another API rework: less abstraction leakage

1 files changed, 90 insertions, 3 deletions

diff --git a/shared-bindings/bleio/Descriptor.c b/shared-bindings/bleio/Descriptor.c
index db8d393d1..39fd21d88 100644
--- a/shared-bindings/bleio/Descriptor.c
+++ b/shared-bindings/bleio/Descriptor.c
@@ -29,6 +29,7 @@
 #include "py/objproperty.h"
 #include "py/runtime.h"
 #include "shared-bindings/bleio/Attribute.h"
+#include "shared-bindings/bleio/Characteristic.h"
 #include "shared-bindings/bleio/Descriptor.h"
 #include "shared-bindings/bleio/UUID.h"
 
@@ -41,12 +42,98 @@
 //| Descriptors are attached to BLE characteristics and provide contextual
 //| information about the characteristic.
 //|
-//| A Descriptors cannot be created directly. A new local Descriptors can be created
-//| and attached to a Descriptors by calling `Service.add_characteristic()`.
+//| There is no regular constructor for a Descriptor. A new local Descriptor can be created
+//| and attached to a Characteristic by calling `Descriptor.add_to_characteristic()`.
 //| Remote Descriptor objects are created by `Central.discover_remote_services()`
 //| or `Peripheral.discover_remote_services()` as part of remote Characteristics
 //| in the remote Services that are discovered.
 
