istream-metawrap: Support seeking if underlying stream supports seeking

diff --git a/src/lib-fs/istream-metawrap.c b/src/lib-fs/istream-metawrap.c
index 0bd2f1932a8f73faf4056b494e14dbf004f37c05..afec0dbb8719a46f9a257ac16dbe225c85086ae0 100644 (file)
--- a/src/lib-fs/istream-metawrap.c
+++ b/src/lib-fs/istream-metawrap.c
@@ -62,6 +62,20 @@ static ssize_t i_stream_metawrap_read(struct istream_private *stream)
        return i_stream_read_copy_from_parent(&stream->istream);
 }
 
+static void
+i_stream_metawrap_seek(struct istream_private *stream,
+                      uoff_t v_offset, bool mark ATTR_UNUSED)
+{
+       struct metawrap_istream *mstream = (struct metawrap_istream *)stream;
+
+       /* support seeking only after reading the metadata */
+       i_assert(!mstream->in_metadata ||
+                (mstream->start_offset == 0 && v_offset == 0));
+
+       stream->istream.v_offset = v_offset;
+       stream->skip = stream->pos = 0;
+}
+
 static int i_stream_metawrap_stat(struct istream_private *stream, bool exact)
 {
        struct metawrap_istream *mstream = (struct metawrap_istream *)stream;
@@ -96,11 +110,12 @@ i_stream_create_metawrap(struct istream *input,
        mstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
 
        mstream->istream.read = i_stream_metawrap_read;
-       mstream->istream.stat = i_stream_metawrap_stat;
+       mstream->istream.seek = i_stream_metawrap_seek;
+       mstream->istream.stat = input->seekable ? i_stream_metawrap_stat : NULL;
 
        mstream->istream.istream.readable_fd = input->readable_fd;
        mstream->istream.istream.blocking = input->blocking;
-       mstream->istream.istream.seekable = FALSE;
+       mstream->istream.istream.seekable = input->seekable;
        mstream->in_metadata = TRUE;
        mstream->callback = callback;
        mstream->context = context;