rust-revlog: make `IndexEntryBuilder` build a whole entry

The `IndexEntryBuilder` we have in tests only built part of a revlog
entry before this patch. It's more useful if it can build a full
entry. As part of fixing that, I also added a (non-test)
`IndexEntry::link_revision()`.

Differential Revision: https://phab.mercurial-scm.org/D12564

rust/hg-core/src/revlog/index.rs

@@ -1,528 +1,616 b''
 use std::convert::TryInto;
 use std::ops::Deref;
 
 use byteorder::{BigEndian, ByteOrder};
 
 use crate::errors::HgError;
 use crate::revlog::node::Node;
 use crate::revlog::{Revision, NULL_REVISION};
 
 pub const INDEX_ENTRY_SIZE: usize = 64;
 
 pub struct IndexHeader {
     header_bytes: [u8; 4],
 }
 
 #[derive(Copy, Clone)]
 pub struct IndexHeaderFlags {
     flags: u16,
 }
 
 /// Corresponds to the high bits of `_format_flags` in python
 impl IndexHeaderFlags {
     /// Corresponds to FLAG_INLINE_DATA in python
     pub fn is_inline(self) -> bool {
         return self.flags & 1 != 0;
     }
     /// Corresponds to FLAG_GENERALDELTA in python
     pub fn uses_generaldelta(self) -> bool {
         return self.flags & 2 != 0;
     }
 }
 
 /// Corresponds to the INDEX_HEADER structure,
 /// which is parsed as a `header` variable in `_loadindex` in `revlog.py`
 impl IndexHeader {
     fn format_flags(&self) -> IndexHeaderFlags {
         // No "unknown flags" check here, unlike in python. Maybe there should
         // be.
         return IndexHeaderFlags {
             flags: BigEndian::read_u16(&self.header_bytes[0..2]),
         };
     }
 
     /// The only revlog version currently supported by rhg.
     const REVLOGV1: u16 = 1;
 
     /// Corresponds to `_format_version` in Python.
     fn format_version(&self) -> u16 {
         return BigEndian::read_u16(&self.header_bytes[2..4]);
     }
 
     const EMPTY_INDEX_HEADER: IndexHeader = IndexHeader {
         // We treat an empty file as a valid index with no entries.
         // Here we make an arbitrary choice of what we assume the format of the
         // index to be (V1, using generaldelta).
         // This doesn't matter too much, since we're only doing read-only
         // access. but the value corresponds to the `new_header` variable in
         // `revlog.py`, `_loadindex`
         header_bytes: [0, 3, 0, 1],
     };
 
     fn parse(index_bytes: &[u8]) -> Result<IndexHeader, HgError> {
         if index_bytes.len() == 0 {
             return Ok(IndexHeader::EMPTY_INDEX_HEADER);
         }
         if index_bytes.len() < 4 {
             return Err(HgError::corrupted(
                 "corrupted revlog: can't read the index format header",
             ));
         }
         return Ok(IndexHeader {
             header_bytes: {
                 let bytes: [u8; 4] =
                     index_bytes[0..4].try_into().expect("impossible");
                 bytes
             },
         });
     }
 }
 
 /// A Revlog index
 pub struct Index {
     bytes: Box<dyn Deref<Target = [u8]> + Send>,
     /// Offsets of starts of index blocks.
     /// Only needed when the index is interleaved with data.
     offsets: Option<Vec<usize>>,
     uses_generaldelta: bool,
 }
 
 impl Index {
     /// Create an index from bytes.
     /// Calculate the start of each entry when is_inline is true.
     pub fn new(
         bytes: Box<dyn Deref<Target = [u8]> + Send>,
     ) -> Result<Self, HgError> {
         let header = IndexHeader::parse(bytes.as_ref())?;
 
         if header.format_version() != IndexHeader::REVLOGV1 {
             // A proper new version should have had a repo/store
             // requirement.
             return Err(HgError::corrupted("unsupported revlog version"));
         }
 
         // This is only correct because we know version is REVLOGV1.
         // In v2 we always use generaldelta, while in v0 we never use
         // generaldelta. Similar for [is_inline] (it's only used in v1).
         let uses_generaldelta = header.format_flags().uses_generaldelta();
 
         if header.format_flags().is_inline() {
             let mut offset: usize = 0;
             let mut offsets = Vec::new();
 
             while offset + INDEX_ENTRY_SIZE <= bytes.len() {
                 offsets.push(offset);
                 let end = offset + INDEX_ENTRY_SIZE;
                 let entry = IndexEntry {
                     bytes: &bytes[offset..end],
                     offset_override: None,
                 };
 
                 offset += INDEX_ENTRY_SIZE + entry.compressed_len() as usize;
             }
 
             if offset == bytes.len() {
                 Ok(Self {
                     bytes,
                     offsets: Some(offsets),
                     uses_generaldelta,
                 })
             } else {
                 Err(HgError::corrupted("unexpected inline revlog length")
                     .into())
             }
         } else {
             Ok(Self {
                 bytes,
                 offsets: None,
                 uses_generaldelta,
             })
         }
     }
 
     pub fn uses_generaldelta(&self) -> bool {
         self.uses_generaldelta
     }
 
     /// Value of the inline flag.
     pub fn is_inline(&self) -> bool {
         self.offsets.is_some()
     }
 
