Allow any object (loose or packed) to be retrieved from a repo.

cli/Program.fs

@@ -40,6 +40,21 @@ type AppCommand() =
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
+type DumpRepoObjectSettings() =
+    inherit AppSettings()
+    [<CommandOption( "-o|--obj <OBJ-NAME>" )>]
+    member val ObjName = "" with get, set
+
+type DumpRepoObjectCommand() =
+    inherit Command<DumpRepoObjectSettings>()
+    override this.Execute( ctx, settings ) =
+        if settings.ObjName = "" then
+            failwith "Missing object name."
+        dumpRepoObject settings.RepoDir settings.ObjName
+        0
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
 type DumpPackFileSettings() =
     inherit AppSettings()
     [<CommandOption( "-f|--pack-file <PACK-FILE>" )>]
@@ -85,6 +100,9 @@ let main argv =
     let app = CommandApp<AppCommand>()
     app.Configure( fun cfg ->
         cfg.SetApplicationName( System.AppDomain.CurrentDomain.FriendlyName ) |> ignore
+        cfg.AddCommand<DumpRepoObjectCommand>( "dump-object" ).WithDescription(
+            "Dump an object in a git repo."
+        ) |> ignore
         cfg.AddCommand<DumpPackFileCommand>( "dump-packfile" ).WithDescription(
             "Dump a pack file."
         ) |> ignore

git-guts/GitGuts.fs

@@ -53,6 +53,16 @@ module GitGuts =
 
             buf
 
+    let decompressEntireStream (inp: Stream) =
+        // skip the header
+        inp.ReadByte() |> ignore
+        inp.ReadByte() |> ignore
+        // decompress the rest of the input stream
+        use zstream = new DeflateStream( inp, CompressionMode.Decompress )
+        use buf = new MemoryStream()
+        zstream.CopyTo( buf )
+        buf.ToArray()
+
     let readUntil (inp: Stream) (endByte: byte) =
         // read bytes until the specified end byte is seen
         let rec readBytes () = seq {

git-guts/GitObject.fs

@@ -92,14 +92,28 @@ type TagGitObject( objData ) =
 
 // --------------------------------------------------------------------
 
+// This is used to hold the raw data for objects extracted from a pack.
+type ObjRec = {
+    objType: int
+    objData: byte[]
+}
+
 [<AutoOpen>]
 module GitObject =
 
-    let makeGitObject objType objData =
+    let makeGitObject objRec =
         // create a GitObject-derived object
+        match objRec.objType with
+        | 1 -> (CommitGitObject objRec.objData) :> GitObject
+        | 2 -> (TreeGitObject objRec.objData) :> GitObject
+        | 3 -> (BlobGitObject objRec.objData) :> GitObject
+        | 4 -> (TagGitObject objRec.objData) :> GitObject
+        | _ -> failwithf "Unknown object type: %d" objRec.objType
+
+    let parseObjType objType =
         match objType with
-        | 1 -> (CommitGitObject objData) :> GitObject
-        | 2 -> (TreeGitObject objData) :> GitObject
-        | 3 -> (BlobGitObject objData) :> GitObject
-        | 4 -> (TagGitObject objData) :> GitObject
-        | _ -> failwithf "Unknown object type: %d" objType
+        | "commit" -> 1
+        | "tree" -> 2
+        | "blob" -> 3
+        | "tag" -> 4
+        | _ -> failwithf "Unknown object type: %s" objType

