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#include <libk/stdio.h>
#include <libk/string.h>
#include <limits.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>

/* warning: narrowing conversion of 'uc' from 'unsigned char' to 'char' is
 * ill-formed in C++11 [-Wnarrowing] */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnarrowing"

int
sprintf(char *str, const char *fmt, ...)
{
  int err;
  va_list ap;
  va_start(ap, fmt);
  err = vsprintf(str, fmt, ap);
  va_end(ap);
  return err;
}
int
snprintf(char *str, size_t len, const char *fmt, ...)
{
  int err;
  va_list ap;
  va_start(ap, fmt);
  err = vsnprintf(str, len, fmt, ap);
  va_end(ap);
  return err;
}
int
vsprintf(char *str, const char *fmt, va_list ap)
{
  return vsnprintf(str, INT_MAX, fmt, ap);
}
struct _output_args {
  char *outstr;
  size_t len;
  size_t pos;
};
static int
_vsnprintf_output(const char *str, size_t len, void *state)
{
  struct _output_args *args = (struct _output_args *) state;
  size_t count = 0;
  while (count < len) {
    if (args->pos < args->len) {
      args->outstr[args->pos++] = *str;
    }
    str++;
    count++;
  }
  return count;
}
int
vsnprintf(char *str, size_t len, const char *fmt, va_list ap)
{
  struct _output_args args;
  int wlen;
  args.outstr = str;
  args.len = len;
  args.pos = 0;
  wlen = _printf_engine(&_vsnprintf_output, (void *) &args, fmt, ap);
  if (args.pos >= len)
    str[len - 1] = '\0';
  else
    str[wlen] = '\0';
  return wlen;
}
#define LONGFLAG 0x00000001
#define LONGLONGFLAG 0x00000002
#define HALFFLAG 0x00000004
#define HALFHALFFLAG 0x00000008
#define SIZETFLAG 0x00000010
#define INTMAXFLAG 0x00000020
#define PTRDIFFFLAG 0x00000040
#define ALTFLAG 0x00000080
#define CAPSFLAG 0x00000100
#define SHOWSIGNFLAG 0x00000200
#define SIGNEDFLAG 0x00000400
#define LEFTFORMATFLAG 0x00000800
#define LEADZEROFLAG 0x00001000
#define BLANKPOSFLAG 0x00002000
static char *
longlong_to_string(
    char *buf, uint64_t n, size_t len, unsigned int flag, char *signchar)
{
  size_t pos = len;
  int negative = 0;
  if ((flag & SIGNEDFLAG) && (int64_t) n < 0) {
    negative = 1;
    n = -n;
  }
  buf[--pos] = 0;
  /* only do the math if the number is >= 10 */
  while (n >= 10) {
    int digit = n % 10;
    n /= 10;
    buf[--pos] = digit + '0';
  }
  buf[--pos] = n + '0';
  if (negative)
    *signchar = '-';
  else if ((flag & SHOWSIGNFLAG))
    *signchar = '+';
  else if ((flag & BLANKPOSFLAG))
    *signchar = ' ';
  else
    *signchar = '\0';
  return &buf[pos];
}
static const char hextable[] = { '0', '1', '2', '3', '4', '5', '6', '7',
                                 '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
static const char hextable_caps[] = { '0', '1', '2', '3', '4', '5', '6', '7',
                                      '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
static char *
longlong_to_hexstring(char *buf, uint64_t u, size_t len, unsigned int flag)
{
  size_t pos = len;
  const char *table = (flag & CAPSFLAG) ? hextable_caps : hextable;
  buf[--pos] = 0;
  do {
    unsigned int digit = u % 16;
    u /= 16;
    buf[--pos] = table[digit];
  } while (u != 0);
  return &buf[pos];
}
#if FLOAT_PRINTF
union double_int {
  double d;
  uint64_t i;
};
#define OUT(c) buf[pos++] = (c)
#define OUTSTR(str)                                                           \
  do {                                                                        \
    for (size_t i = 0; (str)[i] != 0; i++)                                    \
