Skip to content
Snippets Groups Projects
printf.c 27.4 KiB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914
///////////////////////////////////////////////////////////////////////////////
// \author (c) Marco Paland (info@paland.com)
//             2014-2019, PALANDesign Hannover, Germany
//
// \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.
//
// \brief Tiny printf, sprintf and (v)snprintf implementation, optimized for speed on
//        embedded systems with a very limited resources. These routines are thread
//        safe and reentrant!
//        Use this instead of the bloated standard/newlib printf cause these use
//        malloc for printf (and may not be thread safe).
//
///////////////////////////////////////////////////////////////////////////////

#include <stdbool.h>
#include <stdint.h>

#include "printf.h"


// define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
// printf_config.h header file
// default: undefined
#ifdef PRINTF_INCLUDE_CONFIG_H
#include "printf_config.h"
#endif


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

// 'ftoa' conversion buffer size, this must be big enough to hold one converted
// float number including padded zeros (dynamically created on stack)
// default: 32 byte
#ifndef PRINTF_FTOA_BUFFER_SIZE
#define PRINTF_FTOA_BUFFER_SIZE    32U
#endif

// support for the floating point type (%f)
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_FLOAT
#define PRINTF_SUPPORT_FLOAT
#endif

// support for exponential floating point notation (%e/%g)
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_EXPONENTIAL
#define PRINTF_SUPPORT_EXPONENTIAL
#endif

// define the default floating point precision
// default: 6 digits
#ifndef PRINTF_DEFAULT_FLOAT_PRECISION
#define PRINTF_DEFAULT_FLOAT_PRECISION  6U
#endif

// define the largest float suitable to print with %f
// default: 1e9
#ifndef PRINTF_MAX_FLOAT
#define PRINTF_MAX_FLOAT  1e9
#endif

// support for the long long types (%llu or %p)
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_LONG_LONG
#define PRINTF_SUPPORT_LONG_LONG
#endif

// support for the ptrdiff_t type (%t)
// ptrdiff_t is normally defined in <stddef.h> as long or long long type
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_PTRDIFF_T
#define PRINTF_SUPPORT_PTRDIFF_T
#endif

///////////////////////////////////////////////////////////////////////////////

// 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_LONG      (1U <<  8U)
#define FLAGS_LONG_LONG (1U <<  9U)
#define FLAGS_PRECISION (1U << 10U)
#define FLAGS_ADAPT_EXP (1U << 11U)


// import float.h for DBL_MAX
#if defined(PRINTF_SUPPORT_FLOAT)
#include <float.h>
#endif


// output function type
typedef void (*out_fct_type)(char character, void* buffer, size_t idx, size_t maxlen);


// wrapper (used as buffer) for output function type
typedef struct {
  void  (*fct)(char character, void* arg);
  void* arg;
} out_fct_wrap_type;


// internal buffer output
static inline void _out_buffer(char character, void* buffer, size_t idx, size_t maxlen)
{
  if (idx < maxlen) {
    ((char*)buffer)[idx] = character;
  }
}


// internal null output
static inline void _out_null(char character, void* buffer, size_t idx, size_t maxlen)
{
  (void)character; (void)buffer; (void)idx; (void)maxlen;
}


// internal _putchar wrapper
static inline void _out_char(char character, void* buffer, size_t idx, size_t maxlen)
{
  (void)buffer; (void)idx; (void)maxlen;
  if (character) {
    _putchar(character);
  }
}


// internal output function wrapper
static inline void _out_fct(char character, void* buffer, size_t idx, size_t maxlen)
{
  (void)idx; (void)maxlen;
  if (character) {
    // buffer is the output fct pointer
    ((out_fct_wrap_type*)buffer)->fct(character, ((out_fct_wrap_type*)buffer)->arg);
  }
}


