簡易版sprintf

kstring.h

#include "kstring.h"
#include <stdio.h>

static const int MAXDIGITS = 20;
static const char char_table[16] 
  = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 
     'a', 'b', 'c', 'd', 'e', 'f'};

int int2str(const int n, const int x, char *str)
{
  char buf[MAXDIGITS+2];
  int i, j;
  int y;
  for(i = 0, y = x > 0? x : -x; (i < MAXDIGITS) && (y != 0); ++i, y = y /n) {
    buf[i] = char_table[y % n];
  }
  if(x < 0) {
    buf[i] = '-';
  } else {
    i--;
  }
  for(j = 0; i >= 0; --i, ++j) {
    str[j] = buf[i];
  }
  str[j] = '\0';
  return j;
}

int uint2str(const unsigned int n, const unsigned int x, char *str)
{
  char buf[MAXDIGITS+2];
  int i, j;
  unsigned int y;
  for(i = 0, y = x; (i < MAXDIGITS) && (y != 0); ++i, y = y /n) {
    buf[i] = char_table[y % n];
  }
  i--;
  for(j = 0; i >= 0; --i, ++j) {
    str[j] = buf[i];
  }
  str[j] = '\0';
  return j;
}


int sprint_int(char *str, const char *format, ...)
{
  int *varg = (int*)(&format + 1);
  int fi, vi;
  char *s;
  for(fi = 0, vi = 0, s = str; format[fi] != '\0'; ++fi) {
    if(format[fi] == '%') {
      if(format[fi+1] == 'd') {
        int n = int2str(10, varg[vi], s);
        s = s + n;
        fi++;
        vi++;
        continue;
      } else if(format[fi+1] == 'u') {
        int n = uint2str(10, varg[vi], s);
        s = s + n;
        fi++;
        vi++;
        continue;
      } else if(format[fi+1] == 'x') {
        int n = uint2str(16, varg[vi], s);
        s = s + n;
        fi++;
        vi++;
        continue;
      }
    }
    *s = format[fi];
    s++;
  }
  *s = '\0'; 
  return 0; 
}

32bit用。64bitバイナリだと可変長引数の扱い方が変わるので動かない。