1 files changed, 68 insertions, 4 deletions

diff --git a/py/objstr.c b/py/objstr.c
index 59547e3cd6..a1d139e83a 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -7,6 +7,7 @@
 #include "nlr.h"
 #include "misc.h"
 #include "mpconfig.h"
+#include "mpqstr.h"
 #include "obj.h"
 #include "runtime0.h"
 #include "runtime.h"
@@ -16,6 +17,11 @@ typedef struct _mp_obj_str_t {
     qstr qstr;
 } mp_obj_str_t;
 
+static mp_obj_t mp_obj_new_str_iterator(mp_obj_str_t *str, int cur);
+
+/******************************************************************************/
+/* str                                                                        */
+
 void str_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
     mp_obj_str_t *self = self_in;
     // TODO need to escape chars etc
@@ -41,16 +47,27 @@ mp_obj_t str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
                 int len = strlen(lhs_str);
                 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 string in such case
+                    if (stop < 0) {
+                        stop = start;
+                    }
+                } else if (stop > len) {
+                    stop = len;
                 }
                 return mp_obj_new_str(qstr_from_strn_copy(lhs_str + start, stop - start));
 #endif
             } else {
                 // Message doesn't match CPython, but we don't have so much bytes as they
                 // to spend them on verbose wording
-                nlr_jump(mp_obj_new_exception_msg(rt_q_TypeError, "index must be int"));
+                nlr_jump(mp_obj_new_exception_msg(MP_QSTR_TypeError, "index must be int"));
             }
 
         case RT_BINARY_OP_ADD:
@@ -73,6 +90,10 @@ mp_obj_t str_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
     return MP_OBJ_NULL; // op not supported
 }
 
+static mp_obj_t str_getiter(mp_obj_t o_in) {
+    return mp_obj_new_str_iterator(o_in, 0);
+}
+
 mp_obj_t str_join(mp_obj_t self_in, mp_obj_t arg) {
     assert(MP_OBJ_IS_TYPE(self_in, &str_type));
     mp_obj_str_t *self = self_in;
@@ -123,7 +144,7 @@ mp_obj_t str_join(mp_obj_t self_in, mp_obj_t arg) {
     return mp_obj_new_str(qstr_from_str_take(joined_str, required_len + 1));
 
 bad_arg:
-    nlr_jump(mp_obj_new_exception_msg(rt_q_TypeError, "?str.join expecting a list of str's"));
+    nlr_jump(mp_obj_new_exception_msg(MP_QSTR_TypeError, "?str.join expecting a list of str's"));
 }
 
 void vstr_printf_wrapper(void *env, const char *fmt, ...) {
@@ -147,7 +168,7 @@ mp_obj_t str_format(int n_args, const mp_obj_t *args) {
                 vstr_add_char(vstr, '{');
             } else if (*str == '}') {
                 if (arg_i >= n_args) {
-                    nlr_jump(mp_obj_new_exception_msg(rt_q_IndexError, "tuple index out of range"));
+                    nlr_jump(mp_obj_new_exception_msg(MP_QSTR_IndexError, "tuple index out of range"));
                 }
                 mp_obj_print_helper(vstr_printf_wrapper, vstr, args[arg_i]);
                 arg_i++;
@@ -167,10 +188,11 @@ const mp_obj_type_t str_type = {
     { &mp_const_type },
     "str",
     str_print, // print
+    NULL, // make_new
     NULL, // call_n
     NULL, // unary_op
     str_binary_op, // binary_op
-    NULL, // getiter
+    str_getiter, // getiter
     NULL, // iternext
     { // method list
         { "join", &str_join_obj },
@@ -191,3 +213,45 @@ qstr mp_obj_str_get(mp_obj_t self_in) {
     mp_obj_str_t *self = self_in;
     return self->qstr;
 }
+
+/******************************************************************************/
+/* str iterator                                                               */
+
+typedef struct _mp_obj_str_it_t {
+    mp_obj_base_t base;
+    mp_obj_str_t *str;
+    machine_uint_t cur;
+} mp_obj_str_it_t;
+
+mp_obj_t str_it_iternext(mp_obj_t self_in) {
+    mp_obj_str_it_t *self = self_in;
+    const char *str = qstr_str(self->str->qstr);
+    if (self->cur < strlen(str)) {
+        mp_obj_t o_out = mp_obj_new_str(qstr_from_strn_copy(str + self->cur, 1));
+        self->cur += 1;
+        return o_out;
+    } else {
+        return mp_const_stop_iteration;
+    }
+}
+
+static const mp_obj_type_t str_it_type = {
+    { &mp_const_type },
+    "str_iterator",
+    NULL, // print
+    NULL, // make_new
+    NULL, // call_n
+    NULL, // unary_op
+    NULL, // binary_op
+    NULL, // getiter
+    str_it_iternext, // iternext
+    { { NULL, NULL }, }, // method str
+};
+
+mp_obj_t mp_obj_new_str_iterator(mp_obj_str_t *str, int cur) {
+    mp_obj_str_it_t *o = m_new_obj(mp_obj_str_it_t);
+    o->base.type = &str_it_type;
+    o->str = str;
+    o->cur = cur;
+    return o;
+}