     /// Return a slice of bytes if `revlog` is inline. Panic if not.
     pub fn data(&self, start: usize, end: usize) -> &[u8] {
         if !self.is_inline() {
             panic!("tried to access data in the index of a revlog that is not inline");
         }
         &self.bytes[start..end]
     }
 
     /// Return number of entries of the revlog index.
     pub fn len(&self) -> usize {
         if let Some(offsets) = &self.offsets {
             offsets.len()
         } else {
             self.bytes.len() / INDEX_ENTRY_SIZE
         }
     }
 
     /// Returns `true` if the `Index` has zero `entries`.
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }
 
     /// Return the index entry corresponding to the given revision if it
     /// exists.
     pub fn get_entry(&self, rev: Revision) -> Option<IndexEntry> {
         if rev == NULL_REVISION {
             return None;
         }
         if let Some(offsets) = &self.offsets {
             self.get_entry_inline(rev, offsets)
         } else {
             self.get_entry_separated(rev)
         }
     }
 
     fn get_entry_inline(
         &self,
         rev: Revision,
         offsets: &[usize],
     ) -> Option<IndexEntry> {
         let start = *offsets.get(rev as usize)?;
         let end = start.checked_add(INDEX_ENTRY_SIZE)?;
         let bytes = &self.bytes[start..end];
 
         // See IndexEntry for an explanation of this override.
         let offset_override = Some(end);
 
         Some(IndexEntry {
             bytes,
             offset_override,
         })
     }
 
     fn get_entry_separated(&self, rev: Revision) -> Option<IndexEntry> {
         let max_rev = self.bytes.len() / INDEX_ENTRY_SIZE;
         if rev as usize >= max_rev {
             return None;
         }
         let start = rev as usize * INDEX_ENTRY_SIZE;
         let end = start + INDEX_ENTRY_SIZE;
         let bytes = &self.bytes[start..end];
 
         // Override the offset of the first revision as its bytes are used
         // for the index's metadata (saving space because it is always 0)
         let offset_override = if rev == 0 { Some(0) } else { None };
 
         Some(IndexEntry {
             bytes,
             offset_override,
         })
     }
 }
 
 impl super::RevlogIndex for Index {
     fn len(&self) -> usize {
         self.len()
     }
 
     fn node(&self, rev: Revision) -> Option<&Node> {
         self.get_entry(rev).map(|entry| entry.hash())
     }
 }
 
 #[derive(Debug)]
 pub struct IndexEntry<'a> {
     bytes: &'a [u8],
     /// Allows to override the offset value of the entry.
     ///
     /// For interleaved index and data, the offset stored in the index
     /// corresponds to the separated data offset.
     /// It has to be overridden with the actual offset in the interleaved
     /// index which is just after the index block.
     ///
     /// For separated index and data, the offset stored in the first index
     /// entry is mixed with the index headers.
     /// It has to be overridden with 0.
     offset_override: Option<usize>,
 }
 
 impl<'a> IndexEntry<'a> {
     /// Return the offset of the data.
     pub fn offset(&self) -> usize {
         if let Some(offset_override) = self.offset_override {
             offset_override
         } else {
             let mut bytes = [0; 8];
             bytes[2..8].copy_from_slice(&self.bytes[0..=5]);
             BigEndian::read_u64(&bytes[..]) as usize
         }
     }
 
     pub fn flags(&self) -> u16 {
         BigEndian::read_u16(&self.bytes[6..=7])
     }
 
     /// Return the compressed length of the data.
     pub fn compressed_len(&self) -> u32 {
         BigEndian::read_u32(&self.bytes[8..=11])
     }
 
     /// Return the uncompressed length of the data.
     pub fn uncompressed_len(&self) -> i32 {
         BigEndian::read_i32(&self.bytes[12..=15])
     }
 
     /// Return the revision upon which the data has been derived.
     pub fn base_revision_or_base_of_delta_chain(&self) -> Revision {
         // TODO Maybe return an Option when base_revision == rev?
         //      Requires to add rev to IndexEntry
 
