prepare for re-encoding each pack object

Author: Byron

Diff for: git-odb/src/pack/bundle.rs

@@ -77,6 +77,7 @@ impl Bundle {
     pub fn verify_checksums<P, C>(
         &self,
         thread_limit: Option<usize>,
+        mode: pack::index::verify::Mode,
         progress: Option<P>,
         make_cache: impl Fn() -> C + Send + Sync,
     ) -> Result<(owned::Id, Option<pack::index::verify::Outcome>), pack::index::verify::Error>
@@ -86,7 +87,7 @@ impl Bundle {
         C: pack::cache::DecodeEntry,
     {
         self.index
-            .verify_checksum_of_index(Some(&self.pack), thread_limit, progress, make_cache)
+            .verify_checksum_of_index(Some(&self.pack), thread_limit, mode, progress, make_cache)
     }
 }
 

Diff for: git-odb/src/pack/data/decoded.rs

@@ -15,7 +15,7 @@ pub struct Entry {
     pub header: Header,
     /// The decompressed size of the object in bytes
     pub decompressed_size: u64,
-    /// absolute offset to compressed object data in the pack
+    /// absolute offset to compressed object data in the pack, just behind the header
     pub data_offset: u64,
 }
 

Diff for: git-odb/src/pack/index/verify.rs

@@ -76,6 +76,17 @@ pub struct Outcome {
     pub pack_size: u64,
 }
 
+/// Various ways in which a pack and index can be verified
+#[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]
+pub enum Mode {
+    /// Validate SHA1 and CRC32
+    Sha1CRC32,
+    /// Validate SHA1 and CRC32, and decode each non-Blob object
+    Sha1CRC32Decode,
+    /// Validate SHA1 and CRC32, and decode and encode each non-Blob object
+    Sha1CRC32DecodeEncode,
+}
+
 /// Verify and validate the content of the index file
 impl index::File {
     pub fn checksum_of_index(&self) -> owned::Id {
@@ -94,6 +105,7 @@ impl index::File {
         &self,
         pack: Option<&pack::data::File>,
         thread_limit: Option<usize>,
+        mode: Mode,
         progress: Option<P>,
         make_cache: impl Fn() -> C + Send + Sync,
     ) -> Result<(owned::Id, Option<Outcome>), Error>
@@ -281,10 +293,9 @@ impl index::File {
                                 });
                             }
                             if let Some(desired_crc32) = index_entry.crc32 {
-                                let actual_crc32 = pack.entry_crc32(
-                                    index_entry.pack_offset,
-                                    (pack_entry_data_offset - index_entry.pack_offset) as usize + consumed_input,
-                                );
+                                let header_size = (pack_entry_data_offset - index_entry.pack_offset) as usize;
+                                let actual_crc32 =
+                                    pack.entry_crc32(index_entry.pack_offset, header_size + consumed_input);
                                 if actual_crc32 != desired_crc32 {
                                     return Err(Error::Crc32Mismatch {
                                         actual: actual_crc32,

Diff for: git-odb/tests/pack/index.rs

@@ -155,8 +155,14 @@ fn pack_lookup() {
         assert_eq!(pack.kind(), pack::data::Kind::V2);
         assert_eq!(pack.num_objects(), idx.num_objects());
         assert_eq!(
-            idx.verify_checksum_of_index(Some(&pack), None, Discard.into(), || DecodeEntryNoop)
-                .unwrap(),
+            idx.verify_checksum_of_index(
+                Some(&pack),
+                None,
+                index::verify::Mode::Sha1CRC32DecodeEncode,
+                Discard.into(),
+                || DecodeEntryNoop
+            )
+            .unwrap(),
             (idx.checksum_of_index(), Some(stats.to_owned()))
         );
         for idx_entry in idx.iter() {
@@ -199,8 +205,10 @@ fn iter() {
         assert_eq!(idx.version(), *version);
         assert_eq!(idx.num_objects(), *num_objects);
         assert_eq!(
-            idx.verify_checksum_of_index(None, None, Discard.into(), || DecodeEntryNoop)
-                .unwrap(),
+            idx.verify_checksum_of_index(None, None, index::verify::Mode::Sha1CRC32Decode, Discard.into(), || {
+                DecodeEntryNoop
+            })
+            .unwrap(),
             (idx.checksum_of_index(), None)
         );
         assert_eq!(idx.checksum_of_index(), hex_to_id(index_checksum));

