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py/sequence: Fix boundary errors when slicing with a negative step.

This commit is contained in:
Damien George 2017-05-17 16:33:07 +10:00
parent d007351b33
commit eb4c37f7a4
1 changed files with 9 additions and 2 deletions
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9
py/sequence.c
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@ -88,15 +88,22 @@ bool mp_seq_get_fast_slice_indexes(mp_uint_t len, mp_obj_t slice, mp_bound_slice
if (start < 0) {
start = len + start;
if (start < 0) {
if (indexes->step < 0) {
start = -1;
} else {
start = 0;
}
}
} else if (indexes->step > 0 && (mp_uint_t)start > len) {
start = len;
} else if (indexes->step < 0 && (mp_uint_t)start > len - 1) {
} else if (indexes->step < 0 && (mp_uint_t)start >= len) {
start = len - 1;
}
if (stop < 0) {
stop = len + stop;
if (stop < 0) {
stop = -1;
}
if (indexes->step < 0) {
stop += 1;
}