[commitgraph] Rename LexPosition to 'file::Position'

That way it's in line with 'graph::Position'

Author: Byron

git-commitgraph/src/file/access.rs

@@ -1,10 +1,12 @@
-use crate::file::commit::Commit;
-use crate::file::{File, LexPosition, COMMIT_DATA_ENTRY_SIZE};
+use crate::file::{self, commit::Commit, File, COMMIT_DATA_ENTRY_SIZE};
 use git_object::{borrowed, HashKind, SHA1_SIZE};
-use std::convert::{TryFrom, TryInto};
-use std::fmt::{Debug, Formatter};
-use std::path::Path;
+use std::{
+    convert::{TryFrom, TryInto},
+    fmt::{Debug, Formatter},
+    path::Path,
+};
 
+/// Access
 impl File {
     /// Returns the commit data for the commit located at the given lex position.
     ///
@@ -13,7 +15,7 @@ impl File {
     /// # Panics
     ///
     /// Panics if `pos` is out of bounds.
-    pub fn commit_at(&self, pos: LexPosition) -> Commit<'_> {
+    pub fn commit_at(&self, pos: file::Position) -> Commit<'_> {
         Commit::new(self, pos)
     }
 
@@ -24,7 +26,7 @@ impl File {
     // copied from git-odb/src/pack/index/access.rs
     /// Returns 20 bytes sha1 at the given index in our list of (sorted) sha1 hashes.
     /// The position ranges from 0 to self.num_commits()
-    pub fn id_at(&self, pos: LexPosition) -> borrowed::Id<'_> {
+    pub fn id_at(&self, pos: file::Position) -> borrowed::Id<'_> {
         assert!(
             pos.0 < self.num_commits(),
             "expected lex position less than {}, got {}",
@@ -50,15 +52,15 @@ impl File {
     }
 
     pub fn iter_commits(&self) -> impl Iterator<Item = Commit<'_>> {
-        (0..self.num_commits()).map(move |i| self.commit_at(LexPosition(i)))
+        (0..self.num_commits()).map(move |i| self.commit_at(file::Position(i)))
     }
 
     pub fn iter_ids(&self) -> impl Iterator<Item = borrowed::Id<'_>> {
-        (0..self.num_commits()).map(move |i| self.id_at(LexPosition(i)))
+        (0..self.num_commits()).map(move |i| self.id_at(file::Position(i)))
     }
 
     // copied from git-odb/src/pack/index/access.rs
-    pub fn lookup(&self, id: borrowed::Id<'_>) -> Option<LexPosition> {
+    pub fn lookup(&self, id: borrowed::Id<'_>) -> Option<file::Position> {
         let first_byte = id.first_byte() as usize;
         let mut upper_bound = self.fan[first_byte];
         let mut lower_bound = if first_byte != 0 { self.fan[first_byte - 1] } else { 0 };
@@ -69,12 +71,12 @@ impl File {
         // it should not be if the bytes match up and the type has no destructor.
         while lower_bound < upper_bound {
             let mid = (lower_bound + upper_bound) / 2;
-            let mid_sha = self.id_at(LexPosition(mid));
+            let mid_sha = self.id_at(file::Position(mid));
 
             use std::cmp::Ordering::*;
             match id.cmp(&mid_sha) {
                 Less => upper_bound = mid,
-                Equal => return Some(LexPosition(mid)),
+                Equal => return Some(file::Position(mid)),
                 Greater => lower_bound = mid + 1,
             }
         }
@@ -83,7 +85,7 @@ impl File {
 
     /// Returns the number of commits in this graph file.
     ///
-    /// The maximum valid `LexPosition` that can be used with this file is one less than
+    /// The maximum valid `Lexfile::Position` that can be used with this file is one less than
     /// `num_commits()`.
     pub fn num_commits(&self) -> u32 {
         self.fan[255]
@@ -96,7 +98,7 @@ impl File {
 
 impl File {
     /// Returns the byte slice for the given commit in this file's Commit Data (CDAT) chunk.
-    pub(crate) fn commit_data_bytes(&self, pos: LexPosition) -> &[u8] {
+    pub(crate) fn commit_data_bytes(&self, pos: file::Position) -> &[u8] {
         assert!(
             pos.0 < self.num_commits(),
             "expected lex position less than {}, got {}",

git-commitgraph/src/file/commit.rs

@@ -1,11 +1,15 @@
-use crate::file::{File, LexPosition};
-use crate::graph::Position;
+use crate::{
+    file::{self, File},
+    graph,
+};
 use byteorder::{BigEndian, ByteOrder};
 use git_object::{borrowed, owned, SHA1_SIZE};
 use quick_error::quick_error;
-use std::convert::{TryFrom, TryInto};
-use std::fmt::{Debug, Formatter};
-use std::slice::Chunks;
+use std::{
+    convert::{TryFrom, TryInto},
+    fmt::{Debug, Formatter},
+    slice::Chunks,
+};
 
