/**
 * @author (c) Eyal Rozenberg <eyalroz1@gmx.com>
 *             2021-2024, Haifa, Palestine/Israel
 * @author (c) Marco Paland (info@paland.com)
 *             2014-2019, PALANDesign Hannover, Germany
 *
 * @note Others have made smaller contributions to this file: see the
 * contributors page at https://github.com/eyalroz/printf/graphs/contributors
 * or ask one of the authors. The original code for exponential specifiers was
 * contributed by Martijn Jasperse <m.jasperse@gmail.com>.
 *
 * @brief Small stand-alone implementation of the printf family of functions
 * (`(v)printf`, `(v)s(n)printf` etc., geared towards use on embedded systems with
 * limited resources.
 *
 * @note the implementations are thread-safe; re-entrant; use no functions from
 * the standard library; and do not dynamically allocate any memory.
 *
 * @license The MIT License (MIT)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/* printf doesn't seem to like aggressive optimizations */
#if defined(__clang__)
  #pragma clang optimize off
#endif

/*
 * Define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H=1 ...) to include the
 * printf_config.h header file
 */
#if PRINTF_INCLUDE_CONFIG_H
#include "printf_config.h"
#endif

#include <libk/printf.h>

#ifdef __cplusplus
#include <cstdint>
#include <climits>
#else
#include <stdint.h>
#include <limits.h>
#include <stdbool.h>
#endif /* __cplusplus */

#if !(defined(__cplusplus) || (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L))
/* C90 */
#if defined(_MSC_VER)
#define inline __inline
#else
#define inline __inline__
#endif /* defined(_MSC_VER) */
#endif /* !(defined(__cplusplus) || (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L)) */

#if PRINTF_ALIAS_STANDARD_FUNCTION_NAMES_HARD
# define printf_    printf
# define sprintf_   sprintf
# define vsprintf_  vsprintf
# define snprintf_  snprintf
# define vsnprintf_ vsnprintf
# define vprintf_   vprintf
#endif /* PRINTF_ALIAS_STANDARD_FUNCTION_NAMES_HARD */


/*
 * 'ntoa' conversion buffer size, this must be big enough to hold one converted
 * numeric number including padded zeros (dynamically created on stack)
 */
#ifndef PRINTF_INTEGER_BUFFER_SIZE
#define PRINTF_INTEGER_BUFFER_SIZE    32
#endif /* PRINTF_INTEGER_BUFFER_SIZE */

/*
 * size of the fixed (on-stack) buffer for printing individual decimal numbers.
 * this must be big enough to hold one converted floating-point value including
 * padded zeros.
 */
#ifndef PRINTF_DECIMAL_BUFFER_SIZE
#define PRINTF_DECIMAL_BUFFER_SIZE    32
#endif

/* Support for the decimal notation floating point conversion specifiers (%f, %F) */
#ifndef PRINTF_SUPPORT_DECIMAL_SPECIFIERS
#define PRINTF_SUPPORT_DECIMAL_SPECIFIERS 1
#endif

/* Support for the exponential notation floating point conversion specifiers (%e, %g, %E, %G) */
#ifndef PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS
#define PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS 1
#endif

/* Support for the length write-back specifier (%n) */
#ifndef PRINTF_SUPPORT_WRITEBACK_SPECIFIER
#define PRINTF_SUPPORT_WRITEBACK_SPECIFIER 1
#endif

/* Default precision for the floating point conversion specifiers (the C standard sets this at 6) */
#ifndef PRINTF_DEFAULT_FLOAT_PRECISION
#define PRINTF_DEFAULT_FLOAT_PRECISION  6
#endif

/* Default choice of type to use for internal floating-point computations */
#ifndef PRINTF_USE_DOUBLE_INTERNALLY
#define PRINTF_USE_DOUBLE_INTERNALLY  1
#endif

/*
 * According to the C languages standard, printf() and related functions must be able to print any
 * integral number in floating-point notation, regardless of length, when using the %f specifier -
 * possibly hundreds of characters, potentially overflowing your buffers. In this implementation,
 * all values beyond this threshold are switched to exponential notation.
 */
#ifndef PRINTF_MAX_INTEGRAL_DIGITS_FOR_DECIMAL
#define PRINTF_MAX_INTEGRAL_DIGITS_FOR_DECIMAL 9
#endif

/*
 * Support for the long long integral types (with the ll, z and t length modifiers for specifiers
 * %d,%i,%o,%x,%X,%u, and with the %p specifier).
 */
#ifndef PRINTF_SUPPORT_LONG_LONG
#define PRINTF_SUPPORT_LONG_LONG 1
#endif

/*
 * The number of terms in a Taylor series expansion of log_10(x) to
 * use for approximation - including the power-zero term (i.e. the
 * value at the point of expansion).
 */
#ifndef PRINTF_LOG10_TAYLOR_TERMS
#define PRINTF_LOG10_TAYLOR_TERMS 4
#endif

#if PRINTF_LOG10_TAYLOR_TERMS <= 1
#error "At least one non-constant Taylor expansion is necessary for the log10() calculation"
#endif

/*
 * Be extra-safe, and don't assume format specifiers are completed correctly
 * before the format string end.
 */
#ifndef PRINTF_CHECK_FOR_NUL_IN_FORMAT_SPECIFIER
#define PRINTF_CHECK_FOR_NUL_IN_FORMAT_SPECIFIER 1
#endif

#define PRINTF_PREFER_DECIMAL     false
#define PRINTF_PREFER_EXPONENTIAL true

/*===========================================================================*/

/* The following will convert the number-of-digits into an exponential-notation literal */
#define PRINTF_CONCATENATE(s1, s2) s1##s2
#define PRINTF_EXPAND_THEN_CONCATENATE(s1, s2) PRINTF_CONCATENATE(s1, s2)
#define PRINTF_FLOAT_NOTATION_THRESHOLD ((floating_point_t) PRINTF_EXPAND_THEN_CONCATENATE(1e,PRINTF_MAX_INTEGRAL_DIGITS_FOR_DECIMAL))

/* internal flag definitions */
#define FLAGS_ZEROPAD     (1U <<  0U)
#define FLAGS_LEFT        (1U <<  1U)
#define FLAGS_PLUS        (1U <<  2U)
#define FLAGS_SPACE       (1U <<  3U)
#define FLAGS_HASH        (1U <<  4U)
#define FLAGS_UPPERCASE   (1U <<  5U)
#define FLAGS_CHAR        (1U <<  6U)
#define FLAGS_SHORT       (1U <<  7U)
#define FLAGS_INT         (1U <<  8U)
  /* Only used with PRINTF_SUPPORT_MSVC_STYLE_INTEGER_SPECIFIERS */
#define FLAGS_LONG        (1U <<  9U)
#define FLAGS_LONG_LONG   (1U << 10U)
#define FLAGS_PRECISION   (1U << 11U)
#define FLAGS_ADAPT_EXP   (1U << 12U)
#define FLAGS_POINTER     (1U << 13U)
  /* Note: Similar, but not identical, effect as FLAGS_HASH */
#define FLAGS_SIGNED      (1U << 14U)
#define FLAGS_LONG_DOUBLE (1U << 15U)
  /* Only used with PRINTF_SUPPORT_MSVC_STYLE_INTEGER_SPECIFIERS */

#ifdef PRINTF_SUPPORT_MSVC_STYLE_INTEGER_SPECIFIERS

#define FLAGS_INT8 FLAGS_CHAR


#if   (SHRT_MAX   == 32767LL)
#define FLAGS_INT16       FLAGS_SHORT
#elif (INT_MAX    == 32767LL)
#define FLAGS_INT16       FLAGS_INT
#elif (LONG_MAX   == 32767LL)
#define FLAGS_INT16       FLAGS_LONG
#elif (LLONG_MAX  == 32767LL)
#define FLAGS_INT16       FLAGS_LONG_LONG
#else
#error "No basic integer type has a size of 16 bits exactly"
#endif