// internal secure strlen
// \return The length of the string (excluding the terminating 0) limited by 'maxsize'
static inline unsigned int _strnlen_s(const char* str, size_t maxsize)
{
  const char* s;
  for (s = str; *s && maxsize--; ++s);
  return (unsigned int)(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 unsigned int conversion
static unsigned int _atoi(const char** str)
{
  unsigned int i = 0U;
  while (_is_digit(**str)) {
    i = i * 10U + (unsigned int)(*((*str)++) - '0');
  }
  return i;
}


// output the specified string in reverse, taking care of any zero-padding
static size_t _out_rev(out_fct_type out, char* buffer, size_t idx, size_t maxlen, const char* buf, size_t len, unsigned int width, unsigned int flags)
{
  const size_t start_idx = idx;

  // pad spaces up to given width
  if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
    for (size_t i = len; i < width; i++) {
      out(' ', buffer, idx++, maxlen);
    }
  }

  // reverse string
  while (len) {
    out(buf[--len], buffer, idx++, maxlen);
  }

  // append pad spaces up to given width
  if (flags & FLAGS_LEFT) {
    while (idx - start_idx < width) {
      out(' ', buffer, idx++, maxlen);
    }
  }

  return idx;
}


// internal itoa format
static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags)
{
  // pad leading zeros
  if (!(flags & FLAGS_LEFT)) {
    if (width && (flags & FLAGS_ZEROPAD) && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
      width--;
    }
    while ((len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = '0';
    }
    while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = '0';
    }
  }

  // handle hash
  if (flags & FLAGS_HASH) {
    if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) {
      len--;
      if (len && (base == 16U)) {
        len--;
      }
    }
    if ((base == 16U) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = 'x';
    }
    else if ((base == 16U) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = 'X';
    }
    else if ((base == 2U) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
      buf[len++] = 'b';
    }
    if (len < PRINTF_NTOA_BUFFER_SIZE) {
      buf[len++] = '0';
    }
  }

  if (len < PRINTF_NTOA_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++] = ' ';
    }
  }

  return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
}


// internal itoa for 'long' type
static size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long value, bool negative, unsigned long base, unsigned int prec, unsigned int width, unsigned int flags)
{
  char buf[PRINTF_NTOA_BUFFER_SIZE];
  size_t len = 0U;

  // no hash for 0 values
  if (!value) {
    flags &= ~FLAGS_HASH;
  }

  // write if precision != 0 and value is != 0
  if (!(flags & FLAGS_PRECISION) || value) {
    do {
      const char digit = (char)(value % base);
      buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
      value /= base;
    } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
  }

  return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
}


// internal itoa for 'long long' type
#if defined(PRINTF_SUPPORT_LONG_LONG)
static size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative, unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags)
{
  char buf[PRINTF_NTOA_BUFFER_SIZE];
  size_t len = 0U;

  // no hash for 0 values
  if (!value) {
    flags &= ~FLAGS_HASH;
  }

  // write if precision != 0 and value is != 0
  if (!(flags & FLAGS_PRECISION) || value) {
    do {
      const char digit = (char)(value % base);
      buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
      value /= base;
    } while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
  }

  return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
}
#endif  // PRINTF_SUPPORT_LONG_LONG


#if defined(PRINTF_SUPPORT_FLOAT)

#if defined(PRINTF_SUPPORT_EXPONENTIAL)
// forward declaration so that _ftoa can switch to exp notation for values > PRINTF_MAX_FLOAT
static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags);
#endif


// internal ftoa for fixed decimal floating point
static size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
{
  char buf[PRINTF_FTOA_BUFFER_SIZE];
  size_t len  = 0U;
  double diff = 0.0;

  // powers of 10
  static const double pow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };

  // test for special values
  if (value != value)
    return _out_rev(out, buffer, idx, maxlen, "nan", 3, width, flags);
  if (value < -DBL_MAX)
    return _out_rev(out, buffer, idx, maxlen, "fni-", 4, width, flags);
  if (value > DBL_MAX)
    return _out_rev(out, buffer, idx, maxlen, (flags & FLAGS_PLUS) ? "fni+" : "fni", (flags & FLAGS_PLUS) ? 4U : 3U, width, flags);

