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py/objstringio: Fix regression with handling SEEK_SET.

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For SEEK_SET, offset should be treated as unsigned, to allow full-width
stream sizes (e.g. 32-bit instead of 31-bit). This is now fully documented
in stream.h. Also, seek symbolic constants are added.
This commit is contained in:
Paul Sokolovsky
2017-08-20 21:32:17 +03:00
parent 168350cd98
commit 0cd9ab7755
2 changed files with 13 additions and 3 deletions
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8
py/objstringio.c
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@@ -118,15 +118,17 @@ STATIC mp_uint_t stringio_ioctl(mp_obj_t o_in, mp_uint_t request, uintptr_t arg,
struct mp_stream_seek_t *s = (struct mp_stream_seek_t*)arg;
mp_uint_t ref = 0;
switch (s->whence) {
case 1: // SEEK_CUR
case MP_SEEK_CUR:
ref = o->pos;
break;
case 2: // SEEK_END
case MP_SEEK_END:
ref = o->vstr->len;
break;
}
mp_uint_t new_pos = ref + s->offset;
if (s->offset < 0) {
// For MP_SEEK_SET, offset is unsigned
if (s->whence != MP_SEEK_SET && s->offset < 0) {
if (new_pos > ref) {
// Negative offset from SEEK_CUR or SEEK_END went past 0.
// CPython sets position to 0, POSIX returns an EINVAL error