#if   (SHRT_MAX   == 2147483647LL)
#define FLAGS_INT32       FLAGS_SHORT
#elif (INT_MAX    == 2147483647LL)
#define FLAGS_INT32       FLAGS_INT
#elif (LONG_MAX   == 2147483647LL)
#define FLAGS_INT32       FLAGS_LONG
#elif (LLONG_MAX  == 2147483647LL)
#define FLAGS_INT32       FLAGS_LONG_LONG
#else
#error "No basic integer type has a size of 32 bits exactly"
#endif

#if   (SHRT_MAX   == 9223372036854775807LL)
#define FLAGS_INT64       FLAGS_SHORT
#elif (INT_MAX    == 9223372036854775807LL)
#define FLAGS_INT64       FLAGS_INT
#elif (LONG_MAX   == 9223372036854775807LL)
#define FLAGS_INT64       FLAGS_LONG
#elif (LLONG_MAX  == 9223372036854775807LL)
#define FLAGS_INT64       FLAGS_LONG_LONG
#else
#error "No basic integer type has a size of 64 bits exactly"
#endif

#endif /* PRINTF_SUPPORT_MSVC_STYLE_INTEGER_SPECIFIERS */


typedef unsigned int printf_flags_t;

#define BASE_BINARY    2
#define BASE_OCTAL     8
#define BASE_DECIMAL  10
#define BASE_HEX      16

typedef uint8_t numeric_base_t;

#if PRINTF_SUPPORT_LONG_LONG
typedef unsigned long long printf_unsigned_value_t;
typedef long long          printf_signed_value_t;
#else
typedef unsigned long printf_unsigned_value_t;
typedef long          printf_signed_value_t;
#endif /* PRINTF_SUPPORT_LONG_LONG */

/*
 * The printf()-family functions return an `int`; it is therefore
 * unnecessary/inappropriate to use size_t - often larger than int
 * in practice - for non-negative related values, such as widths,
 * precisions, offsets into buffers used for printing and the sizes
 * of these buffers. instead, we use:
 */
typedef unsigned int printf_size_t;
#define PRINTF_MAX_POSSIBLE_BUFFER_SIZE INT_MAX
  /*
   * If we were to nitpick, this would actually be INT_MAX + 1,
   * since INT_MAX is the maximum return value, which excludes the
   * trailing '\0'.
   */

#define SIGN(_negative,_x) ( (_negative) ? -(_x) : (_x))

#if (PRINTF_SUPPORT_DECIMAL_SPECIFIERS || PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS)
#include <float.h>
#if FLT_RADIX != 2
#error "Non-binary-radix floating-point types are unsupported."
#endif /* PRINTF_SUPPORT_DECIMAL_SPECIFIERS || PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS */

/**
 * This library supports taking float-point arguments up to and including
 * long double's; but - it currently does _not_ support internal
 * representation and manipulation of values as long doubles; the options
 * are either single-precision `float` or double-precision `double`.
 */
#if PRINTF_USE_DOUBLE_INTERNALLY
typedef double floating_point_t;
#define FP_TYPE_MANT_DIG DBL_MANT_DIG
#else
typedef float  floating_point_t;
#define FP_TYPE_MANT_DIG FLT_MANT_DIG
#endif

#define NUM_DECIMAL_DIGITS_IN_INT64_T 18

#if FP_TYPE_MANT_DIG == 24

typedef uint32_t printf_fp_uint_t;
#define FP_TYPE_SIZE_IN_BITS   32
#define FP_TYPE_EXPONENT_MASK  0xFFU
#define FP_TYPE_BASE_EXPONENT  127
#define FP_TYPE_MAX            FLT_MAX
#define FP_TYPE_MAX_10_EXP     FLT_MAX_10_EXP
#define FP_TYPE_MAX_SUBNORMAL_EXPONENT_OF_10 -38
#define FP_TYPE_MAX_SUBNORMAL_POWER_OF_10 1e-38f
#define PRINTF_MAX_PRECOMPUTED_POWER_OF_10  10

#elif FP_TYPE_MANT_DIG == 53

typedef uint64_t printf_fp_uint_t;
#define FP_TYPE_SIZE_IN_BITS   64
#define FP_TYPE_EXPONENT_MASK  0x7FFU
#define FP_TYPE_BASE_EXPONENT  1023
#define FP_TYPE_MAX            DBL_MAX
#define FP_TYPE_MAX_10_EXP     DBL_MAX_10_EXP
#define FP_TYPE_MAX_10_EXP     DBL_MAX_10_EXP
#define FP_TYPE_MAX_SUBNORMAL_EXPONENT_OF_10 -308
#define FP_TYPE_MAX_SUBNORMAL_POWER_OF_10 1e-308
#define PRINTF_MAX_PRECOMPUTED_POWER_OF_10  NUM_DECIMAL_DIGITS_IN_INT64_T - 1


#else /* FP_TYPE_MANT_DIG is neither 24 nor 53 */
#error "Unsupported floating point type configuration"
#endif /* FP_TYPE_MANT_DIG */
#define FP_TYPE_STORED_MANTISSA_BITS (FP_TYPE_MANT_DIG - 1)

typedef union {
  printf_fp_uint_t  U;
  floating_point_t  F;
} floating_point_with_bit_access;

/*
 * This is unnecessary in C99, since compound initializers can be used,
 * but:
 * 1. Some compilers are finicky about this;
 * 2. Some people may want to convert this to C89;
 * 3. If you try to use it as C++, only C++20 supports compound literals
 */
static inline floating_point_with_bit_access get_bit_access(floating_point_t x)
{
  floating_point_with_bit_access dwba;
  dwba.F = x;
  return dwba;
}

static inline int get_sign_bit(floating_point_t x)
{
  /* The sign is stored in the highest bit */
  return (int) (get_bit_access(x).U >> (FP_TYPE_SIZE_IN_BITS - 1));
}

static inline int get_exp2(floating_point_with_bit_access x)
{
  /*
   * The exponent in an IEEE-754 floating-point number occupies a contiguous
   * sequence of bits (e.g. 52..62 for 64-bit doubles), but with a non-trivial representation: An
   * unsigned offset from some negative value (with the extremal offset values reserved for
   * special use).
   */
  return (int)((x.U >> FP_TYPE_STORED_MANTISSA_BITS ) & FP_TYPE_EXPONENT_MASK) - FP_TYPE_BASE_EXPONENT;
}
#define PRINTF_ABS(_x) SIGN( (_x) < 0, (_x) )

#endif /* (PRINTF_SUPPORT_DECIMAL_SPECIFIERS || PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS) */

/*
 * Note in particular the behavior here on LONG_MIN or LLONG_MIN; it is valid
 * and well-defined, but if you're not careful you can easily trigger undefined
 * behavior with -LONG_MIN or -LLONG_MIN
 */
#define ABS_FOR_PRINTING(_x) ((printf_unsigned_value_t) ( (_x) > 0 ? (_x) : -((printf_signed_value_t)_x) ))

/*
 * wrapper (used as buffer) for output function type
 *
 * One of the following must hold:
 * 1. max_chars is 0
 * 2. buffer is non-null
 * 3. function is non-null
 *
 * ... otherwise bad things will happen.
 */
typedef struct {
  void (*function)(char c, void* extra_arg);
  void* extra_function_arg;
  char* buffer;
  printf_size_t pos;
  printf_size_t max_chars;
} output_gadget_t;