  // test for very large values
  // standard printf behavior is to print EVERY whole number digit -- which could be 100s of characters overflowing your buffers == bad
  if ((value > PRINTF_MAX_FLOAT) || (value < -PRINTF_MAX_FLOAT)) {
#if defined(PRINTF_SUPPORT_EXPONENTIAL)
    return _etoa(out, buffer, idx, maxlen, value, prec, width, flags);
#else
    return 0U;
#endif
  }

  // test for negative
  bool negative = false;
  if (value < 0) {
    negative = true;
    value = 0 - value;
  }

  // set default precision, if not set explicitly
  if (!(flags & FLAGS_PRECISION)) {
    prec = PRINTF_DEFAULT_FLOAT_PRECISION;
  }
  // limit precision to 9, cause a prec >= 10 can lead to overflow errors
  while ((len < PRINTF_FTOA_BUFFER_SIZE) && (prec > 9U)) {
    buf[len++] = '0';
    prec--;
  }

  int whole = (int)value;
  double tmp = (value - whole) * pow10[prec];
  unsigned long frac = (unsigned long)tmp;
  diff = tmp - frac;

  if (diff > 0.5) {
    ++frac;
    // handle rollover, e.g. case 0.99 with prec 1 is 1.0
    if (frac >= pow10[prec]) {
      frac = 0;
      ++whole;
    }
  }
  else if (diff < 0.5) {
  }
  else if ((frac == 0U) || (frac & 1U)) {
    // if halfway, round up if odd OR if last digit is 0
    ++frac;
  }

  if (prec == 0U) {
    diff = value - (double)whole;
    if ((!(diff < 0.5) || (diff > 0.5)) && (whole & 1)) {
      // exactly 0.5 and ODD, then round up
      // 1.5 -> 2, but 2.5 -> 2
      ++whole;
    }
  }
  else {
    unsigned int count = prec;
    // now do fractional part, as an unsigned number
    while (len < PRINTF_FTOA_BUFFER_SIZE) {
      --count;
      buf[len++] = (char)(48U + (frac % 10U));
      if (!(frac /= 10U)) {
        break;
      }
    }
    // add extra 0s
    while ((len < PRINTF_FTOA_BUFFER_SIZE) && (count-- > 0U)) {
      buf[len++] = '0';
    }
    if (len < PRINTF_FTOA_BUFFER_SIZE) {
      // add decimal
      buf[len++] = '.';
    }
  }

  // do whole part, number is reversed
  while (len < PRINTF_FTOA_BUFFER_SIZE) {
    buf[len++] = (char)(48 + (whole % 10));
    if (!(whole /= 10)) {
      break;
    }
  }

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

  if (len < PRINTF_FTOA_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++] = ' ';
    }
  }

  return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
}


#if defined(PRINTF_SUPPORT_EXPONENTIAL)
// internal ftoa variant for exponential floating-point type, contributed by Martijn Jasperse <m.jasperse@gmail.com>
static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
{
  // check for NaN and special values
  if ((value != value) || (value > DBL_MAX) || (value < -DBL_MAX)) {
    return _ftoa(out, buffer, idx, maxlen, value, prec, width, flags);
  }

  // determine the sign
  const bool negative = value < 0;
  if (negative) {
    value = -value;
  }

  // default precision
  if (!(flags & FLAGS_PRECISION)) {
    prec = PRINTF_DEFAULT_FLOAT_PRECISION;
  }

  // determine the decimal exponent
  // based on the algorithm by David Gay (https://www.ampl.com/netlib/fp/dtoa.c)
  union {
    uint64_t U;
    double   F;
  } conv;

