From e3383e9352ca7704e650b07038207719c60b56fb Mon Sep 17 00:00:00 2001
From: Paul Sokolovsky <pfalcon@users.sourceforge.net>
Date: Sun, 20 Aug 2017 21:57:36 +0300
Subject: [PATCH] py/stream: seek: Consistently handle negative offset for
SEEK_SET.
Per POSIX, this is EINVAL, so raises OSError(EINVAL).
---
py/stream.c | 7 ++++++-
tests/io/bytesio_ext2.py | 13 +++++++++++++
tests/io/bytesio_ext2.py.exp | 1 +
3 files changed, 20 insertions(+), 1 deletion(-)
create mode 100644 tests/io/bytesio_ext2.py
create mode 100644 tests/io/bytesio_ext2.py.exp
diff --git a/py/stream.c b/py/stream.c
index 5d1868153..0029a59a7 100644
--- a/py/stream.c
+++ b/py/stream.c
@@ -448,11 +448,16 @@ STATIC mp_obj_t stream_seek(size_t n_args, const mp_obj_t *args) {
struct mp_stream_seek_t seek_s;
// TODO: Could be uint64
seek_s.offset = mp_obj_get_int(args[1]);
- seek_s.whence = 0;
+ seek_s.whence = SEEK_SET;
if (n_args == 3) {
seek_s.whence = mp_obj_get_int(args[2]);
}
+ // In POSIX, it's error to seek before end of stream, we enforce it here.
+ if (seek_s.whence == SEEK_SET && seek_s.offset < 0) {
+ mp_raise_OSError(MP_EINVAL);
+ }
+
int error;
mp_uint_t res = stream_p->ioctl(args[0], MP_STREAM_SEEK, (mp_uint_t)(uintptr_t)&seek_s, &error);
if (res == MP_STREAM_ERROR) {
diff --git a/tests/io/bytesio_ext2.py b/tests/io/bytesio_ext2.py
new file mode 100644
index 000000000..c07ad900c
--- /dev/null
+++ b/tests/io/bytesio_ext2.py
@@ -0,0 +1,13 @@
+try:
+ import uio as io
+except ImportError:
+ import io
+
+a = io.BytesIO(b"foobar")
+try:
+ a.seek(-10)
+except Exception as e:
+ # CPython throws ValueError, but MicroPython has consistent stream
+ # interface, so BytesIO raises the same error as a real file, which
+ # is OSError(EINVAL).
+ print(repr(e))
diff --git a/tests/io/bytesio_ext2.py.exp b/tests/io/bytesio_ext2.py.exp
new file mode 100644
index 000000000..b52e4978a
--- /dev/null
+++ b/tests/io/bytesio_ext2.py.exp
@@ -0,0 +1 @@
+OSError(22,)
--
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