 quick_error! {
     #[derive(Debug)]
@@ -41,7 +45,7 @@ const EXTENDED_EDGES_MASK: u32 = 0x8000_0000;
 
 pub struct Commit<'a> {
     file: &'a File,
-    lex_pos: LexPosition,
+    lex_pos: file::Position,
     // We can parse the below fields lazily if needed.
     commit_timestamp: u64,
     generation: u32,
@@ -51,7 +55,7 @@ pub struct Commit<'a> {
 }
 
 impl<'a> Commit<'a> {
-    pub(crate) fn new(file: &'a File, pos: LexPosition) -> Self {
+    pub(crate) fn new(file: &'a File, pos: file::Position) -> Self {
         let bytes = file.commit_data_bytes(pos);
         Commit {
             file,
@@ -79,7 +83,7 @@ impl<'a> Commit<'a> {
         self.generation
     }
 
-    pub fn iter_parents(&'a self) -> impl Iterator<Item = Result<Position, Error>> + 'a {
+    pub fn iter_parents(&'a self) -> impl Iterator<Item = Result<graph::Position, Error>> + 'a {
         // I didn't find a combinator approach that a) was as strict as ParentIterator, b) supported
         // fuse-after-first-error behavior, and b) was significantly shorter or more understandable
         // than ParentIterator. So here we are.
@@ -93,7 +97,7 @@ impl<'a> Commit<'a> {
         self.file.id_at(self.lex_pos)
     }
 
-    pub fn parent1(&self) -> Result<Option<Position>, Error> {
+    pub fn parent1(&self) -> Result<Option<graph::Position>, Error> {
         self.iter_parents().next().transpose()
     }
 
@@ -131,7 +135,7 @@ pub struct ParentIterator<'a> {
 }
 
 impl<'a> Iterator for ParentIterator<'a> {
-    type Item = Result<Position, Error>;
+    type Item = Result<graph::Position, Error>;
 
     fn next(&mut self) -> Option<Self::Item> {
         let state = std::mem::replace(&mut self.state, ParentIteratorState::Exhausted);
@@ -219,7 +223,7 @@ enum ParentIteratorState<'a> {
 #[derive(Clone, Copy, Debug)]
 enum ParentEdge {
     None,
-    GraphPosition(Position),
+    GraphPosition(graph::Position),
     ExtraEdgeIndex(u32),
 }
 
@@ -231,24 +235,24 @@ impl ParentEdge {
         if raw & EXTENDED_EDGES_MASK != 0 {
             ParentEdge::ExtraEdgeIndex(raw & !EXTENDED_EDGES_MASK)
         } else {
-            ParentEdge::GraphPosition(Position(raw))
+            ParentEdge::GraphPosition(graph::Position(raw))
         }
     }
 }
 
 const LAST_EXTENDED_EDGE_MASK: u32 = 0x8000_0000;
 
 enum ExtraEdge {
-    Internal(Position),
-    Last(Position),
+    Internal(graph::Position),
+    Last(graph::Position),
 }
 
 impl ExtraEdge {
     pub fn from_raw(raw: u32) -> Self {
         if raw & LAST_EXTENDED_EDGE_MASK != 0 {
-            Self::Last(Position(raw & !LAST_EXTENDED_EDGE_MASK))
+            Self::Last(graph::Position(raw & !LAST_EXTENDED_EDGE_MASK))
         } else {
-            Self::Internal(Position(raw))
+            Self::Internal(graph::Position(raw))
         }
     }
 }

git-commitgraph/src/file/init.rs

@@ -4,9 +4,11 @@ use byteorder::{BigEndian, ByteOrder};
 use filebuffer::FileBuffer;
 use git_object::SHA1_SIZE;
 use quick_error::quick_error;
-use std::convert::{TryFrom, TryInto};
-use std::ops::Range;
-use std::path::Path;
+use std::{
+    convert::{TryFrom, TryInto},
+    ops::Range,
+    path::Path,
+};
 
 type ChunkId = [u8; 4];
 

git-commitgraph/src/file/mod.rs

@@ -1,15 +1,18 @@
 //! Operations on a single commit-graph file.
 mod access;
 pub mod commit;
+
 mod init;
+pub use init::Error;
 
 pub use commit::Commit;
 use filebuffer::FileBuffer;
 use git_object::SHA1_SIZE;
-pub use init::Error;
-use std::fmt::{Display, Formatter};
-use std::ops::Range;
-use std::path::PathBuf;
+use std::{
+    fmt::{Display, Formatter},
+    ops::Range,
+    path::PathBuf,
+};
 
 const COMMIT_DATA_ENTRY_SIZE: usize = SHA1_SIZE + 16;
 const FAN_LEN: usize = 256;
@@ -32,16 +35,16 @@ pub struct File {
 
