lib_libvsprintf: avoid recursive functions for integer printing to reduce stack usage

Integer formatting functions in lib_libvsprintf were using recursion to find
highest set digit. This caused *printf to have unnessaserily high stack usage,
and confusing stack-trace when debugging lower level 'obj->put' function.

Formaters "%b", "%o", "%u", "%x" have been verified for full 32-bit range.

Formaters "%llb", "%llo", "%llu", "%llx" have been verified for full 32-bit
range, plus ranges:
  0x8000000000000000..0x80000000ffffffff
  0xffffffff00000000..0xffffffffffffffff
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>

nuttx/include/nuttx/bits.h

+/****************************************************************************
+ * include/nuttx/bits.h
+ *
+ *   Copyright (C) 2015 Jussi Kivilinna. All rights reserved.
+ *   Author: Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_BITS_H
+#define __INCLUDE_NUTTX_BITS_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/compiler.h>
+#include <stdint.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: clzu32
+ *
+ * Description:
+ *   clzu32 counts leading zero bits of unsigned 32-bit integer
+ ****************************************************************************/
+#ifndef HAVE_BUILTIN_CLZ
+unsigned int clzu32(uint32_t n);
+#else
+static inline int clzu32(uint32_t n)
+{
+  if (n == 0)
+    {
+      return 32;
+    }
+
+  if (sizeof(n) == sizeof(unsigned long))
+    {
+      return __builtin_clzl(n);
+    }
+  return __builtin_clz(n);
+}
+#endif
+
+/****************************************************************************
+ * Name: ctzu32
+ *
+ * Description:
+ *   ctzu32 counts trailing zero bits of unsigned 32-bit integer.
+ ****************************************************************************/
+#ifndef HAVE_BUILTIN_CTZ
+unsigned int ctzu32(uint32_t n);
+#else
+static inline int ctzu32(uint32_t n)
+{
+  if (n == 0)
+    {
+      return 32;
+    }
+
+  if (sizeof(n) == sizeof(unsigned long))
+    {
+      return __builtin_ctzl(n);
+    }
+  return __builtin_ctz(n);
+}
+#endif
+
+#ifdef UINT64_MAX
+/****************************************************************************
+ * Name: clzu64
+ *
+ * Description:
+ *   clzu64 counts leading zero bits of unsigned 64-bit integer
+ ****************************************************************************/
+#ifndef HAVE_BUILTIN_CLZ
+unsigned int clzu64(uint64_t n);
+#else
+static inline int clzu64(uint64_t n)
+{
+  if (n == 0)
+    {
+      return 64;
+    }
+
+#ifdef CONFIG_HAVE_LONG_LONG
+  if (sizeof(n) == sizeof(unsigned long long))
+    {
+      return __builtin_clzll(n);
+    }
+#endif
+
+  return __builtin_clzl(n);
+}
+#endif
+
+/****************************************************************************
+ * Name: ctzu64
+ *
+ * Description:
+ *   ctzu64 counts trailing zero bits of unsigned 64-bit integer
+ ****************************************************************************/
+#ifndef HAVE_BUILTIN_CTZ
+unsigned int ctzu64(uint64_t n);
+#else
+static inline int ctzu64(uint64_t n)
+{
+  if (n == 0)
+    {
+      return 64;
+    }
+
+#ifdef CONFIG_HAVE_LONG_LONG