         BigEndian::read_i32(&self.bytes[16..])
     }
 
+    pub fn link_revision(&self) -> Revision {
+        BigEndian::read_i32(&self.bytes[20..])
+    }
+
     pub fn p1(&self) -> Revision {
         BigEndian::read_i32(&self.bytes[24..])
     }
 
     pub fn p2(&self) -> Revision {
         BigEndian::read_i32(&self.bytes[28..])
     }
 
     /// Return the hash of revision's full text.
     ///
     /// Currently, SHA-1 is used and only the first 20 bytes of this field
     /// are used.
     pub fn hash(&self) -> &'a Node {
         (&self.bytes[32..52]).try_into().unwrap()
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::node::NULL_NODE;
 
     #[cfg(test)]
     #[derive(Debug, Copy, Clone)]
     pub struct IndexEntryBuilder {
         is_first: bool,
         is_inline: bool,
         is_general_delta: bool,
         version: u16,
         offset: usize,
         compressed_len: usize,
         uncompressed_len: usize,
         base_revision_or_base_of_delta_chain: Revision,
+        link_revision: Revision,
+        p1: Revision,
+        p2: Revision,
+        node: Node,
     }
 
     #[cfg(test)]
     impl IndexEntryBuilder {
         pub fn new() -> Self {
             Self {
                 is_first: false,
                 is_inline: false,
                 is_general_delta: true,
                 version: 1,
                 offset: 0,
                 compressed_len: 0,
                 uncompressed_len: 0,
                 base_revision_or_base_of_delta_chain: 0,
+                link_revision: 0,
+                p1: NULL_REVISION,
+                p2: NULL_REVISION,
+                node: NULL_NODE,
             }
         }
 
         pub fn is_first(&mut self, value: bool) -> &mut Self {
             self.is_first = value;
             self
         }
 
         pub fn with_inline(&mut self, value: bool) -> &mut Self {
             self.is_inline = value;
             self
         }
 
         pub fn with_general_delta(&mut self, value: bool) -> &mut Self {
             self.is_general_delta = value;
             self
         }
 
         pub fn with_version(&mut self, value: u16) -> &mut Self {
             self.version = value;
             self
         }
 
         pub fn with_offset(&mut self, value: usize) -> &mut Self {
             self.offset = value;
             self
         }
 
         pub fn with_compressed_len(&mut self, value: usize) -> &mut Self {
             self.compressed_len = value;
             self
         }
 
         pub fn with_uncompressed_len(&mut self, value: usize) -> &mut Self {
             self.uncompressed_len = value;
             self
         }
 
         pub fn with_base_revision_or_base_of_delta_chain(
             &mut self,
             value: Revision,
         ) -> &mut Self {
             self.base_revision_or_base_of_delta_chain = value;
             self
         }
 
+        pub fn with_link_revision(&mut self, value: Revision) -> &mut Self {
+            self.link_revision = value;
+            self
+        }
+
+        pub fn with_p1(&mut self, value: Revision) -> &mut Self {
+            self.p1 = value;
+            self
+        }
+
+        pub fn with_p2(&mut self, value: Revision) -> &mut Self {
+            self.p2 = value;
+            self
+        }
+
+        pub fn with_node(&mut self, value: Node) -> &mut Self {
+            self.node = value;
+            self
+        }
+
         pub fn build(&self) -> Vec<u8> {
             let mut bytes = Vec::with_capacity(INDEX_ENTRY_SIZE);
             if self.is_first {
                 bytes.extend(&match (self.is_general_delta, self.is_inline) {
                     (false, false) => [0u8, 0],
                     (false, true) => [0u8, 1],
                     (true, false) => [0u8, 2],
                     (true, true) => [0u8, 3],
                 });
                 bytes.extend(&self.version.to_be_bytes());
                 // Remaining offset bytes.
                 bytes.extend(&[0u8; 2]);
             } else {
                 // Offset stored on 48 bits (6 bytes)
                 bytes.extend(&(self.offset as u64).to_be_bytes()[2..]);
             }
             bytes.extend(&[0u8; 2]); // Revision flags.
             bytes.extend(&(self.compressed_len as u32).to_be_bytes());
             bytes.extend(&(self.uncompressed_len as u32).to_be_bytes());
             bytes.extend(
                 &self.base_revision_or_base_of_delta_chain.to_be_bytes(),
             );
+            bytes.extend(&self.link_revision.to_be_bytes());
+            bytes.extend(&self.p1.to_be_bytes());
+            bytes.extend(&self.p2.to_be_bytes());
+            bytes.extend(self.node.as_bytes());
+            bytes.extend(vec![0u8; 12]);
             bytes
         }
     }
 
     pub fn is_inline(index_bytes: &[u8]) -> bool {
         IndexHeader::parse(index_bytes)
             .expect("too short")
             .format_flags()
             .is_inline()
     }
 
     pub fn uses_generaldelta(index_bytes: &[u8]) -> bool {
         IndexHeader::parse(index_bytes)
             .expect("too short")
             .format_flags()
             .uses_generaldelta()
     }
 
     pub fn get_version(index_bytes: &[u8]) -> u16 {
         IndexHeader::parse(index_bytes)
             .expect("too short")
             .format_version()
     }
 