      OUT((str)[i]);                                                          \
  } while (0)
/* print up to a 4 digit exponent as string, with sign */
static size_t
exponent_to_string(char *buf, int32_t exponent)
{
  size_t pos = 0;
  /* handle sign */
  if (exponent < 0) {
    OUT('-');
    exponent = -exponent;
  } else {
    OUT('+');
  }
  /* see how far we need to bump into the string to print from the right */
  if (exponent >= 1000)
    pos += 4;
  else if (exponent >= 100)
    pos += 3;
  else if (exponent >= 10)
    pos += 2;
  else
    pos++;
  /* print decimal string, from the right */
  uint i = pos;
  do {
    uint digit = (uint32_t) exponent % 10;
    buf[--i] = digit + '0';
    exponent /= 10;
  } while (exponent != 0);
  /* return number of characters printed */
  return pos;
}
static char *
double_to_string(char *buf, size_t len, double d, uint flag)
{
  size_t pos = 0;
  union double_int du = { d };
  uint32_t exponent = (du.i >> 52) & 0x7ff;
  uint64_t fraction = (du.i & ((1ULL << 52) - 1));
  bool neg = !!(du.i & (1ULL << 63));
  /* start constructing the string */
  if (neg) {
    OUT('-');
    d = -d;
  }
  /* longest:
   * 179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000o
   */
  /* look for special cases */
  if (exponent == 0x7ff) {
    if (fraction == 0) {
      /* infinity */
      if (flag & CAPSFLAG)
        OUTSTR("INF");
      else
        OUTSTR("inf");
    } else {
      /* NaN */
      if (flag & CAPSFLAG)
        OUTSTR("NAN");
      else
        OUTSTR("nan");
    }
  } else if (exponent == 0) {
    if (fraction == 0) {
      /* zero */
      OUTSTR("0.000000");
    } else {
      /* denormalized */
      /* XXX does not handle */
      if (flag & CAPSFLAG)
        OUTSTR("DEN");
      else
        OUTSTR("den");
    }
  } else {
    /* see if it's in the range of floats we can easily print */
    int exponent_signed = exponent - 1023;
    if (exponent_signed < -52 || exponent_signed > 52) {
      OUTSTR("<range>");
    } else {
      /* start by walking backwards through the string */
#define OUTREV(c)                                                             \
  do {                                                                        \
    if (&buf[pos] == buf)                                                     \
      goto done;                                                              \
    else                                                                      \
      buf[--pos] = (c);                                                       \
  } while (0)
      pos = len;
      OUTREV(0);
      /* reserve space for the fractional component first */
      for (int i = 0; i <= 6; i++)
        OUTREV('0');
      size_t decimal_spot = pos;
      /* print the integer portion */
      uint64_t u;
      if (exponent_signed >= 0) {
        u = fraction;
        u |= (1ULL << 52);
        u >>= (52 - exponent_signed);
        char *s = longlong_to_string(buf, u, pos + 1, flag, &(char){ 0 });
        pos = s - buf;
      } else {
        /* exponent is negative */
        u = 0;
        OUTREV('0');
      }
      buf[decimal_spot] = '.';
      /* handle the fractional part */
      uint32_t frac = ((d - u) * 1000000) + .5;
      uint i = decimal_spot + 6 + 1;
      while (frac != 0) {
        uint digit = frac % 10;
        buf[--i] = digit + '0';
        frac /= 10;
      }
      if (neg)
        OUTREV('-');
    done:
      /* separate return path, since we've been walking backwards through the
       * string */
      return &buf[pos];
    }
#undef OUTREV
  }
  buf[pos] = 0;
