在syslinux-2.11-1中

#ident "$Id: conio.c,v 1.7 2003/04/10 06:28:08 hpa Exp $"
/* ----------------------------------------------------------------------- *
 *  
 *   Copyright 2001 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Bostom MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * conio.c
 *
 * Output to the screen
 */

#include <stdint.h>
#include "memdisk.h"
#include "conio.h"

int putchar(int ch)
{
  com32sys_t regs;

  if ( ch == '\n' ) {
    /* \n -&gt; \r\n */
    putchar('\r');
  }
 
  regs.eax.w[0] = 0x0e00|(ch&0xff);
  syscall(0x10, &regs, NULL);

  return ch;
}

int puts(const char *s)
{
  int count = 0;

  while ( *s ) {
    putchar(*s);
    count++;
    s++;
  }

  return count;
}

/*
 * Oh, it's a waste of space, but oh-so-yummy for debugging.  It's just
 * initialization code anyway, so it doesn't take up space when we're
 * actually running.  This version of printf() does not include 64-bit
 * support.  "Live with it."
 *
 * Most of this code was shamelessly snarfed from the Linux kernel, then
 * modified.
 */

static inline int
isdigit(int ch)
{
  return (ch &gt;= '0') && (ch <= '9');
}

static int skip_atoi(const char **s)
{
  int i=0;
 
  while (isdigit(**s))
    i = i*10 + *((*s)++) - '0';
  return i;
}

unsigned int atou(const char *s)
{
  unsigned int i = 0;
  while (isdigit(*s))
    i = i*10 + (*s++ - '0');
  return i;
}

static int strnlen(const char *s, int maxlen)
{
  const char *es = s;
  while ( *es && maxlen ) {
    es++; maxlen--;
  }

  return (es-s);
}

#define ZEROPAD    1        /* pad with zero */
#define SIGN    2        /* unsigned/signed long */
#define PLUS    4        /* show plus */
#define SPACE    8        /* space if plus */
#define LEFT    16        /* left justified */
#define SPECIAL    32        /* 0x */
#define LARGE    64        /* use 'ABCDEF' instead of 'abcdef' */

#define do_div(n,base) ({ \
int __res; \
__res = ((unsigned long) n) % (unsigned) base; \
n = ((unsigned long) n) / (unsigned) base; \
__res; })

static char * number(char * str, long num, int base, int size, int precision
    ,int type)
{
  char c,sign,tmp[66];
  const char *digits="0123456789abcdefghijklmnopqrstuvwxyz";
  int i;
 
  if (type & LARGE)
    digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  if (type & LEFT)
    type &= ~ZEROPAD;
  if (base &lt; 2 || base > 36)
    return 0;
  c = (type & ZEROPAD) ? '0' : ' ';
  sign = 0;
  if (type & SIGN) {
    if (num < 0) {
      sign = '-';
      num = -num;
      size--;
    } else if (type & PLUS) {
      sign = '+';
      size--;
    } else if (type & SPACE) {
      sign = ' ';
      size--;
    }
  }
  if (type & SPECIAL) {
    if (base == 16)
      size -= 2;
    else if (base == 8)
      size--;
  }
  i = 0;
  if (num == 0)
    tmp[i++]='0';
  else while (num != 0)
    tmp[i++] = digits[do_div(num,base)];
  if (i > precision)
    precision = i;
  size -= precision;
  if (!(type&(ZEROPAD+LEFT)))
    while(size--&gt;0)
      *str++ = ' ';
  if (sign)
    *str++ = sign;
  if (type & SPECIAL) {
    if (base==8)
      *str++ = '0';
    else if (base==16) {
      *str++ = '0';
      *str++ = digits[33];
    }
  }
  if (!(type & LEFT))
    while (size-- &gt; 0)
      *str++ = c;
  while (i < precision--)
    *str++ = '0';
  while (i-- > 0)
    *str++ = tmp[i];
  while (size-- &gt; 0)
    *str++ = ' ';
  return str;
}

/* Forward decl. needed for IP address printing stuff... */
int sprintf(char * buf, const char *fmt, ...);

int vsprintf(char *buf, const char *fmt, va_list args)
{
  int len;
  unsigned long num;
  int i, base;
  char * str;
  const char *s;
 
  int flags;        /* flags to number() */
 
  int field_width;    /* width of output field */
  int precision;        /* min. # of digits for integers; max
                   number of chars for from string */
  int qualifier;        /* 'h', 'l', or 'L' for integer fields */
 
  for (str=buf ; *fmt ; ++fmt) {
    if (*fmt != '%') {
      *str++ = *fmt;
      continue;
    }
   
    /* process flags */
    flags = 0;
  repeat:
    ++fmt;        /* this also skips first '%' */
    switch (*fmt) {
    case '-': flags |= LEFT; goto repeat;
    case '+': flags |= PLUS; goto repeat;
    case ' ': flags |= SPACE; goto repeat;
    case '#': flags |= SPECIAL; goto repeat;
    case '0': flags |= ZEROPAD; goto repeat;
    }
   
    /* get field width */
    field_width = -1;
    if (isdigit(*fmt))
      field_width = skip_atoi(&fmt);
    else if (*fmt == '*') {
      ++fmt;
      /* it's the next argument */
      field_width = va_arg(args, int);
      if (field_width < 0) {
    field_width = -field_width;
    flags |= LEFT;
      }
    }
   
    /* get the precision */
    precision = -1;
    if (*fmt == '.') {
      ++fmt;   
      if (isdigit(*fmt))
    precision = skip_atoi(&fmt);
      else if (*fmt == '*') {
    ++fmt;
    /* it's the next argument */
    precision = va_arg(args, int);
      }
      if (precision &lt; 0)
    precision = 0;
    }
   
    /* get the conversion qualifier */
    qualifier = -1;
    if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
      qualifier = *fmt;
      ++fmt;
    }
   
    /* default base */
    base = 10;
   
    switch (*fmt) {
    case 'c':
      if (!(flags & LEFT))
    while (--field_width > 0)
      *str++ = ' ';
      *str++ = (unsigned char) va_arg(args, int);
      while (--field_width &gt; 0)
    *str++ = ' ';
      continue;
     
    case 's':
      s = va_arg(args, char *);
      len = strnlen(s, precision);
     
      if (!(flags & LEFT))
    while (len &lt; field_width--)
      *str++ = ' ';
      for (i = 0; i &lt; len; ++i)
    *str++ = *s++;
      while (len &lt; field_width--)
    *str++ = ' ';
      continue;
     
    case 'p':
      if (field_width == -1) {
    field_width = 2*sizeof(void *);
    flags |= ZEROPAD;
      }
      str = number(str,
           (unsigned long) va_arg(args, void *), 16,
           field_width, precision, flags);
      continue;
     
     
    case 'n':
      if (qualifier == 'l') {
    long * ip = va_arg(args, long *);
    *ip = (str - buf);
      } else {
    int * ip = va_arg(args, int *);
    *ip = (str - buf);
      }
      continue;
     
    case '%':
      *str++ = '%';
      continue;
     
      /* integer number formats - set up the flags and "break" */
    case 'o':
      base = 8;
      break;
     
    case 'X':
      flags |= LARGE;
    case 'x':
      base = 16;
      break;
     
    case 'd':
    case 'i':
      flags |= SIGN;
    case 'u':
      break;
     
    default:
      *str++ = '%';
      if (*fmt)
    *str++ = *fmt;
      else
    --fmt;
      continue;
    }
    if (qualifier == 'l')
      num = va_arg(args, unsigned long);
    else if (qualifier == 'h') {
      num = (unsigned short) va_arg(args, int);
      if (flags & SIGN)
    num = (short) num;
    } else if (flags & SIGN)
      num = va_arg(args, int);
    else
      num = va_arg(args, unsigned int);
    str = number(str, num, base, field_width, precision, flags);
  }
  *str = '\0';
  return str-buf;
}

int sprintf(char * buf, const char *fmt, ...)
{
  va_list args;
  int i;
 
  va_start(args, fmt);
  i=vsprintf(buf,fmt,args);
  va_end(args);
  return i;
}

int printf(const char *fmt, ...)
{
  char printf_buf[1024];
  va_list args;
  int printed;

  va_start(args, fmt);
  printed = vsprintf(printf_buf, fmt, args);
  va_end(args);

  puts(printf_buf);

  return printed;
}