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Factor out m_seq_get_fast_slice_indexes() fucntions as sequence helper. 

Takes slice object and sequence length and computes subsequence indexes
for case of slice step=1.
This commit is contained in:
Paul Sokolovsky 2014-02-02 02:38:22 +02:00
parent a9459bc723
commit 7364af2d8c
3 changed files with 33 additions and 20 deletions
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1
py/obj.h
View File

@ -395,3 +395,4 @@ typedef struct _mp_obj_classmethod_t {
// sequence helpers
void mp_seq_multiply(const void *items, uint item_sz, uint len, uint times, void *dest);
bool m_seq_get_fast_slice_indexes(machine_uint_t len, mp_obj_t slice, machine_uint_t *begin, machine_uint_t *end);

22
py/objstr.c
View File

@ -115,26 +115,8 @@ mp_obj_t str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
}
#if MICROPY_ENABLE_SLICE
} else if (MP_OBJ_IS_TYPE(rhs_in, &slice_type)) {
machine_int_t start, stop, step;
mp_obj_slice_get(rhs_in, &start, &stop, &step);
assert(step == 1);
if (start < 0) {
start = lhs_len + start;
if (start < 0) {
start = 0;
}
} else if (start > lhs_len) {
start = lhs_len;
}
if (stop <= 0) {
stop = lhs_len + stop;
// CPython returns empty string in such case
if (stop < 0) {
stop = start;
}
} else if (stop > lhs_len) {
stop = lhs_len;
}
machine_uint_t start, stop;
assert(m_seq_get_fast_slice_indexes(lhs_len, rhs_in, &start, &stop));
return mp_obj_new_str(lhs_data + start, stop - start, false);
#endif
} else {

30
py/sequence.c
View File

@ -23,3 +23,33 @@ void mp_seq_multiply(const void *items, uint item_sz, uint len, uint times, void
dest = (char*)dest + copy_sz;
}
}
bool m_seq_get_fast_slice_indexes(machine_uint_t len, mp_obj_t slice, machine_uint_t *begin, machine_uint_t *end) {
machine_int_t start, stop, step;
mp_obj_slice_get(slice, &start, &stop, &step);
if (step != 1) {
return false;
}
// Unlike subscription, out-of-bounds slice indexes are never error
if (start < 0) {
start = len + start;
if (start < 0) {
start = 0;
}
} else if (start > len) {
start = len;
}
if (stop <= 0) {
stop = len + stop;
// CPython returns empty sequence in such case
if (stop < 0) {
stop = start;
}
} else if (stop > len) {
stop = len;
}
*begin = start;
*end = stop;
return true;
}