diff --git a/base/base_tests/bits_test.cpp b/base/base_tests/bits_test.cpp
index b7a4f415cd..79cac2c797 100644
--- a/base/base_tests/bits_test.cpp
+++ b/base/base_tests/bits_test.cpp
@@ -85,3 +85,18 @@ UNIT_TEST(ZigZagDecode)
   TEST_EQUAL(bits::ZigZagDecode(256U),  128, ());
 }
 
+UNIT_TEST(NumHiZeroBits32)
+{
+  TEST_EQUAL(bits::NumHiZeroBits32(0), 32, ());
+  TEST_EQUAL(bits::NumHiZeroBits32(0xFFFFFFFF), 0, ());
+  TEST_EQUAL(bits::NumHiZeroBits32(0x0FABCDEF), 4, ());
+  TEST_EQUAL(bits::NumHiZeroBits32(0x000000FF), 24, ());
+}
+
+UNIT_TEST(NumHiZeroBits64)
+{
+  TEST_EQUAL(bits::NumHiZeroBits64(0), 64, ());
+  TEST_EQUAL(bits::NumHiZeroBits64(0xFFFFFFFFFFFFFFFFULL), 0, ());
+  TEST_EQUAL(bits::NumHiZeroBits64(0x0FABCDEF0FABCDEFULL), 4, ());
+  TEST_EQUAL(bits::NumHiZeroBits64(0x000000000000FDEFULL), 48, ());
+}
diff --git a/base/bits.hpp b/base/bits.hpp
index f0e5c13345..111c1c36e0 100644
--- a/base/bits.hpp
+++ b/base/bits.hpp
@@ -4,6 +4,7 @@
 #include "assert.hpp"
 
 #include "../std/type_traits.hpp"
+#include "../std/stdint.hpp"
 
 
 namespace bits
@@ -146,4 +147,21 @@ namespace bits
     uint8_t * pData = static_cast<uint8_t *>(p);
     pData[offset >> 3] |= (1 << (offset & 7));
   }
+  
+  // Compute number of zero bits from the most significant bits side. 
+  inline uint32_t NumHiZeroBits32(uint32_t n)
+  {
+    if (n == 0) return 32;
+    uint32_t result = 0;
+    while ((n & (uint32_t(1) << 31)) == 0) { ++result; n <<= 1; }
+    return result;
+  }
+  
+  inline uint32_t NumHiZeroBits64(uint64_t n)
+  {
+    if (n == 0) return 64;
+    uint32_t result = 0;
+    while ((n & (uint64_t(1) << 63)) == 0) { ++result; n <<= 1; }
+    return result;
+  }
 }
diff --git a/coding/arithmetic_codec.cpp b/coding/arithmetic_codec.cpp
index 7a3740d755..0e5a18a392 100644
--- a/coding/arithmetic_codec.cpp
+++ b/coding/arithmetic_codec.cpp
@@ -4,15 +4,7 @@
 #include "reader.hpp"
 
 #include "../base/assert.hpp"
-
-namespace {
-  inline u32 NumHiZeroBits32(u32 n)
-  {
-    u32 result = 0;
-    while ((n & (u32(1) << 31)) == 0) { ++result; n <<= 1; }
-    return result;
-  }
-}
+#include "../base/bits.hpp"
 
 vector<u32> FreqsToDistrTable(vector<u32> const & origFreqs)
 {
@@ -87,7 +79,7 @@ vector<u8> ArithmeticEncoder::Finalize()
   }
   else
   {
-    u32 resultHiBits = NumHiZeroBits32(m_begin ^ last) + 1;
+    u32 resultHiBits = bits::NumHiZeroBits32(m_begin ^ last) + 1;
     u32 value = last & (~u32(0) << (32 - resultHiBits));
     while (value != 0)
     {