xv6-65oo2/user/printf.c
2019-06-11 09:57:14 -04:00

96 lines
1.7 KiB
C

#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include <stdarg.h>
static char digits[] = "0123456789ABCDEF";
static void
putc(int fd, char c)
{
write(fd, &c, 1);
}
static void
printint(int fd, int xx, int base, int sgn)
{
char buf[16];
int i, neg;
uint x;
neg = 0;
if(sgn && xx < 0){
neg = 1;
x = -xx;
} else {
x = xx;
}
i = 0;
do{
buf[i++] = digits[x % base];
}while((x /= base) != 0);
if(neg)
buf[i++] = '-';
while(--i >= 0)
putc(fd, buf[i]);
}
static void
printptr(int fd, uint64 x) {
int i;
putc(fd, '0');
putc(fd, 'x');
for (i = 0; i < (sizeof(uint64) * 2); i++, x <<= 4)
putc(fd, digits[x >> (sizeof(uint64) * 8 - 4)]);
}
// Print to the given fd. Only understands %d, %x, %p, %s.
void
printf(int fd, const char *fmt, ...)
{
va_list ap;
char *s;
int c, i, state;
va_start(ap, fmt);
state = 0;
for(i = 0; fmt[i]; i++){
c = fmt[i] & 0xff;
if(state == 0){
if(c == '%'){
state = '%';
} else {
putc(fd, c);
}
} else if(state == '%'){
if(c == 'd'){
printint(fd, va_arg(ap, int), 10, 1);
} else if(c == 'x') {
printint(fd, va_arg(ap, int), 16, 0);
} else if(c == 'p') {
printptr(fd, va_arg(ap, uint64));
} else if(c == 's'){
s = va_arg(ap, char*);
if(s == 0)
s = "(null)";
while(*s != 0){
putc(fd, *s);
s++;
}
} else if(c == 'c'){
putc(fd, va_arg(ap, uint));
} else if(c == '%'){
putc(fd, c);
} else {
// Unknown % sequence. Print it to draw attention.
putc(fd, '%');
putc(fd, c);
}
state = 0;
}
}
}