+//|   .. method:: add_to_characteristic(characteristic, uuid, *, read_perm=`Attribute.OPEN`, write_perm=`Attribute.OPEN`, max_length=20, fixed_length=False, initial_value=b'')
+//|
+//|   Create a new `Descriptor` object, and add it to this Service.
+//|
+//|   :param bleio.Characteristic characteristic: The characteristic that will hold this descriptor
+//|   :param bleio.UUID uuid: The uuid of the descriptor
+//|   :param int read_perm: Specifies whether the descriptor can be read by a client, and if so, which
+//|      security mode is required. Must be one of the integer values `Attribute.NO_ACCESS`, `Attribute.OPEN`,
+//|      `Attribute.ENCRYPT_NO_MITM`, `Attribute.ENCRYPT_WITH_MITM`, `Attribute.LESC_ENCRYPT_WITH_MITM`,
+//|      `Attribute.SIGNED_NO_MITM`, or `Attribute.SIGNED_WITH_MITM`.
+//|   :param int write_perm: Specifies whether the descriptor can be written by a client, and if so, which
+//|      security mode is required. Values allowed are the same as ``read_perm``.
+//|   :param int max_length: Maximum length in bytes of the descriptor value. The maximum allowed is
+//|      is 512, or possibly 510 if ``fixed_length`` is False. The default, 20, is the maximum
+//|      number of data bytes that fit in a single BLE 4.x ATT packet.
+//|   :param bool fixed_length: True if the descriptor value is of fixed length.
+//|   :param buf initial_value: The initial value for this descriptor.
+//|
+//|   :return: the new `Descriptor`.
+//|
+STATIC mp_obj_t bleio_descriptor_add_to_characteristic(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    // class is arg[0], which we can ignore.
+
+    enum { ARG_characteristic, ARG_uuid, ARG_read_perm, ARG_write_perm,
+           ARG_max_length, ARG_fixed_length, ARG_initial_value };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_characteristic,  MP_ARG_REQUIRED | MP_ARG_OBJ },
+        { MP_QSTR_uuid,  MP_ARG_REQUIRED | MP_ARG_OBJ },
+        { MP_QSTR_read_perm, MP_ARG_KW_ONLY| MP_ARG_INT, {.u_int = SECURITY_MODE_OPEN} },
+        { MP_QSTR_write_perm, MP_ARG_KW_ONLY| MP_ARG_INT, {.u_int = SECURITY_MODE_OPEN} },
+        { MP_QSTR_max_length, MP_ARG_KW_ONLY| MP_ARG_INT, {.u_int = 20} },
+        { MP_QSTR_fixed_length, MP_ARG_KW_ONLY| MP_ARG_BOOL, {.u_bool = false} },
+        { MP_QSTR_initial_value, MP_ARG_KW_ONLY| MP_ARG_OBJ, {.u_obj = mp_const_empty_bytes} },
+    };
+
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    const mp_obj_t characteristic_obj = args[ARG_characteristic].u_obj;
+    if (!MP_OBJ_IS_TYPE(characteristic_obj, &bleio_characteristic_type)) {
+        mp_raise_ValueError(translate("Expected a Characteristic"));
+    }
+
+    const mp_obj_t uuid_obj = args[ARG_uuid].u_obj;
+    if (!MP_OBJ_IS_TYPE(uuid_obj, &bleio_uuid_type)) {
+        mp_raise_ValueError(translate("Expected a UUID"));
+    }
+
+    const bleio_attribute_security_mode_t read_perm = args[ARG_read_perm].u_int;
+    common_hal_bleio_attribute_security_mode_check_valid(read_perm);
+
+    const bleio_attribute_security_mode_t write_perm = args[ARG_write_perm].u_int;
+    common_hal_bleio_attribute_security_mode_check_valid(write_perm);
+
+    const mp_int_t max_length = args[ARG_max_length].u_int;
+    const bool fixed_length =  args[ARG_fixed_length].u_bool;
+    mp_obj_t initial_value = args[ARG_initial_value].u_obj;
+
+    // Length will be validated in common_hal.
+    mp_buffer_info_t initial_value_bufinfo;
+    if (initial_value == mp_const_none) {
+        if (fixed_length && max_length > 0) {
+            initial_value = mp_obj_new_bytes_of_zeros(max_length);
+        } else {
+            initial_value = mp_const_empty_bytes;
+        }
+    }
+    mp_get_buffer_raise(initial_value, &initial_value_bufinfo, MP_BUFFER_READ);
+
+    bleio_descriptor_obj_t *descriptor = m_new_obj(bleio_descriptor_obj_t);
+    descriptor->base.type = &bleio_descriptor_type;
+
+    // Range checking on max_length arg is done by the common_hal layer, because
+    // it may vary depending on underlying BLE implementation.
+    common_hal_bleio_descriptor_construct(
+        descriptor, MP_OBJ_TO_PTR(characteristic_obj), MP_OBJ_TO_PTR(uuid_obj),
+        read_perm, write_perm,
+        max_length, fixed_length, &initial_value_bufinfo);
+
+    common_hal_bleio_characteristic_add_descriptor(characteristic_obj, descriptor);
+
+    return MP_OBJ_FROM_PTR(descriptor);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(bleio_descriptor_add_to_characteristic_fun_obj, 3, bleio_descriptor_add_to_characteristic);
+STATIC MP_DEFINE_CONST_CLASSMETHOD_OBJ(bleio_descriptor_add_to_characteristic_obj, MP_ROM_PTR(&bleio_descriptor_add_to_characteristic_fun_obj));
+
 //|   .. attribute:: uuid
 //|
 //|     The descriptor uuid. (read-only)
@@ -115,7 +202,7 @@ const mp_obj_property_t bleio_descriptor_value_obj = {
 };
 
 STATIC const mp_rom_map_elem_t bleio_descriptor_locals_dict_table[] = {
-    // Properties
+    { MP_ROM_QSTR(MP_QSTR_add_to_characteristic), MP_ROM_PTR(&bleio_descriptor_add_to_characteristic_obj) },
     { MP_ROM_QSTR(MP_QSTR_uuid), MP_ROM_PTR(&bleio_descriptor_uuid_obj) },
     { MP_ROM_QSTR(MP_QSTR_characteristic), MP_ROM_PTR(&bleio_descriptor_characteristic_obj) },
     { MP_ROM_QSTR(MP_QSTR_value), MP_ROM_PTR(&bleio_descriptor_value_obj) },