마음의 안정을 찾기 위하여 - C언어의 printf 함수의 소스
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C언어의 printf 함수의 소스
VC, MFC, C++ | 2007/12/12 10:00



/*
 Copyright 2001, 2002 Georges Menie (www.menie.org)
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.
    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/*
 putchar is the only external dependency for this file,
 if you have a working putchar, just remove the following
 define. If the function should be called something else,
 replace outbyte(c) by your own function call.
*/
#define putchar(c) outbyte(c)
static void printchar(char **str, int c)
{
 extern int putchar(int c);
 if (str) {
  **str = c;
  ++(*str);
 }
 else (void)putchar(c);
}
#define PAD_RIGHT 1
#define PAD_ZERO 2
static int prints(char **out, const char *string, int width, int pad)
{
 register int pc = 0, padchar = ' ';
 if (width > 0) {
  register int len = 0;
  register const char *ptr;
  for (ptr = string; *ptr; ++ptr) ++len;
  if (len >= width) width = 0;
  else width -= len;
  if (pad & PAD_ZERO) padchar = '0';
 }
 if (!(pad & PAD_RIGHT)) {
  for ( ; width > 0; --width) {
   printchar (out, padchar);
   ++pc;
  }
 }
 for ( ; *string ; ++string) {
  printchar (out, *string);
  ++pc;
 }
 for ( ; width > 0; --width) {
  printchar (out, padchar);
  ++pc;
 }
 return pc;
}
/* the following should be enough for 32 bit int */
#define PRINT_BUF_LEN 12
static int printi(char **out, int i, int b, int sg, int width, int pad, int letbase)
{
 char print_buf[PRINT_BUF_LEN];
 register char *s;
 register int t, neg = 0, pc = 0;
 register unsigned int u = i;
 if (i == 0) {
  print_buf[0] = '0';
  print_buf[1] = '\0';
  return prints (out, print_buf, width, pad);
 }
 if (sg && b == 10 && i < 0) {
  neg = 1;
  u = -i;
 }
 s = print_buf + PRINT_BUF_LEN-1;
 *s = '\0';
 while (u) {
  t = u % b;
  if( t >= 10 )
   t += letbase - '0' - 10;
  *--s = t + '0';
  u /= b;
 }
 if (neg) {
  if( width && (pad & PAD_ZERO) ) {
   printchar (out, '-');
   ++pc;
   --width;
  }
  else {
   *--s = '-';
  }
 }
 return pc + prints (out, s, width, pad);
}
static int print(char **out, int *varg)
{
 register int width, pad;
 register int pc = 0;
 register char *format = (char *)(*varg++);
 char scr[2];
 for (; *format != 0; ++format) {
  if (*format == '%') {
   ++format;
   width = pad = 0;
   if (*format == '\0') break;
   if (*format == '%') goto out;
   if (*format == '-') {
    ++format;
    pad = PAD_RIGHT;
   }
   while (*format == '0') {
    ++format;
    pad |= PAD_ZERO;
   }
   for ( ; *format >= '0' && *format <= '9'; ++format) {
    width *= 10;
    width += *format - '0';
   }
   if( *format == 's' ) {
    register char *s = *((char **)varg++);
    pc += prints (out, s?s:"(null)", width, pad);
    continue;
   }
   if( *format == 'd' ) {
    pc += printi (out, *varg++, 10, 1, width, pad, 'a');
    continue;
   }
   if( *format == 'x' ) {
    pc += printi (out, *varg++, 16, 0, width, pad, 'a');
    continue;
   }
   if( *format == 'X' ) {
    pc += printi (out, *varg++, 16, 0, width, pad, 'A');
    continue;
   }
   if( *format == 'u' ) {
    pc += printi (out, *varg++, 10, 0, width, pad, 'a');
    continue;
   }
   if( *format == 'c' ) {
    /* char are converted to int then pushed on the stack */
    scr[0] = *varg++;
    scr[1] = '\0';
    pc += prints (out, scr, width, pad);
    continue;
   }
  }
  else {
  out:
   printchar (out, *format);
   ++pc;
  }
 }
 if (out) **out = '\0';
 return pc;
}
/* assuming sizeof(void *) == sizeof(int) */
int printf(const char *format, ...)
{
 register int *varg = (int *)(&format);
 return print(0, varg);
}
int sprintf(char *out, const char *format, ...)
{
 register int *varg = (int *)(&format);
 return print(&out, varg);
}
#ifdef TEST_PRINTF
int main(void)
{
 char *ptr = "Hello world!";
 char *np = 0;
 int i = 5;
 unsigned int bs = sizeof(int)*8;
 int mi;
 char buf[80];
 mi = (1 << (bs-1)) + 1;
 printf("%s\n", ptr);
 printf("printf test\n");
 printf("%s is null pointer\n", np);
 printf("%d = 5\n", i);
 printf("%d = - max int\n", mi);
 printf("char %c = 'a'\n", 'a');
 printf("hex %x = ff\n", 0xff);
 printf("hex %02x = 00\n", 0);
 printf("signed %d = unsigned %u = hex %x\n", -3, -3, -3);
 printf("%d %s(s)%", 0, "message");
 printf("\n");
 printf("%d %s(s) with %%\n", 0, "message");
 sprintf(buf, "justif: \"%-10s\"\n", "left"); printf("%s", buf);
 sprintf(buf, "justif: \"%10s\"\n", "right"); printf("%s", buf);
 sprintf(buf, " 3: %04d zero padded\n", 3); printf("%s", buf);
 sprintf(buf, " 3: %-4d left justif.\n", 3); printf("%s", buf);
 sprintf(buf, " 3: %4d right justif.\n", 3); printf("%s", buf);
 sprintf(buf, "-3: %04d zero padded\n", -3); printf("%s", buf);
 sprintf(buf, "-3: %-4d left justif.\n", -3); printf("%s", buf);
 sprintf(buf, "-3: %4d right justif.\n", -3); printf("%s", buf);
 return 0;
}
/*
 * if you compile this file with
 *   gcc -Wall $(YOUR_C_OPTIONS) -DTEST_PRINTF -c printf.c
 * you will get a normal warning:
 *   printf.c:214: warning: spurious trailing `%' in format
 * this line is testing an invalid % at the end of the format string.
 *
 * this should display (on 32bit int machine) :
 *
 * Hello world!
 * printf test
 * (null) is null pointer
 * 5 = 5
 * -2147483647 = - max int
 * char a = 'a'
 * hex ff = ff
 * hex 00 = 00
 * signed -3 = unsigned 4294967293 = hex fffffffd
 * 0 message(s)
 * 0 message(s) with %
 * justif: "left      "
 * justif: "     right"
 *  3: 0003 zero padded
 *  3: 3    left justif.
 *  3:    3 right justif.
 * -3: -003 zero padded
 * -3: -3   left justif.
 * -3:   -3 right justif.
 */
#endif

2007/12/12 10:00 2007/12/12 10:00
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Trackback URL :: 이 글에는 트랙백을 보낼 수 없습니다
From. 리오킴 2007/12/12 13:17
답글달기삭제
printf를 이렇게 복잡하게 -_-;;
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