1 files changed, 30 insertions, 0 deletions
diff --git a/format/packfile/ingest/distance.go b/format/packfile/ingest/distance.go
new file mode 100644
index 00000000..9bc4d886
--- /dev/null
+++ b/format/packfile/ingest/distance.go
@@ -0,0 +1,30 @@
+package ingest
+
+import (
+	"fmt"
+	"io"
+)
+
+// readOfsDistanceFromStream reads one ofs-delta encoded distance.
+func readOfsDistanceFromStream(reader io.ByteReader) (uint64, int, error) {
+	first, err := reader.ReadByte()
+	if err != nil {
+		return 0, 0, fmt.Errorf("read ofs distance first byte: %w", err)
+	}
+
+	dist := uint64(first & 0x7f)
+	consumed := 1
+
+	b := first
+	for b&0x80 != 0 {
+		b, err = reader.ReadByte()
+		if err != nil {
+			return 0, 0, fmt.Errorf("read ofs distance continuation: %w", err)
+		}
+
+		consumed++
+		dist = ((dist + 1) << 7) + uint64(b&0x7f)
+	}
+
+	return dist, consumed, nil
+}