The function returns the last (most-significant) bit set.
Added unit testcase to verify rte_fls_u32().
Signed-off-by: Jerin Jacob <jerin.ja...@caviumnetworks.com>
---
v2:
- Introduce rte_fls_u32()
---
lib/librte_eal/common/include/rte_common.h | 19 +++++++++++++
test/test/test_common.c | 32 ++++++++++++++++++++++
2 files changed, 51 insertions(+)
diff --git a/lib/librte_eal/common/include/rte_common.h
b/lib/librte_eal/common/include/rte_common.h
index cba7bbc1d..87f0f6302 100644
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -473,6 +473,25 @@ rte_log2_u32(uint32_t v)
return rte_bsf32(v);
}
+
+/**
+ * Return the last (most-significant) bit set.
+ *
+ * @note The last (most significant) bit is at position 32.
+ * @note rte_fls_u32(0) = 0, rte_fls_u32(1) = 1, rte_fls_u32(0x80000000) = 32
+ *
+ * @param x
+ * The input parameter.
+ * @return
+ * The last (most-significant) bit set, or 0 if the input is 0.
+ */
+static inline int
+rte_fls_u32(uint32_t x)
+{
+ return (x == 0) ? 0 : 32 - __builtin_clz(x);
+}
+
+
#ifndef offsetof
/** Return the offset of a field in a structure. */
#define offsetof(TYPE, MEMBER) __builtin_offsetof (TYPE, MEMBER)
diff --git a/test/test/test_common.c b/test/test/test_common.c
index 7a67e458e..c6d17baae 100644
--- a/test/test/test_common.c
+++ b/test/test/test_common.c
@@ -188,6 +188,37 @@ test_log2(void)
return 0;
}
+static int
+test_fls(void)
+{
+ struct fls_test_vector {
+ uint32_t arg;
+ int rc;
+ };
+ int expected, rc;
+ uint32_t i, arg;
+
+ const struct fls_test_vector test[] = {
+ {0x0, 0},
+ {0x1, 1},
+ {0x4000, 15},
+ {0x80000000, 32},
+ };
+
+ for (i = 0; i < RTE_DIM(test); i++) {
+ arg = test[i].arg;
+ rc = rte_fls_u32(arg);
+ expected = test[i].rc;
+ if (rc != expected) {
+ printf("Wrong rte_fls_u32(0x%x) rc=%d, expected=%d\n",
+ arg, rc, expected);
+ return TEST_FAILED;
+ }
+ }
+
+ return 0;
+}
+
static int
test_common(void)
{
@@ -196,6 +227,7 @@ test_common(void)
ret |= test_macros(0);
ret |= test_misc();
ret |= test_log2();
+ ret |= test_fls();
return ret;
}
--
2.19.1
