From c5b79003f5fe6aa28a2a028680367839ba8677db Mon Sep 17 00:00:00 2001
From: Niklas Fiekas <niklas.fiekas@backscattering.de>
Date: Thu, 16 Jan 2020 15:09:19 +0100
Subject: bpo-31031: Unify duplicate bits_in_digit and bit_length (GH-2866)

Add _Py_bit_length() to unify duplicate bits_in_digit() and bit_length().
---
 Python/pymath.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'Python')

diff --git a/Python/pymath.c b/Python/pymath.c
index 24b804223e..a08a0e7961 100644
--- a/Python/pymath.c
+++ b/Python/pymath.c
@@ -79,3 +79,18 @@ round(double x)
     return copysign(y, x);
 }
 #endif /* HAVE_ROUND */
+
+static const unsigned int BitLengthTable[32] = {
+    0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
+    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5
+};
+
+unsigned int _Py_bit_length(unsigned long d) {
+   unsigned int d_bits = 0;
+   while (d >= 32) {
+       d_bits += 6;
+       d >>= 6;
+   }
+   d_bits += BitLengthTable[d];
+   return d_bits;
+}
-- 
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