p2(1)
+            .with_node(node2)
+            .build();
+        let contents = vec![entry0_bytes, entry1_bytes, entry2_bytes]
+            .into_iter()
+            .flatten()
+            .collect_vec();
+        std::fs::write(temp.path().join("foo.i"), contents).unwrap();
+        let revlog = Revlog::open(&vfs, "foo.i", None, false).unwrap();
+
+        let entry0 = revlog.get_entry(0).ok().unwrap();
+        assert_eq!(entry0.revision(), 0);
+        assert_eq!(*entry0.node(), node0);
+        assert!(!entry0.has_p1());
+        assert_eq!(entry0.p1(), None);
+        assert_eq!(entry0.p2(), None);
+        let p1_entry = entry0.p1_entry().unwrap();
+        assert!(p1_entry.is_none());
+        let p2_entry = entry0.p2_entry().unwrap();
+        assert!(p2_entry.is_none());
+
+        let entry1 = revlog.get_entry(1).ok().unwrap();
+        assert_eq!(entry1.revision(), 1);
+        assert_eq!(*entry1.node(), node1);
+        assert!(!entry1.has_p1());
+        assert_eq!(entry1.p1(), None);
+        assert_eq!(entry1.p2(), None);
+        let p1_entry = entry1.p1_entry().unwrap();
+        assert!(p1_entry.is_none());
+        let p2_entry = entry1.p2_entry().unwrap();
+        assert!(p2_entry.is_none());
+
+        let entry2 = revlog.get_entry(2).ok().unwrap();
+        assert_eq!(entry2.revision(), 2);
+        assert_eq!(*entry2.node(), node2);
+        assert!(entry2.has_p1());
+        assert_eq!(entry2.p1(), Some(0));
+        assert_eq!(entry2.p2(), Some(1));
+        let p1_entry = entry2.p1_entry().unwrap();
+        assert!(p1_entry.is_some());
+        assert_eq!(p1_entry.unwrap().revision(), 0);
+        let p2_entry = entry2.p2_entry().unwrap();
+        assert!(p2_entry.is_some());
+        assert_eq!(p2_entry.unwrap().revision(), 1);
+    }
+}