/*
 * Note: This function currently assumes it is not passed a '\0' c,
 * or alternatively, that '\0' can be passed to the function in the output
 * gadget. The former assumption holds within the printf library. It also
 * assumes that the output gadget has been properly initialized.
 */
static inline void putchar_via_gadget(output_gadget_t* gadget, char c)
{
  printf_size_t write_pos = gadget->pos++;
    /*
     * We're _always_ increasing pos, so as to count how may characters
     * _would_ have been written if not for the max_chars limitation
     */
  if (write_pos >= gadget->max_chars) {
    return;
  }
  if (gadget->function != NULL) {
    /* No check for c == '\0' . */
    gadget->function(c, gadget->extra_function_arg);
  }
  else {
    /*
     * it must be the case that gadget->buffer != NULL , due to the constraint
     * on output_gadget_t ; and note we're relying on write_pos being non-negative.
     */
    gadget->buffer[write_pos] = c;
  }
}

/* Possibly-write the string-terminating '\0' character */
static inline void append_termination_with_gadget(output_gadget_t* gadget)
{
  printf_size_t null_char_pos;
  if (gadget->function != NULL || gadget->max_chars == 0) {
    return;
  }
  if (gadget->buffer == NULL) {
    return;
  }
  null_char_pos = gadget->pos < gadget->max_chars ? gadget->pos : gadget->max_chars - 1;
  gadget->buffer[null_char_pos] = '\0';
}

/*
 * We can't use putchar_ as is, since our output gadget
 * only takes pointers to functions with an extra argument
 */
static inline void putchar_wrapper(char c, void* unused)
{
  (void) unused;
  putchar_(c);
}

static inline output_gadget_t discarding_gadget(void)
{
  output_gadget_t gadget;
  gadget.function = NULL;
  gadget.extra_function_arg = NULL;
  gadget.buffer = NULL;
  gadget.pos = 0;
  gadget.max_chars = 0;
  return gadget;
}

static inline output_gadget_t buffer_gadget(char* buffer, size_t buffer_size)
{
  printf_size_t usable_buffer_size = (buffer_size > PRINTF_MAX_POSSIBLE_BUFFER_SIZE) ?
    PRINTF_MAX_POSSIBLE_BUFFER_SIZE : (printf_size_t) buffer_size;
  output_gadget_t result = discarding_gadget();
  if (buffer != NULL) {
    result.buffer = buffer;
    result.max_chars = usable_buffer_size;
  }
  return result;
}

static inline output_gadget_t function_gadget(void (*function)(char, void*), void* extra_arg)
{
  output_gadget_t result = discarding_gadget();
  result.function = function;
  result.extra_function_arg = extra_arg;
  result.max_chars = PRINTF_MAX_POSSIBLE_BUFFER_SIZE;
  return result;
}

static inline output_gadget_t extern_putchar_gadget(void)
{
  return function_gadget(putchar_wrapper, NULL);
}

/*
 * internal secure strlen
 * @return The length of the string (excluding the terminating 0) limited by 'maxsize'
 * @note strlen uses size_t, but wes only use this function with printf_size_t
 * variables - hence the signature.
 */
static inline printf_size_t strnlen_s_(const char* str, printf_size_t maxsize)
{
  const char* s;
  for (s = str; *s && maxsize--; ++s);
  return (printf_size_t)(s - str);
}


/*
 * internal test if char is a digit (0-9)
 * @return true if char is a digit
 */
static inline bool is_digit_(char ch)
{
  return (ch >= '0') && (ch <= '9');
}


/* internal ASCII string to printf_size_t conversion */
static printf_size_t atou_(const char** str)
{
  printf_size_t i = 0U;
  while (is_digit_(**str)) {
    i = i * 10U + (printf_size_t)(*((*str)++) - '0');
  }
  return i;
}


/* output the specified string in reverse, taking care of any zero-padding */
static void out_rev_(output_gadget_t* output, const char* buf, printf_size_t len, printf_size_t width, printf_flags_t flags)
{
  const printf_size_t start_pos = output->pos;

  /* pad spaces up to given width */
  if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
    printf_size_t i;
    for (i = len; i < width; i++) {
      putchar_via_gadget(output, ' ');
    }
  }

  /* reverse string */
  while (len) {
    putchar_via_gadget(output, buf[--len]);
  }

  /* append pad spaces up to given width */
  if (flags & FLAGS_LEFT) {
    while (output->pos - start_pos < width) {
      putchar_via_gadget(output, ' ');
    }
  }
}


/*
 * Invoked by print_integer after the actual number has been printed, performing necessary
 * work on the number's prefix (as the number is initially printed in reverse order)
 */
static void print_integer_finalization(output_gadget_t* output, char* buf, printf_size_t len, bool negative, numeric_base_t base, printf_size_t precision, printf_size_t width, printf_flags_t flags)
{
  printf_size_t unpadded_len = len;

  /* pad with leading zeros */
  {
    if (!(flags & FLAGS_LEFT)) {
      if (width && (flags & FLAGS_ZEROPAD) && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
        width--;
      }
      while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_INTEGER_BUFFER_SIZE)) {
        buf[len++] = '0';
      }
    }

    while ((len < precision) && (len < PRINTF_INTEGER_BUFFER_SIZE)) {
      buf[len++] = '0';
    }

    if (base == BASE_OCTAL && (len > unpadded_len)) {
      /* Since we've written some zeros, we've satisfied the alternative format leading space requirement */
      flags &= ~FLAGS_HASH;
    }
  }

  /* handle hash */
  if (flags & (FLAGS_HASH | FLAGS_POINTER)) {
    if (!(flags & FLAGS_PRECISION) && len && ((len == precision) || (len == width))) {
      /*
       * Let's take back some padding digits to fit in what will eventually
       * be the format-specific prefix
       */
      if (unpadded_len < len) {
        len--; /* This should suffice for BASE_OCTAL */
      }
      if (len && (base == BASE_HEX || base == BASE_BINARY) && (unpadded_len < len)) {
        len--; /* ... and an extra one for 0x or 0b */
      }
    }
    if ((base == BASE_HEX) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_INTEGER_BUFFER_SIZE)) {
      buf[len++] = 'x';
    }
    else if ((base == BASE_HEX) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_INTEGER_BUFFER_SIZE)) {
      buf[len++] = 'X';
    }
    else if ((base == BASE_BINARY) && (len < PRINTF_INTEGER_BUFFER_SIZE)) {
      buf[len++] = 'b';
    }
    if (len < PRINTF_INTEGER_BUFFER_SIZE) {
      buf[len++] = '0';
    }
  }

  if (len < PRINTF_INTEGER_BUFFER_SIZE) {
    if (negative) {
      buf[len++] = '-';
    }
    else if (flags & FLAGS_PLUS) {
      buf[len++] = '+';  /* ignore the space if the '+' exists */
    }
    else if (flags & FLAGS_SPACE) {
      buf[len++] = ' ';
    }
  }

  out_rev_(output, buf, len, width, flags);
}

/* An internal itoa-like function */
static void print_integer(output_gadget_t* output, printf_unsigned_value_t value, bool negative, numeric_base_t base, printf_size_t precision, printf_size_t width, printf_flags_t flags)
{
  char buf[PRINTF_INTEGER_BUFFER_SIZE];
  printf_size_t len = 0U;

  if (!value) {
    if ( !(flags & FLAGS_PRECISION) ) {
      buf[len++] = '0';
      flags &= ~FLAGS_HASH;
      /*
       * We drop this flag this since either the alternative and regular modes of the specifier
       * don't differ on 0 values, or (in the case of octal) we've already provided the special
       * handling for this mode.
       */
    }
    else if (base == BASE_HEX) {
      flags &= ~FLAGS_HASH;
      /*
       * We drop this flag this since either the alternative and regular modes of the specifier
       * don't differ on 0 values
       */
    }
  }
  else {
    do {
      const char digit = (char)(value % base);
      buf[len++] = (char)(digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10);
      value /= base;
    } while (value && (len < PRINTF_INTEGER_BUFFER_SIZE));
  }

  print_integer_finalization(output, buf, len, negative, base, precision, width, flags);
}