git-guts/GitRepo.fs

@@ -0,0 +1,69 @@
+namespace git_guts
+
+open System.IO
+open System.Text
+open System.Collections.Generic
+
+// --------------------------------------------------------------------
+
+[<AutoOpen>]
+module GitRepo =
+
+    let rec _findRepoObjRec (repoDir: string) (objName: string) =
+
+        // check if the object is loose
+        let fname = Path.Join( repoDir, sprintf ".git/objects/%s/%s" objName.[0..1] objName.[2..] )
+        if File.Exists( fname ) then
+
+            // yup - get it directly from there
+            use inp = new FileStream( fname, FileMode.Open, FileAccess.Read, FileShare.Read )
+            let data = decompressEntireStream inp
+
+            // extract the object type and size
+            let pos = Seq.findIndex (fun byt -> byt = 0uy) data
+            let header = Encoding.ASCII.GetString( data, 0, pos )
+            let words = header.Split( ' ' )
+            if words.Length <> 2 then
+                failwithf "Unexpected loose object header: %s" header
+            let objType = parseObjType words.[0]
+            let objSize = int( words.[1] )
+
+            // get the object data
+            let objData = data.[ pos+1 .. ]
+            if objData.Length <> objSize then
+                failwithf "Unexpected object data size: %d/%d" objData.Length objSize
+
+            // return the object
+            Some { objType=objType; objData=objData }
+
+        else
+
+            // nope - check all the packs in the repo
+            let fnames = findRepoPacks repoDir
+            try
+                fnames |> Seq.map (fun fname -> _readPackObjRec fname objName _findRepoObjRec) |> Seq.find (fun obj -> obj.IsSome)
+            with
+                | :? KeyNotFoundException -> None
+
+    let findRepoObject repoDir objName =
+        // find the specified object in the repo
+        let objRec = _findRepoObjRec repoDir objName
+        if objRec.IsNone then
+            None
+        else
+            Some( makeGitObject objRec.Value )
+
+    let dumpRepoObject repoDir objName =
+        // find and dump the specified repo object
+        let obj = findRepoObject repoDir objName
+        if obj.IsNone then
+            failwith "Object not found."
+        obj.Value.dumpObj()
+
+    let dumpPackFile fname =
+        // FUDGE! This is a wrapper function that passes in the recursively-called _findRepoObjRec function :-/
+        _dumpPackFile fname _findRepoObjRec
+
+    let dumpPackObject fname objName =
+        // FUDGE! This is a wrapper function that passes in the recursively-called _findRepoObjRec function :-/
+        _dumpPackObject fname objName _findRepoObjRec

git-guts/Pack.fs

@@ -8,7 +8,7 @@ open System.Collections.Generic
 [<AutoOpen>]
 module Pack =
 
-    let dumpPackFile fname =
+    let internal _dumpPackFile fname findRepoObjRecFunc =
 
         // initialize
         if not ( File.Exists fname ) then
@@ -17,13 +17,13 @@ module Pack =
         // figure out what to do
         let extn = Path.GetExtension( fname ).ToLower()
         if extn = ".pack" then
-            _dumpPackDataFile fname
+            _dumpPackDataFile fname findRepoObjRecFunc
         else if extn = ".idx" then
             _dumpPackIndexFile fname
         else
             failwithf "Unknown pack file extension: %s" extn
 
-    let readPackObject fname objName :GitObject option =
+    let _readPackObjRec fname objName findRepoObjRecFunc =
         let fpos = _findObjInPack fname objName
         if fpos.IsNone then
             None
@@ -32,17 +32,24 @@ module Pack =
             let fname2 = changeExtn fname ".pack"
             use inp = new FileStream( fname2, FileMode.Open, FileAccess.Read, FileShare.Read )
             inp.Seek( int64( fpos.Value ), SeekOrigin.Begin ) |> ignore
-            let objType, objData, fpos2 = _readPackObject inp
-            Some ( makeGitObject objType objData )
+            let objRec, fpos2 = _readPackObjRec inp findRepoObjRecFunc
+            Some objRec
 
-    let dumpPackObject fname objName =
+    let readPackObject fname objName findRepoObjRecFunc :GitObject option =
+        let objRec = _readPackObjRec fname objName findRepoObjRecFunc
+        if objRec.IsNone then
+            None
+        else
+            Some ( makeGitObject objRec.Value )
+
+    let _dumpPackObject fname objName findRepoObjRecFunc =
 
         // initialize
         if not ( File.Exists fname ) then
             failwithf "Can't find pack file: %s" fname
 
         // find the specified pack object
-        let obj = readPackObject fname objName
+        let obj = readPackObject fname objName findRepoObjRecFunc
         if obj.IsNone then
             failwith "Object not found."
         obj.Value.dumpObj()

git-guts/PackData.fs

@@ -69,7 +69,7 @@ module PackData =
 
         objData
 
-    let rec internal _readPackObject (inp: Stream) =
+    let rec internal _readPackObjRec (inp: Stream) findRepoObjRecFunc =
 
         // remember where the object starts in the pack data
         let fpos = inp.Position
@@ -91,23 +91,21 @@ module PackData =
         let objSize = getShiftedBytes (byt &&& 0x8F) 0 |> Seq.fold foldShiftedByte 0
 
         // read the object data
-        let mutable objType2 = -1
-        let mutable objData = null
-        let obj =
+        let objRec =
             match objType with
             | 1 | 2 | 3 | 4 -> // commit, tree, blob, tag
-                objData <- decompressStream inp objSize
-                objType2 <- objType
+                let objData = decompressStream inp objSize
+                { objType=objType; objData=objData }
             | 6 -> // ofs_delta
-                let deltaObjAndType = _readOfsDeltaObj inp fpos objSize
-                objData <- snd deltaObjAndType
-                objType2 <- fst deltaObjAndType
+                _readOfsDeltaObjRec inp fpos objSize findRepoObjRecFunc
+            | 7 -> // ref_delta
+                _readRefDeltaObjRec inp fpos objSize findRepoObjRecFunc
             | _ ->
                 failwithf "Unknown object type: %d" objType
 