  return buf;
}
static char *
double_to_hexstring(char *buf, size_t len, double d, uint flag)
{
  size_t pos = 0;
  union double_int u = { d };
  uint32_t exponent = (u.i >> 52) & 0x7ff;
  uint64_t fraction = (u.i & ((1ULL << 52) - 1));
  bool neg = !!(u.i & (1ULL << 63));
  /* start constructing the string */
  if (neg) {
    OUT('-');
  }
  /* look for special cases */
  if (exponent == 0x7ff) {
    if (fraction == 0) {
      /* infinity */
      if (flag & CAPSFLAG)
        OUTSTR("INF");
      else
        OUTSTR("inf");
    } else {
      /* NaN */
      if (flag & CAPSFLAG)
        OUTSTR("NAN");
      else
        OUTSTR("nan");
    }
  } else if (exponent == 0) {
    if (fraction == 0) {
      /* zero */
      if (flag & CAPSFLAG)
        OUTSTR("0X0P+0");
      else
        OUTSTR("0x0p+0");
    } else {
      /* denormalized */
      /* XXX does not handle */
      if (flag & CAPSFLAG)
        OUTSTR("DEN");
      else
        OUTSTR("den");
    }
  } else {
    /* regular normalized numbers:
     * 0x1p+1
     * 0x1.0000000000001p+1
     * 0X1.FFFFFFFFFFFFFP+1023
     * 0x1.FFFFFFFFFFFFFP+1023
     */
    int exponent_signed = exponent - 1023;
    /* implicit 1. */
    if (flag & CAPSFLAG)
      OUTSTR("0X1");
    else
      OUTSTR("0x1");
    /* select the appropriate hex case table */
    const char *table = (flag & CAPSFLAG) ? hextable_caps : hextable;
    int zero_count = 0;
    bool output_dot = false;
    for (int i = 52 - 4; i >= 0; i -= 4) {
      uint digit = (fraction >> i) & 0xf;
      if (digit == 0) {
        zero_count++;
      } else {
        /* output a . the first time we output a char */
        if (!output_dot) {
          OUT('.');
          output_dot = true;
        }
        /* if we have a non zero digit, see if we need to output a string of
         * zeros */
        while (zero_count > 0) {
          OUT('0');
          zero_count--;
        }
        buf[pos++] = table[digit];
      }
    }
    /* handle the exponent */
    buf[pos++] = (flag & CAPSFLAG) ? 'P' : 'p';
    pos += exponent_to_string(&buf[pos], exponent_signed);
  }
  buf[pos] = 0;
  return buf;
}
#undef OUT
#undef OUTSTR
#endif // FLOAT_PRINTF
int
_printf_engine(_printf_engine_output_func out,
               void *state,
               const char *fmt,
               va_list ap)
{
  int err = 0;
  char c;
  unsigned char uc;
  const char *s;
  size_t string_len;
  uint64_t n;
  void *ptr;
  int flags;
  unsigned int format_num;
  char signchar;
  size_t chars_written = 0;
  char num_buffer[32];
#define OUTPUT_STRING(str, len)                                               \
  do {                                                                        \
    err = out(str, len, state);                                               \
    if (err < 0) {                                                            \
      goto exit;                                                              \
    } else {                                                                  \
      chars_written += err;                                                   \
    }                                                                         \
  } while (0)
#define OUTPUT_CHAR(c)                                                        \
  do {                                                                        \
    char __temp[1] = { c };                                                   \
    OUTPUT_STRING(__temp, 1);                                                 \
  } while (0)
  for (;;) {