#if (PRINTF_SUPPORT_DECIMAL_SPECIFIERS || PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS)

/*
 * Stores a fixed-precision representation of a floating-point number relative
 * to a fixed precision (which cannot be determined by examining this structure)
 */
struct floating_point_components {
  int_fast64_t integral;
  int_fast64_t fractional;
    /*
     * ... truncation of the actual fractional part of the floating_point_t value, scaled
     * by the precision value
     */
  bool is_negative;
};

static const floating_point_t powers_of_10[PRINTF_MAX_PRECOMPUTED_POWER_OF_10 + 1] = {
  1e00, 1e01, 1e02, 1e03, 1e04, 1e05, 1e06, 1e07, 1e08, 1e09, 1e10
#if PRINTF_MAX_PRECOMPUTED_POWER_OF_10 > 10
  , 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17
#endif
};

/*
 * Note: This value does not mean that all floating-point values printed with the
 * library will be correct up to this precision; it is just an upper-bound for
 * avoiding buffer overruns and such
 */
#define PRINTF_MAX_SUPPORTED_PRECISION (NUM_DECIMAL_DIGITS_IN_INT64_T - 1)


/*
 * Break up a non-negative, finite, floating-point number into two integral
 * parts of its decimal representation: The number up to the decimal point,
 * and the number appearing after that point - whose number of digits
 * corresponds to the precision value. Example: The components of 12.621
 * are 12 and 621 for precision 3, or 12 and 62 for precision 2.
 */
static struct floating_point_components get_components(floating_point_t number, printf_size_t precision)
{
  struct floating_point_components number_;
  floating_point_t abs_number;
  floating_point_t scaled_remainder;
  floating_point_t remainder;
  const floating_point_t one_half = (floating_point_t) 0.5;
  number_.is_negative = get_sign_bit(number);
  abs_number = SIGN(number_.is_negative, number);
  number_.integral = (int_fast64_t) abs_number;
  scaled_remainder = (abs_number - (floating_point_t) number_.integral) * powers_of_10[precision];
  number_.fractional = (int_fast64_t) scaled_remainder; /* for precision == 0U, this will be 0 */

  remainder = scaled_remainder - (floating_point_t) number_.fractional;

  if ((remainder > one_half) ||
      /* Banker's rounding, i.e. round half to even: 1.5 -> 2, but 2.5 -> 2 */
      ((remainder == one_half) && (number_.fractional & 1U))) {
    ++number_.fractional;
  }
  if ((floating_point_t) number_.fractional >= powers_of_10[precision]) {
    number_.fractional = 0;
    ++number_.integral;
  }

  if (precision == 0U) {
    remainder = abs_number - (floating_point_t) number_.integral;
    if ((remainder == one_half) && (number_.integral & 1U)) {
      /*
       * Banker's rounding, i.e. round half to even:
       * 1.5 -> 2, but 2.5 -> 2
       */
      ++number_.integral;
    }
  }
  return number_;
}

#if PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS
struct scaling_factor {
  floating_point_t raw_factor;
  bool multiply; /* if true, need to multiply by raw_factor; otherwise need to divide by it */
};

static floating_point_t apply_scaling(floating_point_t num, struct scaling_factor normalization)
{
  return normalization.multiply ? num * normalization.raw_factor : num / normalization.raw_factor;
}

static floating_point_t unapply_scaling(floating_point_t normalized, struct scaling_factor normalization)
{
#ifdef __GNUC__
/* accounting for a static analysis bug in GCC 6.x and earlier */
#pragma GCC diagnostic push
#if !defined(__has_warning)
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#elif __has_warning("-Wmaybe-uninitialized")
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif
#endif
  return normalization.multiply ? normalized / normalization.raw_factor : normalized * normalization.raw_factor;
#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif
}

static struct scaling_factor update_normalization(struct scaling_factor sf, floating_point_t extra_multiplicative_factor)
{
  struct scaling_factor result;
  if (sf.multiply) {
    result.multiply = true;
    result.raw_factor = sf.raw_factor * extra_multiplicative_factor;
  }
  else {
    int factor_exp2 = get_exp2(get_bit_access(sf.raw_factor));
    int extra_factor_exp2 = get_exp2(get_bit_access(extra_multiplicative_factor));

    /* Divide the larger-exponent raw raw_factor by the smaller */
    if (PRINTF_ABS(factor_exp2) > PRINTF_ABS(extra_factor_exp2)) {
      result.multiply = false;
      result.raw_factor = sf.raw_factor / extra_multiplicative_factor;
    }
    else {
      result.multiply = true;
      result.raw_factor = extra_multiplicative_factor / sf.raw_factor;
    }
  }
  return result;
}

static struct floating_point_components get_normalized_components(bool negative, printf_size_t precision, floating_point_t non_normalized, struct scaling_factor normalization, int floored_exp10)
{
  struct floating_point_components components;
  floating_point_t scaled;
  bool close_to_representation_extremum;
  floating_point_t remainder;
  floating_point_t prec_power_of_10;
  struct scaling_factor account_for_precision;
  floating_point_t scaled_remainder;
  const floating_point_t rounding_threshold = 0.5;

  components.is_negative = negative;
  scaled = apply_scaling(non_normalized, normalization);

  close_to_representation_extremum = ( (-floored_exp10 + (int) precision) >= FP_TYPE_MAX_10_EXP - 1 );
  if (close_to_representation_extremum) {
    /*
     * We can't have a normalization factor which also accounts for the precision, i.e. moves
     * some decimal digits into the mantissa, since it's unrepresentable, or nearly unrepresentable.
     * So, we'll give up early on getting extra precision...
     */
    return get_components(SIGN(negative, scaled), precision);
  }
  components.integral = (int_fast64_t) scaled;
  remainder = non_normalized - unapply_scaling((floating_point_t) components.integral, normalization);
  prec_power_of_10 = powers_of_10[precision];
  account_for_precision = update_normalization(normalization, prec_power_of_10);
  scaled_remainder = apply_scaling(remainder, account_for_precision);

  components.fractional = (int_fast64_t) scaled_remainder; /* when precision == 0, the assigned value should be 0 */
  scaled_remainder -= (floating_point_t) components.fractional; /* when precision == 0, this will not change scaled_remainder */

  components.fractional += (scaled_remainder >= rounding_threshold);
  if (scaled_remainder == rounding_threshold) {
    /* banker's rounding: Round towards the even number (making the mean error 0) */
    components.fractional &= ~((int_fast64_t) 0x1);
  }
  /*
   * handle rollover, e.g. the case of 0.99 with precision 1 becoming (0,100),
   * and must then be corrected into (1, 0).
   * Note: for precision = 0, this will "translate" the rounding effect from
   * the fractional part to the integral part where it should actually be
   * felt (as prec_power_of_10 is 1)
   */
  if ((floating_point_t) components.fractional >= prec_power_of_10) {
    components.fractional = 0;
    ++components.integral;
  }
  return components;
}
#endif /* PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS */

static void print_broken_up_decimal(
  struct floating_point_components number_, output_gadget_t* output, printf_size_t precision,
  printf_size_t width, printf_flags_t flags, char *buf, printf_size_t len)
{
  if (precision != 0U) {
    /* do fractional part, as an unsigned number */

    printf_size_t count = precision;

