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
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
|
#include <shared/mem.h>
#include <shared/printf.h>
#include <stdarg.h>
#include <stdbool.h>
struct out_state {
void (*back)(void *, const char *, size_t);
void *backarg;
int written;
char *cache;
size_t cpos, clen;
};
static int flush(struct out_state *os) {
if (os->cpos) {
os->back(os->backarg, os->cache, os->cpos);
os->written += os->cpos;
os->cpos = 0;
}
return os->written;
}
static void output(struct out_state *os, const char *buf, size_t len) {
if (os->cpos + len < os->clen) {
memcpy(os->cache + os->cpos, buf, len);
os->cpos += len;
return;
}
flush(os);
os->back(os->backarg, buf, len);
os->written += len;
}
static void output_c(struct out_state *os, char c) {
output(os, &c, 1);
}
struct mods {
char fill_char;
size_t field_width;
};
static void pad(struct out_state *os, struct mods *m, size_t len) {
for (size_t i = 0; len + i < m->field_width; i++)
output(os, &m->fill_char, 1);
}
static void output_uint(struct out_state *os, struct mods *m, unsigned long long n, char sign) {
char buf[sizeof(unsigned long long) * 3];
size_t pos = sizeof(buf);
if (!n) {
buf[--pos] = '0';
} else while (n) {
unsigned long long q = n / 10, r = n % 10;
buf[--pos] = r + '0';
n = q;
}
if (sign) buf[--pos] = sign;
pad(os, m, sizeof(buf) - pos);
output(os, buf + pos, sizeof(buf) - pos);
}
int __printf_internal(const char *fmt, va_list argp,
void (*back)(void*, const char*, size_t), void *backarg)
{
const char *seg = fmt; /* beginning of the current non-modifier streak */
char cache[64];
struct out_state os = {
.back = back,
.backarg = backarg,
.cache = cache,
.cpos = 0,
.clen = sizeof(cache),
};
for (;;) {
char c = *fmt++;
if (c == '\0') {
output(&os, seg, fmt - seg - 1);
return flush(&os);
}
if (c != '%') continue;
output(&os, seg, fmt - seg - 1);
struct mods m = {
.fill_char = ' ',
.field_width = 0,
};
for (bool modifier = true; modifier;) {
c = *fmt++;
switch (c) {
case '0':
m.fill_char = '0';
break;
default:
modifier = false;
break;
}
}
while ('0' <= c && c <= '9') {
m.field_width *= 10;
m.field_width += c - '0';
c = *fmt++;
}
// TODO length modifiers
switch (c) {
unsigned long n, len;
long ns;
char sign;
case 'c':
output_c(&os, va_arg(argp, int));
break;
case 's':
const char *s = va_arg(argp, char*);
if (s) {
len = strlen(s);
pad(&os, &m, len);
output(&os, s, len);
} else {
pad(&os, &m, 0);
}
break;
case 'x':
n = va_arg(argp, unsigned long);
len = 1;
while (n >> (len * 4) && (len * 4) < (sizeof(n) * 8))
len++;
pad(&os, &m, len);
while (len-- > 0) {
char h = '0' + ((n >> (len * 4)) & 0xf);
if (h > '9') h += 'a' - '9' - 1;
output_c(&os, h);
}
break;
case 'u':
n = va_arg(argp, unsigned long);
output_uint(&os, &m, n, 0);
break;
case 'd':
ns = va_arg(argp, int);
sign = 0;
if (ns < 0) {
ns = -ns;
sign = '-';
}
output_uint(&os, &m, (long)ns, sign);
break;
case '%':
output(&os, "%", 1);
break;
}
seg = fmt;
}
}
static void vsnprintf_backend(void *arg, const char *buf, size_t len) {
char **ptrs = arg;
size_t space = ptrs[1] - ptrs[0];
if (len > space) len = space;
memcpy(ptrs[0], buf, len);
ptrs[0] += len;
/* ptrs[1] is the last byte of the buffer, it must be 0.
* on overflow:
* ptrs[0] + (ptrs[1] - ptrs[0]) = ptrs[1] */
*ptrs[0] = '\0';
}
int vsnprintf(char *restrict str, size_t len, const char *restrict fmt, va_list ap) {
char *ptrs[2] = {str, str + len - 1};
return __printf_internal(fmt, ap, vsnprintf_backend, &ptrs);
}
int snprintf(char *restrict str, size_t len, const char *restrict fmt, ...) {
int ret;
va_list argp;
va_start(argp, fmt);
ret = vsnprintf(str, len, fmt, argp);
va_end(argp);
return ret;
}
|