    /* reset the format state */
    flags = 0;
    format_num = 0;
    signchar = '\0';
    /* handle regular chars that aren't format related */
    s = fmt;
    string_len = 0;
    while ((c = *fmt++) != 0) {
      if (c == '%')
        break; /* we saw a '%', break and start parsing format */
      string_len++;
    }
    /* output the string we've accumulated */
    OUTPUT_STRING(s, string_len);
    /* make sure we haven't just hit the end of the string */
    if (c == 0)
      break;
  next_format:
    /* grab the next format character */
    c = *fmt++;
    if (c == 0)
      break;
    switch (c) {
    case '0':
    case '1':
    case '2':
    case '3':
    case '4':
    case '5':
    case '6':
    case '7':
    case '8':
    case '9':
      if (c == '0' && format_num == 0)
        flags |= LEADZEROFLAG;
      format_num *= 10;
      format_num += c - '0';
      goto next_format;
    case '.':
      /* XXX for now eat numeric formatting */
      goto next_format;
    case '%':
      OUTPUT_CHAR('%');
      break;
    case 'c':
      uc = va_arg(ap, unsigned int);
      OUTPUT_CHAR(uc);
      break;
    case 's':
      s = va_arg(ap, const char *);
      if (s == 0)
        s = "<null>";
      flags &= ~LEADZEROFLAG; /* doesn't make sense for strings */
      goto _output_string;
    case '-':
      flags |= LEFTFORMATFLAG;
      goto next_format;
    case '+':
      flags |= SHOWSIGNFLAG;
      goto next_format;
    case ' ':
      flags |= BLANKPOSFLAG;
      goto next_format;
    case '#':
      flags |= ALTFLAG;
      goto next_format;
    case 'l':
      if (flags & LONGFLAG)
        flags |= LONGLONGFLAG;
      flags |= LONGFLAG;
      goto next_format;
    case 'h':
      if (flags & HALFFLAG)
        flags |= HALFHALFFLAG;
      flags |= HALFFLAG;
      goto next_format;
    case 'z':
      flags |= SIZETFLAG;
      goto next_format;
    case 'j':
      flags |= INTMAXFLAG;
      goto next_format;
    case 't':
      flags |= PTRDIFFFLAG;
      goto next_format;
    case 'i':
    case 'd':
      n = (flags & LONGLONGFLAG)   ? va_arg(ap, int64_t)
          : (flags & LONGFLAG)     ? va_arg(ap, long)
          : (flags & HALFHALFFLAG) ? (signed char) va_arg(ap, int)
          : (flags & HALFFLAG)     ? (short) va_arg(ap, int)
          : (flags & SIZETFLAG)    ? va_arg(ap, size_t)
          : (flags & INTMAXFLAG)   ? va_arg(ap, intmax_t)
          : (flags & PTRDIFFFLAG)  ? va_arg(ap, ptrdiff_t)
                                   : va_arg(ap, int);
      flags |= SIGNEDFLAG;
      s = longlong_to_string(
          num_buffer, n, sizeof(num_buffer), flags, &signchar);
      goto _output_string;
    case 'u':
      n = (flags & LONGLONGFLAG)   ? va_arg(ap, uint64_t)
          : (flags & LONGFLAG)     ? va_arg(ap, unsigned long)
          : (flags & HALFHALFFLAG) ? (unsigned char) va_arg(ap, unsigned int)
          : (flags & HALFFLAG)     ? (unsigned short) va_arg(ap, unsigned int)
          : (flags & SIZETFLAG)    ? va_arg(ap, size_t)
          : (flags & INTMAXFLAG)   ? va_arg(ap, uintmax_t)
          : (flags & PTRDIFFFLAG)  ? (uintptr_t) va_arg(ap, ptrdiff_t)
                                   : va_arg(ap, unsigned int);
      s = longlong_to_string(
          num_buffer, n, sizeof(num_buffer), flags, &signchar);
      goto _output_string;
    case 'p':
      flags |= SIZETFLAG | ALTFLAG;
      goto hex;
    case 'X':
      flags |= CAPSFLAG;
      /* fallthrough */
    hex:
    case 'x':
      n = (flags & LONGLONGFLAG)   ? va_arg(ap, uint64_t)