+  if (sizeof(n) == sizeof(unsigned long long))
+    {
+      return __builtin_ctzll(n);
+    }
+#endif
+
+  return __builtin_ctzl(n);
+}
+#endif
+#endif /* UINT64_MAX */
+
+/****************************************************************************
+ * Name: clz
+ *
+ * Description:
+ *   clz counts leading zero bits of unsigned integer
+ ****************************************************************************/
+
+static inline unsigned int clz(unsigned int n)
+{
+  if (sizeof(n) == sizeof(uint16_t))
+    {
+      return clzu32(n) - 16;
+    }
+  else
+    {
+      return clzu32(n);
+    }
+}
+
+/****************************************************************************
+ * Name: clzl
+ *
+ * Description:
+ *   clzl counts leading zero bits of unsigned long integer
+ ****************************************************************************/
+
+static inline unsigned int clzl(unsigned long n)
+{
+#ifdef UINT64_MAX
+  if (sizeof(n) == sizeof(uint64_t))
+    {
+      return clzu64(n);
+    }
+  else
+#endif
+    {
+      return clzu32(n);
+    }
+}
+
+/****************************************************************************
+ * Name: clzll
+ *
+ * Description:
+ *   clzll counts leading zero bits of unsigned long long integer
+ ****************************************************************************/
+
+#ifdef CONFIG_HAVE_LONG_LONG
+static inline unsigned int clzll(unsigned long long n)
+{
+#ifdef UINT64_MAX
+  if (sizeof(n) == sizeof(uint64_t))
+    {
+      return clzu64(n);
+    }
+  else
+#endif
+    {
+      return clzu32(n);
+    }
+}
+#endif
+
+/****************************************************************************
+ * Name: ctz
+ *
+ * Description:
+ *   ctz counts trailing zero bits of unsigned integer.
+ ****************************************************************************/
+
+static inline unsigned int ctz(unsigned int n)
+{
+  if (sizeof(n) == sizeof(uint16_t))
+    {
+      unsigned int ret = ctzu32(n);
+      if (ret > 16)
+        return 16;
+      return ret;
+    }
+  else
+    {
+      return ctzu32(n);
+    }
+}
+
+/****************************************************************************
+ * Name: ctzl
+ *
+ * Description:
+ *   ctzl counts trailing zero bits of unsigned long integer.
+ ****************************************************************************/
+
+static inline unsigned int ctzl(unsigned long n)
+{
+#ifdef UINT64_MAX
+  if (sizeof(n) == sizeof(uint64_t))
+    {
+      return ctzu64(n);
+    }
+  else
+#endif
+    {
+      return ctzu32(n);
+    }
+}
+
+/****************************************************************************
+ * Name: ctzll
+ *
+ * Description:
+ *   ctzll counts trailing zero bits of unsigned long long integer.
+ ****************************************************************************/
+
+#ifdef CONFIG_HAVE_LONG_LONG
+static inline unsigned int ctzll(unsigned long long n)
+{
+#ifdef UINT64_MAX
+  if (sizeof(n) == sizeof(uint64_t))
+    {
+      return ctzu64(n);
+    }
+  else
+#endif
+    {
+      return ctzu32(n);
+    }
+}
+#endif
+
+#endif /* __INCLUDE_NUTTX_BITS_H */