     #[test]
     fn flags_when_no_inline_flag_test() {
         let bytes = IndexEntryBuilder::new()
             .is_first(true)
             .with_general_delta(false)
             .with_inline(false)
             .build();
 
         assert_eq!(is_inline(&bytes), false);
         assert_eq!(uses_generaldelta(&bytes), false);
     }
 
     #[test]
     fn flags_when_inline_flag_test() {
         let bytes = IndexEntryBuilder::new()
             .is_first(true)
             .with_general_delta(false)
             .with_inline(true)
             .build();
 
         assert_eq!(is_inline(&bytes), true);
         assert_eq!(uses_generaldelta(&bytes), false);
     }
 
     #[test]
     fn flags_when_inline_and_generaldelta_flags_test() {
         let bytes = IndexEntryBuilder::new()
             .is_first(true)
             .with_general_delta(true)
             .with_inline(true)
             .build();
 
         assert_eq!(is_inline(&bytes), true);
         assert_eq!(uses_generaldelta(&bytes), true);
     }
 
     #[test]
     fn test_offset() {
         let bytes = IndexEntryBuilder::new().with_offset(1).build();
         let entry = IndexEntry {
             bytes: &bytes,
             offset_override: None,
         };
 
         assert_eq!(entry.offset(), 1)
     }
 
     #[test]
     fn test_with_overridden_offset() {
         let bytes = IndexEntryBuilder::new().with_offset(1).build();
         let entry = IndexEntry {
             bytes: &bytes,
             offset_override: Some(2),
         };
 
         assert_eq!(entry.offset(), 2)
     }
 
     #[test]
     fn test_compressed_len() {
         let bytes = IndexEntryBuilder::new().with_compressed_len(1).build();
         let entry = IndexEntry {
             bytes: &bytes,
             offset_override: None,
         };
 
         assert_eq!(entry.compressed_len(), 1)
     }
 
     #[test]
     fn test_uncompressed_len() {
         let bytes = IndexEntryBuilder::new().with_uncompressed_len(1).build();
         let entry = IndexEntry {
             bytes: &bytes,
             offset_override: None,
         };
 
         assert_eq!(entry.uncompressed_len(), 1)
     }
 
     #[test]
     fn test_base_revision_or_base_of_delta_chain() {
         let bytes = IndexEntryBuilder::new()
             .with_base_revision_or_base_of_delta_chain(1)
             .build();
         let entry = IndexEntry {
             bytes: &bytes,
             offset_override: None,
         };
 
         assert_eq!(entry.base_revision_or_base_of_delta_chain(), 1)
     }
 
     #[test]
+    fn link_revision_test() {
+        let bytes = IndexEntryBuilder::new().with_link_revision(123).build();
+
+        let entry = IndexEntry {
+            bytes: &bytes,
+            offset_override: None,
+        };
+
+        assert_eq!(entry.link_revision(), 123);
+    }
+
+    #[test]
+    fn p1_test() {
+        let bytes = IndexEntryBuilder::new().with_p1(123).build();
+
+        let entry = IndexEntry {
+            bytes: &bytes,
+            offset_override: None,
+        };
+
+        assert_eq!(entry.p1(), 123);
+    }
+
+    #[test]
+    fn p2_test() {
+        let bytes = IndexEntryBuilder::new().with_p2(123).build();
+
+        let entry = IndexEntry {
+            bytes: &bytes,
+            offset_override: None,
+        };
+
+        assert_eq!(entry.p2(), 123);
+    }
+
+    #[test]
+    fn node_test() {
+        let node = Node::from_hex("0123456789012345678901234567890123456789")
+            .unwrap();
+        let bytes = IndexEntryBuilder::new().with_node(node).build();
+
+        let entry = IndexEntry {
+            bytes: &bytes,
+            offset_override: None,
+        };
+
+        assert_eq!(*entry.hash(), node);
+    }
+
+    #[test]
     fn version_test() {
         let bytes = IndexEntryBuilder::new()
             .is_first(true)
             .with_version(2)
             .build();
 
         assert_eq!(get_version(&bytes), 2)
     }
 }
 
 #[cfg(test)]
 pub use tests::IndexEntryBuilder;