1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
|
#include "stdio.h"
#include "tty.h"
#include <stdarg.h>
int putchar(int ch)
{
tty_putchar((char)ch);
return 0;
}
int puts(const char* str)
{
tty_puts(str);
return 0;
}
static char hex_table[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
static void print_hex(unsigned int n)
{
unsigned mask = 0xF0000000;
unsigned shift = 28;
while(mask)
{
putchar(hex_table[(n & mask) >> shift]);
mask >>= 4;
shift -= 4;
}
}
int printf(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
while(*fmt)
{
char ch = *fmt++;
switch(ch)
{
case '%':
{
switch(*fmt++)
{
case 'c':
putchar(va_arg(ap, int));
break;
case 's':
puts(va_arg(ap, const char*));
break;
case 'x':
print_hex(va_arg(ap, unsigned));
break;
default:
puts("printf: unknown format\n");
break;
}
break;
}
default:
putchar(ch);
break;
}
}
va_end(ap);
return 0;
}
|
