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src/mathutils.c: add aubio_is_power_of_two and aubio_next_power_of_two

--- a/configure.ac

+++ b/configure.ac

@@ -114,7 +114,7 @@

 AC_CHECK_LIB(pthread, pthread_create)

 dnl Check for header files

-AC_CHECK_HEADERS([string.h stdlib.h stdio.h math.h errno.h stdarg.h unistd.h signal.h],,)

+AC_CHECK_HEADERS([string.h stdlib.h stdio.h math.h limits.h errno.h stdarg.h unistd.h signal.h],,)

 AC_CHECK_HEADERS(fftw3.h,,AC_MSG_ERROR([Ouch! missing fftw3.h header]))

 AC_ARG_ENABLE(complex,

   AC_HELP_STRING([--enable-complex],[compile with complex.h [[default=auto]]]),

--- a/src/aubio_priv.h

+++ b/src/aubio_priv.h

@@ -62,6 +62,10 @@

 #include <string.h>

 #endif

+#if HAVE_LIMITS_H

+#include <limits.h> // for CHAR_BIT, in C99 standard

+#endif

+

 #include "types.h"

 /****

--- a/src/mathutils.c

+++ b/src/mathutils.c

@@ -409,6 +409,25 @@

   return aubio_freqtobin (freq, samplerate, fftsize);

 }

+uint_t

+aubio_is_power_of_two(uint_t a) {

+  if ((a & a-1) == 0) {

+    return 1;

+  } else {

+    return 0; 

+  }

+}

+

+uint_t

+aubio_next_power_of_two(uint_t a) {

+  uint_t i;

+  a--;

+  for (i = 0; i < sizeof(uint_t) * CHAR_BIT; i++ ) {

+    a = a | a >> 1;

+  }

+  return a+1;

+}

+

 smpl_t

 aubio_db_spl (fvec_t * o)

 {

--- a/src/mathutils.h

+++ b/src/mathutils.h

@@ -316,6 +316,12 @@

 /** convert midi value (0-128) to frequency (Hz) */

 smpl_t aubio_miditofreq (smpl_t midi);

+/** return 1 if a is a power of 2, 0 otherwise */

+uint_t aubio_is_power_of_two(uint_t a);

+

+/** return the next power of power of 2 greater than a */

+uint_t aubio_next_power_of_two(uint_t a);

+

 /** compute sound pressure level (SPL) in dB

   This quantity is often wrongly called 'loudness'.

--- a/wscript

+++ b/wscript

@@ -53,6 +53,7 @@

   conf.check(header_name='stdio.h')

   conf.check(header_name='math.h')

   conf.check(header_name='string.h')

+  conf.check(header_name='limits.h')

   # optionally use complex.h

   if (Options.options.disable_complex == False):