  conv.F = value;
  int exp2 = (int)((conv.U >> 52U) & 0x07FFU) - 1023;           // effectively log2
  conv.U = (conv.U & ((1ULL << 52U) - 1U)) | (1023ULL << 52U);  // drop the exponent so conv.F is now in [1,2)
  // now approximate log10 from the log2 integer part and an expansion of ln around 1.5
  int expval = (int)(0.1760912590558 + exp2 * 0.301029995663981 + (conv.F - 1.5) * 0.289529654602168);
  // now we want to compute 10^expval but we want to be sure it won't overflow
  exp2 = (int)(expval * 3.321928094887362 + 0.5);
  const double z  = expval * 2.302585092994046 - exp2 * 0.6931471805599453;
  const double z2 = z * z;
  conv.U = (uint64_t)(exp2 + 1023) << 52U;
  // compute exp(z) using continued fractions, see https://en.wikipedia.org/wiki/Exponential_function#Continued_fractions_for_ex
  conv.F *= 1 + 2 * z / (2 - z + (z2 / (6 + (z2 / (10 + z2 / 14)))));
  // correct for rounding errors
  if (value < conv.F) {
    expval--;
    conv.F /= 10;
  }

  // the exponent format is "%+03d" and largest value is "307", so set aside 4-5 characters
  unsigned int minwidth = ((expval < 100) && (expval > -100)) ? 4U : 5U;

  // in "%g" mode, "prec" is the number of *significant figures* not decimals
  if (flags & FLAGS_ADAPT_EXP) {
    // do we want to fall-back to "%f" mode?
    if ((value >= 1e-4) && (value < 1e6)) {
      if ((int)prec > expval) {
        prec = (unsigned)((int)prec - expval - 1);
      }
      else {
        prec = 0;
      }
      flags |= FLAGS_PRECISION;   // make sure _ftoa respects precision
      // no characters in exponent
      minwidth = 0U;
      expval   = 0;
    }
    else {
      // we use one sigfig for the whole part
      if ((prec > 0) && (flags & FLAGS_PRECISION)) {
        --prec;
      }
    }
  }

  // will everything fit?
  unsigned int fwidth = width;
  if (width > minwidth) {
    // we didn't fall-back so subtract the characters required for the exponent
    fwidth -= minwidth;
  } else {
    // not enough characters, so go back to default sizing
    fwidth = 0U;
  }
  if ((flags & FLAGS_LEFT) && minwidth) {
    // if we're padding on the right, DON'T pad the floating part
    fwidth = 0U;
  }

  // rescale the float value
  if (expval) {
    value /= conv.F;
  }

  // output the floating part
  const size_t start_idx = idx;
  idx = _ftoa(out, buffer, idx, maxlen, negative ? -value : value, prec, fwidth, flags & ~FLAGS_ADAPT_EXP);

  // output the exponent part
  if (minwidth) {
    // output the exponential symbol
    out((flags & FLAGS_UPPERCASE) ? 'E' : 'e', buffer, idx++, maxlen);
    // output the exponent value
    idx = _ntoa_long(out, buffer, idx, maxlen, (expval < 0) ? -expval : expval, expval < 0, 10, 0, minwidth-1, FLAGS_ZEROPAD | FLAGS_PLUS);
    // might need to right-pad spaces
    if (flags & FLAGS_LEFT) {
      while (idx - start_idx < width) out(' ', buffer, idx++, maxlen);
    }
  }
  return idx;
}
#endif  // PRINTF_SUPPORT_EXPONENTIAL
#endif  // PRINTF_SUPPORT_FLOAT


// internal vsnprintf
static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const char* format, va_list va)
{
  unsigned int flags, width, precision, n;
  size_t idx = 0U;

  if (!buffer) {
    // use null output function
    out = _out_null;
  }

  while (*format)
  {
    // format specifier?  %[flags][width][.precision][length]
    if (*format != '%') {
      // no
      out(*format, buffer, idx++, maxlen);
      format++;
      continue;
    }
    else {
      // yes, evaluate it
      format++;
    }

    // evaluate flags
    flags = 0U;
    do {
      switch (*format) {
        case '0': flags |= FLAGS_ZEROPAD; format++; n = 1U; break;
        case '-': flags |= FLAGS_LEFT;    format++; n = 1U; break;
        case '+': flags |= FLAGS_PLUS;    format++; n = 1U; break;
        case ' ': flags |= FLAGS_SPACE;   format++; n = 1U; break;
        case '#': flags |= FLAGS_HASH;    format++; n = 1U; break;
        default :                                   n = 0U; break;
      }
    } while (n);