 /// The position of a given commit within a graph file, starting at 0.
 ///
-/// Commits within a graph file are sorted in lexicographical order by OID; a commit's lex position
+/// Commits within a graph file are sorted in lexicographical order by OID; a commit's lexigraphical position
 /// is its position in this ordering. If a commit graph spans multiple files, each file's commits
-/// start at lex position 0, so lex position is unique across a single file but is not unique across
-/// the whole commit graph. Each commit also has a graph position (`GraphPosition`), which is unique
-/// across the whole commit graph. In order to avoid accidentally mixing lex positions with graph
+/// start at lexigraphical position 0, so it is unique across a single file but is not unique across
+/// the whole commit graph. Each commit also has a graph position (`graph::Position`), which is unique
+/// across the whole commit graph. In order to avoid accidentally mixing lexigraphical positions with graph
 /// positions, distinct types are used for each.
 #[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
-pub struct LexPosition(pub u32);
+pub struct Position(pub u32);
 
-impl Display for LexPosition {
+impl Display for Position {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         self.0.fmt(f)
     }

git-commitgraph/src/graph/access.rs

@@ -1,12 +1,12 @@
 use crate::{
-    file::{Commit, File, LexPosition},
-    graph::{Graph, Position},
+    file::{self, Commit, File},
+    graph::{self, Graph},
 };
 use git_object::borrowed;
 
-/// Access convenience
+/// Access
 impl Graph {
-    pub fn commit_at(&self, pos: Position) -> Commit<'_> {
+    pub fn commit_at(&self, pos: graph::Position) -> Commit<'_> {
         let r = self.lookup_by_pos(pos);
         r.file.commit_at(r.lex_pos)
     }
@@ -16,7 +16,7 @@ impl Graph {
         Some(r.file.commit_at(r.lex_pos))
     }
 
-    pub fn id_at(&self, pos: Position) -> borrowed::Id<'_> {
+    pub fn id_at(&self, pos: graph::Position) -> borrowed::Id<'_> {
         let r = self.lookup_by_pos(pos);
         r.file.id_at(r.lex_pos)
     }
@@ -31,7 +31,7 @@ impl Graph {
         self.files.iter().flat_map(|file| file.iter_ids())
     }
 
-    pub fn lookup(&self, id: borrowed::Id<'_>) -> Option<Position> {
+    pub fn lookup(&self, id: borrowed::Id<'_>) -> Option<graph::Position> {
         Some(self.lookup_by_id(id)?.graph_pos)
     }
 
@@ -49,23 +49,23 @@ impl Graph {
                 return Some(LookupByIdResult {
                     file,
                     lex_pos,
-                    graph_pos: Position(current_file_start + lex_pos.0),
+                    graph_pos: graph::Position(current_file_start + lex_pos.0),
                 });
             }
             current_file_start += file.num_commits();
         }
         None
     }
 
-    fn lookup_by_pos(&self, pos: Position) -> LookupByPositionResult<'_> {
+    fn lookup_by_pos(&self, pos: graph::Position) -> LookupByPositionResult<'_> {
         let mut remaining = pos.0;
         for file in &self.files {
             match remaining.checked_sub(file.num_commits()) {
                 Some(v) => remaining = v,
                 None => {
                     return LookupByPositionResult {
                         file,
-                        lex_pos: LexPosition(remaining),
+                        lex_pos: file::Position(remaining),
                     }
                 }
             }
@@ -77,12 +77,12 @@ impl Graph {
 #[derive(Clone)]
 struct LookupByIdResult<'a> {
     pub file: &'a File,
-    pub graph_pos: Position,
-    pub lex_pos: LexPosition,
+    pub graph_pos: graph::Position,
+    pub lex_pos: file::Position,
 }
 
 #[derive(Clone)]
 struct LookupByPositionResult<'a> {
     pub file: &'a File,
-    pub lex_pos: LexPosition,
+    pub lex_pos: file::Position,
 }

tasks.md

@@ -25,6 +25,12 @@
   * [ ] feature-toggled support for serde
   * [ ] ~~make tests depend on checked-in fixtures, instead of generating them (and depend on git on CI), making it easy to recreate them~~
      * the tests currently rely on calling git, see `inspect_refs(…)`
+  * **Questions**
+    * ~~How can `Commit` return Graph positions? It doesn't seem to learn about an offset.~~
+      * Parent IDs are indeed specified as graph positions, not file positions, as they may be in previous commit graph files.
+  * **Still to be done**
+    * A plumbing command to extract some value from the current implementation, maybe statistics, or verification
+    * Application of the command above in a stress test
 * **git-config**
   * A complete implementation, writing a the git remote configuration is needed for finalizing the clone
 * **git-ref**