py/stream: Switch stream close operation from method to ioctl.

This patch moves the implementation of stream closure from a dedicated
method to the ioctl of the stream protocol, for each type that implements
closing.  The benefits of this are:

1. Rounds out the stream ioctl function, which already includes flush,
   seek and poll (among other things).

2. Makes calling mp_stream_close() on an object slightly more efficient
   because it now no longer needs to lookup the close method and call it,
   rather it just delegates straight to the ioctl function (if it exists).

3. Reduces code size and allows future types that implement the stream
   protocol to be smaller because they don't need a dedicated close method.

Code size reduction is around 200 bytes smaller for x86 archs and around
30 bytes smaller for the bare-metal archs.

1 files changed, 13 insertions, 17 deletions

diff --git a/py/objstringio.c b/py/objstringio.c
index 5c50aa317..b405ee21e 100644
--- a/py/objstringio.c
+++ b/py/objstringio.c
@@ -143,6 +143,17 @@ STATIC mp_uint_t stringio_ioctl(mp_obj_t o_in, mp_uint_t request, uintptr_t arg,
         }
         case MP_STREAM_FLUSH:
             return 0;
+        case MP_STREAM_CLOSE:
+            #if MICROPY_CPYTHON_COMPAT
+            vstr_free(o->vstr);
+            o->vstr = NULL;
+            #else
+            vstr_clear(o->vstr);
+            o->vstr->alloc = 0;
+            o->vstr->len = 0;
+            o->pos = 0;
+            #endif
+            return 0;
         default:
             *errcode = MP_EINVAL;
             return MP_STREAM_ERROR;
@@ -159,24 +170,9 @@ STATIC mp_obj_t stringio_getvalue(mp_obj_t self_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(stringio_getvalue_obj, stringio_getvalue);
 
-STATIC mp_obj_t stringio_close(mp_obj_t self_in) {
-    mp_obj_stringio_t *self = MP_OBJ_TO_PTR(self_in);
-#if MICROPY_CPYTHON_COMPAT
-    vstr_free(self->vstr);
-    self->vstr = NULL;
-#else
-    vstr_clear(self->vstr);
-    self->vstr->alloc = 0;
-    self->vstr->len = 0;
-    self->pos = 0;
-#endif
-    return mp_const_none;
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(stringio_close_obj, stringio_close);
-
 STATIC mp_obj_t stringio___exit__(size_t n_args, const mp_obj_t *args) {
     (void)n_args;
-    return stringio_close(args[0]);
+    return mp_stream_close(args[0]);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(stringio___exit___obj, 4, 4, stringio___exit__);
 
@@ -233,7 +229,7 @@ STATIC const mp_rom_map_elem_t stringio_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&mp_stream_write_obj) },
     { MP_ROM_QSTR(MP_QSTR_seek), MP_ROM_PTR(&mp_stream_seek_obj) },
     { MP_ROM_QSTR(MP_QSTR_flush), MP_ROM_PTR(&mp_stream_flush_obj) },
-    { MP_ROM_QSTR(MP_QSTR_close), MP_ROM_PTR(&stringio_close_obj) },
+    { MP_ROM_QSTR(MP_QSTR_close), MP_ROM_PTR(&mp_stream_close_obj) },
     { MP_ROM_QSTR(MP_QSTR_getvalue), MP_ROM_PTR(&stringio_getvalue_obj) },
     { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&mp_identity_obj) },
     { MP_ROM_QSTR(MP_QSTR___exit__), MP_ROM_PTR(&stringio___exit___obj) },