    // evaluate width field
    width = 0U;
    if (_is_digit(*format)) {
      width = _atoi(&format);
    }
    else if (*format == '*') {
      const int w = va_arg(va, int);
      if (w < 0) {
        flags |= FLAGS_LEFT;    // reverse padding
        width = (unsigned int)-w;
      }
      else {
        width = (unsigned int)w;
      }
      format++;
    }

    // evaluate precision field
    precision = 0U;
    if (*format == '.') {
      flags |= FLAGS_PRECISION;
      format++;
      if (_is_digit(*format)) {
        precision = _atoi(&format);
      }
      else if (*format == '*') {
        const int prec = (int)va_arg(va, int);
        precision = prec > 0 ? (unsigned int)prec : 0U;
        format++;
      }
    }

    // evaluate length field
    switch (*format) {
      case 'l' :
        flags |= FLAGS_LONG;
        format++;
        if (*format == 'l') {
          flags |= FLAGS_LONG_LONG;
          format++;
        }
        break;
      case 'h' :
        flags |= FLAGS_SHORT;
        format++;
        if (*format == 'h') {
          flags |= FLAGS_CHAR;
          format++;
        }
        break;
#if defined(PRINTF_SUPPORT_PTRDIFF_T)
      case 't' :
        flags |= (sizeof(ptrdiff_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
        format++;
        break;
#endif
      case 'j' :
        flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
        format++;
        break;
      case 'z' :
        flags |= (sizeof(size_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
        format++;
        break;
      default :
        break;
    }

    // evaluate specifier
    switch (*format) {
      case 'd' :
      case 'i' :
      case 'u' :
      case 'x' :
      case 'X' :
      case 'o' :
      case 'b' : {
        // set the base
        unsigned int base;
        if (*format == 'x' || *format == 'X') {
          base = 16U;
        }
        else if (*format == 'o') {
          base =  8U;
        }
        else if (*format == 'b') {
          base =  2U;
        }
        else {
          base = 10U;
          flags &= ~FLAGS_HASH;   // no hash for dec format
        }
        // uppercase
        if (*format == 'X') {
          flags |= FLAGS_UPPERCASE;
        }

        // no plus or space flag for u, x, X, o, b
        if ((*format != 'i') && (*format != 'd')) {
          flags &= ~(FLAGS_PLUS | FLAGS_SPACE);
        }

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

        // convert the integer
        if ((*format == 'i') || (*format == 'd')) {
          // signed
          if (flags & FLAGS_LONG_LONG) {
#if defined(PRINTF_SUPPORT_LONG_LONG)
            const long long value = va_arg(va, long long);
            idx = _ntoa_long_long(out, buffer, idx, maxlen, (unsigned long long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
#endif
          }
          else if (flags & FLAGS_LONG) {
            const long value = va_arg(va, long);
            idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
          }
          else {
            const int value = (flags & FLAGS_CHAR) ? (char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int);
            idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
          }
        }
        else {
          // unsigned
          if (flags & FLAGS_LONG_LONG) {
#if defined(PRINTF_SUPPORT_LONG_LONG)
            idx = _ntoa_long_long(out, buffer, idx, maxlen, va_arg(va, unsigned long long), false, base, precision, width, flags);
#endif
          }
          else if (flags & FLAGS_LONG) {
            idx = _ntoa_long(out, buffer, idx, maxlen, va_arg(va, unsigned long), false, base, precision, width, flags);
          }
          else {
            const unsigned int value = (flags & FLAGS_CHAR) ? (unsigned char)va_arg(va, unsigned int) : (flags & FLAGS_SHORT) ? (unsigned short int)va_arg(va, unsigned int) : va_arg(va, unsigned int);
            idx = _ntoa_long(out, buffer, idx, maxlen, value, false, base, precision, width, flags);
          }
        }
        format++;
        break;
      }
#if defined(PRINTF_SUPPORT_FLOAT)
      case 'f' :
      case 'F' :
        if (*format == 'F') flags |= FLAGS_UPPERCASE;
        idx = _ftoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
        format++;
        break;
#if defined(PRINTF_SUPPORT_EXPONENTIAL)
      case 'e':
      case 'E':
      case 'g':
      case 'G':
        if ((*format == 'g')||(*format == 'G')) flags |= FLAGS_ADAPT_EXP;
        if ((*format == 'E')||(*format == 'G')) flags |= FLAGS_UPPERCASE;
        idx = _etoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
        format++;
        break;
#endif  // PRINTF_SUPPORT_EXPONENTIAL
#endif  // PRINTF_SUPPORT_FLOAT
      case 'c' : {
        unsigned int l = 1U;
        // pre padding
        if (!(flags & FLAGS_LEFT)) {
          while (l++ < width) {
            out(' ', buffer, idx++, maxlen);
          }
        }
        // char output
        out((char)va_arg(va, int), buffer, idx++, maxlen);
        // post padding
        if (flags & FLAGS_LEFT) {
          while (l++ < width) {
            out(' ', buffer, idx++, maxlen);
          }
        }
        format++;
        break;
      }

