1 files changed, 74 insertions, 0 deletions
diff --git a/py/objslice.c b/py/objslice.c
new file mode 100644
index 0000000000..03607e4c3e
--- /dev/null
+++ b/py/objslice.c
@@ -0,0 +1,74 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <assert.h>
+
+#include "nlr.h"
+#include "misc.h"
+#include "mpconfig.h"
+#include "obj.h"
+#include "runtime0.h"
+
+#if MICROPY_ENABLE_SLICE
+
+// TODO: This implements only variant of slice with 2 integer args only.
+// 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_slice_t;
+
+void slice_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t o_in) {
+    mp_obj_slice_t *o = o_in;
+    print(env, "slice(" INT_FMT ", " INT_FMT ")", o->start, o->stop);
+}
+
+const mp_obj_type_t slice_type = {
+    { &mp_const_type },
+    "slice",
+    slice_print,
+    NULL, // call_n
+    NULL, // unary_op
+    NULL, // binary_op
+    NULL, // getiter
+    NULL, // iternext
+    { { NULL, NULL }, }, // method list
+};
+
+// 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);
+    o->base.type = &slice_type;
+    o->start = start;
+    o->stop = stop;
+    return (mp_obj_t)o;
+}
+
+void mp_obj_slice_get(mp_obj_t self_in, machine_int_t *start, machine_int_t *stop, machine_int_t *step) {
+    assert(MP_OBJ_IS_TYPE(self_in, &slice_type));
+    mp_obj_slice_t *self = self_in;
+    *start = self->start;
+    *stop = self->stop;
+    *step = 1;
+}
+
+#endif