Diff for: gitoxide-core/src/lib.rs

@@ -51,13 +51,15 @@ pub struct Context<W1: io::Write, W2: io::Write> {
     /// Otherwise, usually use as many threads as there are logical cores.
     /// A value of 0 is interpreted as no-limit
     pub thread_limit: Option<usize>,
+    pub mode: index::verify::Mode,
 }
 
 impl Default for Context<Vec<u8>, Vec<u8>> {
     fn default() -> Self {
         Context {
             output_statistics: None,
             thread_limit: None,
+            mode: VerifyMode::Sha1CRC32,
             out: Vec::new(),
             err: Vec::new(),
         }
@@ -95,6 +97,7 @@ pub fn verify_pack_or_pack_index<P, W1, W2>(
     Context {
         mut out,
         mut err,
+        mode,
         output_statistics,
         thread_limit,
     }: Context<W1, W2>,
@@ -132,7 +135,7 @@ where
                     Err(e)
                 })
                 .ok();
-            idx.verify_checksum_of_index(pack.as_ref(), thread_limit, progress, || -> EitherCache {
+            idx.verify_checksum_of_index(pack.as_ref(), thread_limit, mode, progress, || -> EitherCache {
                 if output_statistics.is_some() {
                     // turn off acceleration as we need to see entire chains all the time
                     EitherCache::Left(pack::cache::DecodeEntryNoop)

Diff for: src/plumbing/lean.rs

@@ -10,6 +10,22 @@ mod options {
         /// print the program version.
         pub version: bool,
 
+        #[argh(switch)]
+        /// Decode and parse tags, commits and trees to validate their correctness beyond hashing correctly.
+        ///
+        /// Malformed objects should not usually occur, but could be injected on purpose or accident.
+        /// This will reduce overall performance.
+        pub decode: bool,
+
+        #[argh(switch)]
+        /// Decode and parse tags, commits and trees to validate their correctness, and re-encode them.
+        ///
+        /// This flag is primarily to test the implementation of encoding, and requires to decode the object first.
+        /// Encoding an object after decoding it should yield exactly the same bytes.
+        /// This will reduce overall performance even more, as re-encoding requires to transform zero-copy objects into
+        /// owned objects, causing plenty of allocation to occour.
+        pub re_encode: bool,
+
         #[argh(option, short = 't')]
         /// the amount of threads to use for some operations.
         ///

Diff for: tasks.md

@@ -6,16 +6,16 @@
   * [ ] ~~support streamed objects (similar to how it's done with loose objects)~~ - no need, all slices support io::Read, and we don't
         actually support streaming, so let's net unify 'interfaces' on a low level like this.
 * **owned objects**
-  * [ ] encode object
+  * [x] encode object
     * [x] blob
     * [x] tag
     * [x] tree
     * [x] commit
-  * [ ] write loose
 * **pack verify**
   * add '--some-flag' to run every non-blob through a decode/encode cycle to see if all objects can be parsed
   * add that to the stress test
 * **plumbing - explode pack**
+  * [ ] write loose object
   * [ ] single threaded
   * [ ] multi-threaded
   * [ ] progress

Diff for: tests/stateless-journey.sh

@@ -61,6 +61,12 @@ title "CLI ${kind}"
           expect_run $SUCCESSFULLY "$exe_plumbing" verify-pack --statistics "$PACK_INDEX_FILE"
         }
       )
+      (with "decode"
+        it "verifies the pack index successfully and with desired output, and decodes all objects" && {
+          WITH_SNAPSHOT="$snapshot/plumbing-verify-pack-index-success" \
+          expect_run $SUCCESSFULLY "$exe_plumbing" verify-pack --decode "$PACK_INDEX_FILE"
+        }
+      )
       if test "$kind" = "max"; then
       (with "statistics (JSON)"
         it "verifies the pack index successfully and with desired output" && {