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comparison src/usr/printf.c @ 0:53676d1f5817 default tip

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author tobaru
date Sun, 04 Feb 2018 17:54:49 +0900
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-1:000000000000 0:53676d1f5817
1 #include "types.h"
2 #include "stat.h"
3 #include "user.h"
4
5 static void
6 putc(int fd, char c)
7 {
8 write(fd, &c, 1);
9 }
10
11 static void
12 printint(int fd, int xx, int base, int sgn)
13 {
14 static char digits[] = "0123456789ABCDEF";
15 char buf[16];
16 int i, neg;
17 uint x;
18
19 neg = 0;
20 if(sgn && xx < 0){
21 neg = 1;
22 x = -xx;
23 } else {
24 x = xx;
25 }
26
27 i = 0;
28 do{
29 buf[i++] = digits[x % base];
30 }while((x /= base) != 0);
31 if(neg)
32 buf[i++] = '-';
33
34 while(--i >= 0)
35 putc(fd, buf[i]);
36 }
37
38 // Print to the given fd. Only understands %d, %x, %p, %s.
39 void
40 printf(int fd, char *fmt, ...)
41 {
42 char *s;
43 int c, i, state;
44 uint *ap;
45
46 state = 0;
47 ap = (uint*)(void*)&fmt + 1;
48 for(i = 0; fmt[i]; i++){
49 c = fmt[i] & 0xff;
50 if(state == 0){
51 if(c == '%'){
52 state = '%';
53 } else {
54 putc(fd, c);
55 }
56 } else if(state == '%'){
57 if(c == 'd'){
58 printint(fd, *ap, 10, 1);
59 ap++;
60 } else if(c == 'x' || c == 'p'){
61 printint(fd, *ap, 16, 0);
62 ap++;
63 } else if(c == 's'){
64 s = (char*)*ap;
65 ap++;
66 if(s == 0)
67 s = "(null)";
68 while(*s != 0){
69 putc(fd, *s);
70 s++;
71 }
72 } else if(c == 'c'){
73 putc(fd, *ap);
74 ap++;
75 } else if(c == '%'){
76 putc(fd, c);
77 } else {
78 // Unknown % sequence. Print it to draw attention.
79 putc(fd, '%');
80 putc(fd, c);
81 }
82 state = 0;
83 }
84 }
85 }