      case 's' : {
        const char* p = va_arg(va, char*);
        unsigned int l = _strnlen_s(p, precision ? precision : (size_t)-1);
        // pre padding
        if (flags & FLAGS_PRECISION) {
          l = (l < precision ? l : precision);
        }
        if (!(flags & FLAGS_LEFT)) {
          while (l++ < width) {
            out(' ', buffer, idx++, maxlen);
          }
        }
        // string output
        while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
          out(*(p++), buffer, idx++, maxlen);
        }
        // post padding
        if (flags & FLAGS_LEFT) {
          while (l++ < width) {
            out(' ', buffer, idx++, maxlen);
          }
        }
        format++;
        break;
      }

      case 'p' : {
        width = sizeof(void*) * 2U;
        flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
#if defined(PRINTF_SUPPORT_LONG_LONG)
        const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
        if (is_ll) {
          idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16U, precision, width, flags);
        }
        else {
#endif
          idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)((uintptr_t)va_arg(va, void*)), false, 16U, precision, width, flags);
#if defined(PRINTF_SUPPORT_LONG_LONG)
        }
#endif
        format++;
        break;
      }

      case '%' :
        out('%', buffer, idx++, maxlen);
        format++;
        break;

      default :
        out(*format, buffer, idx++, maxlen);
        format++;
        break;
    }
  }

  // termination
  out((char)0, buffer, idx < maxlen ? idx : maxlen - 1U, maxlen);

  // return written chars without terminating \0
  return (int)idx;
}


///////////////////////////////////////////////////////////////////////////////

int printf_(const char* format, ...)
{
  va_list va;
  va_start(va, format);
  char buffer[1];
  const int ret = _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
  va_end(va);
  return ret;
}


int sprintf_(char* buffer, const char* format, ...)
{
  va_list va;
  va_start(va, format);
  const int ret = _vsnprintf(_out_buffer, buffer, (size_t)-1, format, va);
  va_end(va);
  return ret;
}


int snprintf_(char* buffer, size_t count, const char* format, ...)
{
  va_list va;
  va_start(va, format);
  const int ret = _vsnprintf(_out_buffer, buffer, count, format, va);
  va_end(va);
  return ret;
}


int vprintf_(const char* format, va_list va)
{
  char buffer[1];
  return _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
}


int vsnprintf_(char* buffer, size_t count, const char* format, va_list va)
{
  return _vsnprintf(_out_buffer, buffer, count, format, va);
}


int fctprintf(void (*out)(char character, void* arg), void* arg, const char* format, ...)
{
  va_list va;
  va_start(va, format);
  const out_fct_wrap_type out_fct_wrap = { out, arg };
  const int ret = _vsnprintf(_out_fct, (char*)(uintptr_t)&out_fct_wrap, (size_t)-1, format, va);
  va_end(va);
  return ret;
}