core: add int.bit_length() when MICROPY_CYPTHON_COMPAT is enabled

This method of integer objects is needed for a port of python3's
decimal.py module.

MICROPY_CPYTHON_COMPAT is enabled by CIRCUITPY_FULL_BUILD.

1 files changed, 11 insertions, 0 deletions

diff --git a/py/objint_longlong.c b/py/objint_longlong.c
index 189049630..0a65098c7 100644
--- a/py/objint_longlong.c
+++ b/py/objint_longlong.c
@@ -45,6 +45,17 @@
 const mp_obj_int_t mp_maxsize_obj = {{&mp_type_int}, MP_SSIZE_MAX};
 #endif
 
+mp_obj_t mp_obj_int_bit_length_impl(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &mp_type_int));
+    mp_obj_int_t *self = self_in;
+    long long val = self->val;
+    return MP_OBJ_NEW_SMALL_INT(
+        (val == 0) ? 0 :
+        (val == MP_SMALL_INT_MIN) ? 8 * sizeof(long long) :
+        (val < 0) ? 8 * sizeof(long long) - __builtin_clzll(-val) :
+             8 * sizeof(long long) - __builtin_clzll(val));
+}
+
 mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf) {
     int delta = 1;
     if (!big_endian) {