nuttx/libs/libc/stdio/lib_dtoa_engine.h

/****************************************************************************
 * libs/libc/stdio/lib_dtoa_engine.h
 *
 *   Copyright © 2018, Keith Packard
 *   All rights reserved.
 *
 * 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 __LIBS_LIBC_STDIO_LIB_DTOA_ENGINE_H
#define __LIBS_LIBC_STDIO_LIB_DTOA_ENGINE_H

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <stdint.h>
#include <float.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#define DTOA_MAX_DIG        DBL_DIG

#define DTOA_MINUS          1
#define DTOA_ZERO           2
#define DTOA_INF            4
#define DTOA_NAN            8
#define DTOA_CARRY          16    /* Carry was to master position. */

#if DBL_MAX_10_EXP >= 1 && DBL_MAX_10_EXP < 2
#  define DTOA_SCALE_UP_NUM 1
#endif
#if DBL_MAX_10_EXP >= 2 && DBL_MAX_10_EXP < 4
#  define DTOA_SCALE_UP_NUM 2
#endif
#if DBL_MAX_10_EXP >= 4 && DBL_MAX_10_EXP < 8
#  define DTOA_SCALE_UP_NUM 3
#endif
#if DBL_MAX_10_EXP >= 8 && DBL_MAX_10_EXP < 16
#  define DTOA_SCALE_UP_NUM 4
#endif
#if DBL_MAX_10_EXP >= 16 && DBL_MAX_10_EXP < 32
#  define DTOA_SCALE_UP_NUM 5
#endif
#if DBL_MAX_10_EXP >= 32 && DBL_MAX_10_EXP < 64
#  define DTOA_SCALE_UP_NUM 6
#endif
#if DBL_MAX_10_EXP >= 64 && DBL_MAX_10_EXP < 128
#  define DTOA_SCALE_UP_NUM 7
#endif
#if DBL_MAX_10_EXP >= 128 && DBL_MAX_10_EXP < 256
#  define DTOA_SCALE_UP_NUM 8
#endif
#if DBL_MAX_10_EXP >= 256 && DBL_MAX_10_EXP < 512
#  define DTOA_SCALE_UP_NUM 9
#endif
#if DBL_MAX_10_EXP >= 512 && DBL_MAX_10_EXP < 1024
#  define DTOA_SCALE_UP_NUM 10
#endif
#if DBL_MAX_10_EXP >= 1024 && DBL_MAX_10_EXP < 2048
#  define DTOA_SCALE_UP_NUM 11
#endif
#if DBL_MAX_10_EXP >= 2048 && DBL_MAX_10_EXP < 4096
#  define DTOA_SCALE_UP_NUM 12
#endif
#if DBL_MAX_10_EXP >= 4096 && DBL_MAX_10_EXP < 8192
#  define DTOA_SCALE_UP_NUM 13
#endif
#if DBL_MAX_10_EXP >= 8192 && DBL_MAX_10_EXP < 16384
#  define DTOA_SCALE_UP_NUM 14
#endif
#if DBL_MAX_10_EXP >= 16384 && DBL_MAX_10_EXP < 32768
#  define DTOA_SCALE_UP_NUM 15
#endif
#if DBL_MAX_10_EXP >= 32768 && DBL_MAX_10_EXP < 65536
#  define DTOA_SCALE_UP_NUM 16
#endif
#if DBL_MAX_10_EXP >= 65536 && DBL_MAX_10_EXP < 131072
#  define DTOA_SCALE_UP_NUM 17
#endif
#if DBL_MIN_10_EXP <= -1 && DBL_MIN_10_EXP > -2
#  define DTOA_SCALE_DOWN_NUM 1
#endif
#if DBL_MIN_10_EXP <= -2 && DBL_MIN_10_EXP > -4
#  define DTOA_SCALE_DOWN_NUM 2
#endif
#if DBL_MIN_10_EXP <= -4 && DBL_MIN_10_EXP > -8
#  define DTOA_SCALE_DOWN_NUM 3
#endif
#if DBL_MIN_10_EXP <= -8 && DBL_MIN_10_EXP > -16
#  define DTOA_SCALE_DOWN_NUM 4
#endif
#if DBL_MIN_10_EXP <= -16 && DBL_MIN_10_EXP > -32
#  define DTOA_SCALE_DOWN_NUM 5
#endif
#if DBL_MIN_10_EXP <= -32 && DBL_MIN_10_EXP > -64
#  define DTOA_SCALE_DOWN_NUM 6
#endif
#if DBL_MIN_10_EXP <= -64 && DBL_MIN_10_EXP > -128
#  define DTOA_SCALE_DOWN_NUM 7
#endif
#if DBL_MIN_10_EXP <= -128 && DBL_MIN_10_EXP > -256
#  define DTOA_SCALE_DOWN_NUM 8
#endif
#if DBL_MIN_10_EXP <= -256 && DBL_MIN_10_EXP > -512
#  define DTOA_SCALE_DOWN_NUM 9
#endif
#if DBL_MIN_10_EXP <= -512 && DBL_MIN_10_EXP > -1024
#  define DTOA_SCALE_DOWN_NUM 10
#endif
#if DBL_MIN_10_EXP <= -1024 && DBL_MIN_10_EXP > -2048
#  define DTOA_SCALE_DOWN_NUM 11
#endif
#if DBL_MIN_10_EXP <= -2048 && DBL_MIN_10_EXP > -4096
#  define DTOA_SCALE_DOWN_NUM 12
#endif
#if DBL_MIN_10_EXP <= -4096 && DBL_MIN_10_EXP > -8192
#  define DTOA_SCALE_DOWN_NUM 13
#endif
#if DBL_MIN_10_EXP <= -8192 && DBL_MIN_10_EXP > -16384
#  define DTOA_SCALE_DOWN_NUM 14
#endif
#if DBL_MIN_10_EXP <= -16384 && DBL_MIN_10_EXP > -32768
#  define DTOA_SCALE_DOWN_NUM 15
#endif
#if DBL_MIN_10_EXP <= -32768 && DBL_MIN_10_EXP > -65536
#  define DTOA_SCALE_DOWN_NUM 16
#endif
#if DBL_MIN_10_EXP <= -65536 && DBL_MIN_10_EXP > -131072
#  define DTOA_SCALE_DOWN_NUM 17
#endif

#define DTOA_ROUND_NUM        (DBL_DIG + 1)

/****************************************************************************
 * Public Types
 ****************************************************************************/

struct dtoa_s
{
  int32_t exp;
  uint8_t flags;
  char digits[DTOA_MAX_DIG + 1];
};

/****************************************************************************
 * Public Data
 ****************************************************************************/

extern const double g_dtoa_scale_up[];
extern const double g_dtoa_scale_down[];
extern const double g_dtoa_round[];

/****************************************************************************
 * Public Function Prototypes
 ****************************************************************************/

int __dtoa_engine(double x, FAR struct dtoa_s *dtoa, int max_digits,
                  int max_decimals);

#endif /* __LIBS_LIBC_STDIO_LIB_DTOA_ENGINE_H */