libio: Move istream_t precache logic into backend implementation

The end goal is to remove direct buffer access from the istream_t
interfaces and make that opaque. For the tar implementation, this
already safes us needless buffer copying, as we essentially allow
the user to read-through from the underlying stream.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/tar/src/iterator.c b/lib/tar/src/iterator.c
index 0940905..532eb8c 100644
--- a/lib/tar/src/iterator.c
+++ b/lib/tar/src/iterator.c
@@ -104,6 +104,12 @@ static int strm_precache(istream_t *strm)
 	tar_istream_t *tar = (tar_istream_t *)strm;
 	sqfs_u64 diff;
 
+	strm->buffer_used -= strm->buffer_offset;
+	strm->buffer_offset = 0;
+
+	if (strm->eof)
+		return 0;
+
 	tar->parent->offset += tar->parent->last_chunk;
 
 	if (!tar->parent->last_sparse) {