format: Move commitgraph and packfile here

1 files changed, 68 insertions, 0 deletions

diff --git a/format/packfile/ingest/drain.go b/format/packfile/ingest/drain.go
new file mode 100644
index 00000000..ed6ec821
--- /dev/null
+++ b/format/packfile/ingest/drain.go
@@ -0,0 +1,68 @@
+package ingest
+
+import (
+	"fmt"
+	"io"
+
+	"codeberg.org/lindenii/furgit/internal/compress/zlib"
+	objectheader "codeberg.org/lindenii/furgit/object/header"
+	objectid "codeberg.org/lindenii/furgit/object/id"
+	objecttype "codeberg.org/lindenii/furgit/object/type"
+	packfmt "codeberg.org/lindenii/furgit/format/packfile"
+)
+
+// drainEntryPayload inflates one entry payload from stream and returns
+// (inflatedLength, oidForBaseEntry).
+func drainEntryPayload(state *ingestState, record objectRecord) (int64, objectid.ObjectID, error) {
+	var zero objectid.ObjectID
+
+	reader, err := zlib.NewReader(state.stream)
+	if err != nil {
+		return 0, zero, &MalformedPackEntryError{Offset: record.offset, Reason: fmt.Sprintf("open zlib stream: %v", err)}
+	}
+
+	defer func() { _ = reader.Close() }()
+
+	var total int64
+
+	if packfmt.IsBaseObjectType(record.packedType) {
+		header, ok := objectheader.Encode(record.packedType, record.declaredSize)
+		if !ok {
+			return 0, zero, &MalformedPackEntryError{Offset: record.offset, Reason: "encode object header"}
+		}
+
+		hashImpl, err := state.algo.New()
+		if err != nil {
+			return 0, zero, err
+		}
+
+		_, _ = hashImpl.Write(header)
+
+		n, err := io.Copy(hashImpl, reader)
+		if err != nil {
+			return 0, zero, &MalformedPackEntryError{Offset: record.offset, Reason: fmt.Sprintf("inflate base object: %v", err)}
+		}
+
+		total = n
+
+		oid, err := objectid.FromBytes(state.algo, hashImpl.Sum(nil))
+		if err != nil {
+			return 0, zero, err
+		}
+
+		return total, oid, nil
+	}
+
+	if record.packedType == objecttype.TypeOfsDelta || record.packedType == objecttype.TypeRefDelta {
+		n, err := io.Copy(io.Discard, reader)
+		if err != nil {
+			return 0, zero, &MalformedPackEntryError{Offset: record.offset, Reason: fmt.Sprintf("inflate delta payload: %v", err)}
+		}
+
+		total = n
+
+		return total, zero, nil
+	}
+
+	return 0, zero, &MalformedPackEntryError{Offset: record.offset, Reason: "unsupported payload type"}
+}