    /* %g/%G mandates we skip the trailing 0 digits... */
    if ((flags & FLAGS_ADAPT_EXP) && !(flags & FLAGS_HASH) && (number_.fractional > 0)) {
      while(true) {
        int_fast64_t digit = number_.fractional % 10U;
        if (digit != 0) {
          break;
        }
        --count;
        number_.fractional /= 10U;

      }
      /*
       * ... and even the decimal point if there are no
       * non-zero fractional part digits (see below)
       */
    }

    if (number_.fractional > 0 || !(flags & FLAGS_ADAPT_EXP) || (flags & FLAGS_HASH) ) {
      while (len < PRINTF_DECIMAL_BUFFER_SIZE) {
        --count;
        buf[len++] = (char)('0' + number_.fractional % 10U);
        if (!(number_.fractional /= 10U)) {
          break;
        }
      }
      /* add extra 0s */
      while ((len < PRINTF_DECIMAL_BUFFER_SIZE) && (count > 0U)) {
        buf[len++] = '0';
        --count;
      }
      if (len < PRINTF_DECIMAL_BUFFER_SIZE) {
        buf[len++] = '.';
      }
    }
  }
  else {
    if ((flags & FLAGS_HASH) && (len < PRINTF_DECIMAL_BUFFER_SIZE)) {
      buf[len++] = '.';
    }
  }

  /*
   * Write the integer part of the number (it comes after the fractional
   * since the character order is reversed)
   */
  while (len < PRINTF_DECIMAL_BUFFER_SIZE) {
    buf[len++] = (char)('0' + (number_.integral % 10));
    if (!(number_.integral /= 10)) {
      break;
    }
  }

  /* pad leading zeros */
  if (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD)) {
    if (width && (number_.is_negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
      width--;
    }
    while ((len < width) && (len < PRINTF_DECIMAL_BUFFER_SIZE)) {
      buf[len++] = '0';
    }
  }

  if (len < PRINTF_DECIMAL_BUFFER_SIZE) {
    if (number_.is_negative) {
      buf[len++] = '-';
    }
    else if (flags & FLAGS_PLUS) {
      buf[len++] = '+';  /* ignore the space if the '+' exists */
    }
    else if (flags & FLAGS_SPACE) {
      buf[len++] = ' ';
    }
  }

  out_rev_(output, buf, len, width, flags);
}

/* internal ftoa for fixed decimal floating point */
static void print_decimal_number(output_gadget_t* output, floating_point_t number, printf_size_t precision, printf_size_t width, printf_flags_t flags, char* buf, printf_size_t len)
{
  struct floating_point_components value_ = get_components(number, precision);
  print_broken_up_decimal(value_, output, precision, width, flags, buf, len);
}

#if PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS

/*
 * A floor function - but one which only works for numbers whose
 * floor value is representable by an int.
 */
static int bastardized_floor(floating_point_t x)
{
  int n;
  if (x >= 0) { return (int) x; }
  n = (int) x;
  return ( ((floating_point_t) n) == x ) ? n : n-1;
}

/*
 * Computes the base-10 logarithm of the input number - which must be an actual
 * positive number (not infinity or NaN, nor a sub-normal)
 */
static floating_point_t log10_of_positive(floating_point_t positive_number)
{
  /*
   * The implementation follows David Gay (https://www.ampl.com/netlib/fp/dtoa.c).
   *
   * Since log_10 ( M * 2^x ) = log_10(M) + x , we can separate the components of
   * our input number, and need only solve log_10(M) for M between 1 and 2 (as
   * the base-2 mantissa is always 1-point-something). In that limited range, a
   * Taylor series expansion of log10(x) should serve us well enough; and we'll
   * take the mid-point, 1.5, as the point of expansion.
   */

  floating_point_with_bit_access dwba = get_bit_access(positive_number);
  /* based on the algorithm by David Gay (https://www.ampl.com/netlib/fp/dtoa.c) */
  int exp2 = get_exp2(dwba);
  floating_point_t z;
  /* drop the exponent, so dwba.F comes into the range [1,2) */
  dwba.U = (dwba.U & (((printf_fp_uint_t) (1) << FP_TYPE_STORED_MANTISSA_BITS) - 1U)) |
           ((printf_fp_uint_t) FP_TYPE_BASE_EXPONENT << FP_TYPE_STORED_MANTISSA_BITS);
  z = (dwba.F - (floating_point_t) 1.5);
  return (
    /* Taylor expansion around 1.5: */
              (floating_point_t) 0.1760912590556812420 /* Expansion term 0: ln(1.5)            / ln(10) */
    + z     * (floating_point_t) 0.2895296546021678851 /* Expansion term 1: (M - 1.5)   * 2/3  / ln(10) */
#if PRINTF_LOG10_TAYLOR_TERMS > 2
    - z*z   * (floating_point_t) 0.0965098848673892950 /* Expansion term 2: (M - 1.5)^2 * 2/9  / ln(10) */
#if PRINTF_LOG10_TAYLOR_TERMS > 3
    + z*z*z * (floating_point_t) 0.0428932821632841311 /* Expansion term 2: (M - 1.5)^3 * 8/81 / ln(10) */
#endif
#endif
    /* exact log_2 of the exponent x, with logarithm base change */
    + (floating_point_t) exp2 * (floating_point_t) 0.30102999566398119521 /* = exp2 * log_10(2) = exp2 * ln(2)/ln(10) */
  );
}


static floating_point_t pow10_of_int(int floored_exp10)
{
  floating_point_with_bit_access dwba;
  int exp2;
  floating_point_t z;
  floating_point_t z2;

  /* A crude hack for avoiding undesired behavior with barely-normal or slightly-subnormal values. */
  if (floored_exp10 == FP_TYPE_MAX_SUBNORMAL_EXPONENT_OF_10) {
    return FP_TYPE_MAX_SUBNORMAL_POWER_OF_10;
  }
  /* Compute 10^(floored_exp10) but (try to) make sure that doesn't overflow */
  exp2 = bastardized_floor(floored_exp10 * (floating_point_t) 3.321928094887362 + (floating_point_t) 0.5);
  z  = floored_exp10 * (floating_point_t) 2.302585092994046 - exp2 * (floating_point_t) 0.6931471805599453;
  z2 = z * z;
  dwba.U = ((printf_fp_uint_t)(exp2) + FP_TYPE_BASE_EXPONENT) << FP_TYPE_STORED_MANTISSA_BITS;
  /*
   * compute exp(z) using continued fractions,
   * see https://en.wikipedia.org/wiki/Exponential_function#Continued_fractions_for_ex
   */
  dwba.F *= 1 + 2 * z / (2 - z + (z2 / (6 + (z2 / (10 + z2 / 14)))));
  return dwba.F;
}

static void print_exponential_number(output_gadget_t* output, floating_point_t number, printf_size_t precision, printf_size_t width, printf_flags_t flags, char* buf, printf_size_t len)
{
  const bool negative = get_sign_bit(number);
  /* This number will decrease gradually (by factors of 10) as we "extract" the exponent out of it */
  floating_point_t abs_number =  SIGN(negative, number);

  int floored_exp10;
  bool abs_exp10_covered_by_powers_table;
  struct scaling_factor normalization;
  struct floating_point_components decimal_part_components;
  int original_floored_exp10;
  bool fall_back_to_decimal_only_mode;
  printf_size_t exp10_part_width;
  printf_size_t decimal_part_width;
  printf_size_t printed_exponential_start_pos;


