unix, stmhal: Implement file.readinto() method.

Also, usocket.readinto(). Known issue is that .readinto() should be available
only for binary files, but micropython uses single method table for both
binary and text files.

py/qstrdefs.h

@@ -437,6 +437,7 @@ Q(BF_LEN)
 #if MICROPY_PY_IO
 Q(_io)
 Q(readall)
+Q(readinto)
 Q(readline)
 Q(readlines)
 Q(FileIO)

py/stream.c

@@ -215,6 +215,27 @@ STATIC mp_obj_t stream_write_method(mp_obj_t self_in, mp_obj_t arg) {
     return mp_stream_write(self_in, bufinfo.buf, bufinfo.len);
 }
 
+STATIC mp_obj_t stream_readinto(mp_obj_t self_in, mp_obj_t arg) {
+    struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)self_in;
+    if (o->type->stream_p == NULL || o->type->stream_p->read == NULL) {
+        // CPython: io.UnsupportedOperation, OSError subclass
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
+    }
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(arg, &bufinfo, MP_BUFFER_WRITE);
+
+    int error;
+    mp_uint_t out_sz = o->type->stream_p->read(o, bufinfo.buf, bufinfo.len, &error);
+    if (out_sz == MP_STREAM_ERROR) {
+        if (is_nonblocking_error(error)) {
+            return mp_const_none;
+        }
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(error)));
+    } else {
+        return MP_OBJ_NEW_SMALL_INT(out_sz);
+    }
+}
+
 STATIC mp_obj_t stream_readall(mp_obj_t self_in) {
     struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)self_in;
     if (o->type->stream_p == NULL || o->type->stream_p->read == NULL) {
@@ -349,6 +370,7 @@ mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self) {
 }
 
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_read_obj, 1, 2, stream_read);
+MP_DEFINE_CONST_FUN_OBJ_2(mp_stream_readinto_obj, stream_readinto);
 MP_DEFINE_CONST_FUN_OBJ_1(mp_stream_readall_obj, stream_readall);
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_unbuffered_readline_obj, 1, 2, stream_unbuffered_readline);
 MP_DEFINE_CONST_FUN_OBJ_2(mp_stream_write_obj, stream_write_method);

py/stream.h

@@ -25,6 +25,7 @@
  */
 
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_read_obj);
+MP_DECLARE_CONST_FUN_OBJ(mp_stream_readinto_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_readall_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_unbuffered_readline_obj);
 MP_DECLARE_CONST_FUN_OBJ(mp_stream_unbuffered_readlines_obj);

stmhal/file.c

@@ -222,6 +222,7 @@ STATIC mp_obj_t file_obj_make_new(mp_obj_t type, mp_uint_t n_args, mp_uint_t n_k
 STATIC const mp_map_elem_t rawfile_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readinto), (mp_obj_t)&mp_stream_readinto_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_readlines), (mp_obj_t)&mp_stream_unbuffered_readlines_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },

tests/io/data/file2

+1234
\ No newline at end of file

tests/io/file_readinto.py

+b = bytearray(30)
+f = open("io/data/file1", "rb")
+print(f.readinto(b))
+print(b)
+f = open("io/data/file2", "rb")
+print(f.readinto(b))
+print(b)

unix/file.c

@@ -177,6 +177,7 @@ STATIC const mp_map_elem_t rawfile_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_fileno), (mp_obj_t)&fdfile_fileno_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readinto), (mp_obj_t)&mp_stream_readinto_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_readlines), (mp_obj_t)&mp_stream_unbuffered_readlines_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },

unix/modsocket.c

@@ -289,6 +289,7 @@ STATIC const mp_map_elem_t usocket_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_makefile), (mp_obj_t)&socket_makefile_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readall), (mp_obj_t)&mp_stream_readall_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readinto), (mp_obj_t)&mp_stream_readinto_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_connect), (mp_obj_t)&socket_connect_obj },