Commit afaaf535 authored by Paul Sokolovsky's avatar Paul Sokolovsky
Browse files

objslice: Support arbitrary objects start, stop, and step.

Older int-only encoding is not expressive enough to support arbitrary slice
assignment operations.
parent 7a4ddd24
......@@ -517,7 +517,7 @@ mp_map_t *mp_obj_dict_get_map(mp_obj_t self_in);
void mp_obj_set_store(mp_obj_t self_in, mp_obj_t item);
// slice
void mp_obj_slice_get(mp_obj_t self_in, machine_int_t *start, machine_int_t *stop, machine_int_t *step);
void mp_obj_slice_get(mp_obj_t self_in, mp_obj_t *start, mp_obj_t *stop, mp_obj_t *step);
// array
uint mp_obj_array_len(mp_obj_t self_in);
......
......@@ -62,13 +62,20 @@ const mp_obj_ellipsis_t mp_const_ellipsis_obj = {{&mp_type_ellipsis}};
// CPython supports 3rd arg (step), plus args can be arbitrary Python objects.
typedef struct _mp_obj_slice_t {
mp_obj_base_t base;
machine_int_t start;
machine_int_t stop;
mp_obj_t start;
mp_obj_t stop;
mp_obj_t step;
} mp_obj_slice_t;
void slice_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t o_in, mp_print_kind_t kind) {
mp_obj_slice_t *o = o_in;
print(env, "slice(" INT_FMT ", " INT_FMT ")", o->start, o->stop);
print(env, "slice(");
mp_obj_print_helper(print, env, o->start, PRINT_REPR);
print(env, ", ");
mp_obj_print_helper(print, env, o->stop, PRINT_REPR);
print(env, ", ");
mp_obj_print_helper(print, env, o->step, PRINT_REPR);
print(env, ")");
}
const mp_obj_type_t mp_type_slice = {
......@@ -77,39 +84,21 @@ const mp_obj_type_t mp_type_slice = {
.print = slice_print,
};
// TODO: Make sure to handle "empty" values, which are signified by None in CPython
mp_obj_t mp_obj_new_slice(mp_obj_t ostart, mp_obj_t ostop, mp_obj_t ostep) {
assert(ostep == NULL);
machine_int_t start = 0, stop = 0;
if (ostart != mp_const_none) {
start = mp_obj_get_int(ostart);
}
if (ostop != mp_const_none) {
stop = mp_obj_get_int(ostop);
if (stop == 0) {
// [x:0] is a special case - in our slice object, stop = 0 means
// "end of sequence". Fortunately, [x:0] is an empty seqence for
// any x (including negative). [x:x] is also always empty sequence.
// but x also can be 0. But note that b""[x:x] is b"" for any x (i.e.
// no IndexError, at least in Python 3.3.3). So, we just use -1's to
// signify that. -1 is catchy "special" number in case someone will
// try to print [x:0] slice ever.
start = stop = -1;
}
}
mp_obj_slice_t *o = m_new(mp_obj_slice_t, 1);
mp_obj_slice_t *o = m_new_obj(mp_obj_slice_t);
o->base.type = &mp_type_slice;
o->start = start;
o->stop = stop;
return (mp_obj_t)o;
o->start = ostart;
o->stop = ostop;
o->step = ostep;
return o;
}
void mp_obj_slice_get(mp_obj_t self_in, machine_int_t *start, machine_int_t *stop, machine_int_t *step) {
void mp_obj_slice_get(mp_obj_t self_in, mp_obj_t *start, mp_obj_t *stop, mp_obj_t *step) {
assert(MP_OBJ_IS_TYPE(self_in, &mp_type_slice));
mp_obj_slice_t *self = self_in;
*start = self->start;
*stop = self->stop;
*step = 1;
*step = self->step;
}
#endif
......@@ -355,6 +355,9 @@ STATIC mp_obj_t str_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
if (!mp_seq_get_fast_slice_indexes(self_len, index, &start, &stop)) {
assert(0);
}
if (start >= stop) {
return MP_OBJ_NEW_QSTR(MP_QSTR_);
}
return str_new(type, self_data + start, stop - start);
}
#endif
......
......@@ -52,12 +52,24 @@ void mp_seq_multiply(const void *items, uint item_sz, uint len, uint times, void
}
bool mp_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) {
mp_obj_t ostart, ostop, ostep;
machine_int_t start, stop;
mp_obj_slice_get(slice, &ostart, &ostop, &ostep);
if (ostep != mp_const_none && ostep != MP_OBJ_NEW_SMALL_INT(1)) {
return false;
}
if (ostart == mp_const_none) {
start = 0;
} else {
start = MP_OBJ_SMALL_INT_VALUE(ostart);
}
if (ostop == mp_const_none) {
stop = len;
} else {
stop = MP_OBJ_SMALL_INT_VALUE(ostop);
}
// Unlike subscription, out-of-bounds slice indexes are never error
if (start < 0) {
start = len + start;
......@@ -67,7 +79,7 @@ bool mp_seq_get_fast_slice_indexes(machine_uint_t len, mp_obj_t slice, machine_u
} else if (start > len) {
start = len;
}
if (stop <= 0) {
if (stop < 0) {
stop = len + stop;
// CPython returns empty sequence in such case
if (stop < 0) {
......
......@@ -768,12 +768,12 @@ unwind_jump:
if (unum == 2) {
obj2 = POP();
obj1 = TOP();
SET_TOP(mp_obj_new_slice(obj1, obj2, NULL));
SET_TOP(mp_obj_new_slice(obj1, obj2, mp_const_none));
} else {
obj1 = mp_obj_new_exception_msg(&mp_type_NotImplementedError, "3-argument slice is not supported");
nlr_pop();
fastn[0] = obj1;
return MP_VM_RETURN_EXCEPTION;
mp_obj_t obj3 = POP();
obj2 = POP();
obj1 = TOP();
SET_TOP(mp_obj_new_slice(obj1, obj2, obj3));
}
DISPATCH();
#endif
......
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