-        ( objType2, objData, fpos )
+        ( objRec, fpos )
 
-    and private _readOfsDeltaObj (inp: Stream) fpos objSize =
+    and private _readOfsDeltaObjRec (inp: Stream) fpos objSize findRepoObjRecFunc =
 
         // read the base object offset
         let offset = int64( readVliBe inp true )
@@ -117,24 +115,43 @@ module PackData =
         // IMPORTANT: The base object could itself be delta'fied.
         let prevPos = inp.Position
         inp.Seek( baseObjOffset, SeekOrigin.Begin ) |> ignore
-        let baseObjType, baseObjData, fpos = _readPackObject inp
+        let baseObjRec, fpos = _readPackObjRec inp findRepoObjRecFunc
         inp.Seek( prevPos, SeekOrigin.Begin ) |> ignore
 
         // reconstruct the delta'fied object
-        let objData = _makeDeltaObj inp baseObjData objSize
+        let objData = _makeDeltaObj inp baseObjRec.objData objSize
 
-        ( baseObjType, objData )
+        { objType=baseObjRec.objType; objData=objData }
 
-    let private _readPackObjects (inp: Stream) = seq {
+    and private _readRefDeltaObjRec (inp: Stream) fpos objSize (findRepoObjRecFunc: string -> string -> ObjRec option) =
+
+        // read the base object name
+        let baseObjName = readObjName inp
+
+        // get the base object
+        let fstream = inp :?> FileStream // NOTE: REF_DELTA's will only work with repo's stored on disk.
+        let dname = Path.GetDirectoryName( fstream.Name )
+        let repoDir = Path.GetFullPath( Path.Join( dname, "../../.." ) )
+        // FUDGE! The algorithm for reconstructing objects from base object(s) is inherently recursive,
+        // and since there isn't a way to forward declare a function, everyone has to pass around
+        // a reference to the _findRepoObjRec function, so that we can use it here :-/
+        let baseObjRec = findRepoObjRecFunc repoDir baseObjName
+
+        // reconstruct the delta'fied object
+        let objData = _makeDeltaObj inp baseObjRec.Value.objData objSize
+
+        { objType=baseObjRec.Value.objType; objData=objData }
+
+    let private _readPackObjects (inp: Stream) findRepoObjRecFunc = seq {
         // read each object
         let endPos = inp.Length - 20L // nb: we ignore the 20-byte checksum at the end
         while inp.Position < endPos do
-            let objType, objData, fpos = _readPackObject inp
-            let obj = makeGitObject objType objData
-            yield obj, fpos, objData
+            let objRec, fpos = _readPackObjRec inp findRepoObjRecFunc
+            let obj = makeGitObject objRec
+            yield obj, objRec, fpos
     }
 
-    let internal _dumpPackDataFile fname =
+    let internal _dumpPackDataFile fname findRepoObjRecFunc =
 
         // initialize
         use inp = new FileStream( fname, FileMode.Open, FileAccess.Read, FileShare.Read )
@@ -143,11 +160,11 @@ module PackData =
         let version, nObjs = _readPackDataHeader inp
 
         // dump each object
-        _readPackObjects inp |> Seq.iteri ( fun objNo row ->
-            let obj, fpos, objData = row
+        _readPackObjects inp findRepoObjRecFunc |> Seq.iteri ( fun objNo row ->
+            let obj, objRec, fpos = row
             AnsiConsole.MarkupLine( makeHeader
                 ( sprintf "OBJECT %d: %s" objNo obj.objType )
-                ( sprintf "(fpos=0x%x, size=%d)" fpos objData.Length )
+                ( sprintf "(fpos=0x%x, size=%d)" fpos objRec.objData.Length )
             )
             printfn ""
             obj.dumpObj()

git-guts/git-guts.fsproj

@@ -13,6 +13,7 @@
     <Compile Include="PackData.fs" />
     <Compile Include="PackIndex.fs" />
     <Compile Include="Pack.fs" />
+    <Compile Include="GitRepo.fs" />
   </ItemGroup>
 
   <ItemGroup>

git-guts/tests/TestPacks.fs

@@ -54,7 +54,7 @@ type TestPacks () =
                 let nObjs = readNboInt inp
                 for objNo = 0 to nObjs-1 do
                     let objName, _, _ = readPackIndexObject inp objNo nObjs
-                    let obj = readPackObject packDataFname objName
+                    let obj = findRepoObject gitTestRepo.repoDir objName
                     Assert.IsTrue( obj.IsSome )
             )