nuttx/include/nuttx/compiler.h

@@ -126,6 +126,13 @@
 # define DSEG
 # define CODE
 
+/* GCC 4.x have __builtin_ctz(|l|ll) and __builtin_clz(|l|ll). */
+
+#if __GNUC__ >= 4
+# define HAVE_BUILTIN_CTZ 1
+# define HAVE_BUILTIN_CLZ 1
+#endif
+
 /* Handle cases where sizeof(int) is 16-bits, sizeof(long) is 32-bits, and
  * pointers are 16-bits.
  */

nuttx/libc/misc/Make.defs

@@ -70,6 +70,7 @@ endif
 # Add the miscellaneous C files to the build
 
 CSRCS += lib_match.c lib_crc32.c lib_crc16.c lib_crc8.c lib_dumpbuffer.c
+CSRCS += lib_clzu32.c lib_clzu64.c lib_ctzu32.c lib_ctzu64.c
 
 ifeq ($(CONFIG_DEBUG),y)
 CSRCS += lib_dbg.c

nuttx/libc/misc/lib_clzu32.c

+/****************************************************************************
+ * libc/misc/lib_clzu32.c
+ *
+ *   Copyright (C) 2015 Jussi Kivilinna. All rights reserved.
+ *   Author: Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <stdint.h>
+#include <nuttx/bits.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: clzu32
+ *
+ * Description:
+ *   clzu32 counts leading zero bits of unsigned 32-bit integer
+ ****************************************************************************/
+#ifndef HAVE_BUILTIN_CLZ
+unsigned int clzu32(uint32_t n)
+{
+  n = n | (n >> 1);
+  n = n | (n >> 2);
+  n = n | (n >> 4);
+  n = n | (n >> 8);
+  n = n | (n >> 16);
+  return 32 - ctzu32(n + 1);
+}
+#endif

nuttx/libc/misc/lib_clzu64.c

+/****************************************************************************
+ * libc/misc/lib_clzu64.c
+ *
+ *   Copyright (C) 2015 Jussi Kivilinna. All rights reserved.
+ *   Author: Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <stdint.h>
+#include <nuttx/bits.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: clzu64
+ *
+ * Description:
+ *   clzu64 counts leading zero bits of unsigned 64-bit integer
+ ****************************************************************************/
+#if defined(UINT64_MAX) && !defined(HAVE_BUILTIN_CLZ)
+unsigned int clzu64(uint64_t n)
+{
+  if ((n >> 32) & 0xFFFFFFFFU)
+    {
+      return clzu32(n >> 32);
+    }
+  else
+    {
+      return clzu32(n) + 32;
+    }
+}
+#endif

nuttx/libc/misc/lib_ctzu32.c

+/****************************************************************************
+ * libc/misc/lib_ctzu32.c
+ *
+ *   Copyright (C) 2015 Jussi Kivilinna. All rights reserved.
+ *   Author: Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <stdint.h>
+#include <nuttx/bits.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: ctzu32
+ *
+ * Description:
+ *   ctzu32 counts trailing zero bits of unsigned 32-bit integer, from
+ *   http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightMultLookup
+ ****************************************************************************/
+#ifndef HAVE_BUILTIN_CTZ
+unsigned int ctzu32(uint32_t n)
+{
+  static const uint8_t table[32] =
+  {
+    0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
+    31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
+  };
+  return n ? table[((uint32_t)((n & -n) * 0x077CB531U)) >> 27] : 32;
+}
+#endif

nuttx/libc/misc/lib_ctzu64.c

+/****************************************************************************
+ * libc/misc/lib_ctzu64.c
+ *
+ *   Copyright (C) 2015 Jussi Kivilinna. All rights reserved.
+ *   Author: Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <stdint.h>
+#include <nuttx/bits.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: ctzu64
+ *
+ * Description:
+ *   ctzu64 counts trailing zero bits of unsigned 64-bit integer
+ ****************************************************************************/
+#if defined(UINT64_MAX) && !defined(HAVE_BUILTIN_CTZ)
+unsigned int ctzu64(uint64_t n)
+{
+  if (n & 0xFFFFFFFFU)
+    {
+      return ctzu32(n);
+    }
+  else
+    {
+      return ctzu32(n >> 32) + 32;
+    }
+}
+#endif

nuttx/libc/stdio/lib_libvsprintf.c

@@ -45,6 +45,7 @@
 #include <string.h>
 
 #include <nuttx/arch.h>
+#include <nuttx/bits.h>
 
 #include "lib_internal.h"
 
@@ -126,6 +127,10 @@
 #  define FMT_PREV     src--                        /* Backup to the previous character */
 #endif
 
+#define U8DIVBY3(a)              ((unsigned int)(a) * 0xABU >> 9)
+#define U8DIVBY4(a)              ((unsigned int)(a) >> 2)
+#define U8DIVBY10(a)             ((unsigned int)(a) * 0xCDU >> 11)
+
 /****************************************************************************
  * Private Type Declarations
  ****************************************************************************/
@@ -216,6 +221,45 @@ static void postjustify(FAR struct lib_outstream_s *obj, uint8_t fmt,