chore(core): Improve naming of SLIP39's T9 mask lookup.

core/embed/extmod/modtrezorcrypto/modtrezorcrypto-slip39.h

@@ -24,7 +24,7 @@
 
 /// package: trezorcrypto.slip39
 
-/// def compute_mask(prefix: int) -> int:
+/// def word_completion_mask(prefix: int) -> int:
 ///     """
 ///     Calculates which buttons still can be pressed after some already were.
 ///     Returns a 9-bit bitmask, where each bit specifies which buttons
@@ -34,17 +34,18 @@
 ///     Example: 110000110 - second, third, eighth and ninth button still can be
 ///     pressed.
 ///     """
-STATIC mp_obj_t mod_trezorcrypto_slip39_compute_mask(mp_obj_t _prefix) {
+STATIC mp_obj_t mod_trezorcrypto_slip39_word_completion_mask(mp_obj_t _prefix) {
   uint16_t prefix = mp_obj_get_int(_prefix);
 
   if (prefix < 1 || prefix > 9999) {
     mp_raise_ValueError(
         "Invalid button prefix (range between 1 and 9999 is allowed)");
   }
-  return mp_obj_new_int_from_uint(compute_mask(prefix));
+  return mp_obj_new_int_from_uint(slip39_word_completion_mask(prefix));
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_slip39_compute_mask_obj,
-                                 mod_trezorcrypto_slip39_compute_mask);
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(
+    mod_trezorcrypto_slip39_word_completion_mask_obj,
+    mod_trezorcrypto_slip39_word_completion_mask);
 
 /// def button_sequence_to_word(prefix: int) -> str:
 ///     """
@@ -90,12 +91,12 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_slip39_word_index_obj,
 STATIC mp_obj_t mod_trezorcrypto_slip39_get_word(mp_obj_t _index) {
   uint16_t index = mp_obj_get_int(_index);
 
-  if (index > 1023) {
+  const char *word = get_word(index);
+  if (word == NULL) {
     mp_raise_ValueError(
         "Invalid wordlist index (range between 0 and 1024 is allowed)");
   }
 
-  const char *word = get_word(index);
   return mp_obj_new_str_copy(&mp_type_str, (const uint8_t *)word, strlen(word));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_slip39_get_word_obj,
@@ -103,8 +104,8 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_trezorcrypto_slip39_get_word_obj,
 
 STATIC const mp_rom_map_elem_t mod_trezorcrypto_slip39_globals_table[] = {
     {MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_slip39)},
-    {MP_ROM_QSTR(MP_QSTR_compute_mask),
-     MP_ROM_PTR(&mod_trezorcrypto_slip39_compute_mask_obj)},
+    {MP_ROM_QSTR(MP_QSTR_word_completion_mask),
+     MP_ROM_PTR(&mod_trezorcrypto_slip39_word_completion_mask_obj)},
     {MP_ROM_QSTR(MP_QSTR_button_sequence_to_word),
      MP_ROM_PTR(&mod_trezorcrypto_slip39_button_sequence_to_word_obj)},
     {MP_ROM_QSTR(MP_QSTR_word_index),

core/mocks/generated/trezorcrypto/slip39.pyi

@@ -2,7 +2,7 @@ from typing import *
 
 
 # extmod/modtrezorcrypto/modtrezorcrypto-slip39.h
-def compute_mask(prefix: int) -> int:
+def word_completion_mask(prefix: int) -> int:
     """
     Calculates which buttons still can be pressed after some already were.
     Returns a 9-bit bitmask, where each bit specifies which buttons

core/src/apps/management/recovery_device/keyboard_slip39.py

@@ -171,7 +171,7 @@ class Slip39Keyboard(ui.Layout):
 
         # find the completions
         word = ""
-        self.mask = slip39.compute_mask(self.button_sequence)
+        self.mask = slip39.word_completion_mask(self.button_sequence)
         if self.is_input_final():
             word = slip39.button_sequence_to_word(self.button_sequence)
 

core/src/trezor/crypto/slip39.py

@@ -114,10 +114,10 @@ KEYBOARD_FULL_MASK = const(0x1FF)
 """All buttons are allowed. 9-bit bitmap all set to 1."""
 
 
-def compute_mask(prefix: str) -> int:
+def word_completion_mask(prefix: str) -> int:
     if not prefix:
         return KEYBOARD_FULL_MASK
-    return slip39.compute_mask(int(prefix))
+    return slip39.word_completion_mask(int(prefix))
 
 
 def button_sequence_to_word(prefix: str) -> str: