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Posted to commits@nuttx.apache.org by xi...@apache.org on 2022/10/28 16:12:08 UTC
[incubator-nuttx] 01/03: lib/math32.h: support LOG2_CEIL/LOG2_FLOOR function at compile time
This is an automated email from the ASF dual-hosted git repository.
xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git
commit 6f208524a177177dec898ae2cff3de10757da953
Author: dongjiuzhu1 <do...@xiaomi.com>
AuthorDate: Tue Oct 25 23:41:36 2022 +0800
lib/math32.h: support LOG2_CEIL/LOG2_FLOOR function at compile time
Signed-off-by: dongjiuzhu1 <do...@xiaomi.com>
---
include/nuttx/lib/math32.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/include/nuttx/lib/math32.h b/include/nuttx/lib/math32.h
index f5ee45b609..c8c79e1037 100644
--- a/include/nuttx/lib/math32.h
+++ b/include/nuttx/lib/math32.h
@@ -27,8 +27,38 @@
#include <nuttx/config.h>
+#include <inttypes.h>
#include <stdint.h>
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* Returns one plus the index of the most significant 1-bit of n,
+ * or if n is zero, returns zero.
+ */
+
+#if UINTPTR_MAX > UINT32_MAX
+# define FLS(n) ((n) & UINT64_C(0xffffffff00000000) ? 32 + \
+ FLS32((size_t)(n) >> 32) : FLS32(n))
+#else
+# define FLS(n) FLS32(n)
+#endif
+
+#define FLS32(n) ((n) & 0xffff0000 ? 16 + FLS16((n) >> 16) : FLS16(n))
+#define FLS16(n) ((n) & 0xff00 ? 8 + FLS8 ((n) >> 8) : FLS8 (n))
+#define FLS8(n) ((n) & 0xf0 ? 4 + FLS4 ((n) >> 4) : FLS4 (n))
+#define FLS4(n) ((n) & 0xc ? 2 + FLS2 ((n) >> 2) : FLS2 (n))
+#define FLS2(n) ((n) & 0x2 ? 1 + FLS1 ((n) >> 1) : FLS1 (n))
+#define FLS1(n) ((n) & 0x1 ? 1 : 0)
+
+/* Returns round up and round down value of log2(n). Note: it can be used at
+ * compile time.
+ */
+
+#define LOG2_CEIL(n) ((n) & (n - 1) ? FLS(n) : FLS(n) - 1)
+#define LOG2_FLOOR(n) (FLS(n) - 1)
+
/****************************************************************************
* Public Types
****************************************************************************/