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#include <stdarg.h>
#include <stdint.h>
enum TYPE {
TYPE_INT = 1,
TYPE_UINT = 2,
TYPE_HEX = 3,
TYPE_STRING = 4,
TYPE_PERCENT = 5
};
enum FLAGS {
FL_ZERO = 1, /* zero padded */
FL_ALT = 2, /* alternate form (effect is type dependent) */
FL_UPPER = 4 /* uppercase */
};
static void hex(char **str, char flags, int fwidth, int size, int x) {
int i, y, len;
char c;
char *prefl = "0x";
char *prefu = "0X";
/* print the prefix, if the alt flag is set */
if(flags & FL_ALT) {
if(flags & FL_UPPER) {
while(*prefu)
*(*str)++ = *prefu++;
} else {
while(*prefl)
*(*str)++ = *prefl++;
}
}
/* calculate the number of digits */
len = 0;
y = x;
for(i = 0; i < sizeof(y) << 1; i++) {
c = ((unsigned int) y >> 28);
if(c)
len++;
y = y << 4;
}
/* print the padding characters (if any) */
c = ' ';
if(flags & FL_ZERO)
c = '0';
for(i = 0; i < fwidth - len; i++)
*(*str)++ = c;
/* actually print the digits */
for(i = 0; i < sizeof(x) << 1; i++) {
c = ((unsigned int) x >> 28) + '0';
if(c > '9') {
c += 0x27;
if(flags & FL_UPPER)
c -= 0x20;
}
if(c != '0')
*(*str)++ = c;
x = x << 4;
}
}
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++;
while(1) {
switch(*fmt) {
case '#':
flags |= FL_ALT;
break;
case '%':
type = TYPE_PERCENT;
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_HEX:
x = va_arg(ap, int);
hex(&str, flags, fwidth, 4, x);
break;
case TYPE_PERCENT:
*str++ = '%';
break;
}
}
*str = 0;
return (str - start);
}
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