strftime.c raw
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <string.h>
4 #include <langinfo.h>
5 #include <locale.h>
6 #include <time.h>
7 #include <limits.h>
8 #include "locale_impl.h"
9 #include "time_impl.h"
10
11 static int is_leap(int y)
12 {
13 /* Avoid overflow */
14 if (y>INT_MAX-1900) y -= 2000;
15 y += 1900;
16 return !(y%4) && ((y%100) || !(y%400));
17 }
18
19 static int week_num(const struct tm *tm)
20 {
21 int val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
22 /* If 1 Jan is just 1-3 days past Monday,
23 * the previous week is also in this year. */
24 if ((tm->tm_wday + 371U - tm->tm_yday - 2) % 7 <= 2)
25 val++;
26 if (!val) {
27 val = 52;
28 /* If 31 December of prev year a Thursday,
29 * or Friday of a leap year, then the
30 * prev year has 53 weeks. */
31 int dec31 = (tm->tm_wday + 7U - tm->tm_yday - 1) % 7;
32 if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
33 val++;
34 } else if (val == 53) {
35 /* If 1 January is not a Thursday, and not
36 * a Wednesday of a leap year, then this
37 * year has only 52 weeks. */
38 int jan1 = (tm->tm_wday + 371U - tm->tm_yday) % 7;
39 if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
40 val = 1;
41 }
42 return val;
43 }
44
45 const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *tm, locale_t loc, int pad)
46 {
47 nl_item item;
48 long long val;
49 const char *fmt = "-";
50 int width = 2, def_pad = '0';
51
52 switch (f) {
53 case 'a':
54 if (tm->tm_wday > 6U) goto string;
55 item = ABDAY_1 + tm->tm_wday;
56 goto nl_strcat;
57 case 'A':
58 if (tm->tm_wday > 6U) goto string;
59 item = DAY_1 + tm->tm_wday;
60 goto nl_strcat;
61 case 'h':
62 case 'b':
63 if (tm->tm_mon > 11U) goto string;
64 item = ABMON_1 + tm->tm_mon;
65 goto nl_strcat;
66 case 'B':
67 if (tm->tm_mon > 11U) goto string;
68 item = MON_1 + tm->tm_mon;
69 goto nl_strcat;
70 case 'c':
71 item = D_T_FMT;
72 goto nl_strftime;
73 case 'C':
74 val = (1900LL+tm->tm_year) / 100;
75 goto number;
76 case 'e':
77 def_pad = '_';
78 case 'd':
79 val = tm->tm_mday;
80 goto number;
81 case 'D':
82 fmt = "%m/%d/%y";
83 goto recu_strftime;
84 case 'F':
85 fmt = "%Y-%m-%d";
86 goto recu_strftime;
87 case 'g':
88 case 'G':
89 val = tm->tm_year + 1900LL;
90 if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
91 else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
92 if (f=='g') val %= 100;
93 else width = 4;
94 goto number;
95 case 'H':
96 val = tm->tm_hour;
97 goto number;
98 case 'I':
99 val = tm->tm_hour;
100 if (!val) val = 12;
101 else if (val > 12) val -= 12;
102 goto number;
103 case 'j':
104 val = tm->tm_yday+1;
105 width = 3;
106 goto number;
107 case 'm':
108 val = tm->tm_mon+1;
109 goto number;
110 case 'M':
111 val = tm->tm_min;
112 goto number;
113 case 'n':
114 *l = 1;
115 return "\n";
116 case 'p':
117 item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
118 goto nl_strcat;
119 case 'r':
120 item = T_FMT_AMPM;
121 goto nl_strftime;
122 case 'R':
123 fmt = "%H:%M";
124 goto recu_strftime;
125 case 's':
126 val = __tm_to_secs(tm) - tm->__tm_gmtoff;
127 width = 1;
128 goto number;
129 case 'S':
130 val = tm->tm_sec;
131 goto number;
132 case 't':
133 *l = 1;
134 return "\t";
135 case 'T':
136 fmt = "%H:%M:%S";
137 goto recu_strftime;
138 case 'u':
