hg-core: define a `DebugData` `Operation`

hg-core: define a `DebugData` `Operation`

Read the content of a `revlog` at a given revision.

Differential Revision: https://phab.mercurial-scm.org/D8959

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-core/src/operations/debugdata.rs	Thu Aug 13 16:22:15 2020 +0200
@@ -0,0 +1,110 @@
+// debugdata.rs
+//
+// Copyright 2020 Antoine Cezar <[e-mail]>
+//
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2 or any later version.
+
+use super::find_root;
+use crate::revlog::revlog::{Revlog, RevlogError};
+use crate::revlog::Revision;
+
+/// Kind of data to debug
+#[derive(Debug, Copy, Clone)]
+pub enum DebugDataKind {
+    Changelog,
+    Manifest,
+}
+
+/// Kind of error encountered by DebugData
+#[derive(Debug)]
+pub enum DebugDataErrorKind {
+    FindRootError(find_root::FindRootError),
+    /// Error when reading a `revlog` file.
+    IoError(std::io::Error),
+    /// The revision has not been found.
+    InvalidRevision,
+    /// A `revlog` file is corrupted.
+    CorruptedRevlog,
+    /// The `revlog` format version is not supported.
+    UnsuportedRevlogVersion(u16),
+    /// The `revlog` data format is not supported.
+    UnknowRevlogDataFormat(u8),
+}
+
+/// A DebugData error
+#[derive(Debug)]
+pub struct DebugDataError {
+    /// Kind of error encountered by DebugData
+    pub kind: DebugDataErrorKind,
+}
+
+impl From<DebugDataErrorKind> for DebugDataError {
+    fn from(kind: DebugDataErrorKind) -> Self {
+        DebugDataError { kind }
+    }
+}
+
+impl From<find_root::FindRootError> for DebugDataError {
+    fn from(err: find_root::FindRootError) -> Self {
+        let kind = DebugDataErrorKind::FindRootError(err);
+        DebugDataError { kind }
+    }
+}
+
+impl From<std::io::Error> for DebugDataError {
+    fn from(err: std::io::Error) -> Self {
+        let kind = DebugDataErrorKind::IoError(err);
+        DebugDataError { kind }
+    }
+}
+
+impl From<RevlogError> for DebugDataError {
+    fn from(err: RevlogError) -> Self {
+        match err {
+            RevlogError::IoError(err) => DebugDataErrorKind::IoError(err),
+            RevlogError::UnsuportedVersion(version) => {
+                DebugDataErrorKind::UnsuportedRevlogVersion(version)
+            }
+            RevlogError::InvalidRevision => {
+                DebugDataErrorKind::InvalidRevision
+            }
+            RevlogError::Corrupted => DebugDataErrorKind::CorruptedRevlog,
+            RevlogError::UnknowDataFormat(format) => {
+                DebugDataErrorKind::UnknowRevlogDataFormat(format)
+            }
+        }
+        .into()
+    }
+}
+
+/// Dump the contents data of a revision.
+pub struct DebugData<'a> {
+    /// Revision or hash of the revision.
+    rev: &'a str,
+    /// Kind of data to debug.
+    kind: DebugDataKind,
+}
+
+impl<'a> DebugData<'a> {
+    pub fn new(rev: &'a str, kind: DebugDataKind) -> Self {
+        DebugData { rev, kind }
+    }
+
+    pub fn run(&mut self) -> Result<Vec<u8>, DebugDataError> {
+        let rev = self
+            .rev
+            .parse::<Revision>()
+            .or(Err(DebugDataErrorKind::InvalidRevision))?;
+
+        let root = find_root::FindRoot::new().run()?;
+        let index_file = match self.kind {
+            DebugDataKind::Changelog => root.join(".hg/store/00changelog.i"),
+            DebugDataKind::Manifest => root.join(".hg/store/00manifest.i"),
+        };
+        let revlog = Revlog::open(&index_file)?;
+        let data = revlog.get_rev_data(rev)?;
+
+        Ok(data)
+    }
+}

--- a/rust/hg-core/src/operations/mod.rs	Fri Sep 04 11:55:07 2020 +0200
+++ b/rust/hg-core/src/operations/mod.rs	Thu Aug 13 16:22:15 2020 +0200
@@ -2,6 +2,7 @@
 //! An operation is what can be done whereas a command is what is exposed by
 //! the cli. A single command can use several operations to achieve its goal.
 
+mod debugdata;
 mod dirstate_status;
 mod find_root;
 mod list_tracked_files;