  /* Determine the decimal exponent */
  if (abs_number == (floating_point_t) 0.0) {
    /* TODO: This is a special-case for 0.0 (and -0.0); but proper handling is required for denormals more generally. */
    floored_exp10 = 0; /* ... and no need to set a normalization factor or check the powers table */
  }
  else  {
    floating_point_t exp10 = log10_of_positive(abs_number);
    floating_point_t p10;
    floored_exp10 = bastardized_floor(exp10);
    p10 = pow10_of_int(floored_exp10);
    /* correct for rounding errors */
    if (abs_number < p10) {
      floored_exp10--;
      p10 /= 10;
    }
    abs_exp10_covered_by_powers_table = PRINTF_ABS(floored_exp10) < PRINTF_MAX_PRECOMPUTED_POWER_OF_10;
    normalization.raw_factor = abs_exp10_covered_by_powers_table ? powers_of_10[PRINTF_ABS(floored_exp10)] : p10;
  }

  if (flags & FLAGS_ADAPT_EXP) {
    /*
     * Note: For now, still assuming we _don't_ fall-back to "%f" mode; we can't decide
     * that until we've established the exact exponent.
     */

    /*
     * In "%g" mode, "precision" is the number of _significant digits_; we must
     * "translate" that  to an actual number of decimal digits.
     */
    precision = (precision > 1) ? (precision - 1U) : 0U;
    flags |= FLAGS_PRECISION;   /* make sure print_broken_up_decimal respects our choice */
  }

  /*
   * We now begin accounting for the widths of the two parts of our printed field:
   * the decimal part after decimal exponent extraction, and the base-10 exponent part.
   * For both of these, the value of 0 has a special meaning, but not the same one:
   * a 0 exponent-part width means "don't print the exponent"; a 0 decimal-part width
   * means "use as many characters as necessary".
   */

#ifdef __GNUC__
/* accounting for a static analysis bug in GCC 6.x and earlier */
#pragma GCC diagnostic push
#if !defined(__has_warning)
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#elif __has_warning("-Wmaybe-uninitialized")
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif
#endif
  normalization.multiply = (floored_exp10 < 0 && abs_exp10_covered_by_powers_table);
#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif
  decimal_part_components =
    (floored_exp10 == 0) ?
    get_components(SIGN(negative, abs_number), precision) :
    get_normalized_components(negative, precision, abs_number, normalization, floored_exp10);

  /*
   * Account for roll-over, e.g. rounding from 9.99 to 100.0 - which effects
   * the exponent and may require additional tweaking of the parts
   * (and saving the floored_exp10 in case we'll need to undo the roll-over).
   */
  original_floored_exp10 = floored_exp10;
  if (decimal_part_components.integral >= 10) {
    floored_exp10++;
    decimal_part_components.integral = 1;
    decimal_part_components.fractional = 0;
  }

  /*
   * Should we want to fall-back to "%f" mode, and only print the decimal part?
   * (and remember we have decreased "precision" by 1
   */
  fall_back_to_decimal_only_mode = (flags & FLAGS_ADAPT_EXP) && (floored_exp10 >= -4) && (floored_exp10 < (int) precision + 1);

  if (fall_back_to_decimal_only_mode) {
    precision = ((int) precision > floored_exp10) ? (unsigned) ((int) precision - floored_exp10) : 0U;
    /* Redo some work :-) */
    floored_exp10 = original_floored_exp10;
    decimal_part_components = get_components(SIGN(negative, abs_number), precision);
    if ((flags & FLAGS_ADAPT_EXP) && floored_exp10 >= -1 && decimal_part_components.integral == powers_of_10[floored_exp10 + 1]) {
      floored_exp10++; /* Not strictly necessary, since floored_exp10 is no longer really used */
      if (precision > 0U) { precision--; }
      /* ... and it should already be the case that decimal_part_components.fractional == 0 */
    }
    /* TODO: What about rollover strictly within the fractional part? */
  }

  /*
   * the floored_exp10 format is "E%+03d" and largest possible floored_exp10 value for a 64-bit double
   * is "307" (for 2^1023), so we set aside 4-5 characters overall
   */
  exp10_part_width = fall_back_to_decimal_only_mode ? 0U : (PRINTF_ABS(floored_exp10) < 100) ? 4U : 5U;

  decimal_part_width =
    ((flags & FLAGS_LEFT) && exp10_part_width) ?
      /*
       * We're padding on the right, so the width constraint is the exponent part's
       * problem, not the decimal part's, so we'll use as many characters as we need:
       */
      0U :
      /*
       * We're padding on the left; so the width constraint is the decimal part's
       * problem. Well, can both the decimal part and the exponent part fit within our overall width?
       */
      ((width > exp10_part_width) ?
        /*
         * Yes, so we limit our decimal part's width.
         * (Note this is trivially valid even if we've fallen back to "%f" mode)
         */
        width - exp10_part_width :
        /*
         * No; we just give up on any restriction on the decimal part and use as many
         * characters as we need
         */
        0U);

  printed_exponential_start_pos = output->pos;
  print_broken_up_decimal(decimal_part_components, output, precision, decimal_part_width, flags, buf, len);

  if (! fall_back_to_decimal_only_mode) {
    putchar_via_gadget(output, (flags & FLAGS_UPPERCASE) ? 'E' : 'e');
    print_integer(output,
                  ABS_FOR_PRINTING(floored_exp10),
                  floored_exp10 < 0, 10, 0, exp10_part_width - 1,
                FLAGS_ZEROPAD | FLAGS_PLUS);
    if (flags & FLAGS_LEFT) {
      /* We need to right-pad with spaces to meet the width requirement */
      while (output->pos - printed_exponential_start_pos < width) {
        putchar_via_gadget(output, ' ');
      }
    }
  }
}
#endif  /* PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS */

static void print_floating_point(output_gadget_t* output, floating_point_t value, printf_size_t precision, printf_size_t width, printf_flags_t flags, bool prefer_exponential)
{
  char buf[PRINTF_DECIMAL_BUFFER_SIZE];
  printf_size_t len = 0U;

  /* test for special values */
  if (value != value) {
    out_rev_(output, "nan", 3, width, flags);
    return;
  }
  if (value < -FP_TYPE_MAX) {
    out_rev_(output, "fni-", 4, width, flags);
    return;
  }
  if (value > FP_TYPE_MAX) {
    out_rev_(output, (flags & FLAGS_PLUS) ? "fni+" : "fni", (flags & FLAGS_PLUS) ? 4U : 3U, width, flags);
    return;
  }

  if (!prefer_exponential &&
      ((value > PRINTF_FLOAT_NOTATION_THRESHOLD) || (value < -PRINTF_FLOAT_NOTATION_THRESHOLD))) {
    /*
     * The required behavior of standard printf is to print _every_ integral-part digit -- which could mean
     * printing hundreds of characters, overflowing any fixed internal buffer and necessitating a more complicated
     * implementation.
     */
#if PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS
    print_exponential_number(output, value, precision, width, flags, buf, len);
#endif
    return;
  }

  /* set default precision, if not set explicitly */
  if (!(flags & FLAGS_PRECISION)) {
    precision = PRINTF_DEFAULT_FLOAT_PRECISION;
  }

  /* limit precision so that our integer holding the fractional part does not overflow */
  while ((len < PRINTF_DECIMAL_BUFFER_SIZE) && (precision > PRINTF_MAX_SUPPORTED_PRECISION)) {
    buf[len++] = '0'; /* This respects the precision in terms of result length only */
    precision--;
  }