139 val = tm->tm_wday ? tm->tm_wday : 7;
140 width = 1;
141 goto number;
142 case 'U':
143 val = (tm->tm_yday + 7U - tm->tm_wday) / 7;
144 goto number;
145 case 'W':
146 val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
147 goto number;
148 case 'V':
149 val = week_num(tm);
150 goto number;
151 case 'w':
152 val = tm->tm_wday;
153 width = 1;
154 goto number;
155 case 'x':
156 item = D_FMT;
157 goto nl_strftime;
158 case 'X':
159 item = T_FMT;
160 goto nl_strftime;
161 case 'y':
162 val = (tm->tm_year + 1900LL) % 100;
163 if (val < 0) val = -val;
164 goto number;
165 case 'Y':
166 val = tm->tm_year + 1900LL;
167 if (val >= 10000) {
168 *l = snprintf(*s, sizeof *s, "+%lld", val);
169 return *s;
170 }
171 width = 4;
172 goto number;
173 case 'z':
174 if (tm->tm_isdst < 0) {
175 *l = 0;
176 return "";
177 }
178 *l = snprintf(*s, sizeof *s, "%+.4ld",
179 tm->__tm_gmtoff/3600*100 + tm->__tm_gmtoff%3600/60);
180 return *s;
181 case 'Z':
182 if (tm->tm_isdst < 0) {
183 *l = 0;
184 return "";
185 }
186 fmt = __tm_to_tzname(tm);
187 goto string;
188 case '%':
189 *l = 1;
190 return "%";
191 default:
192 return 0;
193 }
194 number:
195 switch (pad ? pad : def_pad) {
196 case '-': *l = snprintf(*s, sizeof *s, "%lld", val); break;
197 case '_': *l = snprintf(*s, sizeof *s, "%*lld", width, val); break;
198 case '0':
199 default: *l = snprintf(*s, sizeof *s, "%0*lld", width, val); break;
200 }
201 return *s;
202 nl_strcat:
203 fmt = __nl_langinfo_l(item, loc);
204 string:
205 *l = strlen(fmt);
206 return fmt;
207 nl_strftime:
208 fmt = __nl_langinfo_l(item, loc);
209 recu_strftime:
210 *l = __strftime_l(*s, sizeof *s, fmt, tm, loc);
211 if (!*l) return 0;
212 return *s;
213 }
214
215 size_t __strftime_l(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm, locale_t loc)
216 {
217 size_t l, k;
218 char buf[100];
219 char *p;
220 const char *t;
221 int pad, plus;
222 unsigned long width;
223 for (l=0; l<n; f++) {
224 if (!*f) {
225 s[l] = 0;
226 return l;
227 }
228 if (*f != '%') {
229 s[l++] = *f;
230 continue;
231 }
232 f++;
233 pad = 0;
234 if (*f == '-' || *f == '_' || *f == '0') pad = *f++;
235 if ((plus = (*f == '+'))) f++;
236 width = strtoul(f, &p, 10);
237 if (*p == 'C' || *p == 'F' || *p == 'G' || *p == 'Y') {
238 if (!width && p!=f) width = 1;
239 } else {
240 width = 0;
241 }
242 f = p;
243 if (*f == 'E' || *f == 'O') f++;
244 t = __strftime_fmt_1(&buf, &k, *f, tm, loc, pad);
245 if (!t) break;
246 if (width) {
247 /* Trim off any sign and leading zeros, then
248 * count remaining digits to determine behavior
249 * for the + flag. */
250 if (*t=='+' || *t=='-') t++, k--;
251 for (; *t=='0' && t[1]-'0'<10U; t++, k--);
252 if (width < k) width = k;
253 size_t d;
254 for (d=0; t[d]-'0'<10U; d++);
255 if (tm->tm_year < -1900) {
256 s[l++] = '-';
257 width--;
258 } else if (plus && d+(width-k) >= (*p=='C'?3:5)) {
259 s[l++] = '+';
260 width--;
261 }
262 for (; width > k && l < n; width--)
263 s[l++] = '0';
264 }
265 if (k > n-l) k = n-l;
266 memcpy(s+l, t, k);
267 l += k;
268 }
269 if (n) {
270 if (l==n) l=n-1;
271 s[l] = 0;
272 }
273 return 0;
274 }
275
276 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
277 {
278 return __strftime_l(s, n, f, tm, CURRENT_LOCALE);
279 }
280
281 weak_alias(__strftime_l, strftime_l);
282