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#include <stdarg.h>
#include <stdint.h>
#include <sys/types.h>
enum TYPE {
TYPE_INT = 1,
TYPE_UINT = 2,
TYPE_DEC = 3,
TYPE_OCT = 4,
TYPE_HEX = 5,
TYPE_CHAR = 6,
TYPE_STRING = 7,
TYPE_PERCENT = 8
};
enum FLAGS {
FL_ZERO = 1, /* zero padded */
FL_ALT = 2, /* alternate form (effect is type dependent) */
FL_UPPER = 4 /* uppercase */
};
static void num(char **str, char flags, int base, int fwidth, int x) {
int i, y, len = 0;
char c;
char *s = NULL;
/* print the prefix, if the alt flag is set */
if(x && (flags & FL_ALT) && base == 8)
s = "0";
if(x && (flags & FL_ALT) && base == 16)
s = (flags & FL_UPPER) ? "0X" : "0x";
while(s && *s)
*(*str)++ = *s++;
/* calculate the number of digits */
y = x;
while(y) {
y /= base;
len++;
}
/* print the padding characters (if any) */
for(i = 0; i < fwidth - len; i++)
*((*str)++) = (flags & FL_ZERO) ? '0' : ' ';
*str += len;
s = *str;
while(len--) {
c = (x % base) + '0';
if(c > '9')
c += (flags & FL_UPPER) ? 7 : 39;
*(--s) = c;
x /= base;
}
}
int vsprintf(char *str, char *fmt, va_list ap) {
int x, fwidth;
char flags;
char *s;
char *start = str;
uint8_t type;
while(*fmt) {
if(*fmt != '%') {
*str++ = *fmt++;
continue;
}
type = 0;
flags = 0;
fwidth = 0;
fmt++;
for(;;) {
switch(*fmt) {
case '#':
flags |= FL_ALT;
break;
case '%':
type = TYPE_PERCENT;
goto done;
case 'c':
type = TYPE_CHAR;
goto done;
case 'd':
type = TYPE_DEC;
goto done;
case 'o':
type = TYPE_OCT;
goto done;
case 's':
type = TYPE_STRING;
goto done;
case 'x':
type = TYPE_HEX;
goto done;
case 'X':
type = TYPE_HEX;
flags |= FL_UPPER;
goto done;
default:
/* the first zero enables zero-padding */
if(*fmt == '0' && !fwidth) {
flags |= FL_ZERO;
goto next;
}
/* subsequent numbers indicate field width */
if(*fmt >= '0' && *fmt <= '9') {
fwidth = (fwidth * 10) + (*fmt - '0');
goto next;
}
goto done;
}
next:
fmt++;
}
done:
fmt++;
switch(type) {
case TYPE_STRING:
s = va_arg(ap, char*);
while(*s)
*str++ = *s++;
break;
case TYPE_CHAR:
*str++ = va_arg(ap, char);
break;
case TYPE_DEC:
x = va_arg(ap, int);
num(&str, flags, 10, fwidth, x);
break;
case TYPE_OCT:
x = va_arg(ap, int);
num(&str, flags, 8, fwidth, x);
break;
case TYPE_HEX:
x = va_arg(ap, int);
num(&str, flags, 16, fwidth, x);
break;
case TYPE_PERCENT:
*str++ = '%';
break;
}
}
*str = 0;
return (str - start);
}
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