core/bitarithm: add explicit 32-bit function

core/bitarithm.c

@@ -57,6 +57,17 @@ unsigned bitarithm_bits_set(unsigned v)
     return c;
 }
 
+#if !ARCH_32_BIT
+uint8_t bitarithm_bits_set_u32(uint32_t v)
+{
+    uint8_t c;
+    for (c = 0; v; c++) {
+        v &= v - 1; /* clear the least significant bit set */
+    }
+    return c;
+}
+#endif
+
 const uint8_t MultiplyDeBruijnBitPosition[32] =
 {
     0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,

core/include/bitarithm.h

@@ -115,12 +115,27 @@ static inline unsigned bitarithm_lsb(unsigned v);
 
 /**
  * @brief   Returns the number of bits set in a value
- * @param[in]   v   Input value
+ * @param[in]   v   Input value with platform-dependent word size
  * @return          Number of set bits
  *
  */
 unsigned bitarithm_bits_set(unsigned v);
 
+/**
+ * @brief   Returns the (uint32_t version) number of bits set in a value
+ * @param[in]   v   Input value with 32 bit size
+ * @return          Number of set bits
+ *
+ */
+#if ARCH_32_BIT
+static inline uint8_t bitarithm_bits_set_u32(uint32_t v)
+{
+    return bitarithm_bits_set(v);
+}
+#else
+uint8_t bitarithm_bits_set_u32(uint32_t v);
+#endif
+
 /* implementations */
 
 static inline unsigned bitarithm_lsb(unsigned v)

tests/unittests/tests-core/tests-core-bitarithm.c

@@ -155,7 +155,8 @@ static void test_bitarithm_msb_limit(void)
 static void test_bitarithm_msb_random(void)
 {
     TEST_ASSERT_EQUAL_INT(4, bitarithm_msb(19)); /* randomized by fair
-                                                           dice roll ;-) */
+                                                  * dice roll ;-)
+                                                  */
 }
 
 static void test_bitarithm_msb_16bit(void)
@@ -208,7 +209,13 @@ static void test_bitarithm_bits_set_limit(void)
 static void test_bitarithm_bits_set_random(void)
 {
     TEST_ASSERT_EQUAL_INT(3, bitarithm_bits_set(7)); /* randomized by fair
-                                                        dice roll ;-) */
+                                                      * dice roll ;-)
+                                                      */
+}
+
+static void test_bitarithm_bits_set_u32_random(void)
+{
+    TEST_ASSERT_EQUAL_INT(21, bitarithm_bits_set_u32(4072524027)); /* Source: https://www.random.org/bytes */
 }
 
 Test *tests_core_bitarithm_tests(void)
@@ -244,6 +251,7 @@ Test *tests_core_bitarithm_tests(void)
         new_TestFixture(test_bitarithm_bits_set_one),
         new_TestFixture(test_bitarithm_bits_set_limit),
         new_TestFixture(test_bitarithm_bits_set_random),
+        new_TestFixture(test_bitarithm_bits_set_u32_random),
     };
 
     EMB_UNIT_TESTCALLER(core_bitarithm_tests, NULL, NULL, fixtures);