          : (flags & LONGFLAG)     ? va_arg(ap, unsigned long)
          : (flags & HALFHALFFLAG) ? (unsigned char) va_arg(ap, unsigned int)
          : (flags & HALFFLAG)     ? (unsigned short) va_arg(ap, unsigned int)
          : (flags & SIZETFLAG)    ? va_arg(ap, size_t)
          : (flags & INTMAXFLAG)   ? va_arg(ap, uintmax_t)
          : (flags & PTRDIFFFLAG)  ? (uintptr_t) va_arg(ap, ptrdiff_t)
                                   : va_arg(ap, unsigned int);
      s = longlong_to_hexstring(num_buffer, n, sizeof(num_buffer), flags);
      /* Normalize c, since code in _output_string needs to know that this is
       * printing hex */
      c = 'x';
      /* Altflag processing should be bypassed when n == 0 so that 0x is not
       * prepended to it */
      if (n == 0) {
        flags &= ~ALTFLAG;
      }
      goto _output_string;
    case 'n':
      ptr = va_arg(ap, void *);
      if (flags & LONGLONGFLAG)
        *(int64_t *) ptr = chars_written;
      else if (flags & LONGFLAG)
        *(long *) ptr = chars_written;
      else if (flags & HALFHALFFLAG)
        *(signed char *) ptr = chars_written;
      else if (flags & HALFFLAG)
        *(short *) ptr = chars_written;
      else if (flags & SIZETFLAG)
        *(size_t *) ptr = chars_written;
      else
        *(int *) ptr = chars_written;
      break;
#if FLOAT_PRINTF
    case 'F':
      flags |= CAPSFLAG;
    /* fallthrough */
    case 'f': {
      double d = va_arg(ap, double);
      s = double_to_string(num_buffer, sizeof(num_buffer), d, flags);
      goto _output_string;
    }
    case 'A':
      flags |= CAPSFLAG;
    /* fallthrough */
    case 'a': {
      double d = va_arg(ap, double);
      s = double_to_hexstring(num_buffer, sizeof(num_buffer), d, flags);
      goto _output_string;
    }
#endif
    default:
      OUTPUT_CHAR('%');
      OUTPUT_CHAR(c);
      break;
    }
    /* move on to the next field */
    continue;
    /* shared output code */
  _output_string:
    string_len = strlen(s);
    if (flags & LEFTFORMATFLAG) {
      /* left justify the text */
      OUTPUT_STRING(s, string_len);
      unsigned int written = err;
      /* pad to the right (if necessary) */
      for (; format_num > written; format_num--)
        OUTPUT_CHAR(' ');
    } else {
      /* right justify the text (digits) */
      /* if we're going to print a sign digit,
         it'll chew up one byte of the format size */
      if (signchar != '\0' && format_num > 0)
        format_num--;
      /* output the sign char before the leading zeros */
      if (flags & LEADZEROFLAG && signchar != '\0')
        OUTPUT_CHAR(signchar);
      /* Handle (altflag) printing 0x before the number */
      /* Note that this needs to be done before padding the number */
      if (c == 'x' && (flags & ALTFLAG)) {
        OUTPUT_CHAR('0');
        OUTPUT_CHAR(flags & CAPSFLAG ? 'X' : 'x');
        /* Width is adjusted so i.e printf("%#04x", 0x02) -> 0x02 instead of
         * 0x0002 */
        if (format_num >= 2) {
          format_num -= 2;
        }
      }
      /* pad according to the format string */
      for (; format_num > string_len; format_num--)
        OUTPUT_CHAR(flags & LEADZEROFLAG ? '0' : ' ');
      /* if not leading zeros, output the sign char just before the number */
      if (!(flags & LEADZEROFLAG) && signchar != '\0')
        OUTPUT_CHAR(signchar);
      /* output the string */
      OUTPUT_STRING(s, string_len);
    }
    continue;
  }
#undef OUTPUT_STRING
#undef OUTPUT_CHAR
exit:
  return (err < 0) ? err : (int) chars_written;
}

#pragma GCC diagnostic pop