#if PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS
  if (prefer_exponential)
    print_exponential_number(output, value, precision, width, flags, buf, len);
  else
#endif
    print_decimal_number(output, value, precision, width, flags, buf, len);
}

#endif  /* (PRINTF_SUPPORT_DECIMAL_SPECIFIERS || PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS) */

/*
 * Advances the format pointer past the flags, and returns the parsed flags
 * due to the characters passed
 */
static printf_flags_t parse_flags(const char** format)
{
  printf_flags_t flags = 0U;
  do {
    switch (**format) {
      case '0': flags |= FLAGS_ZEROPAD; (*format)++; break;
      case '-': flags |= FLAGS_LEFT;    (*format)++; break;
      case '+': flags |= FLAGS_PLUS;    (*format)++; break;
      case ' ': flags |= FLAGS_SPACE;   (*format)++; break;
      case '#': flags |= FLAGS_HASH;    (*format)++; break;
      default : return flags;
    }
  } while (true);
}

static inline void format_string_loop(output_gadget_t* output, const char* format, va_list args)
{
#if PRINTF_CHECK_FOR_NUL_IN_FORMAT_SPECIFIER
#define ADVANCE_IN_FORMAT_STRING(cptr_) do { (cptr_)++; if (!*(cptr_)) return; } while(0)
#else
#define ADVANCE_IN_FORMAT_STRING(cptr_) (cptr_)++
#endif

  while (*format)
  {
    printf_flags_t flags;
    printf_size_t width;
    printf_size_t precision;
    if (*format != '%') {
      /* A regular content character */
      putchar_via_gadget(output, *format);
      format++;
      continue;
    }
    /* We're parsing a format specifier: %[flags][width][.precision][length] */
    ADVANCE_IN_FORMAT_STRING(format);

    flags = parse_flags(&format);

    /* evaluate width field */
    width = 0U;
    if (is_digit_(*format)) {
      /*
       * Note: If the width is negative, we've already parsed its
       * sign character '-' as a FLAG_LEFT
       */
      width = (printf_size_t) atou_(&format);
    }
    else if (*format == '*') {
      const int w = va_arg(args, int);
      if (w < 0) {
        flags |= FLAGS_LEFT;    /* reverse padding */
        width = (printf_size_t)-w;
      }
      else {
        width = (printf_size_t)w;
      }
      ADVANCE_IN_FORMAT_STRING(format);
    }

    /* evaluate precision field */
    precision = 0U;
    if (*format == '.') {
      flags |= FLAGS_PRECISION;
      ADVANCE_IN_FORMAT_STRING(format);
      if (*format == '-') {
        do {
          ADVANCE_IN_FORMAT_STRING(format);
        } while (is_digit_(*format));
        flags &= ~FLAGS_PRECISION;
      }
      else if (is_digit_(*format)) {
        precision = atou_(&format);
      }
      else if (*format == '*') {
        const int precision_ = va_arg(args, int);
        if (precision_ < 0) {
          flags &= ~FLAGS_PRECISION;
        }
        else {
          precision = precision_ > 0 ? (printf_size_t) precision_ : 0U;
        }
        ADVANCE_IN_FORMAT_STRING(format);
      }
    }

    /* evaluate length field */
    switch (*format) {
#ifdef PRINTF_SUPPORT_MSVC_STYLE_INTEGER_SPECIFIERS
      case 'I' : {
        ADVANCE_IN_FORMAT_STRING(format);
        /* Greedily parse for size in bits: 8, 16, 32 or 64 */
        switch(*format) {
          case '8':               flags |= FLAGS_INT8;
            ADVANCE_IN_FORMAT_STRING(format);
            break;
          case '1':
            ADVANCE_IN_FORMAT_STRING(format);
          if (*format == '6') { format++; flags |= FLAGS_INT16; }
            break;
          case '3':
            ADVANCE_IN_FORMAT_STRING(format);
            if (*format == '2') { ADVANCE_IN_FORMAT_STRING(format); flags |= FLAGS_INT32; }
            break;
          case '6':
            ADVANCE_IN_FORMAT_STRING(format);
            if (*format == '4') { ADVANCE_IN_FORMAT_STRING(format); flags |= FLAGS_INT64; }
            break;
          default: break;
        }
        break;
      }
#endif
      case 'l' :
        flags |= FLAGS_LONG;
        ADVANCE_IN_FORMAT_STRING(format);
        if (*format == 'l') {
          flags |= FLAGS_LONG_LONG;
          ADVANCE_IN_FORMAT_STRING(format);
        }
        break;
      case 'L' :
        flags |= FLAGS_LONG_DOUBLE;
        ADVANCE_IN_FORMAT_STRING(format);
        break;
      case 'h' :
        flags |= FLAGS_SHORT;
        ADVANCE_IN_FORMAT_STRING(format);
        if (*format == 'h') {
          flags |= FLAGS_CHAR;
          ADVANCE_IN_FORMAT_STRING(format);
        }
        break;
      case 't' :
        flags |= (sizeof(ptrdiff_t) <= sizeof(int) ) ? FLAGS_INT : (sizeof(ptrdiff_t) == sizeof(long)) ? FLAGS_LONG : FLAGS_LONG_LONG;
        ADVANCE_IN_FORMAT_STRING(format);
        break;
      case 'j' :
        flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
        ADVANCE_IN_FORMAT_STRING(format);
        break;
      case 'z' :
        flags |= (sizeof(size_t) <= sizeof(int) ) ? FLAGS_INT : (sizeof(size_t) == sizeof(long)) ? FLAGS_LONG : FLAGS_LONG_LONG;
        ADVANCE_IN_FORMAT_STRING(format);
        break;
      default:
        break;
    }

    /* evaluate specifier */
    switch (*format) {
      case 'd' :
      case 'i' :
      case 'u' :
      case 'x' :
      case 'X' :
      case 'o' :
      case 'b' : {
        numeric_base_t base;

        if (*format == 'd' || *format == 'i') {
          flags |= FLAGS_SIGNED;
        }

        if (*format == 'x' || *format == 'X') {
          base = BASE_HEX;
        }
        else if (*format == 'o') {
          base =  BASE_OCTAL;
        }
        else if (*format == 'b') {
          base =  BASE_BINARY;
        }
        else {
          base = BASE_DECIMAL;
          flags &= ~FLAGS_HASH; /* decimal integers have no alternative presentation */
        }

        if (*format == 'X') {
          flags |= FLAGS_UPPERCASE;
        }

        format++;
        /* ignore '0' flag when precision is given */
        if (flags & FLAGS_PRECISION) {
          flags &= ~FLAGS_ZEROPAD;
        }

        if (flags & FLAGS_SIGNED) {
          /* A signed specifier: d, i or possibly I + bit size if enabled */

          if (flags & FLAGS_LONG_LONG) {
#if PRINTF_SUPPORT_LONG_LONG
            const long long value = va_arg(args, long long);
            print_integer(output, ABS_FOR_PRINTING(value), value < 0, base, precision, width, flags);
#endif
          }
          else if (flags & FLAGS_LONG) {
            const long value = va_arg(args, long);
            print_integer(output, ABS_FOR_PRINTING(value), value < 0, base, precision, width, flags);
          }
          else {
            /*
             * We never try to interpret the argument as something potentially-smaller than int,
             * due to integer promotion rules: Even if the user passed a short int, short unsigned
             * etc. - these will come in after promotion, as int's (or unsigned for the case of
             * short unsigned when it has the same size as int)
             */
            const int value =
              (flags & FLAGS_CHAR) ? (signed char) va_arg(args, int) :
              (flags & FLAGS_SHORT) ? (short int) va_arg(args, int) :
              va_arg(args, int);
            print_integer(output, ABS_FOR_PRINTING(value), value < 0, base, precision, width, flags);
          }
        }
        else {
          /* An unsigned specifier: u, x, X, o, b */

          flags &= ~(FLAGS_PLUS | FLAGS_SPACE);

          if (flags & FLAGS_LONG_LONG) {
#if PRINTF_SUPPORT_LONG_LONG
            print_integer(output, (printf_unsigned_value_t) va_arg(args, unsigned long long), false, base, precision, width, flags);
#endif
          }
          else if (flags & FLAGS_LONG) {
            print_integer(output, (printf_unsigned_value_t) va_arg(args, unsigned long), false, base, precision, width, flags);
          }
          else {
            const unsigned int value =
              (flags & FLAGS_CHAR) ? (unsigned char)va_arg(args, unsigned int) :
              (flags & FLAGS_SHORT) ? (unsigned short int)va_arg(args, unsigned int) :
              va_arg(args, unsigned int);
            print_integer(output, (printf_unsigned_value_t) value, false, base, precision, width, flags);
          }
        }
        break;
      }
#if PRINTF_SUPPORT_DECIMAL_SPECIFIERS
      case 'f' :
      case 'F' : {
        floating_point_t value = (floating_point_t) (flags & FLAGS_LONG_DOUBLE ? va_arg(args, long double) : va_arg(args, double));
        if (*format == 'F') flags |= FLAGS_UPPERCASE;
        print_floating_point(output, value, precision, width, flags, PRINTF_PREFER_DECIMAL);
        format++;
        break;
      }
#endif
#if PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS
      case 'e':
      case 'E':
      case 'g':
      case 'G': {
        floating_point_t value = (floating_point_t) (flags & FLAGS_LONG_DOUBLE ? va_arg(args, long double) : va_arg(args, double));
        if ((*format == 'g')||(*format == 'G')) flags |= FLAGS_ADAPT_EXP;
        if ((*format == 'E')||(*format == 'G')) flags |= FLAGS_UPPERCASE;
        print_floating_point(output, value, precision, width, flags, PRINTF_PREFER_EXPONENTIAL);
        format++;
        break;
      }
#endif  /* PRINTF_SUPPORT_EXPONENTIAL_SPECIFIERS */
      case 'c' : {
        printf_size_t l = 1U;
        /* pre padding */
        if (!(flags & FLAGS_LEFT)) {
          while (l++ < width) {
            putchar_via_gadget(output, ' ');
          }
        }
        /* char output */
        putchar_via_gadget(output, (char) va_arg(args, int) );
        /* post padding */
        if (flags & FLAGS_LEFT) {
          while (l++ < width) {
            putchar_via_gadget(output, ' ');
          }
        }
        format++;
        break;
      }

      case 's' : {
        const char* p = va_arg(args, char*);
        if (p == NULL) {
          out_rev_(output, ")llun(", 6, width, flags);
        }
        else {
          printf_size_t l = strnlen_s_(p, precision ? precision : PRINTF_MAX_POSSIBLE_BUFFER_SIZE);
          /* pre padding */
          if (flags & FLAGS_PRECISION) {
            l = (l < precision ? l : precision);
          }
          if (!(flags & FLAGS_LEFT)) {
            while (l++ < width) {
              putchar_via_gadget(output, ' ');
            }
          }
          /* string output */
          while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision)) {
            putchar_via_gadget(output, *(p++));
            --precision;
          }
          /* post padding */
          if (flags & FLAGS_LEFT) {
            while (l++ < width) {
              putchar_via_gadget(output, ' ');
            }
          }
        }
        format++;
        break;
      }

      case 'p' : {
        uintptr_t value;
        width = sizeof(void*) * 2U + 2; /* 2 hex chars per byte + the "0x" prefix */
        flags |= FLAGS_ZEROPAD | FLAGS_POINTER;
        value = (uintptr_t)va_arg(args, void*);
        (value == (uintptr_t) NULL) ?
          out_rev_(output, ")lin(", 5, width, flags) :
          print_integer(output, (printf_unsigned_value_t) value, false, BASE_HEX, precision, width, flags);
        format++;
        break;
      }

      case '%' :
        putchar_via_gadget(output, '%');
        format++;
        break;

      /*
       * Many people prefer to disable support for %n, as it lets the caller
       * engineer a write to an arbitrary location, of a value the caller
       * effectively controls - which could be a security concern in some cases.
       */
#if PRINTF_SUPPORT_WRITEBACK_SPECIFIER
      case 'n' : {
        if       (flags & FLAGS_CHAR)      *(va_arg(args, char*))      = (char) output->pos;
        else if  (flags & FLAGS_SHORT)     *(va_arg(args, short*))     = (short) output->pos;
        else if  (flags & FLAGS_LONG)      *(va_arg(args, long*))      = (long) output->pos;
#if PRINTF_SUPPORT_LONG_LONG
        else if  (flags & FLAGS_LONG_LONG) *(va_arg(args, long long*)) = (long long int) output->pos;
#endif /* PRINTF_SUPPORT_LONG_LONG */
        else                               *(va_arg(args, int*))       = (int) output->pos;
        format++;
        break;
      }
#endif /* PRINTF_SUPPORT_WRITEBACK_SPECIFIER */

      default :
        putchar_via_gadget(output, *format);
        format++;
        break;
    }
  }
}

/* internal vsnprintf - used for implementing _all library functions */
static int vsnprintf_impl(output_gadget_t* output, const char* format, va_list args)
{
  /*
   * Note: The library only calls vsnprintf_impl() with output->pos being 0. However, it is
   * possible to call this function with a non-zero pos value for some "remedial printing".
   */
  format_string_loop(output, format, args);

  /* termination */
  append_termination_with_gadget(output);

  /* return written chars without terminating \0 */
  return (int)output->pos;
}

/*===========================================================================*/

int vprintf_(const char* format, va_list arg)
{
  output_gadget_t gadget = extern_putchar_gadget();
  return vsnprintf_impl(&gadget, format, arg);
}

int vsnprintf_(char* s, size_t n, const char* format, va_list arg)
{
  output_gadget_t gadget = buffer_gadget(s, n);
  return vsnprintf_impl(&gadget, format, arg);
}

int vsprintf_(char* s, const char* format, va_list arg)
{
  return vsnprintf_(s, PRINTF_MAX_POSSIBLE_BUFFER_SIZE, format, arg);
}

int vfctprintf(void (*out)(char c, void* extra_arg), void* extra_arg, const char* format, va_list arg)
{
  output_gadget_t gadget;
  if (out == NULL) { return 0; }
  gadget = function_gadget(out, extra_arg);
  return vsnprintf_impl(&gadget, format, arg);
}

int printf_(const char* format, ...)
{
  int ret;
  va_list args;
  va_start(args, format);
  ret = vprintf_(format, args);
  va_end(args);
  return ret;
}

int sprintf_(char* s, const char* format, ...)
{
  int ret;
  va_list args;
  va_start(args, format);
  ret = vsprintf_(s, format, args);
  va_end(args);
  return ret;
}

int snprintf_(char* s, size_t n, const char* format, ...)
{
  int ret;
  va_list args;
  va_start(args, format);
  ret = vsnprintf_(s, n, format, args);
  va_end(args);
  return ret;
}

int fctprintf(void (*out)(char c, void* extra_arg), void* extra_arg, const char* format, ...)
{
  int ret;
  va_list args;
  va_start(args, format);
  ret = vfctprintf(out, extra_arg, format, args);
  va_end(args);
  return ret;
}

